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Why is the Universe Accelerating?  [PDF]
Sean M. Carroll
Physics , 2003, DOI: 10.1063/1.1848314
Abstract: The universe appears to be accelerating, but the reason why is a complete mystery. The simplest explanation, a small vacuum energy (cosmological constant), raises three difficult issues: why the vacuum energy is so small, why it is not quite zero, and why it is comparable to the matter density today. I discuss these mysteries, some of their possible resolutions, and some issues confronting future observations.
Whole grain for whom and why?  [cached]
Wenche Fr?lich,Per ?man
Food & Nutrition Research , 2010, DOI: 10.3402/fnr.v54i0.5056
Abstract: A definition of whole grain is a critical first step in investigating health claims for whole grain and its products. Today, there is no internationally accepted definition of whole grain. Some existing definitions are broad and commodity-based, including grains with similar end uses, while others are more restricted. Scientific knowledge must be the basis for inclusion of certain grains. It is better to start with a restricted list of grains (a precautionary principle) and extend this as more knowledge becomes available. An exact definition of the raw materials (milled, cracked, crushed, rolled, or flaked) and knowledge of the components providing health effects would appear to be crucial issues for the European authorities when approving health claims. It is important that health claims are evidence-based, sustainable, and officially validated.
Genesis and the tipping pencil; why the Universe is flat  [PDF]
Ronald J. Adler
Physics , 2011,
Abstract: In a room with five cosmologists there there may easily be ten theories of cosmogenesis. Cosmogenesis is a popular topic for speculation because it is philosophically deep and because such speculations are unlikely to be proven wrong in the near future. The scenario we present here was intended mainly as a pedagogical illustration or toy model, but it turns out to possibly have a more serious and interesting result - a rationale for the spatial flatness of the Universe. Our basic assumptions are that the cosmological scale factor obeys the standard Friedman equation of general relativistic cosmology and that the equation is dominated by a cosmological constant term and a curvature term; the dynamics of the Universe is then (approximately) the same as that of a tipping pencil. The scale factor cannot remain at an unstable initial value of zero and must increase (i.e. the Universe must come into existence) according to the uncertainty principle, that is due to quantum fluctuations; in other words we propose in a precise but limited context an answer to Heidegger's famous question "Why is there something rather than nothing." The mechanism is the same as that whereby an idealized pencil balanced on its point cannot remain so and must tip over. If it is moreover assumed that the Universe expands at the minimum asymptotic rate consistent with the uncertainty principle then the result is spatial flatness.
How and Why the Universe Began  [PDF]
Roger Ellman
Physics , 1999,
Abstract: Before the universe there was nothing, absolute nothing. That is the starting point because it is the only starting point that requires no cause, no explanation nor justification of its existence. But, that starting point has two impediments to the universe, or anything, coming into existence from it. First is the problem of change from nothing to something without, at least initially, an infinite rate of change, which is impossible. Second is the problem of change from nothing to something without violating conservation, which must be maintained. Mathematical analysis develops the sole solution to both problems. That is that the beginning had to be of a +/-[1 - cosine] form. That solution indicates the fundamental nature of matter, energy and field.
Why Does the Universe Expand ?  [PDF]
T. Padmanabhan
Physics , 2010, DOI: 10.1007/s10714-010-1025-1
Abstract: The purpose of the paper is five-fold: (a) Argue that the question in the title can be presented in a meaningful manner and that it requires an answer. (b) Discuss the conventional answers and explain why they are unsatisfactory. (c) Suggest that a key ingredient in the answer could be the instability arising due to the `wrong' sign in the Hilbert action for the kinetic energy term corresponding to expansion factor. (d) Describe how this idea connects up with another peculiar feature of our universe, viz. it spontaneously became more and more classical in the course of evolution. (e) Provide a speculative but plausible scenario, based on the thermodynamic perspective of gravity, in which one has the hope for relating the thermodynamic and cosmological arrows of time.
A vacuum component of the Universe must evolve  [PDF]
Vladimir Burdyuzha
Physics , 2010,
Abstract: The evolution of a vacuum component of the Universe is investigated in the quantum as well as the classical regimes. Probably our Universe has arisen as a vacuum fluctuation and very probably that it has had a high symmetry for Planckian parameters. Besides, vacuum energy density has to be a positive one. In the early epochs during its cooling the Universe had been losing the high symmetry by phase transitions since condensates of quantum fields carried negative contributions (78 orders) to its positive energy density. It was the period of the Universe evolution during the first parts of the first second of its life. After the last phase transition (quark-hadron) the vacuum energy `has hardened'. In this moment its energy density can be calculated using the Zeldovich's formula inserting an average value of the pseudo-Goldstone boson masses (pi-mesons) that characterizes this chromodynamical vacuum. The chiral symmetry was then lost. Dynamics of the equilibrium vacuum after its `hardness' is considered by applying the holographic conception. In this case the Universe has been losing vacuum energy (45 orders) on organization of new quantum states during 13.76 x 10^9 years. Using this conception we can get solution of the cosmological constant problem. 123 crisis orders problem may be resolved. The density of vacuum energy cannot have a constant value in principle because of the new quantum states are organized during expansion of the Universe but the equation of state vacuum w= - 1 should be naturally constant. The density of vacuum energy from z=0 up to z=10^11 is also calculated in the classical regime of the Universe evolution.
Why is Universe so dark ?  [PDF]
M. Sami
Physics , 2014,
Abstract: In this presentation prepared for a general audience, we briefly mention the shortcomings of standard model of universe. We then focus on the late time inconsistency of the model dubbed age crisis whose resolution requires the presence of a repulsive effect that could be sourced either by dark energy or by a large scale modification of gravity. By and large, our description is based upon Newtonian cosmology which is simple and elegant despite of its limitations. On heuristic grounds, we explain how a tiny mass of graviton could account for late time cosmic acceleration. We also include a brief discussion on the underlying physics of Type Ia supernovae explosion and the direct confirmation of late time acceleration of Universe by the related observations.
Why the Universe is Just So  [PDF]
Craig J. Hogan
Physics , 1999, DOI: 10.1103/RevModPhys.72.1149
Abstract: Some properties of the world are fixed by physics derived from mathematical symmetries, while others are selected from an ensemble of possibilities. Several successes and failures of ``anthropic'' reasoning in this context are reviewed in the light of recent developments in astrobiology, cosmology and unification physics. Specific issues raised include our spacetime location (including the reason for the present age of the universe), the timescale of biological evolution, the tuning of global cosmological parameters, and the origin of the Large Numbers of astrophysics and the parameters of the Standard Model. Out of the twenty parameters of the Standard Model, the basic behavior and structures of the world (nucleons, nuclei, atoms, molecules, planets, stars, galaxies) depend mainly on five of them: $m_e,m_u,m_d,\alpha,$ and $\alpha_G$ (where $m_{proton}$ and $\alpha_{QCD}$ are taken as defined quantities). Three of these appear to be independent in the context of Grand Unified Theories (that is, not fixed by any known symmetry) and at the same time have values within a very narrow window which provides for stable nucleons and nuclei and abundant carbon. The conjecture is made that the two light quark masses and one coupling constant are ultimately determined even in the ``Final Theory'' by a choice from a large or continuous ensemble, and the prediction is offered that the correct unification scheme will not allow calculation of $(m_d-m_u)/m_{proton}$ from first principles alone.
Why the Initial Infinite Singularity of the Universe is Not There  [PDF]
Marcelo Samuel Berman
Physics , 2009, DOI: 10.1007/s10773-009-0007-0
Abstract: We "explain", using a Classical approach, how the Universe was created out of "nothing", i.e., with no input of initial energy. This is a Universe with no-initial infinite singularity of energy density.
Why is the Temperature of the Universe 2.726K?  [PDF]
M. S. Turner
Physics , 1993, DOI: 10.1126/science.262.5135.861
Abstract: NASA's Cosmic Background Explorer (COBE) Satellite has recently made the most accurate measurement of the temperature of the Universe determining it to be $2.726\pm 0.01\,$K. In trying to understand why the temperature has this value, one is led to discover the most fundamental features of the Universe---an early, radiation-dominated epoch, enormous entropy per nucleon, synthesis of the light elements around three minutes after the bang, and a small excess of matter over antimatter---as well as some of the most pressing issues in cosmology today, the development of structure in the Universe and the identification of the nature of the ubiquitous dark matter.
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