Is Dark Energy Dynamical Prospects for an Answer

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可见光能量转移,英文

可见光能量转移,英文Visible Light Energy Transfer.Visible light energy transfer is a fundamental process that occurs widely in nature and has numerous applicationsin various fields, ranging from biochemistry and physics to engineering and technology. This process involves the transfer of energy from one excited state to another, typically through photons of visible light.The energy transfer process can be understood by considering the interaction of light with matter. When visible light interacts with matter, it can be absorbed, reflected, refracted, scattered, or emitted. Absorption occurs when the light's energy is transferred to the matter, exciting electrons to higher energy levels. Reflection occurs when the light bounces off the surface of the matter without transferring energy. Refraction occurs when thelight changes direction as it passes through different media, and scattering occurs when the light's direction ischanged due to interactions with particles within the matter.Energy transfer through visible light typically occurs through one of two mechanisms: radiative transfer or non-radiative transfer. Radiative transfer involves the emission and absorption of photons by matter, while non-radiative transfer involves energy transfer through electronic interactions without the emission of photons.In radiative transfer, the excited state of a molecule or atom can decay by emitting a photon, which is then absorbed by another molecule or atom, exciting it to a higher energy state. This process is known as fluorescence or phosphorescence, depending on the lifetime of the excited state. Fluorescence occurs when the excited state decays rapidly, emitting a photon before the energy is lost to the environment, while phosphorescence occurs when the excited state decays slowly, emitting a photon after a delay.Non-radiative transfer, on the other hand, occursthrough electronic interactions between molecules or atoms without the emission of photons. This process can involve energy transfer through electron exchange, dipole-dipole interactions, or electron transfer mechanisms. In these cases, the excited state of one molecule or atom can transfer its energy to another molecule or atom without the emission of a photon, resulting in a more efficient energy transfer process.The efficiency of visible light energy transfer depends on several factors, including the properties of the matter involved, the wavelength of the light, and the environment. For example, the absorption and emission spectra of molecules or atoms determine the wavelengths of light that can be effectively transferred. Additionally, the presence of other molecules or atoms in the environment can affect the rate and efficiency of energy transfer through interactions such as collisions or resonance energy transfer.Visible light energy transfer has numerous applications in various fields. In biochemistry, it plays a crucial rolein photosynthesis, the process by which plants convert light energy into chemical energy. Additionally, visible light energy transfer is used in optical sensors and imaging techniques to detect and quantify molecular interactions and concentrations. In the field of photovoltaics, visible light energy transfer is harnessed to convert sunlight into electrical energy through the photovoltaic effect.Moreover, visible light energy transfer has been extensively studied in the context of organic photochemistry, where it is used to induce chemical reactions through the absorption of visible light. This process, known as photoinduced electron transfer (PET), involves the transfer of an electron from one molecule to another upon absorption of light, leading to chemical transformations. PET reactions are widely used in organic synthesis, photocatalysis, and photovoltaic devices.In summary, visible light energy transfer is a fundamental process that occurs widely in nature and has numerous applications in various fields. It involves thetransfer of energy from one excited state to another through photons of visible light, and can occur through radiative or non-radiative mechanisms. The efficiency of energy transfer depends on the properties of the matter involved, the wavelength of the light, and the environment. Understanding and harnessing the power of visible light energy transfer has the potential to revolutionize fields such as biochemistry, photovoltaics, and organic photochemistry.。

The physics of dark energy and its applications

The physics of dark energy and itsapplicationsDark energy is a mysterious force that pervades the entire universe. Its presence has been confirmed through various astronomical observations and cosmological studies, yet its nature and origin remain unknown. In this article, we will explore the physics of dark energy and some of its potential applications in astrophysics and beyond.What is Dark Energy?Dark energy is a hypothetical form of energy that permeates all of space and acts as a repulsive force, causing the expansion of the universe to accelerate. The concept of dark energy was first proposed in the late 1990s, after astronomers discovered that distant galaxies were receding from us at a faster rate than expected. This suggested that the universe was expanding at an accelerating rate, which could not be explained by the known laws of physics.One possible explanation for this phenomenon is the existence of a cosmological constant, which is a term in Einstein's theory of general relativity that represents a repulsive force. However, the value of the cosmological constant required to explain the observed acceleration is much smaller than what would be predicted by quantum field theory, leading to the cosmological constant problem.Another possible explanation is that dark energy is a dynamical field that varies with time and space, known as quintessence. This theory proposes that the acceleration of the universe is driven by the potential energy of a scalar field that permeates all of space.Despite numerous efforts to detect and study dark energy, its nature remains elusive. It is believed to account for about 70% of the total energy content of the universe, making it the dominant component of the universe's energy budget.How is Dark Energy Studied?Dark energy cannot be directly observed or measured in a laboratory, as it interacts very weakly with matter and radiation. Instead, scientists rely on its effects on the expansion of the universe and the large-scale structure of galaxies and galaxy clusters.One of the most important observational probes of dark energy is the cosmic microwave background (CMB) radiation, which is the residual heat left over from the Big Bang. Variations in the CMB provide clues about the geometry and evolution of the universe, as well as the distribution of matter and dark energy.Another powerful tool for studying dark energy is the observation of Type Ia supernovae, which are exploding stars that have a known brightness and can be used as standard candles to measure distances in the universe. By observing how the brightness of these supernovae changes over time, astronomers can infer the expansion rate of the universe and the presence of dark energy.Other methods for studying dark energy include weak gravitational lensing, which measures the distortion of light from distant galaxies as it passes through the intervening matter, and baryon acoustic oscillations, which are periodic ripples in the density of matter that provide a standard ruler for cosmological distances.Applications of Dark EnergyAlthough the nature of dark energy remains enigmatic, its potential applications in astrophysics and beyond have been explored by scientists and engineers.One of the most promising applications of dark energy is in the design of advanced propulsion systems for space exploration. Because dark energy is a repulsive force that acts over long distances, it could be harnessed to propel spacecraft to velocities approaching the speed of light. However, this requires understanding the nature of dark energy more deeply and developing technology that can manipulate it.Another possible application of dark energy is in the development of new materials and energy sources. Some researchers have proposed using the unique properties of dark energy to create exotic materials that could be used in electronics, optics, and other fields.Finally, dark energy could have implications for our understanding of the fundamental physics of the universe. Some theories propose that dark energy is related to the properties of fundamental particles and forces, and that a deeper understanding of dark energy could lead to a unified theory of physics.ConclusionThe physics of dark energy remains one of the most intriguing and challenging topics in modern cosmology. Its presence has been confirmed by numerous observational probes, but its true nature and origin remain elusive. Nevertheless, the potential applications of dark energy in space exploration, materials science, and fundamental physics make it an area of active research and speculation. As we continue to explore the mysteries of the universe, dark energy will undoubtedly play a central role in our quest for understanding.。

暗能量与反弹宇宙学中若干问题

(II) Early Universe Application: Bouncing Scenario Introduction to Standard Big-Bang Theory and Inflation; Bouncing Scenario; Calculation on perturbation and signatures on observations; Other properties of bouncing scenario
(IV)Summary
（I） Topics on Dark Energy
DARK ENERGY: A MYSTERIOUS FORCE DRIVING THE ACCELERATION OF THE UNIVERSE
Einstein Equation:
Characteristics of DE: negative pressure, non-clustering…
2.Double-field Quintom model
2.Single simple component
For multi-components:
3.Single scalar field model with Higher Derivatives
3.Minimally coupling to Gravity 4.Non-scalar models (such as spinor, vector, etc)
Candidates of Dark Energy:
I. Cosmological Constant: w=-1;
II. Quintessence -1<w<1;
III. Phantom
w<-1;

Possible Effects of Dark Energy on the Detection of Dark Matter Particles

a r X i v :h e p -p h /0503120v 1 14 M a r 2005Possible Eﬀects of Dark Energy on the Detection of Dark MatterParticlesPeihong Gu,1Xiao-Jun Bi,2Zhi-Hai Lin,1and Xinmin Zhang 11Institute of High Energy Physics,Chinese Academy of Sciences,P.O.Box 918-4,Beijing 100049,P.R.China2Key laboratory of particle astrophysics,Institute of High Energy Physics,Chinese Academy of Sciences,P.O.Box 918-3,Beijing 100049,P.R.China (Dated:February 2,2008)Abstract We study in this paper the possible inﬂuence of the dark energy on the detection of the dark matter particles.In models of dark energy described by a dynamical scalar ﬁeld such as the Quintessence,its interaction with the dark matter will cause the dark matter particles such as the neutralino vary as a function of space and time.Given a speciﬁc model of the Quintessence and its interaction in this paper we calculate numerically the corrections to the neutralino masses and the induced spectrum of the neutrinos from the annihilation of the neutralinos pairs in the core of the Sun.This study gives rise to a possibility of probing for dark energy in the experiments of detecting the dark matter particles.Recent observational data from supernovae(SN)Ia[1]and cosmic microwave background radiation(CMBR)[2]strongly support for the‘cosmic concordance’model,in which the Universe is spatiallyﬂat with4%baryon matter,23%of cold dark matter(DM)and 73%of dark energy(DE).The baryon matter is well described by the standard model of the particle physics,however the nature of the dark matter and the dark energy remains unknown.There have been many proposals in the literature for the dark matter candidates the-oretically.From the point of view of the particle physics,the leading candidates for cold dark matter are the axion and the neutralino.Various experiments in the search directly or indirectly for these dark matter particles are currently under way.Regarding dark energy,the simplest candidate seems to be a remnant small cosmological constant.However,many physicists are attracted by the idea that dark energy is due to a dynamical component,such as a canonical scalarﬁeld Q,named Quintessence[3].Being a dynamical component,the scalarﬁeld of the dark energy is expected to interact with the other matters[4].There are many discussions on the explicit couplings of quintessence to baryons,dark matter,photons and neutrinos.These interactions if exist will open up the possibilities of probing non-gravitationally for the dark energy.In this paper we consider the possible eﬀects of the dark energy models which interact with the dark matter in the detection of the dark matter particles.Speciﬁcally we will study the inﬂuence of the dark energy on the neutralino masses in the Sun,and then calculate the neutrino spectrum annihilated from the neutralino pairs in the core of the Sun.We start with a coupled system of the interacting dark energy and the dark matter with the Lagrangian generally given byL eff=L DM+Lφ+L int,(1)where L DM and Lφare the free Lagrangian for dark matter and dark energy and the inter-action part is given byL int=−12M2S(φ)S2−gχΛ∂µφ¯ψγµψ−g SΛφ∂µφ∂µS− g isuch as the neutralino to be the dark matter particle and focus on the interactions which aﬀect the dark matter particles via the mass terms.Being a function of the quintessence scalarφthe mass of the dark matter particle will vary during the evolution of the universe.As shown in Refs.[5,6,7]this helps solve the coincidence problem.Furthermore,this type of interactions will aﬀect the cosmic structure formation[8],and the power spectrum of CMB[9].In this paper we will present a new possible eﬀect of the interacting dark energy with the dark matter in the detection of the dark matter particles.There are in general two diﬀerent ways,direct and indirect,in the detections of the dark matter particles.The direct detection records the recoil energy of the detector nuclei when the dark matter particles scatter oﬀthem as they pass through the Earth and interact with the matter.The indirect detection observes the annihilation products by the dark matter particles.Obviously the expected detection rates depend on the mass of the dark matter particles.In the presence of the interaction the mass of the dark matter particle will vary as a function of time and also space,and consequently the dark energy will inﬂuence the detection.To determine the mass of neutralino as a function of space we need to know the value of the dark energy scalarﬁeld as a function of space.Taking into account the back reaction of the interaction between the dark matter and the dark energy the eﬀective potential of the dark energy scalar as a function of the energy density of the cold dark matterρχ(φ)is given byV eff=ρχ(φ)+V(φ).(3) For diﬀerent dark matter densities the values of dark energy scalarﬁeld are expected to be diﬀerent,and consequently the mass of dark matter particles will also be diﬀerent.For example,the mass of the dark matter particle in the center of the Milky Way could be diﬀerent from that in the halo near the solar system.Therefore,the gamma ray spectrum, or the synchrotron radiation spectrum,from the galactic center could be diﬀerent from that in the nearby halo.Especially for the neutralino dark matter particle its mass measured at the future linear collider(LC)or the large hadron collider(LHC)on the Earth may be diﬀerent from that measured in other places in the Milky Way,such as in the galactic center.Similarly,the spectrum of the dark matter radiation in the Milky Way might also be diﬀerent from other galaxies in the local group.In the following we will consider a speciﬁc model of the Quintessence and its interaction with the dark matter particle,the neutralino,and then study its eﬀects on the indirect detection via the process of the neutralinos annihilation into neutrinos.The dark energy potential which we take isV(φ)=V0eβφ/m p,(4) and the interaction between the dark energy and the dark matter particle are given byMχ(φ)=Mχ0 1+λχφ(y q¯Q L Hq R).(6)m pThe parameterλB above characterizing the strength of this type of interaction will be shown below to be strongly constrained.However,since the baryon density inside the Sun is much higher than any other matter densities,this interaction in Eq.(6)will be important to our study in this paper as well as that on the neutrino oscillations[14,17,18].The Eq.(5)shows that the mass of the dark matter particles varies during the evolution of the Universe.At the present time the mass of the neutralino dark matter particle is given by Eq.(5)with the scalarﬁeldφevaluated at the present timeφ0.This type of physics associated with the mass varying dark matter particles have been proposed and studied in the literature[6,9,19],but in these studies the masses of the dark matter particle are constant in space.In this paper we consider the case that neutralino masses vary as afunction of space,for instance the neutralino mass in the Sun diﬀers from that evaluated on the cosmological scale.The eﬀective potential of the dark energy scalar at the inner of the Sun or the Earth is given byV eff =ρB (φ)+ρχ(φ)+V (φ),(7)where ρB (φ)is the mass density of the baryon matter and ρχ(φ)=n χM χ(φ).Here it’s straightforward to obtain ρB (φ)=ρB 0−λB ρB 0φdφφ=φmin=0.(8)The contributions to the equation above from the dark matter and baryon are proportional to λB ρB and λχρχrespectively.Sincethe ρχis about 15orders of magnitude smaller than ρB in the core of the Sun [20],the inﬂuence of the dark matter on the eﬀective potential of the dark energy scalar can be safely ignored ifλB ≫λχρχβln λB ρBM cos χ=1+λχβV 0m p .(11)In Eq.(11)φ0is the cosmological value of the scalar ﬁeld at the present time.To satisfy the cosmological observations on the dark energy our numerical results show that φ0=−0.51m p ,V 0=4.2×10−47GeV 4and β=1and λχ=0.1which we have mentioned above.10-510-410-310-210-1100200300400500600700800900E µ(GeV)ΦµM χ=170GeV M χ=1TeVFIG.1:Spectra of the muons induced by the neutrinos from the annihilation of the neutralino dark matter particles in the core of the Sun with m χ=1TeV and in the cosmological scale with m χ=170GeV.The spectra are normalized at 10GeV and calculated by using the DarkSUSY package [23].The baryon energy density of the Sun ρ⊙B is about 2.5g/cm 3.However due to thelogarithm in Eq.(10),the eﬀect on the dark matter mass is insensitive to the baryon mass density ρB .For example,the baryon density in the Sun ρ⊙B is about a quarter of that inthe Earth,which causes that M ⊙χis about 2%smaller than the value at the Earth in ournumerical calculation for λB =10−9.The parameter λB is constrained by the tests on the gravitational inverse square law [21]and the tests on the equivalence principle [22]to be λB <∼O (10−2).Here we point out that the presence of the interaction of the dark energy with the baryon in Eq.(6)makes the baryon mass density also varyδρBρB =−λB βV 0.(12)If taking ρB (φmin )to be the baryon density in the Earth (which is similar to the baryon density of the Sun),δρB (φmin )indicates the correction of the dark energy to baryon mass in the Earth.The proton mass has been measured very precisely on the Earth with an error of 10−8.If we take as an example that δρB /ρB <10−8we obtain an upper limit on λB ,λB <10−9,which we use in the numerical calculation.Now we have φmin ≃49m p and consequently M ⊙χ/M cos χ≃6.In Fig.1we plot the muonspectra induced by the neutrino from the dark matter annihilation in the center of the Sun and in the cosmological scale.We choose the dark matter mass in the Sun to be1TeV, while the dark matter mass in the cosmological scale is about1TeV/6=170GeV.From the ﬁgure one can see clearly the diﬀerence in the neutrino spectra.On the cosmological scale the dark energy scalar is homogeneously distributed,however in this case it is inhomogeneous,which gives rise to energy densityρφin the Sun.From Eqs.(4)and(10)we haveρφρB =λB[4]See,for example,X.Zhang,Plenary talk at12th International Conference on Supersymmetryand Uniﬁcation of Fundamental Interactions(SUSY04),Tsukuba,Japan,17-23Jun2004, hep-ph/0410292,and references therein.[5] elli,M.Pietroni,and A.Riotto,Phys.Lett.B571,115(2003).[6]U.Franca and R.Rosenfeld,Phys.Rev.D69,063517(2004).[7]X.J.Bi,B.Feng,H.Li,and X.Zhang,hep-ph/0412002.[8]Adi Nusser,S.S.Gubser,and P.J.E.Peebles,astro-ph/0412586.[9]M.B.Hoﬀman,astro-ph/0307350.[10]P.Q.Hung,hep-ph/0010126.This paper is on the interaction between the quintessence andthe sterile neutrinos.[11]P.Gu,X.Wang,and X.Zhang,Phys.Rev.D68,087301(2003).[12]R.Fardon,A.E.Nelson,and N.Weiner,astro-ph/0309800.[13]P.Q.Hung and H.Pas,astro-ph/0311131.[14] D.B.Kaplan,A.E.Nelson,and N.Weiner,Phys.Rev.Lett.93,091801(2004).[15]R.D.Peccei,Phys.Rev.D71,023527(2005);Nucl.Phys.Proc.Suppl.137,277(2004).[16]X.Zhang,hep-ph/0410292;H.Li,Z.Dai,and X.Zhang,hep-ph/0411228.[17] E.I.Guendelman and A.B.Kaganovich,hep-th/0411188.[18]V.Barger,P.Huber,and D.Marfatia,hep-ph/0502196.[19]G.W.Anderson and S.M.Carroll,astro-ph/9711288;G.R.Farrar and P.J.E.Peebles,Astro-phys.J.604,1(2004).[20]G.Bertone,D.Hooper,and J.Silk,Phys.Rept.405,279(2005).[21] E.G.Adelberger,B.R.Heckel,and A.E.Nelson,Annu.Rev.Nucl.Part.Sci.53,77(2003).[22]Y.Su et.al.,Phys.Rev.D50,3614(1994);G.L.Smith et.al.,Phys.Rev.D61,022001(2000).[23]P.Gondolo et.al.,JCAP0407,008(2004).。

Supernova Acceleration Probe Studying Dark Energy with Type Ia Supernovae

a r X i v :a s t r o -p h /0507459v 1 19 J u l 2005Supernova Acceleration Probe:Studying Dark Energy withType Ia SupernovaeA White Paper to the Dark Energy Task ForceJ.Albert 1,G.Aldering 2,S.Allam 3,W.Althouse 4,R.Amanullah 5,J.Annis 3,P.Astier 6,M.Aumeunier 7,8,S.Bailey 2,C.Baltay 9,E.Barrelet 6,S.Basa 8,C.Bebek 2,L.Bergstr¨o m 5,G.Bernstein 10,M.Bester 11,B.Besuner 11,B.Bigelow 12,R.Blandford 4,R.Bohlin 12,A.Bonissent 7,C.Bower 13,M.Brown 12,M.Campbell 12,W.Carithers 2,D.Cole 14,mins 2,W.Craig 4,T.Davis 15,2,K.Dawson 2,C.Day 2,M.DeHarveng 8,F.DeJongh 3,S.Deustua 16,H.Diehl 3,T.Dobson 11,S.Dodelson 3,A.Ealet 7,8,R.Ellis 1,W.Emmet 9,D.Figer 12,D.Fouchez 7,M.Frerking 14,J.Frieman 3,A.Fruchter 12,D.Gerdes 12,L.Gladney 10,G.Goldhaber 11,A.Goobar 5,D.Groom 2,H.Heetderks 11,M.Hoﬀ2,S.Holland 2,M.Huﬀer 4,L.Hui 3,D.Huterer 17,B.Jain 10,P.Jelinsky 11,C.Juramy 6,A.Karcher 2,S.Kent 3,S.Kahn 4,A.Kim 2,W.Kolbe 2,B.Krieger 2,G.Kushner 2,N.Kuznetsova 2,fever 2,moureux 2,mpton 11,O.Le F`e vre 8,V.Lebrun 8,M.Levi 2∗,P.Limon 3,H.Lin 3,E.Linder 2,S.Loken 2,W.Lorenzon 12,R.Malina 8,L.Marian 10,J.Marriner 3,P.Marshall 4,R.Massey 18,A.Mazure 8,B.McGinnis 2,T.McKay 12,S.McKee 12,R.Miquel 2,B.Mobasher 12,N.Morgan 9,E.M¨o rtsell 5,N.Mostek 13,S.Mufson 13,J.Musser 13,R.Nakajima 10,P.Nugent 2,H.Olus .eyi 2,R.Pain 6,N.Palaio 2,D.Pankow 11,J.Peoples 3,S.Perlmutter 2†,D.Peterson 2,E.Prieto 8,D.Rabinowitz 9,A.Refregier 19,J.Rhodes 1,14,N.Roe 2,D.Rusin 10,V.Scarpine 3,M.Schubnell 12,M.Seiﬀert 14,M.Sholl 11,H.Shukla 11,G.Smadja 20,R.M.Smith 1,G.Smoot 11,J.Snyder 9,A.Spadafora 2,F.Stabenau 10,A.Stebbins 3,C.Stoughton 3,A.Szymkowiak 9,G.Tarl´e 12,K.Taylor 1,A.Tilquin 7,A.Tomasch 12,D.Tucker 3,D.Vincent 6,H.von der Lippe 2,J-P.Walder 2,G.Wang 2,A.Weinstein 1,W.Wester 3,M.White 11saul@ melevi@16AmericanAstronomical Society 17Universityof Chicago18Cambridge University 19CEA,Saclay,France20IPNL,CNRS-IN2P3,Villeurbanne,France ∗Co-PI †PInova distance measurements up to their funda-mental systematic limit;strict requirements on the monitoring of each supernova’s properties leads to the need for a space-based mission.Results from pre-SNAP experiments,which characterize fundamental SN Ia properties,will be used to op-timize the SNAP observing strategy to yield data, which minimize both systematic and statistical uncertainties.With early R&D funding,we have achieved technological readiness and the collabo-ration is poised to begin construction.Pre-JDEM AO R&D support will further reduce technical and cost risk.Speciﬁc details on the SNAP mission can be found in Aldering et al.(2004,2005).1.1.Overview of Goals and TechniquesThe primary goal of the SNAP supernova pro-gram is to provide a dataset which gives tight constraints on parameters which characterize the dark-energy,e.g.w0and w a where w(a)=w0+ w a(1−a).SNAP data can also be used to di-rectly test and discriminate among speciﬁc dark-energy models.We will do so by building the Hub-ble diagram of high-redshift supernovae,the same methodology used in the original discovery of the acceleration of the expansion of the Universe that established the existence of dark energy(Perlmut-ter et al.1998;Garnavich et al.1998;Riess et al. 1998;Perlmutter et al.1999).The SNAP SN Ia program focuses on minimiz-ing the systematicﬂoor of the supernova method through the use of characterized supernovae that can be sorted into subsets based on subtle signa-tures of heterogeneity.Subsets may be deﬁned based on host-galaxy morphology,spectral-feature strength and velocity,early-time behavior,inter alia.Independent cosmological analysis of each subset of“like”supernovae can be compared to give conﬁdence that the results are free from sig-niﬁcant systematics.Conversely,analysis between supernova subsets at the same redshift can iden-tify further systematics controls.While theories of the supernova progenitor and explosion mech-anism can guide the establishment of subset cri-teria,such understanding is not required–only comprehensive measurements are–for robustness of the cosmological results.The level of robustness is tied to the quality of data with which supernovae are distinguished.Statistical mission requirements are fundamentally bound by the systematic limi-tations of the experiment.1.2.Description of the Baseline ProposalSNAP is a2-m space telescope(shown in Fig-ure1)with a0.7square-degree instrumented focal plane imager(shown in Figure2)and a low res-olution R∼100integral-ﬁeld-unit spectrograph (schematic shown in Figure3).Both instruments are sensitive to the0.4–1.7µm wavelength range. The two SNAP deep-surveyﬁelds each subtends 7.5square degrees and each is observed approx-imately every four days over the time-scales of supernova light-curve evolution in each of nine passbands.The passbands have resolution∼4.5 and are logarithmically distributed over the full wavelength range.Targeted spectrographic obser-vations are made of discovered supernovae with exposure times tuned to the sourceﬂux.The magnitude depths for individual scans and co-added images of the SNAP supernovaﬁelds are calculated for eachﬁlter.Table1shows the limit-ing S/N=5AB magnitude for eachﬁlter in the “Deep”supernova survey,for point sources that are not contaminated with cosmic rays.The limit-ing magnitude for any given point is probabilistic, due to the random occurrence of cosmic rays.In a single scan of the deep survey,77%of point sources will have no cosmic-ray contamination in any of the four dithered images while98%will have one or fewer cosmic-contaminated image,only slightly reducing signal-to-noise.2.Precursor ObservationsAny precursor mission that characterizes the fundamental properties of SNe Ia and their ap-plicability as distance indicators is important for optimizing the observing strategy and data anal-ysis of SNAP.Low-redshift surveys provide high signal-to-noise,comprehensive observations of well-charac-terized SNe Ia and could provide speciﬁc require-ments for the observation of light-curve or spec-troscopic features linked to SN Ia heterogeneity and homogeneity.Heterogeneous features provide a handle to probe the systematic limitations of our distance indicator and form the criteria by which “like”supernova subsets are deﬁned.Conversely, current distance measurements to supernovae may be found not to be optimal;a diﬀerent mix of ob-Table1The SNAP AB magnitude survey depth for a point source S/N=5.a Filterλeff(˚A)∆λ(˚A)Deep Survey(AB mag)Wide-ﬁeld Survey Panoramic 14400100027.930.628.326.7 25060115027.930.628.326.8 35819132227.830.528.226.8 46691152027.830.428.126.8 57695174927.830.428.126.8 68849201127.730.328.026.7 710177231327.530.127.826.6 811704266027.530.127.826.6 913459305927.430.027.726.51.5 degreeFig.2.—The SNAP focal plane working concept. The two-axis symmetry of the imagerﬁlters allows any90◦rotation to scan aﬁxed strip of the sky and measure all objects in all nineﬁlter types.The im-ager covers0.7square degrees.Underlying theﬁl-ters,there are362k x2k HgCdTe NIR devices and 363.5k x3.5k CCDs on a140K passively-cooled focal plane.The six CCDﬁlter types and three NIRﬁlters are arranged so that vertical or hori-zontal scans of the array through an observation ﬁeld will measure all objects in allﬁlters.The false colors indicateﬁlters with the same bandpass.The central rectangle and solid circle are the spectro-graph body and its light access port,respectively. The spectrum of a supernova is taken by placing the star in the spectrograph port by steering the satellite.The four small,isolated squares are the star guider CCDs.The inner and outer radii are 129and284mm,respectively.Fig. 3.—A schematic spectrograph optical de-sign.The beam is going out from the slicer(on the bottom right)to a prism disperser back faced coated by a dichroic.The visible light(blue path) is reﬂected and the IR light(in red)continue to a second prism used to reach the required spectral dispersion.The two beams are therefore focused on two detectors.The dimensions of the spectro-graph are approximately400×80×100mm.See Ealet et al.(2003)for more details.dark-energy properties,especially the time vari-ation of the equation of state.3.1.Sources of Systematic UncertaintyHigh-redshift supernova searches have been proceeding since the late1980’s(Norgaard-Nielsen et al.1989;Couch et al.1989;Perlmutter et al. 1995,1997,1998,1999;Schmidt et al.1998;Riess et al.1998;Tonry et al.2003;Knop et al.2003; Riess et al.2004).Particularly since the discov-ery of the accelerating expansion of the Universe, the high-redshift supernova methodology for mea-suring cosmological parameters has been critically scrutinized for sources of systematic uncertainty. Below(and summarized in Table2)is a lists of these sources where we highlight in bold the fea-tures speciﬁc to SNAP that allow systematic con-trol.Generically,the need for high signal-to-noise observations over a broad wavelength range for 0.1<z<1.7supernovae,as well as the truncation of ground-observatory light curves of high-redshift supernova at high-Galactic latitude,point to the necessity of a space mission.Table2SNAP Control of Sources of Astrophysical Systematic Uncertainty Systematic Control3.1.1.Evolution of the Supernova Sample as aFunction of RedshiftThe luminosity function of supernovae may evolve as a function of redshift resulting in cor-responding biases in distance-modulus determina-tions(Perlmutter et al.1995).Although like su-pernovae have the same redshift-independent lu-minosity,their relative rate of occurrence may evolve in redshift.SNAP addresses this problem by identifying subsets of supernovae“identical”in luminosity and color,applying the dark-energy analysis to each,and optimally combining the subset re-sults intoﬁnal cosmology measurements.We exploit the fact that supernovae cannot change their brightness in one measured wavelength range without aﬀecting brightness somewhere else in the spectral time series—an eﬀect that is well-captured by expanding atmosphere computer models(e.g.H¨oﬂich&Khokhlov1996;Lentz et al. 2000;H¨oﬂich et al.2003).Well-characterized su-pernovae can be sorted into subsets based on sub-tle signatures of heterogeneity.Subsets may be de-ﬁned based on host-galaxy morphology,spectral-feature strength and velocity,early-time behavior, and light-curve characteristics.There are a number of supernova parameters that are observed to exhibit heterogeneity beyond the single-parameter description.The following features need to be monitored to check for sys-tematic bias in supernova distances.Premaximum spectral screening:Broad-light-curve supernovae can be distinguished by hav-ing either peculiar(e.g.SN1991T)or“normal”(e.g.SNe1999ee and2000E)pre-maximum spec-tra.In addition,there are extremely peculiar sin-gleton events technically classiﬁed as SNe Ia which bear little observational resemblance to their more standard counterparts.These include SN2000cx (Li et al.2001;Candia et al.2003),SN2001ay (Phillips et al.2003),SN2002cx(Li et al.2003), and SN2002ic(Deng et al.2004).These extreme events are easily identiﬁed through their premax-imum peculiar spectra,Hydrogen emission,and high expansion velocities.Spectral-feature velocities:The diversity in the velocity of the6100˚A SiII feature atﬁxed epochs has been noted(Branch&van den Bergh1993; Hatano et al.2000).Garavini et al.(2004)and Benetti et al.(2004)have examined the velocity as a function of supernova phase andﬁnd that large subset of objects tightly cluster within a103 km s−1range for any given epoch.A smaller sub-set with much higher velocity dispersion can be partially distinguished through accurate measure-ments of the SiII feature velocity.Spectral-feature velocity evolution:Benetti et al.(2004)ﬁnd that supernovae cluster when parameterized by the rate of change of the SiII feature velocity˙v and luminosity.Resolution of the velocity gradients requires measurement of˙v to a few km s−1d−1from spectra between peak and40SN-frame days after peak brightness.Spectral-line-ratio:At t<−10,the ratio of line depths of SiII(λ6150˚A)and SiII(λ5800˚A),R(SiII) (Nugent et al.1995),has a range greater than0.1. The subpopulation of supernovae with high veloc-ity gradients also have distinct R(SiII)evolution; they sharply decrease until t=−5andﬂatten out whereas other supernovae show no evolution for the same time range(Benetti et al.2004).Light-curve evolution:There are a series of supernovae that exhibit systematic deviations in light-curve shape and color(e.g.Hamuy et al. 1996;Richmond et al.1995;Krisciunas et al.2003; Pignata et al.2004).The ranges displayed in the optical light curves can be summarized as follows: 1mag10days before maximum and0.2mag5 days before maximum,0.1mag20-30days after maximum,and0.2-0.3mag60days after maxi-mum.Color:There is evidence that color is a second parameter correlated with peak magnitude(Tripp 1998;Saha et al.1999;Tripp&Branch1999;Par-odi et al.2000).Dust extinction and intrinsic su-pernova color can be distinguished as supernovae get brighter in I as V−I color becomes red,the opposite eﬀect from dust.Color measurements whose propagated uncertainties in the extinction correction are less than the intrinsic B peak mag-nitude dispersion correspond to B−V measured to0.07mag and V−I to0.5mag.Polarization:Normal-and broad-light-curve supernovae have demonstrated varying degrees of polarization(Howell et al.2001).Detection of po-larization is extremely diﬃcult for all but the near-est supernovae and is unrealistic to require in any cosmological survey.Spectroscopy may then serve as a proxy for polarization measurements through their correlation with high and quickly evolving SiII velocities.The SNAP instrumentation suite is de-signed to provide the data necessary for the subclassiﬁcation process.SNAP will ob-tain broadband photometry over the full supernova-frame optical region,withﬁne light-curve sampling tuned to natural su-pernova time scales.The SNAP spectro-graph also covers the supernova-frame op-tical region with resolution tuned to the widths of the supernova features.We expect that any residual luminosity and color biases will be smaller than the dispersion observed in the local supernova sample since this represents heterogeneous and diverse supernova-progenitor environments(Branch2001).This assumption will be tested by intensive precur-sor supernova-characterization experiments and SNAP itself.3.1.2.K-correctionA given observing passband is sensitive to dif-ferent supernova-rest-frame spectral regions.K-corrections are used to put these diﬀering photom-etry measurements onto a consistent rest-frame passband(Kim,Goobar,&Perlmutter1996;Nu-gent,Kim,&Perlmutter2002).The SNAP ﬁlter-set number,density,and shapes are tuned to give<0.02mag dispersion for the full catalog of currently available SN Ia spectra(Davis et al.2004).The situation will improve further for the conﬁned analysis of supernova subsamples with the expanded spectral library provided by on-going surveys and SNAP itself.3.1.3.Galactic ExtinctionExtinction maps of our own Galaxy are uncer-tain by∼1–10%depending on direction(Schlegel, Finkbeiner,&Davis1998).Supernovaﬁelds can be chosen toward the low-extinction Galactic caps where uncertainty can then be controlled to< 0.5%in brightness.These levels of uncertainty have negligible eﬀect on the measurement of w0 and w a(Kim&Miquel2005).Spitzer obser-vations will allow an improved mapping between color excesses(e.g.of Galactic halo subdwarfs in the SNAPﬁeld)and Galactic extinction by dust (Lockman&Condon2005).3.1.4.Cross-Passband CalibrationUncertainties in calibration are one of the im-portant limiting factors in probing the dark energy with supernovae.Distance measurements funda-mentally rely on the comparison ofﬂuxes in dif-ferent passbands:for determining the relative dis-tances of supernovae at diﬀerent redshifts and for color measurements for determining the dust ab-sorption of a single supernova.The relationship between passband calibration and w0and w a is strongly dependent on the speciﬁcs of the cross-band correlations.Simula-tion studies(Kim&Miquel2005)demonstrate the strict fundamental limits in the measurement of dark-energy parameters due to uncorrelated cross-band calibration uncertainty.Signiﬁcantly larger correlated uncertainties can be tolerated(Kim et al.2004).These studies provide requirements for the SNAP calibration program.3.1.5.Extinction by Host-Galaxy DustExtinction from host-galaxy dust can signiﬁ-cantly reduce the observed brightness of a dis-covered supernova.SNAP’s9-band photom-etry will identify the properties of the ob-scuring dust and gas,and thus the amount of extinction suﬀered by individual super-novae.Incoherent scatter in dust properties yields no bias but increased statistical uncertainty in the dark-energy parameters(Linder&Miquel 2004).Systematic host-galaxy extinction uncer-tainty can be introduced if an incorrect mean dust-extinction law is used in the analysis.This can be minimized by distinguishing and exclud-ing highly-extincted supernovae from the analysis.To give a quantitative example,sup-pose that the Cardelli et al.(1989)model ac-curately describes host-galaxy extinction and an R V=3.1dust is used in the analysis and the 4400–5900˚A rest-frame color is used to determine A V.We calculate that if drift in the mean of the true dust extinction models is constrained to have 2.4<R V<4.4,the vast majority of supernova which have A B<0.1(Hatano,Branch,&Deaton 1998)would have distance-modulus bias of<0.02 mag.3.1.6.Gravitational LensingInhomogeneities along the supernova line of sight can gravitationally magnify or demagnify the supernovaﬂux and shift the mode of the super-nova magnitude distribution by<∼3%dependingon redshift(Holz&Linder2005).Gravitational lensing magniﬁcation is achromatic and unbiased inﬂux so eﬀectively contributes a statistical uncer-tainty that can be reduced below1%in distance if large numbers(>∼70)of supernovae are ob-tained per0.1redshift bin.The eﬀectiveﬂux dispersion induced by lensing goes asσ=0.088z (Holz&Linder2005).3.1.7.Non-SN Ia ContaminationOther supernova types are on average fainter than SNe Ia and their contamination could bias their Hubble diagram(Perlmutter et al.1999). Observed supernovae must be positively identi-ﬁed as SN Ia.As some Type Ib and Ic super-novae have spectra and brightnesses that other-wise mimic those of SNe Ia(Filippenko1997),a spectrum covering the deﬁning rest frame Si II6150˚A feature and SII features for ev-ery supernova at maximum will provide a pure sample.3.1.8.Malmquist BiasAﬂux-limited sample preferentially detects the intrinsically brighter members of any population of sources.The amount of magnitude bias de-pends on details of the search but can reach the level of the intrinsic magnitude dispersion of a standard candle(Teerikorpi1997).Directly cor-recting this bias would rely on knowledge of the SN Ia luminosity function,which may change with lookback time.A detection threshold fainter than peak by at leastﬁve times the intrin-sic SN Ia luminosity dispersion ensures sam-ple completeness with respect to intrinsic super-nova brightness,eliminating this bias(Kim et al. 2004).3.1.9.Extinction by Hypothetical Gray DustA systematics-limited experiment must ac-count for speculative but reasonable sources of uncertainty such as gray dust.As opposed to normal dust,gray dust is postulated to pro-duce wavelength-independent absorption in opti-cal bands(Aguirre1999;Aguirre&Haiman2000). Although models for gray-dust grains dim blue and red optical light equally,near-infrared light (∼1-2µm)is less aﬀected.Cross-wavelength calibrated spectra extending to wavelength regions where“gray”dust is no longer gray will detect and correct for the hypotheticallarge-grain dust.Numerous observations already severely limit the cosmological eﬀects of such a component(Goobar,Bergstr¨o m,&M¨o rtsell 2002).3.2.Statistical Supernova SampleThe statistical supernova sample appropriate for experiments with the presence of systematic uncertainty has been considered in the Fisher-matrix analysis of Linder&Huterer(2003)and validated with our independent Monte Carlo anal-ysis.They examined the measurement precision of dark-energy parameters as a function of red-shift depth considering2000SNe Ia measured in the range0.1≤z≤z max,along with300low-redshift SNe Ia from the Nearby Supernova Fac-tory(Aldering et al.2002).They concluded that a SN Ia sample extending to redshifts of z∼1.7 is crucial for realistic experiments in which some systematic uncertainties remain after all statisti-cal corrections are applied.Ignoring systematic uncertainties can lead to claims that are too opti-mistic.Statistically,∼2000SNe Ia well-characterized “Branch-normal”supernovae provide systematic-uncertainty limited measurements of the dark-energy parameter w a.These represent the cream, z<1.7supernovae of the∼10000total and ∼4000well-characterized SNAP SNe Ia,that can provide robust cosmological measurements(e.g. non-peculiar,low-extinction).This large sample is necessary to allow model-independent checks for any residual systematics or reﬁned standardization parameters,since the sample will be subdivided in a multidimensional parameter space of redshift, light curve-width,host properties,etc.The large number of lower signal-to-noise light curves from supernovae at z>1.7will provide an extended redshift bin in which to check for consistency with the core sample.We require a statistical measurement uncer-tainty for the peak magnitude corrected for ex-tinction and shape inhomogeneity roughly equal to the current intrinsic magnitude dispersion of supernovae,∼0.15mag.4.Quantiﬁcation of Dark EnergyExpected measurement precisions of the dark-energy parameters w0and w′(=w a/2)for the SNAP supernova program are summarized in Ta-ble3and shown in Figure4.Since SNAP is a systematics-limited experiment,any improve-ments in our projection of systematic uncertainty will be directly reﬂected in improvements in our w0–w′measurements.We determine precisions for twoﬁducialﬂat universes withΩM=0.3,one in which the dark energy is attributed to a cosmolog-ical constant and the other to a SUGRA-inspired dark-energy model(Brax&Martin2000).Fig.4.—The68%conﬁdence region in the dark-energy parameters forﬁducial cosmological con-stant(labeled withΛ)and supergravity(labeled with S)universes.The blue solid curves show the results of the supernova simulation and as-sociated systematic-error model,with a Planck prior on the distance to the surface of last scat-tering,and an assumedﬂat universe.We deﬁne w′≡−dw/d ln a|z=1.See Albert et al.(2005)for constraints including the weak lensing half of the mission.If the universe is taken to be spatiallyﬂat,the SN data(with Planck prior on the distance to the surface of last scattering)determineΩM to 0.01.The present value of the dark energy equa-tion of state is constrained within0.09and the physically crucial dynamical clue of the equation of state time variation is bounded to within0.19. Note that these constraints are systematics lim-ited;much tighter constraints would be obtained if systematics were ignored.Table3also high-Table3SNAP1-σuncertainties in dark-energy parameters,with conservative systematics for the supernova and the shear power-spectrum measurement from a1000sq.deg.one-year weak-lensing survey.Note:These uncertainties are systematics-limited,not statisticslimited.σΩMσΩwσwσw′SNAP SN;w=−10.020.05······SNAP SN+WL;w=−10.010.01······SNAP SN;σΩM=0.03prior;ﬂat;w(z)=w0+2w′(1−a)···0.030.090.31SNAP SN;Planck prior;ﬂat;w(z)=w0+2w′(1−a)···0.010.090.19 SNAP SN+WL;ﬂat;w(z)=w0+2w′(1−a)···0.0050.050.11Fiducial Universe:ﬂat,ΩM=0.3,SUGRA-inspired dark energyNote.—Cosmological and dark-energy parameter precisions for twoﬁducialﬂat universes withΩM=0.3,one in which the dark energy is attributed to a Cosmological Constant and the other to a SUGRA-inspired dark-energy model.The parameter precisions then depend on the choice of data set,priors from other experiments(e.g.Planck measurement of the distance to the surface of last scattering), assumptions on theﬂatness of the universe,and the model for the behavior of w.SNAP is a systematics-limited experiment so any improvements in our projection of systematic uncertainty will be directly reﬂected in improvements in our w0–w′measurements.In this paper we deﬁne w′≡−dw/d ln a|z=1.SNAP can accumulate a wide-ﬁeld weak-lensing survey at a rate of1000sq.deg.per year of observation.lights the signiﬁcant value added by measurements of the shear power spectrum with the complemen-tary SNAP weak-lensing program.The precise,homogeneous,deep supernova data set can alternatively be analyzed in a non-parametric,uncorrelated bin,or eigenmode method(Huterer&Starkman2003;Huterer& Cooray2005).One can also obtain the expansion history a(t)itself,e.g.Linder(2003).5.Project Risks and StrengthsThe proposed experiment is a self-contained su-pernova program which is desensitized to cross-experimental calibration,one of the largest sources of systematic uncertainty.The SNAP instrumen-tation suite provides access to any supernova ob-servable anticipated to be important for reducing uncertainties in supernova distances.The SNAP collaboration is large and diverse, which has allowed for substantial eﬀorts to be sup-ported in science reach,computer framework and simulation,calibration approaches,and photo-detector technology development and testing.Our ongoing R&D eﬀorts have placed us at a point of technological readiness to commence construction of the experiment.The major risk to the SNAP collaboration is that a stretch in the JDEM decision making pro-cess and follow-on project funding will lead to a dissipation of the present eﬀorts as people drift oﬀto other intermediate projects.6.Requisite technology R&DA few areas of the SNAP mission implementa-tion require development to achieveﬂight readi-ness.No new technologies are required,rather particular instances of the technology as chosen by SNAP require some maturation.At present, the SNAP R&D program is primarily funded by the Department of Energy(DOE),with addi-tional support to collaborators from NSF,NASA, CNES,and CNRS/IN2P3for related activities. The SNAP mission architecture has undergone nu-merous studies(GSFC/IMDC,GSFC/ISAL,and JPL/Team-X),has been reviewed several times by external teams of experts at the request of DOE and NSF,and has been extensively presented and discussed at a variety of international conferences.Thus,SNAP is a relatively well-advanced concept, and the internally self-consistent reference model presented here is now ready for more reﬁned opti-mization.R&D has focused on1)SNAP-speciﬁc detector development,both visible and near infrared,2)in-tegralﬁeld unit spectrograph design,3)cold front-end electronics,4)calibration procedures and sup-portingﬂight hardware,5)achievable telescope point stability studies,6)on-board data handling, and7)achievable telemetry rate studies.All of these areas are maturing at a rapid rate and there appear to be no show stoppers for a SNAP JDEM response.Visible detectors:The visible portion of the im-ager is an array of36silicon CCDs with extended red response and improved radiation tolerance. SNAP will materially beneﬁt from an advanced technology based on fully depleted backside illu-minated high resistivity silicon.The development work is DOE funded and is taking place at LBNL and at commercial foundries.We are also devel-oping custom integrated circuits for the electronic readout.NIR detectors:The NIR portion of the imager requires362kx2k format devices.We are evalu-ating HgCdTe devices available from two vendors. Development work funded by DOE is under way to improve the dark current,read noise,and quan-tum eﬃciency.We are also exploring InGaAs as a backup photoactive material.One NIR vendor will provide a cold front-end ASIC for their detec-tors.For the other,we are leveraging the work we have done for the CCDs to provide cold front-end ASICs.Spectrograph:This is a simple two-prism de-sign with no technology challenges except its in-tegralﬁeld unit(IFU).An image-slicer IFU with the requisite size and eﬃciency have been built for ground-based astronomy,and will beﬂown as part of the JWST NIRSPEC.The image slicer R&D is funded by CNES and CNRS/IN2P3.Telescope:This has been studied by the God-dard/ISAL and four prospective space optics sup-pliers.Two industry study contracts are in place to evaluate the design,manufacturability,and testability of the telescope.Studies and vendor discussions have shown that the pointing stability requirements can be met with today’s spacecraft。

英语作文我的发明

In the realm of innovation and creativity,my invention stands as a testament to the boundless potential of human ingenuity.This essay will delve into the conception,design, and potential impact of my invention,which I have named the EcoPulse.The Genesis of an IdeaThe idea for the EcoPulse was born out of a deep concern for the environment and the pressing need for sustainable energy solutions.As I observed the detrimental effects of fossil fuels on our planet,I was inspired to create a device that could harness renewable energy in a novel and efficient manner.Design and FunctionalityThe EcoPulse is a compact,multifunctional device that captures and converts various forms of renewable energy into usable electrical power.It is equipped with solar panels, wind turbines,and piezoelectric sensors that can generate electricity from the kinetic energy of moving water or even the vibrations from footsteps.The design incorporates a sleek,aerodynamic structure that allows it to be easily mounted on rooftops or integrated into urban landscapes.The use of lightweight,durable materials ensures that the EcoPulse is both costeffective and environmentally friendly.Innovations and TechnologiesAt the heart of the EcoPulse lies a proprietary energy management system that optimizes the conversion and storage of energy.This system uses advanced algorithms to predict energy demand and adjust the devices energy capture and storage accordingly.The result is a highly efficient energy source that can power homes,businesses,and even small communities.One of the key innovations of the EcoPulse is its ability to store energy in a compact, longlasting battery.This battery is made from nontoxic materials and has a lifespan significantly longer than conventional batteries,reducing waste and the environmental impact of battery disposal.Potential ImpactThe EcoPulse has the potential to revolutionize the way we think about and use energy. By providing a reliable,clean,and sustainable source of power,it can help to reduce our dependence on fossil fuels and mitigate the effects of climate change.Moreover,the EcoPulse is designed to be accessible and affordable,making it a viable option for individuals and communities in both developed and developing nations.This could lead to a significant reduction in energy poverty and contribute to global efforts to achieve universal access to electricity.Future ProspectsAs the world continues to grapple with the challenges of energy scarcity and environmental degradation,the EcoPulse represents a beacon of hope.With ongoing research and development,I envision the EcoPulse not only as a standalone device but as part of a larger,interconnected network of smart energy systems that can adapt to the everchanging needs of our planet.In conclusion,my invention,the EcoPulse,is more than just a device it is a symbol of our collective potential to innovate,to adapt,and to create a brighter,cleaner,and more sustainable future for all.。

Dark Energy Accelerating the Cosmos

Dark Energy Accelerating the Cosmos Dark energy, the mysterious force that is accelerating the expansion of the universe, has been a topic of intense scientific research and debate in recent years. This enigmatic phenomenon challenges our understanding of the fundamental forces and laws of the universe, leaving scientists and cosmologists grappling with profound questions about the nature of space, time, and the cosmos. As we delve into the complexities of dark energy, it becomes evident that its implications extend far beyond the realm of astrophysics, touching upon existential and philosophical inquiries that have captivated human curiosity for centuries.From a scientific perspective, the discovery of dark energy has revolutionized our understanding of the universe on a cosmic scale. Initially, astronomers observed that the expansion of the universe was not slowing down as expected due to the gravitational pull of matter, but rather, it was accelerating at an ever-increasing rate. This unexpected revelation prompted the formulation of the concept of dark energy, a repulsive force that permeates the fabric of space and drives the expansion of the cosmos. The existence of dark energy has been supported by various astronomical observations, such as the measurements of distant supernovae and the cosmic microwave background radiation, providing compelling evidence for its existence.The implications of dark energy extend beyond the realm of astrophysics, permeating into the realm of existential and philosophical inquiries. The profound realization that the majority of the universe is composed of dark energy, a mysterious and elusive entity that defies our current understanding, raises existential questions about the nature of reality and our place within the cosmos. It challenges our perceptions of the universe as a static and predictable entity, inviting us to contemplate the enigmatic forces that shape the fabric of space and time. This realization evokes a sense of awe and wonder, igniting a deep-seated curiosity about the mysteries that lie beyond the boundaries of our current knowledge.Furthermore, the discovery of dark energy has sparked intense debate and speculation within the scientific community, fueling a quest for new theories and models that can account for its perplexing properties. The enigmatic nature of dark energy has promptedcosmologists to reconsider and refine existing theories of the universe, such as the nature of gravity and the behavior of fundamental particles. This pursuit of knowledge has led to a renaissance in theoretical physics, as scientists grapple with the profound implications of dark energy and strive to unravel its mysteries.On a more personal level, the concept of dark energy evokes a sense of humility and wonder at the vastness and complexity of the universe. It invites us to contemplate our place within the cosmic tapestry, prompting introspection and philosophical contemplation about the nature of existence and the fundamental forces that govern the universe. The realization that the majority of the universe is composed of dark energy, an invisible and enigmatic force that eludes direct detection, humbles our perceptions of the cosmos and invites us to embrace the unknown with a sense of curiosity and wonder.In conclusion, the enigmatic phenomenon of dark energy presents a profound challenge to our understanding of the universe, sparking intense scientific inquiry and philosophical contemplation. Its discovery has revolutionized our perceptions of the cosmos, prompting a renaissance in theoretical physics and cosmology as scientists strive to unravel its mysteries. Beyond its scientific implications, dark energy invites us to ponder existential and philosophical questions about the nature of reality and our place within the vast cosmic tapestry. As we continue to grapple with the profound implications of dark energy, we are reminded of the enduring human quest for knowledge and understanding, as we seek to unravel the mysteries that lie beyond the boundaries of our current knowledge.。

新型无机闪烁体的能量分辨率(中英文对照)

成都理工大学学生毕业设计（论文）外文译文极，（b）光电子是后来ηNph，（c）这些∝ηNph电子在第一倍增极和到达（d）倍增极的k（k = 1，2…）放大后为δk 并且我们假设δ1=δ2=δ3=δk=δ的，并且δ/δ1≈1的。

我们可以得出：R2=Rlid2=5.56δ/[∝ηNph（δ-1）] ≈5.56/Nel （3）Nel表示第一次到达光电倍增管的数目。

在试验中，δ1≈10＞δ2=δ3=δk，因此，在实际情况下，我们可以通过（3）看出R2的值比实际测得大。

请注意，对于一个半导体二极管（不倍增极结构）（3）也适用。

那么Nel就是是在二极管产生电子空穴对的数目。

在物质不均匀，光收集不完整，不相称和偏差的影响从光电子生产过程中的二项式分布及电子收集在第一倍增极不理想的情况下，例如由于阴极不均匀性和不完善的重点，我们有：R2=Rsci2+Rlid2≈5.56[(νN-1/Nel)+1/Nel] (4)νN光子的产生包括所有非理想情况下的收集和1/Nel的理想情况。

为了说明，我们在图上显示，如图1所示。

ΔE/E的作为伽玛射线能量E的函数，为碘化钠：铊闪烁耦合到光电倍增管图。

1。

对ΔE/E的示意图（全曲线）作为伽玛射线能量E功能的碘化钠：铊晶体耦合到光电倍增管。

虚线/虚线代表了主要贡献。

例如见[9,10]。

对于Rsci除了1/（Nel）1/2的组成部分，我们看到有两个组成部分，代表在0-4％的不均匀性，不完整的光收集水平线，等等，并与在0-400代表非相称keV的最大曲线。

表1给出了E=662Kev时的数值（137Cs）在传统的闪烁体资料可见。

从图一我们可以清楚的看到在低能量E＜100Kev，如果Nel，也就是Nph增大的话，是可以提高能量分辨率的。

这是很难达到的，因为光额产量已经很高了（见表1）在能量E＞300Kev时，Rsci主要由能量支配其能量分辨率，这是没办法减小Rsci 的。

然而，在下一节我们将会讲到，可以用闪烁体在高能量一样有高的分辨率。

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A. Method
Our parameter set includes M – a “nuisance” parameter combining the supernova absolute magnitude and the Hubble constant – and the matter density Ωm, present dark energy equation of state w0, and time variation w′. We assume a ﬂat universe, which current CMB data are
w˙
≡
dw dt
=
H
dw d ln a
<∼
H,
(1)
w′
≡
dw d ln a
<∼
1.
(2)
We caution that our notions of naturalness do not con-
strain the universe to actually act that way! In §II we examine what the quality of the most recent
Is Dark Energy Dynamical? Prospects for an Answer
Eric V. Linder & Ramon Miquel Physics Division, Lawrence Berkeley Laboratory, Berkeley, CA 94720
Recent data advances oﬀer the exciting prospect of a ﬁrst look at whether dark energy has a dynamical equation of state or not. While formally theories exist with a constant equation of state, they are nongeneric – Einstein’s cosmological constant is a notable exception. So limits on the time variation, w′, directly tell us crucial physics. Two recent improvements in supernova data from the Hubble Space Telescope allow important steps forward in constraining the dynamics of dark energy, possessing the ability to exclude models with w′ >∼ 1, if the universe truly has a cosmological constant. These data bring us much closer to the “systematics” era, where further improvements will come predominantly from more accurate, not merely more, observations. We examine the possible gains and point out the complementary roles of space and ground based observations in the near future. To achieve the leap to precision understanding of dark energy in the next generation will require specially designed space based measurements; we estimate the conﬁdence level of detection of dynamics (e.g. distinguishing between w′ = 0 and w′ = 1) will be ∼ 1.8σ after the ongoing generation, improving to more than 6.5σ in the dedicated space generation.
2
consistent with but future measurements will further reﬁne. As our ﬁducial cosmology we adopt Ωm = 0.28 and a cosmological constant. For the CMB prior we take the WMAP determination of the reduced distance to last scattering measured with a 3.3% relative precision. Similarly, a gaussian prior of 0.03 on Ωm is used. The major role of the priors is to break degeneracies between parameters rather than determine w′ per se. Neither of these priors is fully descriptive of the complementary probe data, but are adequate approximations for the level of precision desired for the estimation of w0 and w′.
arXiv:astro-ph/0409411v2 8 Nov 2004
I. INTRODUCTION
The acceleration of the expansion of the universe represents a critical mystery. To the physicist this raises questions about Einstein’s general relativity, quantum physics, and extra dimensions. To the interested spectator it contains the determination of the fate of the universe.
We will not learn a unique answer to all these questions without an overall theory for the dark energy causing the acceleration – one possibility for which is Einstein’s cosmological constant. But a major question that is directly accessible is whether the dark energy is dynamical, possessing a variation in time, suﬃcient in itself to rule out a cosmological constant. Observations of the expansion, most clearly and directly at present through the use of Type Ia supernovae as calibrated candles for the distanceredshift behavior, can constrain the physics through the measured properties of the dark energy.
supernovae data can tell us about the magnitude of w′. We emphasize that this is an illustrative look, based on estimated types of data numbers and accuracy, rather than the actual data themselves. Possible future samples involving more data and better data are examined in §III to see how they give the greatest leverage on improving our knowledge of the dynamic nature of dark energy. We conclude in §IV with thoughts on what new advances are required to understand the fate of our universe.
ng the nature of dark energy, we consider three forms of data currently available. Type Ia supernovae (SN) magnitudes and redshifts play a central role in tracing the expansion history of the universe, and led to the discovery of the acceleration [1, 2]. When expanding the description of dark energy to include not only the contribution of its energy density but its present equation of state w0 and a measure of its time variation w′, other types of data are crucial to break the degeneracies between the parameters. So we also consider cosmic microwave background (CMB) measurements of the distance to the last scattering surface, and a prior on the matter density Ωm from large scale structure surveys. The role of CMB complementarity with SN measurements was emphasized in [3].