Варна юни 2008 Процеси в ранната Вселена Даниела П. Кирилова ИА БАН. - презентация

1 Варна юни 2008 Процеси в ранната Вселена Даниела П. Кирилова ИА БАН

2 Вместо въведение Мястото ни във Вселената не е уникално! Барионното вещество от което се състоим ние, планетите, звездите.... е незначителна съставляваща компонента на Вселената ! Наблюдателни свидетелства и теоретични указания за количеството на различните компоненти, пространствено разпределение Химичен състав на барионното вещество ~75% H, 25% He, Z

3 Вместо въведение Мястото ни във Вселената не е уникално! Аристарх предлага хелиоцентричната система: Слънцето, не Земята е център на планетната ни система. Коперник възражда и утвърждава хелиоцентричната система, която преди него е в забвение цели 1800 г.. Шепли Х г. – Слънчевата система не е в центъра на Галактиката,а в покрайнините и. Хъбъл Е – Нашата Галактика не е уникална, съществуват множество други. Хъбъл и Хюмасон - Еднородно и изотропно разширение на Вселената Космологичен принцип: Вселената е еднородна и изотропна на големи мащаби. Откриване на реликтовия микровълнови фон с поразителна изотропия Космологичния принцип днес има наблюдателно потвърждение. (LSS,CMB)

4 Cosmological Principle is not exact at small scales Obviously : Sitting in the lecture room is not the same as sitting at the beach… Conditions on the Earth are much more preferable for us than those of the outerspace … The Universe is inhomogeneous at the scales of planetary systems. Suns interior is quite different from the interstellar regions. The conditions within a galaxy differ from those of IGM, etc. Inhomogeneous at galaxy scales, at the scale of galaxy clusters On a scale below 100 Mpc a variety of large scale structures exist: clusters of galaxies, superclusters and voids.

5 Clusters of galaxies are the largest gravitationally-collapsed objects. Clusters are grouped into superclusters of galaxies, joined by filaments and walls of galaxies. In b/n lie large voids, deprived of galaxies, almost 50 Mpc across. Recent extremely large galaxy surveys, 2dF and Sloan Digital Sky Survey, have surveyed large volumes of few Gps. Superclusters and voids are likely to be the biggest structures. At scales Mpc the Universe begin to appear smooth. This key assumption of cosmology for the previous decades is also confirmed now observationally by CMB. Cosmological Principle is exact at large scales > 200 Mpc (containing mlns of galaxies). It is a property of the global Universe. Large-scale smoothness Convincing observations about the smoothness of matter distribution on large scales exist :

6 The furthest we can see…14 billion ly Very wide-angle view of almost the entire night sky, by NASA's WMAP satellite, shows the furthest light we can see. It is also the oldest: The light was emitted shortly after the Big Bang, and has been traveling through space for 13.7 billion years to us. In this "baby picture" of the universe, the red and yellow patches are regions that are just a few millionths of a degree hotter than the blue and black areas. This tiny difference helped seed the formation of galaxies out of the shapeless gas that filled the early universe. CMB, the remnant heat from the Big Bang, has a temperature which is highly uniform over the entire sky. This fact strongly supports the notion that the gas which emitted this radiation long ago was very uniformly distributed.

7 The RW Metric In case CP holds the most general expression for a space-time metric which has a (3D) maximally symmetric subspace of a 4D space-time is the Robertson-Walker metric: c = 1 assumed. By rescaling the radial coordinate the curvature constant k may have only the discrete values +1, 1, or 0 corresponding to closed, open, or spatially flat geometries. The observed homogeneity and isotropy enable us to describe the overall geometry and evolution of the Universe in terms of two cosmological parameters accounting for the spatial curvature and the overall expansion (or contraction) of the Universe.

8 Състав на Вселената Съвременните наблюдателни данни указват на съществуването на поне 4 компонента на Вселената: Лъчение /релативистки частици/ Пренебрежима днес, доминираща на Ранните стадии в еволюцията на Вселената Барионно вещество (обичайното ни вещество, р и n) Тъмна (хладна) материя (Скрита маса) Не е директно детектирана, само указания Съставлява доминиращата част на веществото в днешната Вселена. Тъмна енергия Има доминираща роля в пълната плътност на енергията. Представлява предизвикателство за физиката на частците, макар принципно да може да бъде описана просто като космологична константа или вакуумна енергия. Барионното вещество от което се състоим ние, планетите, звездите.... е незначителна съставляваща компонента на Вселената ! 4% - бариони, 23% - тъмна материя, над 73% тъмна енергия

9 Наблюдателни свидетелства и теоретични указания за количеството и характеристиките на различните компоненти Dark matter, Dark energy CMB, relic neutrino, baryons

10 Dark Matter Observational and theoretical indications, Forms, Candidates

11 Indications: Rotation Curves - The dependence of the velocity of rotation of an object on its distance from the galactic center.

12 Exploring Galactic Rotation Spiral tracers in optical observations: supergiants, HII regions, Pop I cepheids photo in blue light establishes distinctly the spiral arms Dust doesnt stop radiowaves In radio observations: Both neutral H-line (21 cm) from H clouds and the emission millimeter CO- line from giant molecular clouds are used as tracers. Radio and optical observations of gas and stars in galaxies enable us to determine the distribution of mass in these systems.

13 DM at galactic and galaxy cluster scale The rotation curve for the galaxy NGC3198 from Begeman 1989 Fritz Zwicky of Caltech discovered the presence of dark matter on a much larger scale through his studies of galactic clusters. Recent measurements have found that certain galaxy clusters (and binary galaxies) have M/L ratios up to 300

14 Gravitational Lensing The mass inferred for galaxies is roughly ten times larger than the mass that can be associated with stars, gas and dust in a Galaxy. This mass discrepancy has been confirmed by observations of gravitational lensing, the bending of light predicted by Einstein's theory of GR. By measuring how the background galaxies are distorted by the foreground cluster the cluster mass is measured.

15 Sloan Digital Sky Survey SDSS is the most ambitious astronomical survey ever undertaken. It will provide detailed optical images covering more than a quarter of the sky, and a 3-dimensional map of about a million galaxies and quasars. SDSS uses 2.5-meter telescope on Apache Point, NM, equipped with two powerful special-purpose instruments. The 120-megapixel camera can image 1.5 square degrees of sky at a time, about eight times the area of the full moon. A pair of spectrographs fed by optical fibers can measure spectra of (and hence distances to) more than 600 galaxies and quasars in a single observation. The SDSS completed its first phase of operations in SDSS-I imaged more than 8,000 square degrees of the sky in five bandpasses, detecting nearly 200 million celestial objects, and it measured spectra of more than 675,000 galaxies, 90,000 quasars, and 185,000 stars.

16 Galaxies Distribution vers Theoretical Simulations DM is required in order to enable gravity to amplify the small fluctuations in CMB enough to form the large-scale structures that we see in the universe today.

17 Energy-Matter Balance – CMB results WMAP measures the density of baryonic and non-baryonic matter to an accuracy of better than 5%. It determined the properties of the non-baryonic matter: the interactions of the non- baryonic matter with itself, its mass and its interactions with ordinary matter all affect the details of the cosmic microwave background fluctuation spectrum. WMAP determined that the universe is flat: the mean energy density is equal to the critical density (within a 2% margin of error), equivalent to a 9.9 x g/cm3 (5.9 protons per cubic meter). 4% Atoms, 23% Cold Dark Matter, 73% Dark Energy. Thus 96% of the energy density in the universe is in a form that has never been directly detected in the laboratory. Fast moving neutrinos do not play any major role in the evolution of structure in the universe. They would have prevented the early clumping of gas in the universe, delaying the emergence of the first stars, in conflict with the new WMAP data.

18 Forms of DM Dark matter (DM) candidates are usually split into two broad categories, with the second category being further sub-divided: Baryonic Non-Baryonic hot dark matter (HDM) and cold dark matter (CDM), depending on their respective masses and speeds. CDM candidates travel at slow speeds (hence "cold") or have little pressure, while HDM candidates move rapidly (hence "hot").

19 Candidates for DM MACHOS If a star's mass is less than one twentieth of our Sun, its core is not hot enough to burn either hydrogen or deuterium, so it shines only by virtue of its gravitational contraction, not luminous enough to be directly detectable by our telescopes. Brown Dwarfs and similar objects have been nicknamed MACHOs (MAssive Compact Halo Objects).star's Supermassive Black Holes, thought to power distant quasars. WIMPs (Weakly Interacting Massive Particles) or non-baryonic matter, produced shortly after the Big Bang most of the universe is made of some mysterious form of energy whose nature is completely unknown.

20 Dark Energy The big surprise of the past decade was the discovery that the expansion of the universe is speeding up! SN I m data. Something is driving the universe apart. The source of this acceleration is not understood yet. It is nicknamed dark energy. Whatever it is, it appears to make up most of the mass of the universe – around 70%. Most of the universe is made of some mysterious form of energy whose nature is completely unknown…..

21 How do we know that the expansion of the universe is speeding up? By comparing its expansion today with how fast it was expanding in the distant past: By observing the motions of galaxies at different distances, astronomers can tell how fast the universe was expanding at different times in the past. determine the distance to a galaxy: The technique rests on the happy accident that when a certain type of star dies, it explodes with a spectacular flash whose inherent brightness is known (SNI). Sometime around 5 billion years ago, the universe began accelerating - its expansion getting faster and faster, rather than gradually slowing down.

22 Expansion History of the Universe

23 Nature of Dark Energy an energy of empty space Why space should contain the observed amount of energy and not, say, much more or much less? new form of energy, called quintessence Unlike the energy of space envisioned by Einstein, quintessence would have the property that it could vary from place to place and moment to moment. Existing evidence tends to disfavor quintessence. Accelerating universe signals a new aspect of the law of gravity. An effect of extra dimensions of space One of the extra dimensions (predicted by supersymmetry of space can mimic the effect of a dark energy by causing the expansion of our three-dimensional space to accelerate.

24 Energy-Matter Balance – CMB results WMAP measures the density of baryonic and non-baryonic matter to an accuracy of better than 5%. It determined the properties of the non-baryonic matter: the interactions of the non- baryonic matter with itself, its mass and its interactions with ordinary matter all affect the details of the cosmic microwave background fluctuation spectrum. WMAP determined that the universe consists of 4% Atoms, 23% Cold Dark Matter, 73% Dark Energy. Thus 96% of the energy density in the universe is in a form that has never been directly detected in the laboratory. The data places new constraints on the Dark Energy. It seems more like a "cosmological constant" than a negative-pressure energy field called "quintessence". But quintessence is not ruled out.

25 Observational Milestones of Hot Big Bang Cosmology The expansion of the Universe Observation that galaxies were generally receding from us provided the first evidence for the Universe expansion. SN observations pointed to an accelerated expansion The abundance of the light elements The light elements abundances provide evidence for a hotter and denser early Universe, when these elements have been fused from protons and neutrons. Point to non-baryonic DM. The cosmic microwave background radiation The cosmic microwave background radiation is the remnant heat left over from the Big Bang. It points to a hot early Universe. Points to a flat LambdaCDM dominated accelerating Universe now.

26 Theoretical Milestones Einstein Theory of Gravitation Friedmann equations of Motion Contemporary Physics, Astrophysics, Thermodynamics, Quantum Field Theory Gamow, Lemaitre, Piebles, Zeldovich, Novikov, Dolgov, Linde, Turner, Kolb

27 The matter content is usually modelled as a perfect fluid with a stress- energy tensor in the rest frame of the fluid: Friedmann expansion driven by an ideal fluid is isentropic, dS=0 Frequently used relation between the scale factor and temperature in an expanding Universe : R(t)~1/T

28 Уравнение на състоянието

29 The Hot Early Universe The Big Bang Model (Referred to as the Standard Model) predicts the existence of hot stage Law of expansion RD universe: MD universe: Vacuum dominated universe: H=cost. Having in mind the different dependence of radiation and matter density on R(t) and T~ 1/R, it is obvious that there was an epoch of radiation dominance - RD

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31 Expansion History of the Universe

32 How do we know that the expansion of the universe is speeding up? by comparing its expansion today with how fast it was expanding in the distant past: By observing the motions of galaxies at different distances, astronomers can tell how fast the universe was expanding at different times in the past. determine the distance to a galaxy: The technique rests on the happy accident that when a certain type of star dies, it explodes with a spectacular flash whose inherent brightness is known (SNI). Sometime around 5 billion years ago, the universe began accelerating - its expansion getting faster and faster, rather than gradually slowing down.

33 Brief History of the Universe Inflation Reheating Unified interactions ( sec) Generation of matter-antimatter asymmetry Primordial Nucleosynthesis (first 3 minutes). CMB formation ( years) Galaxy formation (10 9 years)

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