Dark energy, dark matter and the Chaplygin gas

What is dark matter?
About 65 years ago, the first time that evidence of the existence of dark matter. At that time, Fulizizha Popovich found a large cluster of galaxies in the galaxy has a very high velocity, unless the quality of galaxy clusters is based on the number of calculations in which stars are more than 100 times the value, or cluster of galaxies can not bound lives of these galaxies. After decades of observation and analysis confirmed this. Although the nature of dark matter is still unknown, but by 80 years, accounting for about 20% of the energy density of dark matter to be widely accepted.
What is dark matter?
now we know that dark matter has become an important part of the universe. The total mass of dark matter is ordinary matter, 6.3 times the energy density in the universe, accounting for 1 / 4, but also important is that dark matter dominated the formation of cosmic structures. Now the nature of dark matter remains a mystery, but assuming it is a weak interaction of subatomic particles, then the resulting large-scale structure of the universe is consistent with the observations. Recently, however, the structure of galaxies and galaxy subanalysis shows that this assumption and the difference between observations, which at the same time provide a variety of possible dark matter theory was useless. Small-scale structure through the density, distribution, evolution and its environment studies can distinguish between these potential dark matter model for the nature of dark matter to bring a new dawn.

高三宇宙奥秘英语阅读理解30题1<背景文章>Black holes are one of the most fascinating and mysterious phenomena in the universe. A black hole is formed when a massive star collapses at the end of its life. The gravitational pull of a black hole is so strong that nothing, not even light, can escape from it.The formation of a black hole begins with the collapse of a massive star. As the star runs out of fuel, it can no longer support its own weight and begins to collapse. The collapse continues until the star reaches a critical density, at which point it becomes a black hole.Black holes have several unique characteristics. One of the most notable is their event horizon, which is the boundary beyond which nothing can escape. Another characteristic is their intense gravitational field, which can distort the space and time around them.Black holes can have a significant impact on the surrounding celestial bodies. They can attract and swallow nearby stars and planets, and their gravitational pull can also affect the orbits of other celestial bodies.Scientists are still working to understand black holes better. They use a variety of tools and techniques, such as telescopes and computer simulations, to study these mysterious objects. Despite significant progressin recent years, there is still much that we don't know about black holes.1. What is a black hole formed by?A. A small star collapsing.B. A massive star collapsing.C. A planet collapsing.D. A moon collapsing.答案：B。

(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;

Mass / Energy Density
Scientists have measured the density of the universe by studying clusters of galaxies. We can call it either mass density or energy density. Einstein proved that mass and energy are the same with his equation E = mc2. He’s also the guy to blame for this curved space-time stuff. (learn more)
But . . .
But outer stars do not rotate correctly! If gravity causes galaxies to rotate, as we assume it does, then outer stars should behave much like the planets of our solar system. Inner planets rotate faster and outer planets rotate slower. This is called Keplerian motion. (learn more) In galaxies, however, both inner and outer stars rotate at about the same speed.
The Universe
Cosmologists study the birth and death of the universe. They also study its properties including its shape. Recent observation indicate that the universe is flat.

The mysteries of the universe DarkmatterDark matter is one of the most intriguing and perplexing mysteries of the universe. It is a substance that makes up about 27% of the universe, yet it cannot be seen or detected directly. Scientists have been studying dark matter for decades, trying to understand its properties and how it interacts with the rest of the universe. Despite numerous experiments and observations, dark matter continues to elude detection, leaving scientists with more questions than answers. One of the main reasons why dark matter is so elusive is because it does not emit, absorb, or reflect any electromagnetic radiation, such as light. This means that it cannot be observed using traditional telescopes or other instruments that rely on detecting light. Instead, scientists have to rely on indirect methods, such as studying the gravitational effects of dark matter on visible matter, to infer its presence. This has made the study of dark matter incredibly challenging, as its properties remain largely unknown. The existence of dark matter was first proposed in the 1930s by Swiss astronomer Fritz Zwicky, who noticed discrepanciesin the velocities of galaxies within galaxy clusters. Zwicky observed that the visible matter in the clusters was not enough to account for the gravitational forces holding the galaxies together. He hypothesized that there must be some form of invisible matter, which he called "dunkle Materie" or dark matter, that was responsible for the missing mass. Since then, numerous studies and observations have provided evidence for the existence of dark matter, but its exact nature remains a mystery. One of the leading theories about dark matter is that it is made up of a new type of elementary particle that does not interact with electromagnetic forces. These particles, known as weakly interacting massive particles (WIMPs), are thought to only interact with gravity and the weak nuclear force, making them extremely difficult to detect. Scientists have been conducting experiments in deep underground laboratories and using sophisticated detectors to try to capture these elusive particles, but so far, no direct evidence of dark matter particles has been found. Another theory about dark matter is that itcould be composed of primordial black holes, which are small, dense objects thatformed in the early universe. These black holes would be invisible to telescopes but could still exert gravitational effects on visible matter. While this theory is less favored than the WIMP hypothesis, it is still being considered as a possible explanation for dark matter. Despite the lack of direct evidence, the presence of dark matter is crucial for our understanding of the universe. Without dark matter, galaxies would not have enough mass to hold themselves together, and the universe would look very different from what we observe today. Dark matter plays a vital role in shaping the large-scale structure of the universe, influencing the distribution of galaxies and the formation of galaxy clusters. Understanding dark matter is essential for our understanding of the universe's past, present, and future. In conclusion, dark matter remains one of the most enigmatic and challenging mysteries of the universe. Despite decades of research and numerous experiments, scientists have yet to directly detect this elusive substance. The study of dark matter continues to push the boundaries of our knowledge and understanding of the cosmos, forcing us to rethink our fundamental assumptions about the nature of the universe. As technology advances and new experiments are conducted, we may one day unlock the secrets of dark matter and unravel its mysteries. Until then, dark matter will continue to intrigue and fascinate scientists and laypeople alike, as we strive to uncover the hidden truths of the universe.。

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).。

想要了解的事物英语作文There are so many things in this world that I want to understand better. From the smallest particles that make up the universe to the grandest mysteries of the cosmos, the sheer vastness of human knowledge and the unknown is both humbling and exhilarating. Every day, new discoveries are being made that expand the boundaries of what we know, and I find myself constantly in awe of the incredible complexity and beauty of our reality.One of the areas I'm most fascinated by is the field of quantum physics. The counterintuitive behaviors of subatomic particles, like the fact that they can exist in multiple states simultaneously, have always captivated me. I would love to gain a deeper understanding of concepts like quantum entanglement, wave-particle duality, and the uncertainty principle. How can particles that are separated by vast distances instantly influence each other? What is the true nature of reality at the most fundamental level? These are the kinds of questions that keep me up at night, pondering the very fabric of existence.At the same time, I'm also deeply interested in the workings of the human mind and consciousness. How do our brains process information and give rise to the rich inner experience of thoughts, emotions, and sensations? What is the relationship between the physical brain and the subjective self? The field of neuroscience has made incredible strides in mapping the neural pathways and mechanisms underlying various cognitive functions, but there is still so much we don't understand about the emergent phenomenon of consciousness.I'm also endlessly curious about the origins and evolution of life on our planet. How did the first self-replicating molecules arise from the primordial soup, and what were the key evolutionary steps that led to the incredible diversity of life we see today? What are the fundamental principles and mechanisms that drive the evolution of species, and how do they interact with the ever-changing environment? The more I learn about biology and the history of life, the more I realize how little we truly know about the origins and mechanics of the living world.Another area that fascinates me is the vastness of the cosmos and our place within it. The scale of the universe, with its billions of galaxies separated by unimaginable distances, is almost incomprehensible to the human mind. What is the true nature of space and time? How did the universe begin, and what is its ultimatefate? Will we ever unravel the mysteries of dark matter and dark energy, the enigmatic components that seem to make up the majority of the universe? The more we learn, the more questions arise, and I'm driven to understand our place in this grand cosmic tapestry.Of course, there are also countless aspects of the human experience that I wish I could understand better. What are the roots of human behavior, and how do our evolutionary and cultural histories shape the way we think and act? How do we form meaningful connections with others, and what are the psychological and neurological underpinnings of love, empathy, and social bonds? What is the nature of consciousness, and how do subjective experiences emerge from the physical brain? These are the kinds of deep, existential questions that captivate me and drive my curiosity.Ultimately, I believe that the pursuit of knowledge and understanding is one of the most noble and rewarding endeavors a human being can undertake. The more we learn about the world and the universe around us, the more we realize how much we still have to discover. And with each new insight, we gain a deeper appreciation for the incredible complexity and beauty of our reality. It is a never-ending journey of exploration and discovery, and I am honored to be a part of it. There is simply so much I want tounderstand, and I can't wait to continue on this wondrous path of learning and growth.。

关于mysteries的英语作文Title: The Enigma of Mysteries.In the vast expanse of human existence, mysteries have always been an integral part of our lives. They are the unknown forces, the unexplained phenomena, and theenigmatic secrets that captivate our imaginations andprompt us to delve deeper into the recesses of the unknown. Mysteries have existed throughout history, across cultures, and in every sphere of human endeavour. They are as old as civilization itself and continue to fascinate us even inthe age of advanced technology and scientific understanding.The allure of mysteries lies in their nature of being both intriguing and perplexing. They are the puzzles that challenge our intellectual capabilities and push the boundaries of our understanding. They are the voids in the fabric of reality that beg for explanation, yet oftenremain enigmatic even in the face of the most diligent investigation.One of the oldest and most enduring mysteries is the question of the origin of life itself. How did the complex machinery of life emerge from the primordial soup of chemicals? How did the first cells come to be, and how did they evolve into the diverse array of organisms we see today? This mystery is compounded by the equally enigmatic question of consciousness how does the brain, a collection of neurons and synapses, give rise to the subjective experience of being alive?Another enduring mystery is the question of the universe's origin and ultimate fate. How did the universe begin with a cataclysmic event known as the Big Bang, and what lies beyond its expanding boundaries? What is the nature of dark matter and dark energy, the mysterious forces that seem to shape the universe's destiny? And what will become of the universe in the distant future will it continue to expand indefinitely, or will it collapse in upon itself in a cataclysmic end?Mysteries also abound in the realm of human history andculture. The ancient civilizations of Egypt, Mesopotamia, and Peru, with their monumental temples and intricate hieroglyphics, are repositories of secrets that have perplexed scholars for centuries. The lost cities of Atlantis and Mu, and the enigmatic legends of El Dorado and the Fountain of Youth, continue to captivate the imaginations of adventurers and explorers.The human mind itself is a mystery. How does the brain process information, store memories, and generate thoughts and emotions? Why do we dream, and what do our dreams reveal about the inner workings of the mind? The study of neuroscience and psychology has yielded valuable insights into these questions, but the mysteries of the mind remain as elusive as ever.In the realm of science, there are mysteries that challenge our understanding of the fundamental laws of nature. Quantum mechanics, with its paradoxical nature and counterintuitive predictions, has been described as the "mystery of mysteries" by some physicists. The enigmatic properties of quantum particles, such as superposition andentanglement, have defied our classical understanding of reality and continue to baffle even the most seasoned scientists.The enduring appeal of mysteries lies in theirpotential to reveal deeper truths about the universe and ourselves. They are the gaps in our knowledge that drive us to explore, to question, and to seek answers. They are the engines of scientific inquiry and human progress. And while some mysteries may never be fully resolved, the pursuit of knowledge and understanding remains an essential part of our human nature.In conclusion, mysteries are an integral part of human existence, and their enigma continues to captivate us. They challenge our understanding, prompt us to inquire, and drive us to explore. As we delve deeper into the recesses of the unknown, we not only gain new insights into the universe and ourselves, but we also honour the enduring spirit of curiosity and wonder that is unique to the human species.。

Quintessential Leptogenesis III. Interacting with Dark Matter: mass varying Neutralino Quintessino Dark Matter
Dark Energy and neutrinos：
Any connection between Dark Energy and neutrinos? 1. ΛCDM: (10 ev) (m ) m 2. QCDM: m 10 eV M
II.
Implications in CMB: W. Hu astro-ph/0410680 R. Caldwell and Doran: astro-ph/0501104 G. Zhao, J. Xia, M. Li, B. Feng and X. Zhang: astro-ph/0507482
III. Different from cosmological constant, Quintessence and Phantom in the determination of the evolutions and the fate of the universe A lot of studies on the evolution of UNIVERSE with w across -1 just give one example: Oscillating Quintom
Two comments: 1. Parameterization dependent 2. Effects of perturbations
w( z ) w0 w1 z
Astro-ph/0507170
Astro-ph/0507482
W1 = 20

黑暗物质高中英语Dark Matter: An Enigma in the CosmosThe universe is a vast and mysterious expanse, filled with countless celestial bodies, each with its own unique story to tell. Among the many wonders that captivate the scientific community, one stands out as a true enigma: dark matter. This elusive and perplexing phenomenon has been the subject of intense research and speculation for decades, as scientists strive to unravel its secrets and understand its role in shaping the very fabric of the universe.At its core, dark matter is a hypothetical form of matter that cannot be directly observed, yet its existence is inferred from its gravitational effects on the visible matter and the structure of the universe. Unlike the familiar matter that makes up the stars, planets, and the very world we inhabit, dark matter does not interact with electromagnetic radiation, rendering it invisible to our telescopes and other instruments. It is this very property that has made it so challenging to study and understand.The first inklings of dark matter's existence can be traced back to the early 20th century, when Swiss astronomer Fritz Zwicky observed themotion of galaxies within the Coma Cluster. He noticed that the galaxies were moving at much higher speeds than expected, suggesting the presence of a significant amount of unseen mass holding the cluster together. This observation laid the foundation for the concept of dark matter, though it would take decades before the scientific community fully embraced the idea.As our understanding of the universe has evolved, the evidence for dark matter has become increasingly compelling. Observations of the cosmic microwave background radiation, the leftover glow from the Big Bang, have revealed intricate patterns that can only be explained by the presence of a substantial amount of dark matter. Additionally, gravitational lensing, the bending of light by massive objects, has provided further confirmation of dark matter's existence, as the observed lensing effects are far greater than can be accounted for by visible matter alone.Despite the overwhelming evidence, the nature of dark matter remains elusive. Scientists have proposed numerous theories to explain its composition, ranging from exotic subatomic particles to modifications of our understanding of gravity. The search for dark matter particles, such as weakly interacting massive particles (WIMPs) and axions, has become a major focus of particle physics research, with scientists around the world employing sophisticated detectors and experiments in an attempt to directly observe these elusiveentities.One of the most intriguing aspects of dark matter is its role in the formation and evolution of the universe. Cosmological models suggest that dark matter was a crucial component in the early stages of the universe, providing the gravitational scaffolding upon which the first structures, such as galaxies and galaxy clusters, were able to form. Without the stabilizing influence of dark matter, the universe as we know it may have never come into being.As researchers continue to delve deeper into the mysteries of dark matter, they are also confronted with the broader implications of its existence. The discovery of dark matter has challenged our understanding of the fundamental laws of physics, forcing us to re-examine our theories and potentially pave the way for revolutionary new insights. The search for dark matter has also sparked the imagination of the public, captivating the minds of scientists and science enthusiasts alike, as they collectively strive to unravel one of the greatest unsolved puzzles of our time.In the pursuit of understanding dark matter, scientists have employed a wide range of cutting-edge technologies and techniques. From the construction of massive underground detectors designedto capture the faint signals of dark matter particles, to the development of sophisticated computer simulations that model thebehavior of dark matter on cosmic scales, the quest to unlock the secrets of this elusive substance has driven the field of astrophysics and cosmology to new frontiers.As the search for dark matter continues, the scientific community remains hopeful that a breakthrough is on the horizon. The potential rewards of such a discovery are immense, as it could not only shed light on the nature of the universe but also lead to a deeper understanding of the fundamental forces that govern our reality. Whether the answer lies in the detection of exotic particles, the refinement of our theories of gravity, or some entirely unexpected revelation, the pursuit of dark matter remains one of the most captivating and high-stakes endeavors in the realm of scientific exploration.In the end, the mystery of dark matter serves as a poignant reminder of the limitless boundaries of human knowledge and the boundless potential of the universe to surprise and inspire us. As we continue to push the boundaries of our understanding, we are reminded that the greatest discoveries often lie in the shadows, waiting to be uncovered by the curious and the courageous. The pursuit of dark matter, therefore, is not just a quest for scientific knowledge, but a testament to the human spirit's unwavering determination to unravel the deepest secrets of the cosmos.。

科技英语阅读（EST科技英语阅读（EST Reading）课后习题答案Unit 1 MathematicsPart I EST Reading1. Who is Bertrand Russell?Bertrand Arthur William Russell (b.1872 –d.1970) was a British philosopher, logician, essayist and social critic best known for his work in mathematical logic and analytic philosophy. His most influential contributions include his defense of logicism (the view that mathematics is in some important sense reducible to logic), his refining of the predicate calculus introduced by Gottlob Frege (which still forms the basis of most contemporary logic), his defense of neutral monism (the view that the world consists of just one type of substance that is neither exclusively mental nor exclusively physical), and his theories of definite descriptions and logical atomism. Russell is generally recognized as one of the founders of modern analytic philosophy, and is regularly credited with being one of the most important logicians of the twentieth century.2. What is Russell’s Paradox?Russell discovered the paradox that bears his name in 1901, while working on his Principles of Mathematics (1903). The paradox arises in connection with the set of all sets that are not members of themselves. Such a set, if it exists, will be a member of itself if and only if it is not a member of itself. The paradox is significant since, using classical logic, all sentences are entailed by a contradiction. Russell's discovery thus prompted a large amount of work in logic, set theory, and the philosophy and foundations of mathematics.Section C Post-reading TaskReading Comprehension1. Directions: Work on your own and fill in the blanks with the main idea.Part 1 (Para. 1): Brief introduction to Russell’s paradoxPart 2 (Paras. 2-5): The effect of Russell’s paradox on Gottlob Frege’s system.Para. 2: Russell’s paradox dealt a heavy blow to Frege’s attempts to develop a foundation for all of mathematics using symbolic logic.Para. 3: An illustration of Russell’s parado x in terms of sets Para. 4: Contradiction found in the set.Para. 5: Frege noticed the devastating effect of Russell’s paradox on his system and inability to solve it.Part 3 (Paras. 6-8): Solutions offered by mathematicians to Russel’s paradoxPara. 6: Russell’s own response to the paradox with his "theory of types."Para. 7: Zermelo's solution to Russell's paradoxPara. 8: What became of the effort to develop a logical foundation for all of mathematics?Part 4 (Para. 9): Correspondence between Russell and Frege on the paradoxVocabulary and Structure2. Directions: Complete the sentences with the words given in the brackets. Change the form if necessary.1) The key to unraveling such apparent paradoxes is to characterize the initial set of possibilities ("initial" meaning before you receive any extra information) and then to eliminate possibilities based on that extra information. (base)2) Indeed, this separation of meaning is reflected by the definition of "weak" in the OALD, with adistinct sense reserved for its use when pertaining to that of solutions (definition)3) The resulting radical pollution control programme outlined by Nixon, calling for a 90 per cent reduction in vehicle emissions by 1980, not only led to him being credited (albeit briefly) as policy initiator of an environmental clean-up but also provided him with the chance to deal a blow to one of his most important opponents in the 1972 elections, Edmund Muskie (blow)4) Singapore's continuing investments in education and training has brought a tenfold increase in our pool of Information Technology professionals and the Singapore worker has been consistently rated by BERI as the world's best in terms of technical skills, attitude and productivity. (term)5) In this work he was led to topology, a still new kind of mathematics related to geometry, and to the study of shapes (compact manifolds) of all dimensions. (lead)6) If there is no allowable string which spans the whole graph, then we can search in the same way as described above, but wherever the required path does not exist in the tree, check if that position in the tree is flagged for end-of-word (way)7) During the past century, steps forward in physics have often come in the form of newly found particles; in engineering, more complex devices; in astronomy, farther planets and stars; in biology, rarer genes; and in chemistry, more useful materials and medications. (form)8) A second reason for measurements is the more theoretical, put by Love as " the discovery of numerical relations between thequantities that can be measured to serve as a basis for the inductive determination of the form of the intrinsic energy function. " (serve)9) Thus the optimum conditions for coastal terrace development would seem to be areas with small tidal ranges. Finally, tidal range is an important factor in the generation of tidal currents which may locally become of geomorphological importance (become)10) The original double entrance doors to the booking hall had been replaced by an utterly incongruous picture window as had adjacent booking hall and waiting room windows. (replace)3. Directions: Reorder the disordered parts of a sentence to makea complete sentence.1) A simple way to describe topology is as a 'rubber sheet geometry' — topologists study those properties of shapes that remain the same when the shapes are stretched or compressed.2) Since the mid-1990s scientists have floated the idea that representations of numeric quantities, whether expressed as digits or as written words, are codified by the parietal cortex, a higher-processing region in the brain located just above the forehead.3) As activity was monitored, located just above the forehead ,researchers noted changes under the assumption that the brain reduces activity as it becomes accustomed to a stimulus and then reactivates when a novel stimulus is presented.4) That has not stopped physicists from devising new algorithms for the devices, which can calculate a lot faster than ordinary computers—in fact, exponentially faster, in quite a literal sense.5) Such a device would be made of metamaterial, a thicket ofmetal rings or other shapes that bends light in funny ways.4. Directions: Change the following sentences into nominalized ones.1) The passage of night could be marked by the appearance of 18 of these stars.2) The full proof of Fermat's Last Theorem is contained in these two papers.3) The concept of fixed-length hours, however, did not originate until the Hellenistic period.4) There is a probability that my first sock is red because only one of the remaining three socks is red.5) The importance of accurate data in quantitative modeling is central to using Bayes's theorem to calculate the probability of the existence of God.Discourse Understanding1. C. A "3 percent margin of error" means that there is a 95 percent chance that the survey result will be within 3 percent of the population value.2. E. How is it that a survey of only 1,000 people can reach this level of accuracy?3. G. The margin of error depends inversely on the square root of the sample size.4. A. The margin of error is a mathematical abstraction, and there are a number of reasons why actual errors in surveys are larger.5. F. Finally, the 3 percent margin of error is an understatement because opinions change. Section A Pre-reading Task1. Who discovered the Mandelbrot set?This is not a trick question, not easy to answer. Many peopleincluding Mandelbrot have laid claim to the discovery.2. Why was the set named after Benoit B. Mandelbrot?The set is named after Benoit B. Mandelbrot, a mathematician at the IBM Thomas J. Watson Research Center because he coined the term fractal to describe phenomena (such as coastlines, snowflakes, mountains and trees) whose patterns repeat themselves at smaller and smaller scales.3. Why has there been so much controversy about who discovered the Mandelbrot set? Mandelbrot claims that he and he alone discovered the Mandelbrot set, but there are other mathematicians who have challenged his claim.4. What did the challengers say abo ut Mandelbrot’s claim of discovery?Two mathematicians said that they independently discovered and described the set at about the same time as Mandelbrot did. And another mathematician also asserted that his work on the set not only predated Mandelbrot's efforts but also helped to guide them5. Why did some professors support Mandelbrot’s claim?Mandelbrot deserves to have the set named after him, because his efforts brought the set to the attention of both the public and of the pure-mathematics community.Section C Post-reading TaskLanguage in Use1. Match the Chinese in the left column with the English in the right column.迭代函数iterative function优先权之争priority battle分形特征fractal properties有意义make sense以越来越小的规模重复同一模式patterns repeat themselves at smaller and smaller scales混沌理论chaos theory季刊a quarterly journal数学界the mathematics community波纹线crisp lines会议公报proceedings of a conference2. Join the following short sentences into longer ones.e.g. a. A fractal is generally a rough or fragmented geometric shape .b. The shape can be subdivided in parts.c. each part is (at least approximately) a reduced-size copy of the whole, a property calledd. each part has a property of self-similarity.e.g. A fractal is generally "a rough or fragmented geometric shape that can be subdivided in parts, each of which is (at least approximately) a reduced-size copy of the whole", a property called self-similarity.1) In addition to coining the term "fractal" to describe objects and surfaces which are irregular at various dimensions of scale, he also introduced such concepts as "fractal dimensions" and the particular fractal known as the Mandelbrot set, frequently represented with the mathematical formula z → z2 + c.2) It appeared that things were settling into a pleasant and fruitful routine, with his school lessons supplemented by long talks with his uncle about classical analysis, the iterative work of Pierre Fatou and the equally fascinating Julia Sets generated by Gaston Julia3) Just as the youthful Mandelbrot had passed his college entrance exams by translating algebraic problems intogeometrical problems, and solving them by intuitively deducing the "perfected" shape, he here realized there was something deeper, something mathematical, behind these strange patterns.4) But the beauty in Mandelbrot's models was not that they generated a deceitful randomness, but that they could generate graphed data whose visual pattern accurately mimicked the visual patterns created by real phenomena。

1. Introduction
Now is the time to be a cosmologist. We have obtained through remarkable technological advances and heroic and ingenious experimental efforts a direct and extraordinarily detailed picture of the early Universe and maps of the distribution of matter on the largest scales in the Universe today. We have, moreover, an elegant and precisely quantitative physical model for the origin and evolution of the Universe. However, the model invokes new physics, beyond the standard model plus general relativity, not just once, but at least thrice: (1) Inflation, the physical mechanism for making the early Universe look precisely as it does, posits some new ultra-high-energy physics; we don’t know, however, what it is. (2) The growth of large-scale-structure and the dynamics of galaxies and galaxy clusters requires that we invoke the existence of collisionless particles or objects; we don’t know what this stuff is. (3) The accelerated expansion of the Universe requires the introduction of a new term, of embarrassingly small value, in Einstein’s equation, a modification of general relativity, and/or the introduction of some negative-pressure “dark energy,” again, the nature of which remains a mystery.

Passage 5The Universe's Invisible HandBy Christopher J. ConseliceDark energy (暗能量) does more than hurry along the expansion of the universe. It also has a stranglehold on the shape and spacing of galaxiesWhat took us so long? Only in 1998 did astronomers discover we had been missing nearly three quarters of the contents of the universe, the so-called dark energy--an unknown form of energy that surrounds each of us, tugging at us ever so slightly, holding the fate of the cosmos in its grip, but to which we are almost totally blind. Some researchers, to be sure, had anticipated that such energy existed, but even they will tell you that its detection ranks among the most revolutionary discoveries in 20th-century cosmology. Not only does dark energy appear to make up the bulk of the universe, but its existence, if it stands the test of time, will probably require the development of new theories of physics.Scientists are just starting the long process of figuring out what dark energy is and what its implications are. One realization has already sunk in: although dark energy betrayed its existence through its effect on the universe as a whole, it may also shape the evolution of the universe's inhabitants--stars, galaxies, galaxy clusters. Astronomers may have been staring at its handiwork for decades without realizing it.暗能量不仅仅会加速宇宙膨胀。

If dark energy properties are time dependent, so are other basic physical parameters
27
Big Bang Cosmology
Homogeneous, isotropic universe (flat universe)

H0 is the Hubble expansion parameter today energy density in the critical density 3H c (G=c=1 units) 8

M M / c is the fraction of the matter 2
What is the Dark Energy?
David Spergel
Princeton University
1
One of the most challenging problems in Physics

Several cosmological observations demonstrated that the expansion of the universe is accelerating What is causing this acceleration?



3
Contents of the universe (from current observations)
Baryons (4%) Dark matter (23%) Dark energy: 73% Massive neutrinos: 0.1%
Spatial curvature: very close to 0

大学里给我印象最深的科目英语作文The Biggest Wow Subject in CollegeHi there! I'm just a kid, but I got to visit a college recently and let me tell you, it was super cool! My big sister is a student there and she showed me around the whole campus. We went into some of the classroom buildings and I got to see what kinds of things college kids learn about. There was one subject that really stuck out to me and made me go "WOW!" - I'm talking about astronomy!In the astronomy classroom, there were all these gigantic posters of planets, stars, galaxies, and nebulas all over the walls. The pictures were so colorful and amazing-looking. I could have stared at them for hours. My sister told me those were actual photographs taken by powerful telescopes in space! How crazy is that?The professor who teaches astronomy seemed really excited about his subject too. He had so much energy as he talked about all the incredible things in our universe. He showed the class these awesome computer simulations of how stars are born, how black holes work, and what the big bang theory is all about. Icouldn't believe how much mind-blowing stuff there is out in space!After the class, my sister took me to the observatory on campus. That's a special building with a massive telescope on the roof that lets you look really far out into space. The observatory guy let me take a peek through the telescope and I saw Saturn! I could actually make out its rings circling around it. I felt like I was in a spaceship getting an up-close view. So rad!My sister told me that in astronomy, you learn about the life cycles of stars, how galaxies form over billions of years, and all the mysteries of things like dark matter, black holes, and other weird space phenomena. She said astronomers are like detectives trying to unravel the secrets of the whole universe. Just thinking about how vast space is and how much we still don't understand about it melts my brain!I got to attend one of the night观星(stargazing) events the astronomy department holds. They had super high-tech telescopes and laser pointers set up on the campus observatory deck. The professors pointed out different stars, planets, star clusters, nebulas, and even a couple galaxies to us. I'd never realized just how many incredible things are out there in the night sky before.After that field trip, I was hooked! Astronomy quickly became my new favorite subject that I can't wait to take when I'm older. I started checking out every astronomy book I could find from the library. I bought a little telescope for my bedroom too so I can do my own backyard stargazing. Who knows, maybe I'll grow up to be an astronomer someday and get to explore the cosmos for a living. How awesome would that be?Whenever I look up at the stars twinkling in the night sky now, I think about how those stars may have whole planets circling them with their own moons. Maybe there's even planets out there like Earth with furry or scaly aliens living on them! I wonder what they look like and if they look up at their skies and get dazzled by the Universe's brilliance too.There are just so many fascinating mysteries about space that astronomers are still trying to solve. Like what lies at the centers of black holes? What's causing the universe's expansion to accelerate? How did those crazy swirling spiral galaxies form in the first place? What's the deal with dark matter and dark energy? And are we really alone as the only intelligent life in this incomprehensibly huge universe?When I get overwhelmed thinking about the immense scale of everything in space, I remind myself of something theastronomy professor said - that everything, including humans, derived from the same cloud of cosmic gases and dust left over from the Big Bang 13.8 billion years ago. All the material that makes up the planets, stars, galaxies, and even our own bodies originated from that same primordial cosmic soup. Isn't that simply mind-boggling?So in a way, we're all profoundly connected to and part of this incredible, vast universe constantly putting on a dazzling show for us. Studying astronomy gives you such an amazing perspective on our tiny little place in the grand scheme of it all. And it fills me with a sense of wonder and appreciation for the spectacularly complex and beautiful cosmos surrounding us.I may only be a kid, but getting exposed to the marvelous subject of astronomy at that college visit gave me a new passion and made me see the universe with fresh eyes of awe. I can't wait to dive deeper into learning about it. If you ever get the chance to take an astronomy class, do it! Your mind will be totally blown by the awesomeness of space. Trust me on that one!。

中国天眼的探索与未来In the vastness of the universe, the Chinese Astronomy community has made a remarkable leap forward with the construction of the Five-hundred-meter Aperture Spherical Telescope (FAST), also known as the "Chinese Eye". This massive scientific instrument, located in Guizhou province, China, represents a significant milestone in the history of astronomical research.The Chinese Eye, with its巨大口径, is the largest single-aperture radio telescope in the world. Its size and sensitivity allow it to capture faint radio signals from deep space, enabling astronomers to peer further into the mysteries of the universe than ever before. This telescope is not only a tool for basic research but also holds the potential to make groundbreaking discoveries in areas such as pulsar studies, the search for extraterrestrial intelligence, and the exploration of the early universe.The technology behind the Chinese Eye is noteworthy. The precision engineering and innovative design have overcome numerous challenges to bring this remarkable instrument to life. The use of high-performance materialsand advanced manufacturing techniques have ensured that the telescope can operate effectively in a challenging environment, while its automated systems and cutting-edge software allow for seamless data collection and analysis.The impact of the Chinese Eye on the scientific community has been profound. Its contributions to astronomy are already being felt worldwide, as researchers fromaround the globe collaborate to analyze the vast amounts of data it generates. The telescope's ability to detect weak signals has led to new insights into the structure and evolution of the universe, challenging our understanding of cosmic phenomena.Looking ahead, the potential of the Chinese Eye is limitless. With its enhanced capabilities, astronomers hope to answer some of the fundamental questions about our place in the universe. Could there be other intelligent lifeforms beyond Earth? What are the secrets of dark matter and dark energy that govern the universe's expansion? The Chinese Eye could hold the key to unlocking these mysteries. Moreover, the Chinese Eye serves as a testament to the country's dedication to scientific research and innovation.Its construction and operation showcase China's commitmentto scientific exploration and the promotion of knowledgeand understanding. This dedication is not only reflected in the Chinese Eye but also in other cutting-edge scientific projects that are pushing the boundaries of human understanding.In conclusion, the Chinese Eye represents a remarkable achievement in the field of astronomy. Its impact on scientific research and our understanding of the universeis profound and will continue to grow as more data is collected and analyzed. The future of this telescope is bright, and its contributions to the scientific community will undoubtedly be remembered for generations.**中国天眼的探索与未来**在浩瀚无垠的宇宙中，中国天文学界通过建设五百米口径球面射电望远镜（FAST），又称“中国天眼”，取得了显著进展。

2
B.M. Sch¨ afer, G.A. Caldera-Cabral and R. Maartens
model ΛCDM ΛΓ CDM φCDM φΓ CDM Ωm 0.25 0.25 0.25 0.25 σ8 0.8 0.8 0.8 0.8 ns 1 1 1 1 w0 -1 -1 −2 3 −2 3 wa 0 0 1 −3 1 −3 Γ 0 0
1 3 1 3
a very powerful observational probe for investigating the influence of dark energy on structure formation and the geometry of the universe (Schneider et al. 1992; Mellier 1999; Bartelmann & Schneider 2001; Refregier 2003), even in the nonlinear regime of structure formation (Jain & Seljak 1997; Bernardeau et al. 1997; Benabed & Bernardeau 2001). Lensing data is best used in tomographic measurements for constraining dark energy equation of state properties (Hu 1999, 2002; Heavens 2003; Jain & Taylor 2003), where one either measures the power spectrum or the bispectrum of a weak lensing quantity (Kilbinger & Schneider 2005; Schneider & Bartelmann 1997; Bernstein & Jain 2004; Dodelson & Zhang 2005). Supplementing the recent paper by La Vacca & Colombo (2008), who derived lensing bounds on interacting models from weak lensing power spectra, we focus on bispectrum tomography, and we use a more general, albeit phenomenological cosmological model. Bispectra have the advantage that the perturbative treatment is easier to carry out and that they are sensitive on the transition from linear to nonlinear dynamics in structure formation. After introducing the cosmological model and the peculiarities of gravitational lensing in the decaying CDM models in Sect. 2, we compute the weak lensing bispectrum and tomographic measurements in Sect. 3. Fisher-constraints on cosmological parameters are derived in Sect. 4 and the main results are summarised in Sect. 5. The parameter accuracies are forecast for the weak lensing survey proposed for the Dark UNiverse Explorer1 (DUNE). For the fiducial model, we take a spatially flat ΛCDM cosmology with w = −1, adiabatic initial conditions and stable CDM (Γ = 0). Specific parameter choices are H0 = 100h km/ s/Mpc with h = 0.72, Ωm = 0.25, σ8 = 0.8 and ns = 1.