Dark Matter The Case of Sterile Neutrino
暗物质成品
What is dark matter?
About 65 years ago, the first time that evidence of the existence of dark matter. At that time, Fulizizha Popovich found a large cluster of galaxies in the galaxy has a very high velocity, unless the quality of galaxy clusters is based on the number of calculations in which stars are more than 100 times the value, or cluster of galaxies can not bound lives of these galaxies. After decades of observation and analysis confirmed this. Although the nature of dark matter is still unknown, but by 80 years, accounting for about 20% of the energy density of dark matter to be widely accepted.
What is dark matter?
now we know that dark matter has become an important part of the universe. The total mass of dark matter is ordinary matter, 6.3 times the energy density in the universe, accounting for 1 / 4, but also important is that dark matter dominated the formation of cosmic structures. Now the nature of dark matter remains a mystery, but assuming it is a weak interaction of subatomic particles, then the resulting large-scale structure of the universe is consistent with the observations. Recently, however, the structure of galaxies and galaxy subanalysis shows that this assumption and the difference between observations, which at the same time provide a variety of possible dark matter theory was useless. Small-scale structure through the density, distribution, evolution and its environment studies can distinguish between these potential dark matter model for the nature of dark matter to bring a new dawn.
犯罪心理1-5季名言
Season 5◎Episode 1: Nameless, Faceless（2009.09.23）●a weak man has doubts before a decision.A strong man has them afterwards.——Karl krauss 【卡尔·克劳斯（上世纪上半叶最杰出德语作家和语言大师之一，1874 - 1936）：弱者在决策前迟疑，强者则反之。
】（Rossi）（本集片尾没有出现名言）◎Episode 2: Haunted（2009.09.30）●one need not be a chamber to be haunted.one need not be a house.The brain has corridors surpassing material place.——Emily dickinson【艾米莉·狄金森（美国诗人，1830 - 1886 ）：无需亲临幽室便能体味精神折磨，无需亲临暗宅，思想能带你穿越置身其中。
】（Hotch）●there is no witness so dreadful, no accuser so terri ble,as the conscience that dwells in the heart of every man.——Polybius【波里比阿（古希腊历史学家，约公元前204 - 122年）：没有可怕至极的证人，没有恐怖之至的原告，因为良心存在于每个人心中。
】（Hotch）◎Episode 3: Reckoner（2009.10.07）●Justice without force is powerless.Force without justice is tyrannical.——Blaise Pascal【帕斯卡（法国哲学家，1623 - 1662）：正义缺少武力是无能，武力缺少正义是暴政。
Investigating the Nature of Dark Matter
Investigating the Nature of DarkMatterThe phrase “dark matter” has become a buzzword in modern astrophysics as well as popular culture, and yet we still know very little about what dark matter really is. It is a mysterious substance that makes up 27% of the universe and that cannot be observed directly, but can only be inferred from the gravitational effects it has on visible matter. Therefore, dark matter is a topic of intense research and debate in the scientific community. In this article, we will explore the key aspects of dark matter and the different ways scientists are working to uncover its nature.What is Dark Matter?As mentioned, dark matter is a substance that does not emit, absorb or reflect light, hence its name. It does not interact strongly with electromagnetic forces, but it does with gravity, which is why its presence can be inferred from the gravitational effects it has on visible matter. One of the most well-known examples of this is the rotation curve of spiral galaxies. According to the laws of classical mechanics, the velocity of stars and gas in a galaxy should decrease as one moves away from the center, as the gravitational attraction of the visible matter decreases. However, observations have shown that the velocity remains constant or even increases, suggesting that there is an invisible mass that is causing this anomaly. This invisible mass is the dark matter.Another piece of evidence for the existence of dark matter is the distribution of matter in the universe as revealed by the cosmic microwave background radiation, which is the afterglow of the Big Bang. The pattern of temperature fluctuations in this radiation shows that the matter in the universe is not distributed evenly, but is rather clumped up in large structures such as galaxies and clusters of galaxies. However, this clumping up cannot be explained solely by the gravitational influence of visible matter; there must be an additional source of gravity, i.e. dark matter, to explain the observed distribution.Moreover, measurements of the large-scale structure of the universe, such as the distribution of galaxies and galaxy clusters, also point to the existence of dark matter.What is Dark Matter Made of?Despite its importance in shaping the structure of the universe, the identity of dark matter remains unknown. There are several hypotheses about what dark matter might be made of, but none of them has been conclusively proven yet. One popular hypothesis is that dark matter is composed of weakly interacting massive particles (WIMPs), which are hypothetical particles that would interact with normal matter only through the weak nuclear force and gravity. The idea is that WIMPs were produced in the early universe when it was hot and dense, and have been moving around freely ever since. If they collide with normal matter, they would transfer some of their energy and momentum, producing detectable signals. In fact, several experiments have been designed to detect WIMP interactions, such as the Large Underground Xenon (LUX) experiment and the Super Cryogenic Dark Matter Search (SuperCDMS).Another hypothesis is that dark matter is made of axions, which are theoretical particles that were originally proposed to explain a different problem in physics, the strong CP problem. The idea is that axions would be very light and weakly interacting, making them difficult to detect, but would still affect the motion of galaxies and other cosmic structures. The Axion Dark Matter eXperiment (ADMX) is currently searching for evidence of axions in a laboratory at the University of Washington.A third hypothesis is that dark matter is composed of primordial black holes, which are black holes that were formed by the collapse of a density fluctuation in the early universe. The idea is that these black holes could have a mass range that would make them more likely to be dark matter, and that their interactions with normal matter could produce observable effects. However, this hypothesis is less favored by most researchers, as the formation and stability of such black holes would require very specific conditions.ConclusionDespite decades of research, the nature of dark matter remains one of the most intriguing and elusive topics in astrophysics. It remains a theoretical construct that cannot be directly observed, but its effects on the motion and structure of the cosmos are undeniable. Researchers are continuing to study dark matter using a variety of tools and techniques, from telescopes that measure gravitational lensing to underground experiments that look for WIMP interactions. The hope is that someday we will finally be able to unravel the mystery of what dark matter is made of, and in doing so, gain a better understanding of the universe and our place in it.。
Evolution of the Fine Structure Constant Driven by Dark Matter and the Cosmological Constan
Physics Department, McGill University, 3600 University St, Montreal,Quebec H3A 2T8, Canada
D´ epartement de Physique, Universit´ e du Qu´ ebec ` a Montr´ eal C.P. 8888, Succ. Centre-Ville, Montr´ eal, Qu´ ebec, Canada, H3C 3P8
1
Introduction
Speculations that fundamental constants may vary in time and/or space go back to the original idea of Dirac [1]. Despite the reputable origin, this idea has not received much attention during the last fifty years for the two following reasons. First, there exist various sensitive experimental checks that coupling constants do not change (See, e.g. [2]). Second, for a long time there has not been any credible theoretical framework which would predict such changes. Our theoretical mindset, however, has changed since the advent of the string theory. One of the most interesting low-energy features of string theory is the possible presence of a massless scalar particle, the dilaton, whose vacuum expectation value defines the size of the effective gauge coupling constants. A change in the dilaton v.e.v. induces a change in the fine structure constant as well as the other gauge and Yukawa couplings. The stabilization of the dilaton v.e.v., which usually renders the dilaton massive, represents one of the fundamental challenges to be addressed before string theory can aspire to describe the observable world. Besides the dilaton, string theory often predicts the presence of other massless or nearly massless moduli fields, whose existence may influence particle physics and cosmology and may also change the effective values of the coupling constants as well. Independent of the framework of string theory, Bekenstein [3] formulated a dynamical model of “changing α”. The model consists of a massless scalar field which has a linear −1 φFµν F µν , where M∗ is an associated coupling to the F 2 term of the U (1) gauge field, M∗ mass scale and thought to be of order the Planck scale. A change in the background value of φ, can be interpreted as a change of the effective coupling constant. Bekenstein noticed that F 2 has a non-vanishing matrix element over protons and neutrons, of order (10−3 − 10−2 )mN . This matrix element acts as a source in the φ equation of motion and naturally leads to the cosmological evolution of the φ field driven by the baryon energy density. Thus, the change in φ translates into a change in α on a characteristic time scale comparable to the lifetime of the Universe or larger. However, the presence of a massless scalar field φ in the theory leads to the existence of an additional attractive force which does not respect Einstein’s weak universality principle. The extremely accurate checks of the latter [4] lead to a firm lower limit on M∗ , M∗ /MPl > 103 that confines possible changes of α to the range ∆α < 10−10 − 10−9 for 0 < z < 5 [3, 5]. This range is five orders of magnitude tighter than the change ∆α/α ≃ 10−5 indicated in the observations of quasar absorption spectra at z = 0.5 − 3.5 and recently reported by Webb et al. [6]. Given the potential fundamental importance of such a result, one should remain cautious until this result is independently verified. Nevertheless, leaving aside the issue regarding the reliability of the conclusions reached by Webb et al. [6], it is interesting to explore the possibility of constructing a dynamical model, including 1
Accomodating Solar and Atmospheric Neutrino Deficits, Hot Dark Matter, and a Double Beta De
arXiv:hep-ph/9402231v2 9 Feb 1994
−6 2 2 −3 a)Small − angle MSW, ∆m2 ei ∼ 6 × 10 eV , sin 2θei ∼ 7 × 10 ,
2
−6 2 2 b)Large − angle MSW, ∆m2 ei ∼ 9 × 10 eV , sin 2θei ∼ 0.6, −10 eV2 , sin2 2θ ∼ 0.9. c)Vacuum oscillation, ∆m2 ei ei ∼ 10
(1)
Of these, (a) is favored over (b) by the fits to the solar neutrino data [9], and both (b) and (c) are disfavored by information from the neutrino burst from supernova 1987A [11]. B. Atmospheric Neutrino Deficit The second set of experiments indicating non-zero neutrino masses and mixings has to do with atmospheric νµ ’s and νe ’s arising from the decays of π ’s and K ’s and the subsequent decays of secondary muons produced in the final states of the π and K decays. In the underground experiments the νµ and ν ¯µ produce muons and the νe and ν ¯e lead to e± . Observations of µ± and e± indicate a far lower value for νµ and ν ¯µ than suggested by na¨ ıve counting arguments which imply that N (νµ + ν ¯µ ) = 2N (νe + ν ¯e ). More precisely, the ratio of µ events to e-events can be normalized to the ratio of calculated fluxes to reduce flux uncertainties, giving [3] R(µ/e) = 0.60 ± 0.07 ± 0.05 (Kamiokande), = 0.54 ± 0.05 ± 0.12 (IMB), = 0.69 ± 0.19 ± 0.09 (Soudan II). Combining these results with observations of upward going muons by Kamiokande [3], IMB [3], and Baksan [12] and the negative Fr´ ejus [13] and NUSEX [14] results leads to the conclusion [15] that neutrino oscillations can give an explanation of these results, provided
The mysteries of the universe Dark matter
The mysteries of the universe DarkmatterDark matter is one of the most enigmatic and perplexing concepts in the field of astrophysics and cosmology. It is a substance that makes up a significantportion of the universe, yet it remains largely elusive and mysterious to scientists. The existence of dark matter was first proposed in the 1930s by Swiss astronomer Fritz Zwicky, who observed that the visible matter in the Coma galaxy cluster could not account for the gravitational forces that were holding thecluster together. This led him to hypothesize the presence of unseen "dark" matter that was responsible for the gravitational effects. Since then, numerous observations and experiments have provided compelling evidence for the existenceof dark matter, but its true nature continues to elude researchers. One of the most compelling lines of evidence for dark matter comes from the study of the rotation curves of galaxies. When astronomers measure the velocities of stars and gas in a galaxy as a function of their distance from the galactic center, theyfind that the velocities do not decrease as expected with increasing distance. Instead, the velocities remain constant or even increase, indicating the presence of additional unseen mass that is providing the gravitational pull to keep thestars and gas in their orbits. This discrepancy between the observed motion of galactic objects and the visible matter in galaxies has led scientists to conclude that there must be a significant amount of dark matter present in galaxies, outweighing the visible matter by a factor of about six to one. Another piece of evidence for dark matter comes from the study of the large-scale structure of the universe. Observations of the cosmic microwave background radiation, the afterglow of the Big Bang, have revealed subtle patterns in the distribution of matter onthe largest scales. These patterns can be explained by the presence of dark matter, which exerts gravitational forces to shape the distribution of galaxies and galaxy clusters in the universe. Additionally, the gravitational lensing of distant galaxies by intervening mass concentrations, such as galaxy clusters, provides further evidence for the presence of dark matter. The bending of light from these distant galaxies can only be explained by the gravitational influence of unseenmass, which is consistent with the properties of dark matter. Despite the overwhelming evidence for the existence of dark matter, its true nature remains a profound mystery. Dark matter does not emit, absorb, or reflect light, making it invisible to telescopes and other instruments that rely on electromagnetic radiation for detection. This has made it incredibly challenging for scientists to directly observe and study dark matter, leading to a wide range of theoretical and experimental efforts to uncover its properties. One of the leading candidates for the identity of dark matter is a type of particle that interacts only weakly with ordinary matter and electromagnetic forces, known as a weakly interacting massive particle (WIMP). WIMPs are a theoretical class of particles that arise in extensions of the standard model of particle physics, and they are thought to have been produced in the early universe in sufficient quantities to account for the observed abundance of dark matter today. Numerous experiments around the world are dedicated to detecting WIMPs through their rare interactions with ordinary matter, such as through the recoil of atomic nuclei in underground detectors or the production of secondary particles in particle accelerators. Another potential explanation for dark matter is the existence of primordial black holes, which are hypothesized to have formed in the early universe from the gravitational collapse of overdense regions. These black holes would not emit significant amounts oflight or other radiation, making them difficult to detect directly. However, their gravitational influence on surrounding matter could betray their presence, and ongoing observational campaigns are searching for the signatures of primordial black holes in the universe. In addition to these particle-based and astrophysical explanations, some scientists have proposed modifications to the laws of gravity as an alternative to dark matter. These modified gravity theories seek to explain the observed gravitational effects in galaxies and galaxy clusters without invoking the presence of additional unseen mass. While these theories have had some success in reproducing certain observational data, they have yet to provide a comprehensive and consistent explanation for the full range of evidence for dark matter. The search for dark matter continues to be a vibrant and active area of research in astrophysics and particle physics. New generations of experiments are pushing the boundaries of sensitivity and precision in the huntfor dark matter particles, while astronomers are mapping the distribution ofmatter in the universe with ever-increasing detail. The discovery of dark matter would represent a profound breakthrough in our understanding of the fundamental constituents of the universe and the forces that govern its evolution. It would also have far-reaching implications for our understanding of the cosmos, from the formation of galaxies and galaxy clusters to the ultimate fate of the universe itself. The quest to unravel the mysteries of dark matter is not just ascientific endeavor, but also a deeply human one. It speaks to our innatecuriosity about the nature of the universe and our place within it. Therealization that the majority of the matter in the universe is invisible and fundamentally different from the matter we interact with on a daily basis is both humbling and awe-inspiring. It challenges our preconceived notions of the cosmos and forces us to confront the limits of our current understanding. The search for dark matter is a testament to the human spirit of exploration and discovery, as we strive to push the boundaries of knowledge and unlock the secrets of the universe. In conclusion, dark matter remains one of the most captivating and tantalizing mysteries in modern science. Its existence is supported by a wealth of observational evidence, yet its true nature continues to elude us. Whether it is composed of exotic particles, primordial black holes, or a modification of thelaws of gravity, the discovery of dark matter would revolutionize our understanding of the cosmos and our place within it. The ongoing quest to uncover the secrets of dark matter is a testament to the enduring human spirit ofcuriosity and exploration, as we continue to push the boundaries of knowledge and strive to unlock the mysteries of the universe.。
The Science of Dark Matter and Its Discovery
The Science of Dark Matter and ItsDiscoveryIntroductionDark matter is an elusive substance that makes up about 27% of the universe. It neither emits nor absorbs light, making it invisible to telescopes. Scientists have been studying dark matter for decades, and its discovery is considered one of the greatest mysteries of modern physics. In this article, we will delve into the science of dark matter, its properties, and the research that has led to its discovery.What is Dark Matter?Dark matter is a hypothetical substance that does not interact with light or any other form of electromagnetic radiation. It is invisible to telescopes, but its presence is inferred from its gravitational effects on objects that emit light. Dark matter is thought to be five times more abundant than visible matter, which is what stars, planets, and galaxies are made of.The Properties of Dark MatterAlthough scientists have yet to observe dark matter directly, they have been able to infer its properties from its gravitational effects. Dark matter is thought to be cold, meaning that its particles move relatively slowly. It is also believed to be non-interacting, meaning that it does not interact with other particles except through the force of gravity.Dark matter is widely thought to be made up of weakly interacting massive particles (WIMPs), which are particles that interact with each other only through the weak force and gravity. Other proposed candidates for dark matter particles include axions and sterile neutrinos, but these have not been observed directly.The Search for Dark MatterThe search for dark matter has been ongoing for several decades. One of the most promising methods for detecting dark matter involves looking for the energetic particles that result from the annihilation of dark matter particles. This method is called indirect detection and involves searching for gamma rays, neutrinos, or cosmic rays that are produced by the decay or annihilation of dark matter particles.Another way to detect dark matter is through the direct detection method, which involves looking for the recoil of atomic nuclei in a detector after they have been struck by dark matter particles. This method requires a sophisticated detector that can detect even the slightest signal. Several experiments are currently underway to detect dark matter particles using these methods.Discovery of Dark MatterThe discovery of dark matter can be traced back to the 1930s when Swiss astronomer Fritz Zwicky observed that the visible matter in the Coma cluster of galaxies was not enough to hold the cluster together. He hypothesized the presence of invisible matter that was holding the cluster together, which he called dark matter.Over the years, other scientists have provided evidence for the existence of dark matter. In the 1970s, Vera Rubin and Kent Ford studied the rotation curves of galaxies and found that the observed mass could not account for the observed rotation speeds. They concluded that there must be more mass in the form of dark matter that was holding the galaxies together.More recently, the European Space Agency’s Planck satellite produced a detailed map of the cosmic microwave background radiation, which is thought to be leftover radiation from the Big Bang. The map provided strong evidence for the existence of dark matter and its abundance in the universe.ConclusionThe discovery of dark matter is one of the most exciting and challenging areas of modern physics. Scientists continue to search for dark matter using a variety of methods, including indirect and direct detection. Although dark matter has yet to be observeddirectly, its presence and properties can be inferred from its gravitational effects on visible matter. As we continue to unravel the mysteries of dark matter, we are sure to gain new insights and a deeper understanding of the universe we inhabit.。
The-Dark-Triad-of-personality-and-unethical-behavior-at-different-times-of-day
The Dark Triad of personality and unethical behavior at different times of dayKarolin Roeser a ,Victoria E.McGregor a ,Sophia Stegmaier a ,Johanna Mathew a ,Andrea Kübler a ,Adrian Meule b ,⁎a Institute of Psychology,University of Würzburg,Marcusstr.9-11,D-97070Würzburg,GermanybDepartment of Psychology and Center for Cognitive Neuroscience,University of Salzburg,Hellbrunner Str.34,A-5020Salzburg,Austriaa b s t r a c ta r t i c l e i n f o Article history:Received 10August 2015Accepted 1September 2015Available online 10September 2015Keywords:Dark Triad Narcissism PsychopathyMachiavellianism MoralityMorning Morality EffectThe Dark Triad of personality –narcissism,Machiavellianism,and psychopathy –is characterized by callous ma-nipulation and social exploitation.Thus,dark personalities should be more prone to unethical behavior.Unethical behavior has been shown to vary during the course of the day with individuals displaying lower morality in the evening (Morning Morality Effect,MME).Hence,the present study investigated the association between the Dark Triad and unethical behavior as a function of time of day in an experimental design.Participants (N =195)com-pleted the study either in the morning or in the evening.In one task,participants had the choice to cheat on a fictitious partner for monetary bene fit at the partner's expense.In a second task,they had the opportunity to lie about their performance for personal gain.Machiavellianism scores positively predicted unethical behavior in the first task.In the second task,psychopathy scores positively predicted lying.Neither could the MME be rep-licated,nor did time of day moderate the in fluence of the Dark Triad on unethical behavior.Thus,the present study indicates that the dark traits are differentially related to aspects of unethical behavior,such that Machiavel-lians display a preference for complex deception,while psychopaths engage in impulsive cheating.©2015Elsevier Ltd.All rights reserved.1.1.IntroductionThe Dark Triad of personality (Paulhus &Williams,2002)comprises three socially aversive and malevolent personality traits,namely narcis-sism,Machiavellianism,and psychopathy.Narcissism is characterized by grandiosity,entitlement,dominance,and superiority (Raskin &Hall,1979),Machiavellianism can be described as a manipulative per-sonality (Paulhus &Williams,2002),and individuals with psychopathic traits have high sensation seeking and impulsivity along with callous af-fect and low empathy (Hare,1985).Although offensive,the Dark Triad traits do not represent pathological concepts per se.Instead,individuals with dark personalities may very well be within the normal range of functioning (Furnham,Richards,&Paulhus,2013).The three traits have distinct theoretical origins.Narcissism and psy-chopathy were originally proposed to represent mental disorders,which found their way into mainstream personality research by the development of the Narcissistic Personality Inventory (NPI,Raskin &Hall,1979)and the Self-Report Psychopathy (SRP)scale (Hare,1985),respectively.The concept of Machiavellianism has a philosophical background as it is named for Niccolo Machiavelli,a politician and phi-losopher in the Florentine Republic around 1500.Machiavellianism emerged as a personality trait through the work of Christie and Geis(1970),who delineated the Mach-IV as a measure of Machiavellianism.Despite their different etiologies,these personalities share common features,for example disagreeableness (Paulhus &Williams,2002),ma-nipulation and callousness (Jones &Figueredo,2013),and social exploi-tation (Jonason,Li,&Teicher,2010).However,they are not equivalent,but rather “overlapping but distinct constructs ”(Paulhus &Williams,2002,p.556).Since the original publication of the concept in 2002,the Dark Triad has gained much scienti fic attention.Among various outcome mea-sures,for example workplace behavior (O'Boyle,Forsyth,Banks,&McDaniel,2012)or mating strategies (Jonason,Li,Webster,&Schmitt,2009),unethical behavior has been related to the dark traits:Psychopa-thy and Machiavellianism predicted exam copying and plagiarism,respectively (Nathanson,Paulhus,&Williams,2006;Williams,Nathanson,&Paulhus,2010).Baughman,Jonason,Lyons,and Vernon (2014)found that the Dark Triad,especially Machiavellianism and psy-chopathy,was associated with lying in an academic context,but also with dishonesty toward mates.Jonason,Lyons,Baughman,and Vernon (2014)reported that dark personalities make use of various inter-and intra-sexual deception tactics,suggesting that the Dark Triad traits re flect cheating strategies.Kouchaki and Smith (2014)investigated cheating as a form of un-ethical behavior,but from a very different perspective:In four indepen-dent experiments,it was demonstrated that participants engaged in more unethical behavior in the afternoon compared to the morningPersonality and Individual Differences 88(2016)73–77⁎Corresponding author.E-mail address:adrian.meule@sbg.ac.at (A.Meule)./10.1016/j.paid.2015.09.0020191-8869/©2015Elsevier Ltd.All rightsreserved.Contents lists available at ScienceDirectPersonality and Individual Differencesj o u r n a l h o me p a g e :ww w.e l s e v i e r.c o m /l o c a t e /p a i dhours.To explain this so-called Morning Morality Effect(MME),the au-thors referred to the strength model of self-regulation.According to this model,the capacity to exert self-control relies on a limited resource that depletes when demanded(Baumeister,Bratslavsky,Muraven,&Tice, 1998;Muraven&Baumeister,2000).Self-control comprises the ability to resist temptations and the willpower to act according to moral stan-dards.Indeed,it has been shown that the depletion of self-regulatory re-sources negatively affects ethical behavior(Gino,Schweitzer,Mead,& Ariely,2011;Mead,Baumeister,Gino,Schweitzer,&Ariely,2009). Given that many situations in daily life require self-control(Hofmann, Baumeister,Forster,&Vohs,2012),self-control resources might dimin-ish gradually throughout the day,resulting in a greater likelihood of self-regulatory failures,including lying or cheating,in the afternoon or evening as compared to the morning hours.In one of their experiments,Kouchaki and Smith(2014)found that lower moral awareness in the afternoon me-diated the effect of time of day on cheating.Moreover,they report that moral disengagement moderated the MME such that the MME was espe-cially evident in those with a low propensity to morally disengage.As previous studies have demonstrated an influence of the Dark Triad and time of day on unethical behavior,the present study aimed at bringing these aspects together.Participants completed the study ei-ther in the morning or in the evening,which included a measure of Dark Triad personality traits and two tasks,in which they could cheat or lie.In contrast to previous studies,we decided to operationalize cheating and lying experimentally instead of using self-report questionnaires.It was expected that(1)individuals would be more likely to cheat or lie in the evening than in the morning,thus replicating the MME,and that (2)higher scores on Dark Triad personality traits would be associated with a higher likelihood of cheating or lying.In the original study by Kouchaki and Smith(2014),individual differences(moral disengage-ment)moderated the MME.As the Dark Triad should comprise a ten-dency to morally disengage,we also explored possible interactive effects between time of day and scores on Dark Triad personality traits. Specifically,we examined the possibility that unethical behavior in the evening would be particularly observed in individuals scoring high on Dark Triad traits or vice versa.1.2.Methods1.2.1.ParticipantsData were collected via an online survey tool(https://www. soscisurvey.de/).The link to the study was distributed via social net-works,local online platforms and student mailing lists.As an incentive, participants who completed the study had the chance to win one out of ten online shopping vouchers.A total of N=243participants started the survey,but data from n=48participants were excluded from anal-yses because they did not complete the entire study.Thefinal sample comprised n=195participants(70.8%female,n=138).Mean age was M=25.73years(SD=6.96)and mean sleep duration during the past night was M=7.26h(SD=1.43).1.2.2.Measures1.2.2.1.Short Dark Triad(SD3)The SD3(Jones&Paulhus,2014)assesses the Dark Triad personality traits with27items(nine items per subscale).Items are scored on a five-point scale ranging from strongly disagree to strongly agree.The psychopathy subscale includes items related to impulsivity,callous manipulation and antisocial behavior.The Machiavellianism subscale includes items related to cynicism and manipulation tactics.The narcis-sism subscale includes items related to selfishness and a sense of gran-diosity.Internal consistencies wereα=.76(Machiavellianism),α= .68(narcissism),andα=.69(psychopathy)in the current study and, thus,comparable to those reported in the validation studies(Jones& Paulhus,2014).1.2.2.2.Global vigor and affect(GVA)The GVA instrument(Monk,1989)was used to control for partici-pants'current vigor and affective state.It consists of eight items asking for current alertness,sadness,tension,effort,happiness,weariness, calmness,and sleepiness.Participants respond on a visual analog scale anchored very little(0)and very much(100).Global vigor is calculated with the formula[(alert)+300−(sleepy)−(effort)−(weary)]/4 and global affect with the formula[(happy)+(calm)+200−(sad)−(tense)]/4.Each formula yields a value between0and100 with higher values indicating higher vigor and more positive affect, respectively.1.2.2.3.Message-TaskTo operationalize unethical behavior we used a decision-making task(Gneezy,2005),in which participants had the opportunity to lie in order to allegedly raise the amount of the voucher(see below).The task was slightly changed as compared to the task used by Kouchaki and Smith(2014):The payment options mentioned in our task were higher and had greater differences than those used by Kouchaki and Smith(2014)to increase the probability of cheating.Participants were told that a second player would be involved.This second player wasfic-titious,which the participants did not know.Participants were given two payment options.Thefirst option was for the benefit of the second player,the second option was in favor of the participant:“Option1:You will receive5.00€,whereas Player2will receive15.00€.”and“Option2: You will receive7.00€,whereas Player2will receive5.00€.”Participants were told that the actual payment would depend on Player2's choice. To inform Player2about the payment options,participants had to choose between two messages,which allegedly would be sent toficti-tious Player2.Thefirst message was veracious,the second message var-iation was a lie:“Message A:Option1can bring you more money than Option2.”versus“Message B:Option2will bring you more money than Option1.”Deciding to lie was therefore clearly linked to afinancial incentive in this task.In the current study,22.1%(n=43)participants chose the dishonest message option.1.2.2.4.Matrix-TaskAs a second task to operationalize unethical behavior,we used a vi-sual search task as used by Mazar,Amir,and Ariely(2008)and Kouchaki and Smith(2014).In this task,participants were able to increase their profit level by making false statements about their performance.Partic-ipants were presented a total of20matrices.Each matrix contained three rows and four columns consisting of a total of12-digit numbers with one or two decimals(Fig.1)and was presented for15s.During these15s,participants had tofind two numbers which summed up to 10.Of the20presented matrices,13were solvable.Each presentation was followed by a page,on which the participant had to indicate wheth-er he or she had found the two numbers or not.Indicating that the ma-trix was solved resulted in a profit increase of2.50€.Choosing the option“Not found”did not yield any profit increase.It was notexpected Fig.1.Example of a matrix used in the Matrix-Task to operationalize unethical behavior.74K.Roeser et al./Personality and Individual Differences88(2016)73–77to name or remember the two numbers after the15s,therefore the re-sult was not checked,which enabled participants to cheat.The order of the matrices was programmed in a way that thefirst seven matrices were solvable.Afterwards,a randomly determined sequence of the re-maining13matrices followed,which was identical for all subjects. This visual search task does not require mathematical skills or above-average intelligence(Mazar et al.,2008).The mean number of lies in the current study was M=1.15(SD=1.71,range0–7).1.2.3.ProcedureData were collected between7and10a.m.and4–7p.m.without randomized assignment,that is,participants could choose freely if they participated in the morning or in the evening.As a cover story, participants were told that the study investigated cognitive abilities at different times of day.They were also informed about the opportunity to win one out of ten online shopping vouchers and that the vouchers' value could be increased during the tasks.After providing the sociodemographic information,participants completed the GVA,the Matrix-,and the Message-Task.The SD3was presented at the end of the survey.Finally,participants were debriefed.They were informed about thefictitiousness of the partner in the Message-Task and that the vouchers hadfixed values of57€each.1.2.4.Data analysesDifferences in age,sleep duration,GVA scores,and sex distribution between individuals who participated in the morning or in the evening were tested with independent t-tests andχ2-test,respectively.Differ-ences in SD3scores between men and women were compared with in-dependent t-tests.Associations between SD3scores and continuous study variables were examined with Pearson correlation coefficients.Logistic regression analyses were used to examine predictors of choice in the Message-Task(message A[honest]coded0and message B[dishonest]coded1).Three models were run for each SD3subscale separately with time of day,SD3subscale and the interaction term time of day×SD3subscale as predictor variables.In step2,variables that were associated with SD3scores(sex and GVA scores,see below) were entered as covariates.Linear regression analyses were used to examine predictors of the number of lies in the Matrix-Task.Three models were run for each SD3subscale separately with time of day,SD3subscale and the interac-tion term time of day×SD3subscale as predictor variables.In step2, variables that were associated with SD3scores(sex and GVA scores, see below)were entered as covariates.All regression analyses were conducted using PROCESS for SPSS(Hayes,2013).Continuous predictor variables were mean-centered before calculating the product terms.For all statistical tests,exact p-values are reported,except when p b.001.p-Values of≥0.05are denoted as ns.1.3.Results1.3.1.Participant characteristicsOne-hundred eleven individuals participated in the morning and84 individuals participated in the evening.Groups did not differ in age, sleep duration,global vigor,global affect(all t s b1.78,ns)or sex distri-bution(χ2(1)=1.20,ns).Men scored higher than women on all three subscales of the SD3(Machiavellianism:M men=3.10,SD=0.67vs. M women=2.69,SD=0.52;psychopathy:M men=2.31,SD=0.55vs. M women=1.78,SD=0.49;narcissism:M men=2.92,SD=0.55vs. M women=2.69,SD=0.55;all t s N2.65,p b.01).Global affect was negatively correlated with scores on the Machiavellianism(r=−.17, p=.02)and psychopathy subscales(r=−.24,p=.001).Scores on the Machiavellianism subscale were positively correlated with scores on the psychopathy(r=.49,p b.001)and narcissism subscales(r=.26,p b.001).Scores on the psychopathy subscale were positively corre-lated with scores on the narcissism subscale(r=.31,p b.001).1.3.2.Message-TaskMachiavellianism scores predicted message choice such that higher scores were associated with a higher likelihood of selecting the dishon-est message(Table1).This effect was not moderated by time of day.In-cluding potential covariates revealed that global vigor also predicted message choice such that a higher current vigor was associated with a lower likelihood of selecting the dishonest message(Table1).This, however,did not influence the association between Machiavellianism and message choice.None of the other variables significantly predicted message choice.1.3.3.Matrix-TaskPsychopathy scores predicted the number of lies such that higher scores were associated with a higher number of lies(Table2).This effect was not moderated by time of day.Including potential covariates did not influence the association between psychopathy and number of lies and none of the other variables significantly predicted number of lies.1.4.DiscussionThe present study aimed at investigating if people are more likely to cheat or lie in the evening,if personality features,namely the Dark Triad of personality,are associated with these behaviors and if time of day and personality are interactively associated with these outcomes.Ourfirst hypothesis referred to replicating the MME(Kouchaki&Smith,2014). However,time of day did not affect cheating or lying in our study,that is,the MME could not be replicated.A possible reason might be that our study did not include a randomized assignment.Instead,partic-ipants chose their preferred time of participation.This might have resulted in a self-selection bias such that the depletion of the self-regulatory resource might have been less pronounced in people who decided to participate in the evening.Therefore,the MME may have not emerged,because the self-regulatory resource in individ-uals participating in the evening was not sufficiently depleted.How-ever,in the original publication by Kouchaki and Smith(2014),the MME occurred no matter whether participants self-selected their preferred time of participation or were randomly assigned into the morning or afternoon session.Previous studies have shown that motivation and success impor-tance can compensate for self-control resource depletion(Muraven& Slessareva,2003;Stewart,Wright,Hui,&Simmons,2009).Given that the current sample was recruited from the investigators'social environ-ment,their motivation and effort might have been stronger than in par-ticipants in the original study.Further,our sample–specifically in the Matrix Task–was extremely honest and thus,we had little variance in these data.However,Kouchaki and Smith(2014)demonstrated the MME in both undergraduate students and U.S.adults.Although the MME has been replicated by Koukachi and Smith themselves,future replication studies by other research teams are necessary to determine if the MME may only occur in certain samples(e.g.,may dependent on culture)or under specific circumstances.Our second hypothesis was that Dark Triad traits would be associat-ed with a higher likelihood of unethical behavior.In contrast to previous studies,we did not rely on self-reports orfictitious scenarios,but oper-ationalized cheating and lying situations.Although it has been shown that dark personalities report using various tactics of social influence (Jonason&Webster,2012),we found that Machiavellianism and psy-chopathy were differentially related to cheating and lying in our two tasks.The Message-Task included afictitious partner and a sophisticat-ed cover story,requiring a high amount of cognitive effort.In this task, Machiavellianism positively predicted cheating.The Matrix-Task,in75K.Roeser et al./Personality and Individual Differences88(2016)73–77contrast,animated participants to lie via a quick and simple click,which was related to higher scores on psychopathy.Indeed,it has been shown that psychopathy is closely related to dysfunctional impulsivity stem-ming from poor self-regulation(Jones&Paulhus,2011).In a study by Baughman et al.(2014),who investigated self-reported lying frequency, all three Dark Triad traits were associated with lying.However,this as-sociation was entirely attributable to psychopathy and Machiavellian-ism.Consistent with ourfindings,Baughman et al.(2014)report that Machiavellianism was related to planning and constructing original and detailed deception.In line with previousfindings,narcissism did not predict unethical behavior in the current study.A possible explanation might be that nar-cissism is the“brightest”,that is,the least malicious,among the Dark Triad traits(Rauthmann&Kolar,2012,2013).Moreover,Jonason and Tost(2010)found low self-control in psychopaths and to some extent in Machiavellians,but not in narcissists.Taken together,these results suggest that among the dark personalities,narcissists might be least susceptible to moral disengagement.Our third hypothesis was that time of day and Dark Triad personality may be interactively related to unethical behavior.For example,Gunia, Barnes,and Sah(2014)argue that unethical behavior cannot simply be explained by individual characteristics or a given situation.Instead,the interplay between personal and situational features(person×situation fit)may determine whether people behave unethically or not.However, this idea was not supported in the current study.Thus,results suggest that the unethical behavior displayed by individuals scoring high onTable1Results of logistic regression analyses predicting message choice in the Message-Task.N=195Step1Step2B SE p95%CI B SE p95%CIMachiavellianismTime of day0.230.36ns−0.47,0.940.130.39ns−0.63,0.88 Machiavellianism0.680.30.020.09,1.280.980.36.010.27,1.70 Time of day×Machiavellianism−0.060.60ns−1.24,1.120.010.65ns−1.27,1.29 Sex––––−0.550.45ns−1.43,0.34 Global affect––––−0.010.01ns−0.03,0.02 Global vigor––––−0.020.01.02−0.04,−0.00PsychopathyTime of day0.160.35ns−0.53,0.850.060.37ns−0.67,0.78 Psychopathy0.100.31ns−0.51,0.720.000.37ns−0.73,0.74 Time of day×psychopathy0.480.62ns−0.73,1.690.540.64ns−0.72,1.79 Sex––––−0.120.45ns−1.00,0.77 Global affect––––−0.010.01ns−0.03,0.01 Global vigor––––−0.020.01.04−0.04,−0.00NarcissismTime of day0.230.35ns−0.46,0.920.150.37ns−0.59,0.88 Narcissism0.400.31ns−0.22,1.020.520.34ns−0.14,1.18 Time of day×narcissism0.200.64ns−1.06,1.450.120.66ns−1.18,1.42 Sex––––−0.230.41ns−1.04,0.58 Global affect––––−0.010.01ns−0.03,0.01 Global vigor––––−0.020.01.04−0.04,−0.00Notes.Significant predictors are printed in boldface.Table2Results of linear regression analyses predicting the number of lies in the Matrix-Task.N=195Step1Step2B SE p95%CI B SE p95%CIMachiavellianismTime of day−0.070.25ns−0.56,0.42−0.110.26ns−0.62,0.40 Machiavellianism0.160.21ns−0.25,0.570.100.23ns−0.35,0.56 Time of day×Machiavellianism0.110.42ns−0.71,0.930.060.43ns−0.78,0.90 Sex––––0.490.29ns−0.09,1.07 Global affect––––0.010.01ns−0.01,0.03 Global vigor––––−0.000.01ns−0.02,0.01PsychopathyTime of day−0.110.25ns−0.59,0.38−0.120.25ns−0.62,0.38 Psychopathy0.510.22.020.07,0.940.550.25.030.05,1.05 Time of day×psychopathy0.170.44ns−0.69,1.030.100.44ns−0.77,0.97 Sex––––0.240.30ns−0.36,0.84 Global affect––––0.010.01ns−0.00,0.03 Global vigor––––−0.000.01ns−0.02,0.01NarcissismTime of day−0.080.25ns−0.58,0.41−0.150.26ns−0.67,0.36 Narcissism0.060.22ns−0.38,0.50−0.090.23ns−0.55,0.36 Time of day×narcissism−0.520.46ns−1.42,0.39−0.620.46ns−1.54,0.29 Sex––––0.550.28ns−0.01,1.10 Global affect––––0.010.01ns−0.01,0.03 Global vigor––––−0.000.01ns−0.02,0.01Notes.Significant predictors are printed in boldface.76K.Roeser et al./Personality and Individual Differences88(2016)73–77Machiavellianism and psychopathy appears to be unaffected by momentary circumstances such as time of day.While the procedure used in the current study may have high ecological validity,future studies are needed on the MME or daytime-dependent behaviors of dark personalities using randomized assign-ment to experimental conditions.Another limitation may be that poten-tial confounding variables like motivation or cognitive abilities were not assessed,which may relate to personality styles or may change throughout the day.However,we did control for current vigor and af-fect,which did not influence ourfindings.This is consistent with the re-sults of Kouchaki and Smith(2014),who excluded changes in affective states as an alternative explanation for the MME.Finally,the current sample consisted predominantly of highly academically educated female university students.Thus,our sample may have had high self-regulatory skills not affected by time of day.Although sex was unrelated to task performance,it would be desirable to investigate more heteroge-neous samples(regarding age,education,etc.)in future studies.According to the present study,unethical behavior can be consid-ered a function of personality,namely Machiavellianism and psychopa-thy,and,to some extent,a matter of reduced mental vigor.We conclude that the Dark Triad traits are differentially related to aspects of unethical behavior,such that Machiavellians display a preference for complex de-ception,while psychopaths engage in impulsive cheating.This adds to a better understanding of how dark personalities interact with their social environment.AcknowledgmentsAM is supported by a grant of the European Research Council(ERC-StG-2014639445NewEat).ReferencesBaughman,H.M.,Jonason,P.K.,Lyons,M.,&Vernon,P.A.(2014).Liar liar pants onfire: Cheater strategies linked to the Dark Triad.Personality and Individual Differences,71, 35–38.Baumeister,R.F.,Bratslavsky,E.,Muraven,M.,&Tice,D.M.(1998).Ego depletion:Is the active self a limited resource?Journal of Personality and Social Psychology,74, 1252–1265.Christie,R.,&Geis,F.L.(1970).Studies on Machaivellism.New York:Academic Press. Furnham,A.,Richards,S.C.,&Paulhus,D.L.(2013).The Dark Triad of personality:A 10year review.Social and Personality Psychology Compass,7,199–216.Gino,F.,Schweitzer,M.E.,Mead,N.L.,&Ariely,D.(2011).Unable to resist temptation: How self-control depletion promotes unethical anizational Behavior and Human Decision Processes,115,191–203.Gneezy,U.(2005).Deception:The role of consequences.American Economic Review,95, 384–394.Gunia,B.C.,Barnes,C.M.,&Sah,S.(2014).The morality of larks and owls:Unethical be-havior depends on chronotype as well as time of day.Psychological Science,25, 2272–2274.Hare,R.D.(1985).Comparison of procedures for the assessment of psychopathy.Journal of Consulting and Clinical Psychology,53,7–16.Hayes,A.F.(2013).Introduction to mediation,moderation,and conditional process analysis.New York:The Guilford Press.Hofmann,W.,Baumeister,R.F.,Forster,G.,&Vohs,K.D.(2012).Everyday temptations:An experience sampling study of desire,conflict,and self-control.Journal of Personality and Social Psychology,102,1318–1335.Jonason,P.K.,&Tost,J.(2010).I just cannot control myself:The Dark Triad and self-control.Personality and Individual Differences,49,611–615.Jonason,P.K.,&Webster,G.D.(2012).A protean approach to social influence:Dark Triad personalities and social influence tactics.Personality and Individual Differences,52, 521–526.Jonason,P.K.,Li,N.P.,&Teicher,E.A.(2010).Who is James Bond?:The Dark Triad as an agentic social style.Individual Differences Research,8,111–120.Jonason,P.K.,Li,N.P.,Webster,G.D.,&Schmitt,D.P.(2009).The Dark Triad:facilitating a short-term mating strategy in men.European Journal of Personality,23,5–18. Jonason,P.K.,Lyons,M.,Baughman,H.M.,&Vernon,P.A.(2014).What a tangled web we weave:The Dark Triad traits and deception.Personality and Individual Differences,70, 117–119.Jones,D.N.,&Figueredo,A.J.(2013).The core of darkness:Uncovering the heart of the dark triad.European Journal of Personality,27,521–531.Jones,D.N.,&Paulhus,D.L.(2011).The role of impulsivity in the Dark Triad of personality.Personality and Individual Differences,51,679–682.Jones,D.N.,&Paulhus,D.L.(2014).Introducing the Short Dark Triad(SD3):A brief mea-sure of dark personality traits.Assessment,21,28–41.Kouchaki,M.,&Smith,I.H.(2014).The morning morality effect:The influence of time of day on unethical behavior.Psychological Science,25,95–102.Mazar,N.,Amir,O.,&Ariely,D.(2008).The dishonesty of honest people:A theory of self-concept maintenance.Journal of Marketing Research,45,633–644.Mead,N.L.,Baumeister,R.F.,Gino,F.,Schweitzer,M.E.,&Ariely,D.(2009).Too tired to tell the truth:Self-control resource depletion and dishonesty.Journal of Experimental Social Psychology,45,594–597.Monk,T.H.(1989).A visual analog scale technique to measure global vigor and affect.Psychiatry Research,27,89–99.Muraven,M.,&Baumeister,R.F.(2000).Self-regulation and depletion of limited re-sources:Does self-control resemble a muscle?Psychological Bulletin,126,247–259. Muraven,M.,&Slessareva,E.(2003).Mechanisms of self-control failure:Motivation and limited resources.Personality and Social Psychology Bulletin,29,894–906. Nathanson,C.,Paulhus,D.L.,&Williams,K.M.(2006).Predictors of a behavioral measure of scholastic cheating:Personality and competence but not demographics.Contemporary Educational Psychology,31,97–122.O'Boyle,E.H.,Forsyth,D.R.,Banks,G.C.,&McDaniel,M.A.(2012).A meta-analysis of the Dark Triad and work behavior:A social exchange perspective.The Journal of Applied Psychology,97,557–579.Paulhus,D.L.,&Williams,K.M.(2002).The Dark Triad of personality:Narcissism,Machi-avellianism,and psychopathy.Journal of Research in Personality,36,556–563. Raskin,R.N.,&Hall,C.S.(1979).A narcissistic personality inventory.Psychological Reports, 45,590.Rauthmann,J.F.,&Kolar,G.P.(2012).How“dark”are the Dark Triad traits?Examining the perceived darkness of narcissism,Machiavellianism,and psychopathy.Personality and Individual Differences,53,884–889.Rauthmann,J.F.,&Kolar,G.P.(2013).Positioning the Dark Triad in the interpersonal circumplex:The friendly-dominant narcissist,hostile-submissive Machiavellian,and hostile-dominant psychopath?Personality and Individual Differences,54,622–627. Stewart,C.C.,Wright,R.A.,Hui,S.K.A.,&Simmons,A.(2009).Outcome expectancy as a moderator of mental fatigue influence on cardiovascular response.Psychophysiology,46,1141–1149.Williams,K.M.,Nathanson,C.,&Paulhus,D.L.(2010).Identifying and profiling scholastic cheaters:Their personality,cognitive ability,and motivation.Journal of Experimental Psychology.Applied,16,293–307.77K.Roeser et al./Personality and Individual Differences88(2016)73–77。
- 1、下载文档前请自行甄别文档内容的完整性，平台不提供额外的编辑、内容补充、找答案等附加服务。
- 2、"仅部分预览"的文档,不可在线预览部分如存在完整性等问题,可反馈申请退款(可完整预览的文档不适用该条件!)。
- 3、如文档侵犯您的权益，请联系客服反馈,我们会尽快为您处理(人工客服工作时间：9:00-18:30)。
a rXiv:as tr o-ph/73673v127Mar271DARK MATTER:THE CASE OF STERILE NEUTRINO ∗Mikhail Shaposhnikov Institut de Th´e orie des Ph´e nom`e nes Physiques,Ecole Polytechnique F´e d´e rale de Lausanne,CH-1015Lausanne,Switzerland An extension of the Standard Model by three right-handed neutrinos with masses smaller than the electroweak scale (the νMSM)can explain simultaneously dark matter and baryon asymmetry of the Universe,being consistent with the data on neutrino oscilla-tions.A dark matter candidate in this theory is the sterile neutrino with the mass in keV range.We discuss the constraints on the properties of this particle and mechanisms of their cosmological production.Baryon asymmetry generation in this model is reviewed.Crucial experiments that can confirm or rule out the νMSM are briefly discussed.1.Introduction There is compelling evidence that the Minimal Standard Model (MSM)of strong and electroweak interactions is not complete.There are several experimental facts that cannot be explained by the MSM.These are neutrino oscillations,the presence of dark matter in the Universe,the baryon asymmetry of the Universe,its flatness,and the existence of cosmological perturbations necessary for structure formation.Indeed,in the MSM neutrinos are strictly massless and do not oscillate.The MSM does not have any candidate for non-baryonic dark matter.Moreover,with the present experimental limit on the Higgs mass,the high-temperature phase transi-tion,required for electroweak baryogenesis,is absent.In addition,it is a challenge to use CP-violation in Kobayashi-Maskawa mixing of quarks to produce baryonasymmetry in the MSM.Finally,the couplings of the single scalar field of the MSM are too large for the Higgs boson to play the role of the inflaton.This means that the MSM is unlikely to be a good effective field theory up to the Planck scale.In 1–3it was proposed that a simple extension of the MSM by three singlet right-handed neutrinos and by a real scalar field (inflaton)with masses smaller than the electroweak scale may happen to be a correct effective theory up to some high-energy scale,which may be as large as the Planck scale.This model was called “the νMSM”,underlying the fact that it is the extension of the MSM in the neutrino sector.Contrary to Grand Unified Theories,the νMSM does not have any internal2hierarchy problem,simply because it is a theory with a single mass scale.Moreover, as the energy behaviour of the gauge couplings in this theory is the same as in the MSM,the absence of gauge-coupling unification in it indicates that there may be no grand unification,in accordance with our assumption of the validity of this theory up to the Planck scale.As well as the MSM,theνMSM does not provide any explanation why the weak scale is much smaller than the Planck scale.Similarly to the MSM,all the parameters of theνMSM can be determined experimentally since only accessible energy scales are present.As we demonstrated in,1,2theνMSM can explain simultaneously dark matter and baryon asymmetry of the Universe being consistent with neutrino masses and mixings observed experimentally.Moreover,in3we have shown that inclusion of an inflaton with scale-invariant couplings to thefields of theνMSM allows us to have inflation and provides a common source for electroweak symmetry breaking and Majorana neutrino masses of singlet fermions–sterile neutrinos.The role of the dark matter is played by the lightest sterile neutrino with mass m s in the keV range.In addition,the coherent oscillations of two other,almost degenerate,sterile neutrinos lead to the creation of baryon asymmetry of the Universe2through the splitting of the lepton number between active and sterile neutrinos4and electroweak sphalerons.5For review of other astrophysical applications of sterile neutrinos see talk by Peter Biermann at this conference.6In this talk I review the structure of theνMSM and discuss its dark matter candidate–sterile neutrino.The baryogenesis in this model is briefly reviewed. 2.TheνMSMIf three singlet right-handed fermions N I are added to the Standard Model,the most general renormalizable Lagrangian describing all possible interactions has the form:M ILνMSM=L MSM+¯N I i∂µγµN I−FαI¯LαN IǫΦ∗−[M D]T(2)M I3 is valid.Though it is known that the masses of active neutrinos are smaller than O(1)eV,it is clear that the scale of Majorana neutrino masses cannot be extracted. This is simply because the total number of physical parameters describing mνis equal to9(three absolute values of neutrino masses,three mixing angles and three CP-violating phases),which is two times smaller than the number of new parameters in theνMSM.A most popular proposal7is to say that the Yukawa couplings F in the active-sterile interactions are of the same order of magnitude as those in the quark and charged lepton sector.This choice is usually substantiated by aesthetic considera-tions,but is not following from any experiment.Then one has to introduce a new energy scale,M I∼1010−1015GeV,which may be related to grand unification.The model with this choice of M I has several advantages in comparison with the MSM: it can explain neutrino masses and oscillations,and give rise to baryon asymme-try of the Universe through leptogenesis8and anomalous electroweak number non-conservation at high temperatures.5However,it cannot explain the dark matter as the low energy limit of this theory is simply the MSM with non-zero active neutrino masses coming from dimensionfive operators.On a theoretical side,as a model with two very distinct energy scales it suffers from afine-tuning hierarchy problem M I≫M W.Also,since the energy scale which appears in this scenario is so high, it would be impossible to make a direct check of this conjecture by experimental means.Another suggestion is tofix the Majorana masses of sterile neutrinos in1−10eV energy scale9to accommodate the LSND anomaly.10The theory with this choice of parameters,however,cannot explain the baryon asymmetry of the Universe and does not provide a candidate for dark matter particle.Yet another paradigm is to determine the parameters of theνMSM from avail-able observations,i.e.from requirement that it should explain neutrino oscillations, dark matter and baryon asymmetry of the universe in a unified way.It is this choice that will be discussed below.It does not require introduction of any new en-ergy scale,and M I<M W.In this case the Yukawa couplings must be much smaller than those in the quark sector,F<10−6.The theory has a number of directly testable predictions,which can confirm or reject it.3.Dark matterThough theνMSM does not offer any stable particle besides those already present in the MSM,it contains a sterile neutrino with a life-time exceeding the age of the Universe,provided the corresponding Yukawa coupling is small enough.The decay rate of N1to three active neutrinos and antineutrinos(assuming that N1is the lightest sterile neutrino)is given byΓ3ν=G2F M51θ2M1,m20= α=e,µ,τ|M Dα1|2,(3)4where G F is the Fermi constant.For example,a choice of m0∼O(1)eV and of M1∼O(1)keV leads to a sterile neutrino life-time∼1017years.11 The mass of the sterile dark matter neutrino cannot be too small.An application of the Tremaine-Gunn arguments12to the dwarf spheroidal galaxies13gives the lower bound14M1>0.3keV.If the sterile neutrino mass is in the keV region,it may play a role of warm dark matter.15,16Sterile neutrino free streaming length an matter-radiation equality is given byλF S≃1Mps 1keV3.15 (4) and the mass insideλF S isM F S≃3×1010M⊙ 1keV3.15 3,where<p s>(<p a>)is an average momentum of sterile(active)neutrino at the moment of structure formation,M⊙is the solar mass.One normally defines cold dark matter(CDM)as that corresponding to M F S<105M⊙,hot DM as the one with M F S>1014M⊙,and warm DM as anything in between.Potentially, WDM could solve some problems of the CDM scenario,such as the missing satellites problem17,18and the problem of cuspy profiles in the CDM distributions.19,20 Even stronger constraint on the mass of sterile neutrino comes from the analysis of the cosmic microwave background and the matter power spectrum inferred from Lyman-αforest data21,22:M1>M0 <p s>51e-14 1e-131e-12 1e-111e-10Yu ka w ac o u p lings,fm D[e V ]M 1, keVFig.1.Upper bound on Yukawa coupling constant (left vertical axis)and Dirac mass (right vertical axis)of dark matter sterile neutrino,coming from X-ray observations of Large Magellanic Cloud (LMC)and Milky Way (MW)by XMM-Newton and HEAO-1satellites.characterized by parameter θ.In fact,this mixing is temperature dependent:37θ→θM ≃θ1keV 1/3MeV,whichcorresponds to the temperature of the QCD cross-over for keV scale sterile neutri-nos.This fact makes an exact estimate of the number of produced sterile neutrinos to be a very difficult task (see 36for a discussion of the general formalism for com-putation of sterile neutrino abundance),since T peak happens to be exactly at the point where the quark-gluon plasma is strongly coupled and the dilute hadron gas picture is not valid.The chiral perturbation theory works only at T <50MeV.The perturbation theory in QCD works only at T ≫ΛQCD ,and the convergence is very slow.The lattice simulations work very well for pure gluodynamics.However,no results with three light quarks and with reliable extrapolation to continuum limit are available yet.Also,the treatment of hadronic initial and final states in reactions ν+q →ν+q,q +¯q →ν¯νis quite uncertain.In refs.11,15the computation of sterile neutrino production was done with the use of simplified kinetic equations and without accounting for hadronic degrees of freedom.In 16,38some effects related6to existence of quarks and hadrons in the media were included;the same type of ki-netic equations were used.In39a computation of sterile neutrino production based onfirst principles of statistical physics and quantumfield theory has been done and uncertainties related to hadronic dynamics were analyzed.The results are pre-sented in Fig.2.They correspond to the case when there is no entropy production (S=1)due to decay of heavier sterile neutrinos of theνMSM.40The area above dotted line is certainly excluded:the amount of produced dark matter would lead to over-closer of the universe.The region below dashed line is certainly allowed: the amount of sterile neutrinos produced due to active-sterile transitions is smaller than the amount of dark matter observed.Any point in the region between two solid lines(corresponding to the“most reasonable”model for hadronic contribution39) can lead to dark matter generation entirely due to active-sterile transitions.Maxi-mal variation of the hadronic model,defined in39extends this region to the space between dotted and dashed lines.In the case of entropy production with S>1all these four lines simply move up by a factor S.One can see that the active-sterile mixing can accommodate for all dark matter only if M1<3.5keV,if the“most reasonable”hadronic model is taken.The most conservative limit would correspond to M1<6keV,if all hadronic uncertainties are pushed in the same direction and the uncertainty by a factor of2is admitted for the X-ray bounds.Therefore,if Lyman-αconstraints of23,24are taken for granted, the production of sterile neutrinos due to active-sterile neutrino transitions happens to be too small to account for observed abundance of dark matter.In other words, physics beyond theνMSM is likely to be required to produce dark matter sterile neutrinos.Another option is to assume that the universe contained relatively large lepton asymmetries.41In3it was proposed the theνMSM may be extended by a light inflaton in order to accommodate inflation.To reduce the number of parameters and to have a common source for the Higgs and sterile neutrino masses the inflaton-νMSM couplings can be taken to be scale invariant on the classical level:LνMSM→LνMSM[M→0]+12¯NIc NIχ+h.c.−V(Φ,χ),(5)where the Higgs-inflaton potential is given by:V(Φ,χ)=λ Φ†Φ−α4χ4−171010M 1 / keV1010101010si n 22θFig.2.X-ray constraints from 28,32versus required mixing of sterile neutrino in Dodelson-Widrow scenario.It is assumed that no entropy production from decays of heavier sterile neutrinos of the νMSM is taking place.The area between two solid lines corresponds to all possible variations of mixing angles to different leptonic families for “best choice”hadronic dynamics.39The area between dotted and dashed lines corresponds to most conservative estimate of hadronic uncertain-ties.39neutrino abundance due to inflaton decays:χ→NN is given byΩs ≃0.26ΓM 0m sζ(3).So,for m I ∼300MeV (m I ∼100GeV)the correct Ωs is obtained for m s ∼16−20keV (m s ∼O (10)MeV).A sterile neutrino in this mass range is perfectly consistent with all cosmological and astrophysical observations.As for the bounds on mass versus active–sterile mixing coming from X-ray observations of our galaxy and its dwarf satellites,they are easily satisfied since the production mechanism of sterile neutrinos discussed above has nothing to do with the active–sterile neutrino mixing leading to the radiative mode of sterile neutrino decay.5.Baryon Asymmetry of the UniverseThe baryon (B)and lepton (L)numbers are not conserved in the νMSM.The lep-ton number is violated by the Majorana neutrino masses,while B +L is broken by8the electroweak anomaly.As a result,the sphaleron processes with baryon number non-conservation are in thermal equilibrium for100GeV<T<1012GeV.As for CP-breaking,theνMSM contains6CP-violating phases in the lepton sector and a Kobayashi-Maskawa phase in the quark sector.This makes two of the Sakharov conditions43for baryogenesis satisfied.Similarly to the MSM,this theory does not have an electroweak phase transition with allowed values for the Higgs mass,44mak-ing impossible the electroweak baryogenesis,associated with the non-equilibrium bubble expansion.However,theνMSM contains extra degrees of freedom-sterile neutrinos-which may be out of thermal equilibrium exactly because their Yukawa couplings to ordinary fermions are very small.The latter fact is a key point for the baryogenesis in theνMSM,ensuring the validity of the third Sakharov condition.In4it was proposed that the baryon asymmetry can be generated through CP-violating sterile neutrino oscillations.For small Majorana masses the total lepton number of the system,defined as the lepton number of active neutrinos plus the total helicity of sterile neutrinos,is conserved and equal to zero during the Universe’s evolution.However,because of oscillations the lepton number of active neutrinos becomes different from zero and gets transferred to the baryon number due to rapid sphaleron transitions.Roughly speaking,the resulting baryon asymmetry is equal to the lepton asymmetry at the sphaleron freeze-out.The kinetics of sterile neutrino oscillations and of the transfers of leptonic num-ber between active and sterile neutrino sectors has been worked out in.2The effects to be taken into account include oscillations,creation and destruction of sterile and active neutrinos,coherence in sterile neutrino sector and its lost due to interaction with the medium,dynamical asymmetries in active neutrinos and charged leptons. The corresponding equations are written in terms of the density matrix for sterile neutrinos and concentrations of active neutrinos and are rather lengthy and will not be presented here due to the lack of space.They can be found in the original work.2The corresponding equations are to be solved with the choice of theνMSM parameters consistent with the experiments on neutrino oscillations and with the requirement that dark matter neutrino has the necessary properties.The value of baryon to entropy ratio n B≃1.7·10−10δCP 10−53 M33,swhere M2,3are the masses of the heavier sterile neutrinos,∆M232=M23−M22,and the CP-breaking factorδCP is expressed through the different mixing angles and CP-violating phases,parameterizing the Dirac neutrino masses,and can be O(1), given the present experimental data on neutrino oscillations.This shows that the correct baryon asymmetry of the Universe n B9 It is interesting to note that for masses of sterile neutrinos>100GeV the mechanism does not work as the sterile neutrinos equilibrate.Also,the temperature of baryogenesis is rather low,T L≃(∆M2M P l)11011. A.D.Dolgov and S.H.Hansen,Astropart.Phys.16(2002)339.12.S.Tremaine and J.E.Gunn,Phys.Rev.Lett.42(1979)407.13. D.N.C.Lin and S.M.Faber,Astrophys.J.266(1983)L21.14.J.J.Dalcanton and C.J.Hogan,Astrophys.J.561(2001)35.15.S.Dodelson and L.M.Widrow,Phys.Rev.Lett.72(1994)17.16.K.Abazajian,G.M.Fuller and M.Patel,Phys.Rev.D64(2001)023501.17. B.Moore et al.,Astrophys.J.524(1999)L19.18.P.Bode,J.P.Ostriker and N.Turok,Astrophys.J.556(2001)93.19.T.Goerdt et al.,Mon.Not.Roy.Astron.Soc.368(2006)1073.20.G.Gilmore et al.,arXiv:astro-ph/0608528.21.S.H.Hansen,J.Lesgourgues,S.Pastor and J.Silk,Mon.Not.Roy.Astron.Soc.333(2002)544.22.M.Viel,J.Lesgourgues,M.G.Haehnelt,S.Matarrese and A.Riotto,Phys.Rev.D71(2005)063534.23.U.Seljak,A.Makarov,P.McDonald and H.Trac,Phys.Rev.Lett.97(2006)191303.24.M.Viel,J.Lesgourgues,M.G.Haehnelt,S.Matarrese and A.Riotto,Phys.Rev.Lett.97(2006)071301.25.K.Abazajian,G.M.Fuller and W.H.Tucker,Astrophys.J.562(2001)593.26. A.Boyarsky,A.Neronov,O.Ruchayskiy and M.Shaposhnikov,Mon.Not.Roy.As-tron.Soc.370(2006)213.27. A.Boyarsky,A.Neronov,O.Ruchayskiy and M.Shaposhnikov,Phys.Rev.D74(2006)103506.28. A.Boyarsky,A.Neronov,O.Ruchayskiy,M.Shaposhnikov and achev,Phys.Rev.Lett.97(2006)261302.29.S.Riemer-Sorensen,S.H.Hansen and K.Pedersen,Astrophys.J.644(2006)L33.30. C.R.Watson,J.F.Beacom,H.Yuksel and T.P.Walker,Phys.Rev.D74(2006)033009.31.S.Riemer-Sorensen,K.Pedersen,S.H.Hansen and H.Dahle,astro-ph/0610034.32. A.Boyarsky,J.Nevalainen and O.Ruchayskiy,astro-ph/0610961.33. A.Boyarsky,O.Ruchayskiy and M.Markevitch,astro-ph/0611168.34.K.N.Abazajian,M.Markevitch,S.M.Koushiappas and R.C.Hickox,arXiv:astro-ph/0611144.35. A.Boyarsky,J.W.d.Herder,A.Neronov and O.Ruchayskiy,arXiv:astro-ph/0612219.36.T.Asaka,ine and M.Shaposhnikov,JHEP0606(2006)053.37.R.Barbieri and A.Dolgov,Phys.Lett.B237(1990)440.38.K.Abazajian,Phys.Rev.D73(2006)063513.39.T.Asaka,ine and M.Shaposhnikov,JHEP0701(2007)091.40.T.Asaka,M.Shaposhnikov and A.Kusenko,Phys.Lett.B638(2006)401.41.X.Shi and G.M.Fuller,Phys.Rev.Lett.82(1999)2832.42. A.D.Linde,Phys.Lett.B129(1983)177.43. A.D.Sakharov,Pisma ZhETF5(1967)32.44.K.Kajantie,ine,K.Rummukainen and M.E.Shaposhnikov,Phys.Rev.Lett.77(1996)2887.45.M.Shaposhnikov,Nucl.Phys.B763(2007)49.46. A.Boyarsky,A.Neronov,O.Ruchayskiy and M.Shaposhnikov,JETP Lett.83(2006)133.47.G.Bernardi et al.,Phys.Lett.B203(1988)332.48.P.Astier et al.[NOMAD Collaboration],Phys.Lett.B506(2001)27.49. F.Bezrukov and M.Shaposhnikov,Phys.Rev.D75(2007)053005.。