Induced quantum metric fluctuations and the validity of semiclassical gravity
Quantum spin liquid emerging in 2D correlated Dirac fermions
量子计算的基本原理
量子计算的基本原理量子计算/量子计算机的概念是著名物理学家费曼于1981年首先提出的。
后来大家试了试才知道，原来真的可以这么玩。
【费曼还首先在Tiny Machine的课堂上首先提出了纳米科学这一个概念，他课堂的学生某种意义是人类第一批纳米科学家。
然后又一个新领域诞生了。
所以现在美国的纳米科学领域的奖叫做费曼纳米技术奖。
类似的，薛定诗有一个一系列讲座叫《What is life》。
他在《生命是什么》里用物理思想诠释了自己对生命的理解。
他把信息、负燧等思想（食物就是负嫡）引入了生命科学，然后分子生物学（生命科学最重要的领域之一）诞生。
】这些行走在人类能力圈边缘的天才物理学家们总是有着这梦幻般的的创作力。
所思所想皆对人类做出巨大贡献。
量子计算的原理实际上应该分为两部分。
一部分是量子计算机的物理原理和物理实现；另一部分是量子算法。
关于物理部分，我直接上郭光灿院士的文章吧。
他是我国量子光学的泰斗级人物。
我自认为不会比他讲的更好。
【USTC物理的强大实力差不多有一半来自于潘建伟院士和郭光灿院士领导的量子物理领域。
郭院士是T立非常和蔼的老人。
我本科期间还向他请教过量子物理相关的问题。
：）】量子计算量子比特可以制备在两个逻辑态O和1的相干叠加态，换句话讲，它可以同时存储O 和1。
考虑一个N个物理比特的存储器，若它是经典存储器，则它只能存储*N个可能数据当中的任一个，若它是量子存储器，则它可以同时存储2小1个数，而且随着N的增加，其存储信息的能力将指数上升，例如，一个250量子比特的存储器（由250个原子构成）可能存储的数达2八250,比现有已知的宇宙中全部原子数目还要多。
由于数学操作可以同时对存储器中全部的数据进行，因此，量子计算机在实施一次的运算中可以同时对2^N个输入数进行数学运算。
其效果相当于经典计算机要重复实施2ΛN次操作，或者采用2小1个不同处理器实行并行操作。
可见，量子计算机可以节省大量的运算资源（如时间、记忆单元等）。
2022年自考专业(英语)英语科技文选考试真题及答案37
2022年自考专业(英语)英语科技文选考试真题及答案一、阅读理解题Directions: Read through the following passages. Choose the best answer and put the letter in the bracket. (20%)1、 (A) With the recent award of the Nobel Prize in physics, the spectacular work on Bose-Einstein condensation in a dilute gas of atoms has been honored. In such a Bose-Einstein condensate, close to temperatures of absolute zero, the atoms lose their individuality and a wave-like state of matter is created that can be compared in many ways to laser light. Based on such a Bose-Einstein condensate researchers in Munich together with a colleague from the ETH Zurich have now been able to reach a new state of matter in atomic physics. In order to reach this new phase for ultracold atoms, the scientists store a Bose-Einstein condensate in a three-dimensional lattice of microscopic light traps. By increasing the strength of the lattice, the researchers are able to dramatically alter the properties of the gas of atoms and can induce a quantum phase transition from the superfluid phase of a Bose-Einsteincondensate to a Mott insulator phase. In this new state of matter it should now be possible to investigate fundamental problems of solid-state physics, quantum optics and atomic physics. For a weak optical lattice the atoms form a superfluid phase of a Bose-Einstein condensate. In this phase, each atom is spread out over the entire lattice in a wave-like manner as predicted by quantum mechanics. The gas of atoms may then move freely through the lattice. For a strong optical lattice the researchers observe a transition to an insulating phase, with an exact number of atoms at each lattice site. Now the movement of the atoms through the lattice is blocked due to therepulsive interactions between them. Some physicists have been able to show that it is possible to reversibly cross the phase transition between these two states of matter. The transition is called a quantum phase transition because it is driven by quantum fluctuations and can take place even at temperatures of absolute zero. These quantum fluctuations are a direct consequence of Heisenberg’s uncertainty relation. Normally phase transitions are driven by thermal fluctuations, which are absent at zero temperature. With their experiment, the researchers in Munich have been able to enter a new phase in the physics of ultracold atoms. In the Mott insulator state theatoms can no longer be described by the highly successful theories for Bose-Einstein condensates. Now theories are required that take into account the dominating interactions between the atoms and which are far less understood. Here the Mott insulator state may help in solving fundamental questions of strongly correlated systems, which are the basis for our understanding of superconductivity. Furthermore, the Mott insulator state opens many exciting perspectives for precision matter-wave interferometry and quantum computing.What does the passage mainly discuss?A.Bose-Einstein condensation.B.Quantum phase transitions.C.The Mott insulator state.D.Optical lattices.2、What will the scientists possibly do by reaching the new state of matter in atomic physics?A.Store a Bose-Einstein condensate in three-dimensional lattice of microscopic light traps.B.Increase the strength of the lattice.C.Alter the properties of the gas of atoms.D.Examine fundamental problems of atomic physics.3、Which of the following is NOT mentioned in relation to aweak optical lattice?A.The atoms form a superfluid phase of a Bose-Einstein condensate.B.Each atom is spread out over the entire lattice.C.The gas of atoms may move freely through the lattice.D.The superfluid phase changes into an insulating phase.4、What can be said about the quantum phase transition?A.It can take place at temperatures of absolute zero.B.It cannot take place above the temperatures of absolute zero.C.It is driven by thermal fluctuations.D.It is driven by the repulsive interactions between atoms.5、The author implies all the following about the Mott insulator state EXCEPT that______.A.the theory of Bose-Einstein condensation can’t possibly account for the atoms in the Mott insulator stateB.not much is known about the dominating interactions between the atoms in the Mott insulator stateC.it offers new approaches to exact quantum computingD.it forms a superfluid phase of a Bose-Einstein condensate6、 (B) Gene therapy and gene-based drugs are two ways we would benefit from our growing mastery of genetic science. But therewill be others as well. Here is one of the remarkable therapies on the cutting edge of genetic research that could make their way into mainstream medicine in the c oming years. While it’s true that just about every cell in the body has the instructions to make a complete human, most of those instructions are inactivated, and with good reason: the last thing you want for your brain cells is to start churning out stomach acid or your nose to turn into a kidney. The only time cells truly have the potential to turn into any and all body parts is very early in a pregnancy, when so-called stem cells haven’t begun to specialize. Most diseases involve the death of healthy cells—brain cells in Alzheimer’s, cardiac cells in heart disease, pancreatic cells in diabetes, to name a few; if doctors could isolate stem cells, then direct their growth, they might be able to furnish patients with healthy replacement tissue. It was incredibly difficult, but last fall scientists at the University of Wisconsin managed to isolate stem cells and get them to grow into neural, gut, muscle and bone cells. The process still can’t be controlled, and may have unforeseen limitations; but if efforts to understand and master stem-cell development prove successful, doctors will have a therapeutic tool of incredible power. The same applies to cloning, whichis really just the other side of the coin; true cloning, as first shown, with the sheep Dolly two years ago, involves taking a developed cell and reactivating the genome within, resenting its developmental instructions to a pristine state. Once that happens, the rejuvenated cell can develop into a full-fledged animal, genetically identical to its parent. For agriculture, in which purely physical characteristics like milk production in a cow or low fat in a hog have real market value, biological carbon copies could become routine within a few years. This past year scientists have done for mice and cows what Ian Wilmut did for Dolly, and other creatures are bound to join the cloned menagerie in the coming year. Human cloning, on the other hand, may be technically feasible but legally and emotionally more difficult. Still, one day it will happen. The ability to reset body cells to a pristine, undeveloped state could give doctors exactly the same advantages they would get from stem cells: the potential to make healthy body tissues of all sorts. And thus to cure disease.That could prove to be a true “miracle cu re”.What is the passage mainly about?A.Tomorrow’s tissue factory.B.A terrific boon to medicine.C.Human cloning.D.Genetic research.7、 According to the passage, it can be inferred that which of the following reflects the author’s opinion?A.There will inevitably be human cloning in the coming year.B.The potential to make healthy body tissues is undoubtedly a boon to human beings.C.It is illegal to clone any kind of creatures in the world.D.It is legal to clone any kind of creatures in the world except human.8、Which of the following is NOT true according to the passage?A.Nearly every cell in the human brain has the instructions to make a complete human.B.It is impossible for a cell in your nose to turn into a kidney.C.It is possible to turn out healthy replacement tissues with isolated stem cells.D.There will certainly appear some new kind of cloned animal in the near future.9、All of the following are steps involved in true cloning EXCEPT_______.A.selecting a stem cellB.taking a developed cellC.reactivating the genome within the developed cellD.resetting the developmental instructions in the cell to its original state10、The word “rejuvenated” in para. 5 is closest in meaning to_______.A.rescuedB.reactivatedC.recalledD.regulated参考答案：【一、阅读理解题】1~5CDDAD6~10DBBA。
2维声学黑洞与1维流体的对应研究
2维声学黑洞与1维流体的对应研究杨晓焕;颜骏;陈海霖;余毅【摘要】The correspondence relationship between two-dimensional black holes and one-dimensional fluid is studied in this paper.The expression of acoustic metric is derived according to the hydromechanics equations,and we obtain some exact black hole solutions in two-dimensional dilaton gravity model.Moreover,the energy density ρ,speed ν and drive potential f in one-dimension fluid are calculated and the physical properties of these fluid parameters are also analyzed and discussed.%研究2维声学黑洞与1维流体的对应关系,在流体力学方程的基础上推导声学度规的表达式,获得了2维dilaton引力模型中的一些精确黑洞解.计算了1维流体中的能量密度ρ,速度ν和驱动势f,还分析和讨论了这些流体参量的物理性质.【期刊名称】《四川师范大学学报（自然科学版）》【年(卷),期】2016(039)006【总页数】7页(P875-881)【关键词】2维引力;声学黑洞;引力-流体对应【作者】杨晓焕;颜骏;陈海霖;余毅【作者单位】四川师范大学物理与电子工程学院, 四川成都 610066;四川师范大学物理与电子工程学院, 四川成都 610066;四川师范大学物理与电子工程学院, 四川成都 610066;四川师范大学物理与电子工程学院, 四川成都 610066【正文语种】中文【中图分类】O351.2高维时空中的引力方程难以求解，2维引力中的场方程相对简单，因此2维引力可以为研究高维空间中的广义相对论提供理想实验室.2维引力与理论物理中的弦理论和共形场论有密切关系,还与纯数学理论中的几何拓扑学和调和映照有一定的联系.近年来,2维引力作为一种Toy模型,有助于人们对4维引力模型及其量子化深人理解,因此对它的研究具有积极的理论意义.在20世纪80年代初,物理学家已开始着手研究2维引力及其相关的量子Liouville理论,分别在光锥规范、共形规范下深入研究了2维引力问题,并在矩阵模型的框架下获得了2维量子引力模型的一些精确解.这些解极大地丰富了人们对弦理论、共形场论甚至临界现象的进一步理解,因此,从各个不同侧面深入研究2维引力模型就显得非常必要了.2维引力的物理性质已经得到了充分研究[1-12].描述2维时空中黑洞的精确的共形场论是在WZW模型中发展起来的，2维dilation引力理论已经被广泛地应用于研究黑洞的蒸发问题.此外，2维高阶引力模型、2维引力的可积与可解性质已分别在共形规范和光锥规范下得到分析.另一方面，在平坦的2维时空中存在一种非线性标量场的作用模型,即sine-Gordon模型,这一模型中存在孤子解.因此,人们自然希望研究2维引力和sine-Gordon物质场的相互作用，通过CGHS模型的框架研究sine-Gordon物质场作用下的黑洞解.文献[13-16]发现了2维引力模型中的sine-Gordon孤子解和sinh-Gordon时空带解.由于天体物理中黑洞表面温度极低，其霍金辐射非常微弱，因此目前尚未观察到这一物理效应.另外，无论在早期宇宙残留物中寻找小型黑洞或者是在粒子物理对撞机中制造出微黑洞，在短期内这些探索的成功机率都很小.由于声波在不均匀流体中的传播性质和光波在弯曲空间中的传播性质非常相似，所以在流体力学实验中可较容易模拟黑洞的物理性质.流体力学的基础方程是连续性方程和Euler方程[17])ν]=F,式中，ρ为流体密度，ν是流体速度，F=-P,P是压力，F是压力P产生的力密度，这时流体假定没有粘滞性.根据速度矢量的关系式(1/2ν2)=(ν·)ν，引入速度式ν=-φ,那么Euler方程变为p)-).再定义h=p/ρ,那么Euler方程约化为在流体中当振动很小和速度很小时，那么流体中的压强和密度相对变化也很小，这时p和ρ可以表示为p=p0+p1,ρ=ρ0+ρ1,p0和ρ0分别代表流体中平衡密度和平衡压强，p1和ρ1表示围绕平衡的微小涨落.当涨落的二阶小量忽略后，那么线性化处理后的速度势所满足的波动方程为∂t2φ=c22φ,这里c表示声速.根据连续性方程(1)式得到∂t ρ1+·(ρ1ν0+ρ0ν1)=0.并且h(p)可展开为如果忽略流体的牛顿引力势和外力的驱动，那么只剩下流体压强产生的作用力，这时利用(7)式对Euler方程(4)进行线性化处理后得到对方程φ0)2=0,φ1=0.方程(9)式可以重新表示为这时有φ1+ν0·φ1),现将(11)式代入(6)式可以得到如下波动方程φ1+ν0·φ1))+·(-ρ0φ1+φ1+ν0·φ1))=0,这一二阶偏微分方程可以描述线性化标量势φ1的传播规律，即这一方程确定了声学扰动的传播形式.为了将流体方程和引力理论联系起来首先定义如下的局域声速再构造一个4×4矩阵根据(13)式和(14)式那么波动方程(12)式可以重新写成这时定义弯曲时空上的达朗贝尔算符为式中这里g=det(gμν)是度规的行列式，并且有根据矩阵(14)式的行列式可以得到因此有所以得到了如下形式的逆声学度规那么声学度规应为这时声学度规的间隔形式可以表示为].2维dilaton引力模型的作用量[18-20]为2b(φ)2-8πG(-V(φ)Λ)},式中，ψ是辅助场，φ是dilaton场，V(φ)是势函数，G是牛顿常数，b、Λ为常数作用量(24)式对应的辅助场方程为引力场方程为ψ)2)+gμν2ψ-μνψ=8πGTμν,φ)-2b(μφνφφ)2),dilaton场方程为这时2维静态度规选择为[21-29]其中，α(x)是度规因子.此时引力物质系统方程组化为α″=-8πGΛV(φ),(αφ命题 1 dilaton场φ和度规α有如下关系：式中，X0是积分常数，下面证明这一关系式.用αφ′乘以(32)式两边得对(31)式两边求导得将(34)式与(35)式联立消去dV/dx后得即φ又因为并且‴-2α′α″)=αα‴.由(37)～(39)式可得φ′)2]=即所以命题1证毕.命题 2 当标量场势能V(φ)=e-2aφ时有式中a是势能常数，下面证明这一关系式成立.当标量场势能取为V(φ)=e-2aφ时,(31)式变为将上式整理得又因为并且φ′)2]=所以即那么(47)式变为式中β=b/a2.化简上式得所以命题2证毕.命题 3 当β=p/(p+2)=1(p→∞)，场方程有如下的黑洞度规和dilaton场解φ(51)式中A、C、E是积分常数，下面证明这一命题成立.由(50)式得α″=-8πGΛe-2aEe-Cx,α‴=8πGΛCe-2aEe-Cx.将α′、α″、α‴带入式命题2中的(41)式的左端得同理，将α″带入(43)式得所以命题3证毕.下面说明命题3得到的2维度规可以描述一种黑洞，取B=8GΛπe-2aE/C2则度规(50)式化为当C>0,x→-∞或C<0,x→+∞时，可知黑洞度规出现奇异性质；当xC=-ln(A/B)/C，同样可知黑洞度规也出现奇异性质，根据曲率R=-α″可计算出不同时空奇点处的曲率分别为所以xC表示黑洞的视界位置，可以为正值或负值.标量场φ(x)在奇点处的性质为φ因此，这个解可以描写2维黑洞，此黑洞的真正奇点位于x→±∞处.黑洞的ADM 质量定义为φ′)2].K是积分常数，可以证明解析解(50)式和(51)式对应的2维黑洞质量为这里，A、C>0,当a>0,由(51)式知系数C越大，φ(x)越强，那么对应的黑洞质量越大.取C=1，E=0，8πG=1，Λ=1，则(50)和(51)式化为命题 4 对(29)式中黑洞度规和时空坐标做如下变换，则黑洞度规可化为声学度规的形式,下面证明这一命题成立.如果使用如下变换[30]则有dx2=ρ02dx2,于是有这时声学度规的表达式为2v0dxdt+dx2].这一度规恰好对应于(23)式中i=j=1的特殊情况.由(65)式可以看出当2M=J时，黑洞的视界为于xc=-ln2M处，这时其对应的声学视界位于c=v0处.命题 5 1维流体力学中的Euler方程和连续方程为ρ0(x)v0(x)A(x)=常数,式中，ρ0是流体密度，p是流体压强，v0是流体速度，f是驱动外力的势，A(x)通量截面，下面证明这一命题.引入如下变换则(70)和(71)式等价于如下方程组这时讨论一种特殊情况，当声速c=常数时有如下关系式并且另外以及将(75)～(78)式代入(73)式命题即可得这一等式成立.另外有(70)式容易得到(71)式，所以命题5成立,再根据Euler方程(70)式和连续性方程(71)式可求出1维流体中的能量密度ρ0(x)、速度v0(x)和驱动势f(x)的如下表达式式中，s是与流体通量A有关的常数，f0是积分常数.当黑洞质量取为M=1/2,声速取为c=1，常数取为s=1，f0=1时，那么可以作出黑洞视界外流体参量，如图1～3所示.当黑洞质量取定时，计算结果表明流体密度随空间坐标增大而增大，而流体速度随空间坐标增大而减小.另外，流体驱动势也随空间坐标增大而减小.根据流体方程组解可以直接看出，当空间坐标不变时，随着黑洞质量的增大，流体密度变大，对应的流体速度变小.本文首先根据流体力学中的连续方程和Euler方程分析了流体中的微小振动，这种振动所对应的速度势满足的方程可以描述声波现象，对流体方程组进行线性化处理后得到密度、压强和速度势涨落满足的波动方程，这一方程也可描述标量势的传播规律.当定义适当的度规张量后，那么波动方程就可化为一个弯曲时空下的标量场方程，由此可以导出声学度规的表达式.其次，本文推导了2维dilaon引力模型中的场方程组，根据3个命题进一步获得了2维度规的解析解，通过物理分析后表明这一解可以描述2维时空中的黑洞，其时空奇点为无穷远处，而视界的位置由势能强度Λ和a所决定.经过适当的坐标变换后发现2维黑洞度规可以变化为对应的声学度规，这时2维引力场方程可与1维流体中的Euler方程发生联系,因此可以求出声学黑洞中的流体密度、压强和驱动势的解析解.当黑洞质量取为定值时，本文对流体速度和驱动势作出了数值图形，并讨论了这些流体参量在空间中的变化规律.另外，2维定态时空中霍金温度定义为4πTH=(dα/dx)|x=xc,代入视界坐标xc=-ln 2M便可求出霍金温度为TH=M/2π,因此2维时空中黑洞质量越大，霍金温度越高，最近，W. G. Unruh 进一步分析了在实验室测量霍金辐射的可能性[31-32]，所以通过流体力学中的一个小型平台可以模拟黑洞中的各种比较复杂的物理现象[33-35].【相关文献】[1] KATANAEV M O, VOLOVICH I V. String model with dynamical geometry and torsion[J]. Phys Lett,1986,B175(4):413-415.[2] KATANAEV M O, VOLOVICH I V. Two dimensional gravity with dynamical torion and strings[J]. Ann Phys,1990,197(1):1-32.[3] 颜骏,胡诗可. 两维量子引力中的一种可解模型[J]. 高能物理与核物理,1991,15(7):598-605.[4] SCHMIDT H J. Scale-invariant gravity in two dimensions[J]. J MathPhys,1991,32(6):1562-1566.[5] 颜骏,陶必友,胡诗可. 两维引力中的一种可积模型[J]. 高能物理与核物理,1993,17(4):322-328.[6] SOLODUKHIN S. On exact integrability of 2-D Poincare gravity[J]. Mod PhysLett,1994,A9(30):2817-2823.[7] KUMMER W, WIDERIN P. Non-einsteinian gravity in d=2:symmetry and current algebra[J]. Mod Phys Lett,1994,A9(15):1407-1413.[8] QIUX M, YAN J, PENG D Y . String theory and an integrable model in two-dimensional gravity with dynamical torsion[J]. 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A two-dimensional Brans-Dicke star model with exotic matter and dark energy [J]. Commun Theor Phys,2009,52(6):1016-1018.[28] 李季根,颜骏,邹伯夏,苏文杰. 奇异物质与暗能量作用的sine-Gordon孤子星模型[J]. 物理学报,2011,60(5):050301.[29] SU W J, YAN J. A sine-Gordon soliton star model with a mix of dark energy and fermi matter[J]. Can J Phys,2012,90:1279-1285.[30] CADONI M. Acoustic analogues of black hole singularities[J]. Phys Rev,2005,D72:0840.[31] UNRUH W G. Experimental black hole evaporation[J]. Phys Rev Lett,1981,46(21):1351-1353.[32] UNRUH W G. Has Hawking radiation been measured[J]. Found Phys,2014,44:532-545.[33] BARCELO C, LIBERATI S, VISSER M. Analogue gravity[J]. Living Rev,Relativity,2011,14:3.[34] FACCIO D. Analogue Gravity Phenomenology[M]. Heidelberg:Springer-Verlog,2013:31-47.[35] VOLOVIK G E. The Universe in a Helium Droplet[M]. Oxfod:Oxford UniversePress,2003:1-15.。
一颗原子的时空之旅英文摘抄
一颗原子的时空之旅英文摘抄In the vast expanse of the universe, amidst the swarming dance of stars and galaxies, there exists a tiny yet remarkable entity—an atom. Its journey through the vastness of space and the depth of time is a story that weaves the threads of quantum mechanics, the secrets of matter, and the grandeur of the cosmos.Imagine this atom, a mere speck of matter, existing in a state of quantum superposition. It floats within the quantum foam of spacetime, a landscape rife with fluctuations and uncertainties. Its existence is not fixed, but rather probabilistic, existing as a cloud of probabilities, a haze of potentialities.As time ticks by, the atom's quantum state collapses, and it materializes into a tangible particle. Its existence solidifies, and it embarks on its odyssey through the universe. Carried by the winds of the interstellar medium, it traverses vast distances, crossing the thresholds ofstar systems and galaxies.Its journey is not without peril. The atom may encounter the fierce radiation of supernovae, the destructive forces of black holes, or the gentle embrace of interstellar dust clouds. Each encounter tests its resilience, and yet, the atom perseveres, its structure intact, its essence unchanged.As it traverses the universe, the atom witnesses the birth and death of stars, the birth and evolution of planets, and the emergence of life itself. It becomes a silent witness to the grand narrative of the cosmos, a tiny player in the grand drama of existence.Eventually, the atom's journey leads it to the surface of a planet, where it joins the tapestry of matter that构成s the very fabric of life. It becomes a part of a leaf, a drop of water, a grain of sand—an integral part of the intricate web of ecosystems.Here, the atom's journey transforms. It interacts with other atoms, swapping electrons, sharing energy, and building complex structures. Its role in the grand scheme of the universe becomes even more profound. It becomes abuilding block of life, a contributor to the diversity and complexity of the biosphere.And then, the cycle continues. As the atom decays and transforms, it releases its energy back into the universe, becoming a photon of light, a particle of radiation, or a fragment of matter once again. Its essence, however, remains unchanged—a tiny speck of matter, a remnant of the quantum foam, a witness to the temporal odyssey of existence.The temporal odyssey of an atom is a mirror reflecting the grandeur and complexity of the universe. It is a story of resilience, transformation, and interconnectedness—a reminder that even the smallest particle of matter plays a crucial role in the vast scheme of existence.**一颗原子的时空之旅**在宇宙的广袤无垠中，星辰与星系交织成一幅绚烂的画卷。
华南师范大学凝聚态物理专业导师简介
凝聚态物理专业导师简介（以姓氏拼音为序）艾保全，男，副教授，硕士生导师。
主研方向是分子马达运动机制、低维材料（纳米）的能量和热的传输、生物非线性噪声效应。
2004年毕业于中山大学，获博士学位。
随后在香港大学及香港浸会大学从事博士后研究工作，2005年9月起华南师范大学教师。
主要从事理论生物物理的研究，包括生物非线性系统中的噪声效应，肌肉运动微观机制，分子马达的运动机制（线性和旋转马达）以及低维材料的热传导等领域的研究。
他以第一作者在Journal of physical chemistry B, Journal of Chemical physics, Physical Review E等 SCI收录国际重要期刊上发表论文32篇。
论文被引用200多次，其中关于肿瘤生长过程中噪声控制的论文被它引50次,关于微管中粒子定向输运的论文被著名综述期刊Reviews Modern of physics引用并介绍我们的相关工作。
主持国家自然科学基金和广东省自然科学基金各一项，并和澳门科技大学，日本产业科技大学以及香港浸会大学等研究组从事合作研究。
主要荣誉：2006年华南师范大学科研优秀工作者.2006年入选广东省“千百十”人才工程培养对象.2005年获得广东省优秀博士学位论文称号.研究兴趣：1.分子马达的研究: 研究分子马达的运动机制，线性分子马达，旋转分子马达，以及分子马达运动方向的控制，效率及其最大值研究，考虑量子效应的分子马达的运动。
2.低维材料（纳米）的能量和热的传输:一维纳米系统中热传导性质的研究及其应用的研究;热二极管,三级管及热(声子)操纵和控制的研究.3.生物非线性系统中的噪声效应: 基因选择过程中的噪声效应; 噪声对肿瘤生长的影响; 细菌生长过程中的噪声效应。
主持科研项目：1.国家自然科学基金2007.1-2009.12,分子马达运动机制的理论研究（旋转）.2.广东省自然科学基金2007.1-2008.12，线性分子马达运动机制的基础研究.发表代表性论文(if>2.0)1.Bao-quan Ai and Liang-Gang Liu, Brownian pump in nonlinear diffusive media,The Journal of Physical Chemistry B 112(2008)95402.Bao-quan Ai and Liang-Gang Liu, Phase shift induces currents in a periodictube, Journal of Chemical Physics 126(2007) 2047063.Bao-quan Ai and Liang-Gang Liu, A channel Brownian pump powered by anunbiased external force, Journal of Chemical Physics , 128 (2008)0247064.Bao-quan Ai and Liang-Gang Liu, The tube wall fluctuation can induce a netcurrent in a periodic tube, Chemical Physics, 344 (2008)185-188.5.Bao-quan Ai and Liang-Gang Liu, Thermal noise can facilitate energytransformation in the presence of entropic barriers, Phys. Rev.E 75(2007)061126.6.Bao-quan Ai and Liang-Gang Liu, Reply to comment on correlated noise in alogistic growth model, Phys. Rev. E 77(2008)013902.7.Bao-quan Ai and Liang-Gang Liu, Facilitated movement of inertial Brownianmotors driven by a load under an asymmetric potential, Phys. Rev.E 76(2007)042103.8.Bao-quan Ai and Liang-Gang Liu, Current in a three-dimensional periodictube with unbiased forces, Phys. Rev. E 74(2006) 051114.9.Bao-quan Ai, Liqiu Wang and Liang-Gang Liu, Transport reversal in a thermalratchet, Phys. Rev. E 72, (2005) 031101.10.Bao-quan Ai, Xian-ju Wang, Guo-tao Liu and Liang-Gang Liu, Correlatednoise in a logistic growth model, Phys. Rev. E 67 (2003)022903.11.Bao-quan Ai, Xian-Ju Wang, Guo-Tao Liu, and Liang-Gang Liu, Efficiencyoptimization in a correlation ratchet with asymmetric unbiased fluctuations, Phys.Rev. E 68 (2003)061105.12.Xian-Ju Wang, Bao-quan Ai, Liang-Gang Liu, Modeling translocation ofparticles on one-dimensional polymer lattices，Phys. Rev. E 64, (2001)906-910.13.Bao-quan Ai and Liang-Gang Liu, Stochastic resonance in a stochastic bistablesystem,Journal of Statistical Mechanics: theory and experiment (2007)P02019.14.Bao-quan Ai and Liang-gang Liu,Efficiency in a temporally asymmetricBrownian motor with stochastic potentials, Journal of Statistical Mechanics: Theory and Experiment (2006)P09016.15.Bao-quan Ai, Guo-Tao Liu, Hui-zhang Xie and Liang-Gang Liu, Efficiency andCurrent in a correlated ratchet, Chaos 14(4)(2004)95716.Bao-quan Ai, Liqiu Wang and Liang-Gang Liu, Flashing motor at hightransition rate, Chaos, solitons & fractals 34( 2007 ) 1265-1271.17.Bao-quan Ai, and Liang-gang Liu, Transport driven by a spatially modulatednoise in a periodic tube, Journal of Physics: Condensed Matter 19(2007) 266215.Email：aibq@陈浩，男，教授，硕士生导师。
宇宙的由来介绍英语作文
宇宙的由来介绍英语作文Title: The Origin of the Universe。
Introduction:The universe, an unfathomable expanse of space, has captivated human curiosity for millennia. In our quest to comprehend its origins, we embark on a journey through time and space, exploring the theories that seek to explain the cosmic genesis.The Big Bang Theory:At the heart of modern cosmology lies the Big Bang theory, a paradigm-shifting concept that traces the universe's birth to a singular, cataclysmic event. According to this model, around 13.8 billion years ago, all matter, energy, space, and time were compressed into an infinitely dense point known as a singularity. In an incomprehensibly rapid expansion, this singularity erupted,giving rise to the universe as we know it.In the aftermath of the Big Bang, the universe was a seething, hot cauldron of energy. As it expanded and cooled, elementary particles formed, eventually coalescing into atoms. Over eons, these atoms condensed into stars, galaxies, and the myriad celestial structures that adornthe cosmos.Cosmic Inflation:Inflation theory expands upon the Big Bang model, positing a brief but exponentially rapid expansion of the universe in its earliest moments. Proposed by physicistAlan Guth in the 1980s, inflationary cosmology reconciles observed cosmic uniformity with the apparent isotropy ofthe universe. It explains why the universe appears homogeneous on large scales despite originating from a tiny, highly non-uniform state.Inflation suggests that a repulsive gravitational force drove the universe to expand exponentially, smoothing outirregularities and setting the stage for the subsequent evolution of cosmic structures. While still a subject of ongoing research and debate, inflationary cosmology offers profound insights into the early universe's dynamics.Multiverse Hypothesis:Beyond our observable universe lies the tantalizing possibility of a multiverse—a vast ensemble of parallel universes with their own distinct properties and laws of physics. The concept of a multiverse emerges from various theoretical frameworks, including string theory and quantum mechanics.In some multiverse models, each universe spawns from a parent universe through processes like cosmic inflation or quantum fluctuations. Each universe may exhibit different physical constants, dimensions, or even fundamental forces, leading to a staggering diversity of cosmic landscapes.While speculative, the multiverse hypothesis offers a compelling explanation for the fine-tuning of ouruniverse's parameters, raising profound questions about the nature of existence and our place within the cosmic tapestry.Conclusion:The quest to unravel the mysteries of the universe's origin continues to inspire awe and wonder in humanity. From the fiery crucible of the Big Bang to the speculative realms of cosmic inflation and the multiverse, our understanding of the cosmos undergoes constant evolution.As we peer ever deeper into the cosmic abyss, we are reminded of the profound interconnectedness of all things and the enduring quest for knowledge that drives us to explore the vast reaches of space and time. In the grand tapestry of existence, the origin of the universe stands as a testament to the boundless curiosity and ingenuity of the human spirit.。
南开大学光子学课程讲义2-2-1-QuantumOptics
光是一种波！
Faraday and Maxwell
Faraday (1840,英国) introduces the concepts of electric and magnetic fields « lines of forces » existing in any point of space
Introduction
Does light consist in waves or particles ?
18th century : Newton 19th century : Fresnel, Maxwell... 1900s : Planck, Einstein 1920s : Quantum mechanics 1950s : Quantum Electrodynamics 1960s : Quantum Optics
Some problems remain
The spectral behaviour of black body radiation is not understood :
u( )
why
the decrease at high frequency ?
Position of spectral lines
光子学基础 -2
Quantum Theory of Light
光量子理论
Old Quantum Theory of Light
早期的光量子理论
• History Electromagnetism Planck and Einstein Quantum Mechanics Quantum Electrodynamics Quantum Optics
用英文的五句话解释薄记循环流程
用英文的五句话解释薄记循环流程The"薄记循环流程"(Feynman Loop Diagram)is a concept from quantum field theory,named after physicist Richard Feynman,who used it to visualize particle interactions in the context of quantum electrodynamics.Here are five sentences in English explaining the Feynman Loop Diagram process:1.Conceptualization:The Feynman Loop Diagram represents the exchange of virtual particles between charged particles,such as electrons and photons,illustrating the interactions that occur at the quantum level.2.Visualization:These diagrams are graphical representations where lines represent particle paths,and vertices indicate interactions,allowing physicists to calculate the probabilities of different interaction outcomes.3.Quantum Corrections:Feynman diagrams,including loop diagrams,are used to calculate quantum corrections to the classical behavior of particles,accounting for the effects of quantum fluctuations.plexity and Accuracy:The more loops a Feynman diagram has,the more complex it is,and the higher the order of the quantum correction it represents,leading to more accurate predictions of physical phenomena.5.Fundamental Understanding:Despite their seemingly simple appearance, Feynman Loop Diagrams provide a deep insight into the fundamental forces and interactions that govern the behavior of particles in the quantum realm.These sentences offer a brief overview of the Feynman Loop Diagram process, highlighting its significance in the field of quantum physics.。
真空衰变（Vacuumdecay）
真空衰变（Vacuum decay）abstractPlease describe the entry in a few words and add a summary right away. Vacuum decay - the basic principle of introducing quantum theory is Werner Haisenberg (Werner, Heisenberg)Uncertainty principle. According to this principle, all attributes of a quantum object are not fully determined. For example, a photon or an electron cannot have definite positions and definite momenta at the same time. For a certain moment, it is impossible to have definite energy. What we are concerned about here is energy uncertainty. Although the energy in the macrocosm is conserved (it neither creates nor disappears), the law fails in the Ahara Koko domain. Energy can spontaneously occur unpredictable changes. The shorter the time interval considered, the greater the quantum random fluctuations. In fact, particles can borrow energy from somewhere we don't know, as soon as the energy is returned. Heisenberg uncertainty principle requires accurate mathematical form the bulk of the energy lending must be quickly returned, and a small amount of borrowing can be kept for a long time.Vacuum decay - more detailsEnergy uncertainty leads to some strange effects, like particles such as photons can suddenly be created out of nothing, but later it immediately disappear again, the probability of occurrence of this phenomenon is a strange effect in the. The particles depend on borrowed energy and therefore survive on borrowed time. We do not see them because they are justlightning flashes, but they do leave traces of their existence in the characteristics of the atomic system, which can be measured. In fact, the usual vacuum is indeed filled with streams of such instantaneous particles, not only photons but also electrons, protons, and other particles. In order to distinguish the instantaneous particles from the permanent particles which we know more, the former is called the imaginary particle, while the latter is called the real particle.Except for the instantaneous, the imaginary particles are exactly the same as the real particles. In fact, if in some way from the outside enough energy to repay the Heisenberg energy borrowing, so it is possible to upgrade the virtual particle real particles, and there is no difference with other species of real particles. For example, a virtual electron can only exist in a typical case10-21 seconds. In its short lifetime, the virtual electron is not stationary; it can pass 10-11 centimeters before it disappears (compared to an atomic diameter of about 10-8)Cm). If the virtual electron gets energy in such a short time (say, from the electromagnetic field), it does not necessarily disappear, but can continue to exist as a completely ordinary electron.Although they can not see these imaginary particles, they are really in the vacuum. This is not only because the vacuum contains a potentially permanent library, but also because although they occur in half true half empty form, the quantum entity of the phantom would still leave traces of theiractivities, but also can detect. One of the effects of virtual photons, for example, is a very small deviation of the energy levels of an atom. They also make minute changes in the electron magnetic moment. These minor but important changes have been accurately measured by spectroscopic techniques.Given that subatomic particles are generally free to move, but that they are subject to various forces associated with the particle type, the above simple quantum vacuum image is to be modified. This force also acts on the corresponding virtual particles. As a result, there may be more than one vacuum. The existence of many possible quantum states is a universal feature of quantum physics. The atomic energy levels are best known. Here, an electron orbiting an atom can have some very definite states of energy, and these states correspond to definite energies. The lowest level is called the ground state, and it is stable. Higher energy levels are called excited states, and they are unstable. If an electron breaks into a higher energy state,It will go down and return to the ground state, and there are more than one way to transition. This excited state has a definite half-life of decay.The same principle applies to vacuum. It can have one or more excited states. These excited states have different energies, but their actual appearances are exactly the same, that is, vacuum. The lowest energy state, that is, the ground state, sometimes called the real vacuum, reflects the fact that it is stable, and corresponds roughly to the vacuum region of today's universe. The excitation vacuum is called the pseudo vacuumstate.It should be said that pseudo vacuum is still a purely theoretical idea, and its nature depends to a great extent on the specific theory used. But the pseudo Vacuum States naturally appear in all the theories that attempt to unify the forces of nature at present. The basic forces now recognized appear to be4: familiar with the daily life of the gravitation and electromagnetic force, and two kinds of short-range nuclear forces, weak and strong. The list used to be longer. For example, electricity and magnetism have been regarded as very different things,The unified process of electricity and magnetism began in the early nineteenth Century. At that time, Hans Christian Oster (Hans, Christian, Oersted) found that the current produced a magnetic field, and Michael FaradMichel Faraday found that the moving magnet produced electricity. It is clear that electricity and magnetism are intrinsically related. But, until 1850s, James Clark MaxwellJames Clerk MaxwellOnly the details of the connection were indicated. Maxwell described these electromagnetic phenomena accurately through a set of mathematical equations, and predicted the existence of electromagnetic waves. It was not long before people realized that light was also an example of such waves, and thatother forms of waves, such as radio waves andX ray. Therefore, two different natural forces on the surface - power and magnetism - are the two manifestations of a single electromagnetic force, which have some of their own unique phenomena.In recent decades, this process of unification has been further developed. According to the current understanding of the electromagnetic force and the weak nuclear force is linked, is part of a single "weak force". Many physicists believe that, as part of the so-called "grand unification" theory, it will prove to be associated with electrical forces in the future. Not only that, allThe 4 forces may be synthesized at a sufficiently deep level into a single force.In an attempt to unify electroweak force and force some grand unified theory predicts a promising inflationary force. A key feature of these theories is that the pseudo vacuum energy is surprisingly large: typically, 1 cubic centimeter spaces contain10^87 Joule energy! Even the size of an atom will have the energy of 10^62 joules. A stimulated atom has only 10^-18The energy of about joules, compared to the latter, is negligible. Therefore, to stimulate the vacuum, requires a lot of energy, but in today's universe in which we hope will not find this state. On the other hand, once there are extremeconditions for the big bang, these figures are more telling.The enormous energy associated with a pseudo vacuum has a strong gravitational effect. This is because energy has mass, and Einstein has pointed it out for us, so it can be attracted by gravity like normal matter. The enormous power of quantum vacuum has great appeal: 1Cubic centimeter pseudo vacuum mass weighs 10^64 tons, which is about the mass of today's observable universe (about 10^48)) still big! Have no use for this abnormal gravity on inflation, which requires some kind of anti gravity process. But the enormous pseudo vacuum energy is associated with the same enormous pseudo vacuum pressure, and this pressure is wonderful. Normally, we don't see pressure as a source of gravity, but this pressure is a source of gravity. In a general object, the gravitational effect of an object's pressure is negligible compared to the gravitational effect of the mass of the body. Such as,The body weight of less than 1/1000000000 is produced by the pressure of the earth's interior, however, this effect does exist, and the system is in a huge pressure, the pressure can be compared with the quality of quasi gravity gravity.In the case of pseudo vacuum, there is tremendous energy, but also a huge pressure similar to it, and its mutual struggle for control over gravity, but the key nature is that the pressure is negative. The pseudo vacuum acts not as repulsion, but as attraction. Now negative pressure has a negative gravitationaleffect, which is called anti gravity. Thus, the gravitational attraction of pseudo vacuum comes down to the competition between the enormous attraction of its energy and the repulsive effects of its negative pressure. The final pressure won, the net effect is to produce a very large repulsive force, it can in an instant the universe burst. This is a huge thrust of inflation, so that the scale of the universe to speed the pace of eachDoubles in 10^-34 seconds.In its intrinsic nature, the pseudo vacuum is unstable. Like all excited quantum states, it decays to return to the ground state - the real vacuum. After dozens of ticks, it decays. As a kind of quantum process, it is bound to show discussed above can not avoid the unpredictability and random fluctuations, these properties are related with the Heisenberg uncertainty principle. This means that the decay is not homogeneous in the whole space, but there is fluctuation. Some theorists believe that these fluctuations may be the reason for the intensity fluctuations observed by cosmic background radiation detection satellites.In the pseudo vacuum decay after the universe regained its normal expansion speed, into the explosion by inflation. The energy enclosed in the pseudo vacuum is released and appears in the form of heat. The inflation produced the huge expansion of the universe cooled until the temperature is close to absolute zero, then inflation ended suddenly again heated to the universeOne thousand and twenty-eightExtreme high temperature. Today, the vast reservoir of heat has almost completely disappeared, leaving behind the cosmic background heat radiation. As a by-product of vacuum energy release, many imaginary particles in quantum vacuum acquire part of their energy and change into solid particles. The remains of these particles have survived until now, becoming 10^48 tons of materials that form you, me, the galaxy, and the entire observable universe.。
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Induced quantum metric fluctuations and the validity of semiclassical gravity
B. L. Hu and Albert Roura
Department of Physics, University of Maryland, College Park, Maryland 20742-4111
Hale Waihona Puke Enric Verdaguer
Departament de F´ ısica Fonamental and CER en Astrof´ ısica, F´ ısica de Part´ ıcules i Cosmologia, Universitat de Barcelona, Av. Diagonal 647, 08028 Barcelona, Spain We propose a criterion for the validity of semiclassical gravity (SCG) which is based on the stability of the solutions of SCG with respect to quantum metric fluctuations. We pay special attention to the two-point quantum correlation functions for the metric perturbations, which contain both intrinsic and induced fluctuations. These fluctuations can be described by the Einstein-Langevin equation obtained in the framework of stochastic gravity. Specifically, the Einstein-Langevin equation yields stochastic correlation functions for the metric perturbations which agree, to leading order in the large N limit, with the quantum correlation functions of the theory of gravity interacting with N matter fields. The homogeneous solutions of the Einstein-Langevin equation are equivalent to the solutions of the perturbed semiclassical equation, which describe the evolution of the expectation value of the quantum metric perturbations. The information on the intrinsic fluctuations, which are connected to the initial fluctuations of the metric perturbations, can also be retrieved entirely from the homogeneous solutions. However, the induced metric fluctuations proportional to the noise kernel can only be obtained from the Einstein-Langevin equation (the inhomogeneous term). These equations exhibit runaway solutions with exponential instabilities. A detailed discussion about different methods to deal with these instabilities is given. We illustrate our criterion by showing explicitly that flat space is stable and a description based on SCG is a valid approximation in that case.
arXiv:gr-qc/0402029v1 4 Feb 2004
I.
INTRODUCTION
In this paper we discuss the conditions underlying the validity of semiclassical gravity (SCG) emphasizing the role of metric fluctuations induced by the quantum matter sources. SCG is based on the self-consistent solutions of the semiclassical Einstein equation for a classical spacetime driven by the expectation value of the stress tensor operator of quantum matter fields. We propose a criterion based on stochastic semiclassical gravity [1, 2] and compare it with the recently proposed criterion by Anderson et al. [3] based on linear response theory. To do this we need to reexamine all the relevant factors old and new contributing to this issue, such as the reduction of higher derivative equations, intrinsic and induced fluctuations, and the relation between stochastic and quantum correlations. It also necessitates some clarification of the relation between our approach based on stochastic dynamics and the linear response approach, and differences with the approach pursued by Ford et al. [4, 5, 6, 7, 8, 9, 10, 11] based on the normal-ordering and integration-by-parts procedures on the stress-energy bitensor. The connection clarified and the bridges built in this process are beneficial to further development of the “bottom-up” approaches to quantum gravity starting from SCG [12, 13, 14, 15]. a. Metric fluctuations SCG accounts for the averaged back reaction of quantum matter fields and can be regarded as a mean field approximation that describes the dynamics of the mean spacetime geometry. However, it does not account for the effects of the fluctuations of spacetime geometry, which can also be very important. Consider, for instance, the metric fluctuations induced by the vacuum fluctuations of the inflaton field in inflationary cosmological models. Those fluctuations play a crucial role in the generation of the primordial inhomogeneities which gave rise to the large scale structure of the present universe as well as the observed anisotropies of the cosmic microwave background of radiation. This paper focuses on the effects of the quantum fluctuations of the metric. We will restrict our treatment to small metric perturbations around a given background geometry. (Of course, a full treatment of those fluctuations would require a complete theory of quantum gravity). We will linearize and quantize those metric perturbations including their interaction with the quantum matter fields. This can be described more precisely in terms of N identical matter fields. Our approach corresponds then to computing the quantum correlation functions for the metric perturbations to leading order in a 1/N expansion. In fact, one can show that the leading order contribution to the quantum correlation functions in a large N expansion is equivalent to the stochastic correlation functions obtained in the context of stochastic semiclassical gravity. Whereas SCG is based on the semiclassical Einstein equation with sources given by the expectation value of the stress tensor operator of the quantum matter fields, stochastic semiclassical gravity is based on the Einstein-Langevin equation, which has in addition sources due to the noise kernel. The noise kernel is the symmetrized connected part of the