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The Cosmological Constant and the String Landscape
"... Theories of the cosmological constant fall into two classes, those in which the vacuum energy is fixed by the fundamental theory and those in which it is adjustable in some way. For each class we discuss key challenges. The string theory landscape is an example of an adjustment mechanism. We discuss ..."
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Theories of the cosmological constant fall into two classes, those in which the vacuum energy is fixed by the fundamental theory and those in which it is adjustable in some way. For each class we discuss key challenges. The string theory landscape is an example of an adjustment mechanism. We discuss the status of this idea, and future directions. Rapporteur talk at the 23rd Solvay Conference in Physics, December, 2005. 1 The cosmological constant I would like to start by drawing a parallel to an earlier meeting — not a Solvay conference, but the 1947 Shelter Island conference. In both cases a constant of nature was at the center of discussions. In each case theory gave an unreasonably large or infinite value for the constant, which had therefore been assumed to vanish for reasons not yet understood, but in each case experiment or observation had recently found a nonzero value. At Shelter
Vcauum energy: myths and reality
 International Journal of Modern Physics A
, 2006
"... We discuss the main myths related to the vacuum energy and cosmological constant, such as: “unbearable lightness of spacetime”; the dominating contribution of zero point energy of quantum fields to the vacuum energy; nonzero vacuum energy of the false vacuum; dependence of the vacuum energy on the ..."
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We discuss the main myths related to the vacuum energy and cosmological constant, such as: “unbearable lightness of spacetime”; the dominating contribution of zero point energy of quantum fields to the vacuum energy; nonzero vacuum energy of the false vacuum; dependence of the vacuum energy on the overall shift of energy; the absolute value of energy only has significance for gravity; the vacuum energy depends on the vacuum content; cosmological constant changes after the phase transition; zeropoint energy of the vacuum between the plates in Casimir effect must gravitate, that is why the zeropoint energy in the vacuum outside the plates must also gravitate; etc. All these and some other conjectures appear to be wrong when one considers the thermodynamics of the ground state of the quantum manybody system, which mimics macroscopic thermodynamics of quantum vacuum. In particular, in spite of the ultraviolet divergence of the zeropoint energy, the natural value of the vacuum energy is comparable with the observed dark energy. That is why the vacuum energy is the plausible candidate for the dark energy. Keywords: 1. Introduction: Old and
Emergent physics: Fermi point scenario
 A
"... The Fermipoint scenario of emergent gravity has the following consequences: gravity emerges together with fermionic and bosonic matter; emergent fermionic matter consists of massless Weyl fermions; emergent bosonic matter consists of gauge fields; Lorentz symmetry persists well above the Planck ene ..."
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The Fermipoint scenario of emergent gravity has the following consequences: gravity emerges together with fermionic and bosonic matter; emergent fermionic matter consists of massless Weyl fermions; emergent bosonic matter consists of gauge fields; Lorentz symmetry persists well above the Planck energy; spacetime is naturally 4dimensional; Universe is naturally flat; cosmological constant is naturally small or zero; underlying physics is based on discrete symmetries; ‘quantum gravity ’ cannot be obtained by quantization of Einstein equations; there is no contradiction between quantum mechanics and gravity; etc.
Vacuum driven accelerated expansion ∗
, 708
"... It has been shown that careful estimation of quantum vacuum energy can yield not only sensible but also experimentally awaited results. The very idea consists in straightforward extraction of gravitationally interacting part of the full vacuum energy by means of gauge transformations. The implementa ..."
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It has been shown that careful estimation of quantum vacuum energy can yield not only sensible but also experimentally awaited results. The very idea consists in straightforward extraction of gravitationally interacting part of the full vacuum energy by means of gauge transformations. The implementation of the idea has been performed in the formalism of effective action, in the language of Schwinger’s proper time and Seeley–DeWitt heat kernel expansion, in the background of the Friedmann–Robertson–Walker geometry. PACS numbers: 95.36.+x Dark energy, 04.62.+v Quantum field theory in curved spacetime, 04.60.m Quantum gravity, 98.80.Es Observational cosmology (including Hubble constant, distance scale, cosmological constant, early Universe, etc.).
Relativity without tears
 Acta Phys.Polon. B
, 2008
"... Special relativity is no longer a new revolutionary theory but a firmly established cornerstone of modern physics. The teaching of special relativity, however, still follows its presentation as it unfolded historically, trying to convince the audience of this teaching that Newtonian physics is natur ..."
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Special relativity is no longer a new revolutionary theory but a firmly established cornerstone of modern physics. The teaching of special relativity, however, still follows its presentation as it unfolded historically, trying to convince the audience of this teaching that Newtonian physics is natural but incorrect and special relativity is its paradoxical but correct amendment. I argue in this article in favor of logical instead of historical trend in teaching of relativity and that special relativity is neither paradoxical nor correct (in the absolute sense of the nineteenth century) but the most natural and expected description of the real spacetime around us valid for all practical purposes. This last circumstance constitutes a profound mystery of modern physics better known as the cosmological constant problem. PACS numbers: 03.30.+p Preface “To the few who love me and whom I love – to those who feel rather than to those who think – to the dreamers and those who put faith in dreams as in the only realities – I offer this Book of Truths, not in its character of TruthTeller, but for the Beauty that abounds in its Truth; constituting it true. To these I present the composition as an ArtProduct alone; let us say as a Romance; or, if I be not urging too lofty a claim, as a Poem. What I here propound is true: – therefore it cannot die: – or if by any means it be now trodden down so that it die, it will rise again ”to the Life Everlasting.” Nevertheless, it is a poem only that I wish this work to be judged after I am dead ” [1]. 1.
Pseudoredundant vacuum energy
, 801
"... We discuss models that can account for today’s dark energy. The underlying cosmological constant may be Planck scale but starts as a redundant coupling which can be eliminated by a field redefinition. The observed vacuum energy arises when the redundancy is explicitly broken, say by a nonminimal co ..."
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We discuss models that can account for today’s dark energy. The underlying cosmological constant may be Planck scale but starts as a redundant coupling which can be eliminated by a field redefinition. The observed vacuum energy arises when the redundancy is explicitly broken, say by a nonminimal coupling to curvature. We give a recipe for constructing models, including R + 1/R type models, that realize this mechanism and satisfy all solar system constraints on gravity. A similar model, based on GaussBonnet gravity, provides a technically natural explanation for dark energy and exhibits an interesting seesaw behavior: a large underlying cosmological constant gives rise to both low and high curvature solutions. Such models could be statistically favored in the string landscape. 1
From semiconductors to quantum gravity: to centenary of Matvei Bronstein
, 2008
"... Investigation of the manybody condensedmatter systems allows us to connect the microscopic physics at the atomic energy scale and the macroscopic physics emerging in the lowenergy corner. It gives some hints on the mechanisms of the formation of the physical laws which our Universe obeys. The pap ..."
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Investigation of the manybody condensedmatter systems allows us to connect the microscopic physics at the atomic energy scale and the macroscopic physics emerging in the lowenergy corner. It gives some hints on the mechanisms of the formation of the physical laws which our Universe obeys. The paper is devoted to the centenary of Matvei Petrovich Bronstein. 1 Ether of 21st century Each epoch in the history of physics has its own specific ether. M. Bronstein [1] The ether of the 21st century is the quantum vacuum. The quantum ether is a new form of matter. This substance has a very peculiar peculiar properties strikingly different from the other forms of matter (solids, liquids, gases, plasmas, Bose condensates, radiation, etc.) and from all the old ethers.
On spectrum of vacuum energy
, 801
"... Abstract. We discuss the problem of the spectral function of vacuum energy. In traditional approach the ultraviolet divergencies of the vacuum energy are cancelled by imposing relations between different quantum fields and their masses. The emergent theories suggest that the microscopic degrees of t ..."
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Abstract. We discuss the problem of the spectral function of vacuum energy. In traditional approach the ultraviolet divergencies of the vacuum energy are cancelled by imposing relations between different quantum fields and their masses. The emergent theories suggest that the microscopic degrees of the underlying quantum vacuum add to the spectral function and their contribution cancels the diverging zero point energy of quantum fields. Examples of the spectral function of the vacuum energy in the condensedmatter systems with relativity emerging at low energy are presented. In the Sakharov induced gravity situation may be even more dramatic: only microscopic (Planck scale) constituent fields contribute to the vacuum energy, while the diverging zeropoint energy of emergent quantum field (gravitational field) is missing. On the other hand consideration of the fermionic condensed matter systems suggests that emergent relativistic fermionic quasiparticles contribute in conventional way as Dirac vacuum. 1.
Short Distance Physics and Initial State Effects on the CMB Power Spectrum
, 809
"... We investigate a modification in the action of inflaton due to noncommutativity leads to a nonstandard initial vacuum and oscillatory corrections in the initial power spectrum. We show that the presence of these oscillations causes a drop in the WMAP χ 2 about ∆χ 2 ∼ 8.5. As a bonus, from the parame ..."
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We investigate a modification in the action of inflaton due to noncommutativity leads to a nonstandard initial vacuum and oscillatory corrections in the initial power spectrum. We show that the presence of these oscillations causes a drop in the WMAP χ 2 about ∆χ 2 ∼ 8.5. As a bonus, from the parameter estimation done in this work, we show that the noncommutative parameters can be precisely bound to 10 16 GeV or 10 4 GeV depending on the inflation scale. 1
Quantum Relaxation of the Cosmological Constant ∗∗
, 2005
"... ABSTRACT: We describe a mechanism that drives the Cosmological Constant to zero value. This mechanism is based on the quantum triviality of λφ 4 field theory and works in AdS space. Some subtleties of the model are discussed. ..."
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ABSTRACT: We describe a mechanism that drives the Cosmological Constant to zero value. This mechanism is based on the quantum triviality of λφ 4 field theory and works in AdS space. Some subtleties of the model are discussed.