An extension of unimodular gravity and the cosmological constant. Since the determinant of the metric now plays a role in the physics, the allowed coordinate . Much later it was revived and reinterpreted as the energy density of space, or vacuum energy, that arises . dim. Hawking and his team profess to have found a way to produce expanding, accelerating universes using a negative cosmological constant by seeking a wave function[3] that can generate the probability of various universes arising from the big bang. The vacua are supersymmetric AdS_4 solutions in flux compactifications of type IIB string theory on orientifolds of Calabi-Yau hypersurfaces. DR. CRAIG: Here it's kind of like a teeter-totter. Mod . Einstein originally posited a nonzero value for the cosmological constant, . A Universe with a positive cosmological constant will have serious implications for string theory since the S-Matrix cannot be well defined and Superstring/M Theory is only formulated in flat Minkowski background. String theory has a large number of solutions for the extra dimensions. It turns out that cosmological constant is conserved in . Before string theory, Albert Einstein was strongly influenced by the concept of an unchanging universe. Idea In theories of gravity and cosmology a cosmological constant refers to an energy contribution associated with the vacuum itself. The corresponding equations resemble those of a Brans-Dicke theory . Duality-symmetric string theory and the cosmological-constant problem Full Record Research Abstract We propose an ansatz for a low-energy effective action {ital {bar S}} for a gravity-plus-matter system which is given by the usual action {ital S} (integral over space-time) {ital divided} by the space-time volume, {ital {bar S}}= {ital S}/ {ital V}. Download Links [arxiv.org] [arxiv.org] . The energy density of the vacuum, Λ, is at least 60 orders of magnitude smaller than several known contributions to it. The mechanism that we introduce generates a well-controlled exponential hierarchy from an appropriate choice of the quantized parameters in the superpotential. We have argued that the generic formulation of string theory leads naturally to dark energy, represented by a positive cosmological constant to lowest order and the intrinsic stringy non-commutativity is the new crucial ingredient responsible for its radiative stability. While I have nothing against the multiverse theory, my view is that the cosmological constant calculation is so obviously wrong that it can be ignored. CiteSeerX - Document Details (Isaac Councill, Lee Giles, Pradeep Teregowda): ABSTRACT: There are two important examples of physical systems which violate the strong energy condition: Universes (like, it would seem, our own) with a positive cosmological constant, and wormholes. . On one side are those who contend, as Albert Einstein once did, that the . ar X iv :2 10 7. 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. We construct a vacuum of string theory in which the magnitude of the vacuum energy is < 10−123 in Planck units. Anthropic ideas can help answer other questions about . String Scale Cosmological Constant (2006) Cached. String theory is known to contain configurations that describe all the observed fundamental forces and matter but with a zero cosmological constant and some new fields. String theory axions appear to be promising candidates for explaining cosmological constant via quintessence. Small cosmological constants in string theory. String theory attempts to link particle physics, the . Cosmological constant, a constant term related to the vacuum energy appearing in the equation of gravitational field, is the simplest possible form of dark energy. — Quanta Magazine, . Holographic principle provides a way out as shown by the AdS/CFT and dS/CFT correspondence, but it remains to be proved if it is . 7. String theory has a large number of solutions for the extra dimensions. It is well known that quantum field theory (QFT) induces a huge value of the cosmological constant (CC), Λ, which is outrageously inconsistent with cosmological observations.We review here some aspects of this fundamental theoretical conundrum (the cosmological constant problem, CCP) and strongly argue in favour of the possibility that the cosmic vacuum density ρ vac may be mildly evolving . The cosmological constant can be interpreted as the energy density of the vacuum, and can arise for at least two reasons. The proposal involves the metric determinant acting as a type of self-adjusting -field without a fine-tuned chemical potential. on the Web Steven Abel and Keith Dienes showed how UV-IR mixing in string theory might address both the hierarchy and cosmological constant problems. potential energy axion quintessence theory axions large number planck scale axion potential string compactifications nonzero cosmological constant unified model . Some would say that the value . would expect the cosmological constant to be around the Planck scale. On the other hand, the number of vacuum states seems to be quite large, The String Theory Landscape rekindled the ashes of an old debate in physics, one that smolders to this day. For each class we discuss key challenges. Also, an effective cosmic-string-like solution of F-theory . The article gives me this impression apparently using a negative cosmological constant. de Sitter vacua of string theory with ρ vac≈ρ obsthus presents an obstruction to bringing the landscape argument for the cosmological constant problem into sharp focus in quantum gravity. This is a scalar term entering into the description of the bosonic string that produces a scalar field term into the effective theory at low energies. Neutralization of the cosmological constant through membrane nucleation was first studied by Brown and Teitelboim [19], and has been further explored in the context of string theory by others [20,21]. I will explain the advances in computing topological data in Calabi-Yau compactifications that led to these solutions, then discuss implications for the cosmological constant problem. The role of cosmological constant in string theories came into the forefront when it was realized that there exists a peculiar equivalence between a class of theories containing gravity and pure gauge theories. metric, i.e. Abstract The mystery of the cosmological constant is probably the most pressing obstacle to significantly improving the models of elementary particle physics derived from string theory. The vacua are supersymmetric AdS_4 solutions in flux compactifications of type IIB string theory on orientifolds of Calabi-Yau hypersurfaces. The string multiverse is special I This way of solving the cosmological constant problem does not work in all theories with many vacua I In a multiverse arising from an (ad-hoc) one-dimensional quantum field theory landscape, most observers see a much larger cosmological constant [Abbott 1985, Brown & Teitelboim 1987] In this paper, we study conditions on the string compactifications under which axion quintessence can happen. Anti-de Sitter space-times have a negative cosmological constant (a number that describes the large-scale geometry of the universe); our universe has a positive one. Conclusion. In quantum field theory, the vacuum is not really "empty," but is filled with fields that briefly appear because of quantum fluctuations. You can either deny string theory because it's . String theory seems to me to have failed to deliver what it had promised in the '80s, and is one of the . The vacua are supersymmetric AdS_4 solutions in flux compactifications of type IIB string theory on orientifolds of Calabi-Yau hypersurfaces. In cosmology, the cosmological constant (usually denoted by the Greek capital letter lambda: Λ), alternatively called Einstein's cosmological constant, is the constant coefficient of a term Albert Einstein temporarily added to his field equations of general relativity.He later removed it. We discuss the field equation in gravity theory for the general class of Lyra Manifold with bulk viscous fluid together with a five dimensional cosmic strings in the presence of cosmological constant Λ is considered. We discuss the field equation in gravity theory for the general class of Lyra Manifold with bulk viscous fluid together with a five dimensional cosmic strings in the presence of cosmological constant Λ is considered. In cosmology, the cosmological constant (usually denoted by the Greek capital letter lambda: Λ), alternatively called Einstein's cosmological constant, is the constant coefficient of a term Albert Einstein temporarily added to his field equations of general relativity.He later removed it. Cosmological Constants by String Theory, released 22 January 2017 1. String theory offers a concrete realization through its landscape of metastable vacua. Abstract:The mystery of the cosmological constant is probably the most pressing obstacle to significantly improving the models of elementary particle physics derived from string theory. Other configurations have different values of the cosmological constant, and are metastable but long-lived. (2006), hep-th/0603249. \gravity", with \cosmological constant" m2; in this interpretation eis the square root of the 1-dim. It has been argued that even if we were able to set the cosmological constant to its present value at low orders in perturbation theory, higher order radiative corrections generate cosmological constant 4 P. This would give cosmological constant which is Much later it was revived and reinterpreted as the energy density of space, or vacuum energy, that arises . . The observed cosmological constant is a factor of 10 60 smaller than theoretical calculations would suggest: the largest mismatch between experiment and theory anywhere in physics! Some would say that the value . The vacuum landscape of string theory can solve the cosmological constant problem, explaining why the energy of empty space is observed to be at least 60 orders of magnitude smaller than several known contributions to it. | Find, read and cite all the research you need on . It also affects quantum mechanics and, in one way, string theory. Einstein's equations are perfectly consistent in any number of dimensions, for open as well as closed universes, for universes with a positive cosmological constant (dark energy) and for universes with a zero or negative cosmological constant. The numerical value of the cosmological constant is calculated using a recently suggested cosmological model and found to be −35 s −2. String Theory Research at UC Berkeley In classical general relativity there are almost no restrictions on spacetime and its matter content. The cosmological constant drives the current accelerating expansion of the universe and what is most perplexing about it is its size. For example, small variations in the relative masses of the electron and proton or in the value of the fine-structure constant would preclude the necessarily rich structure of atoms and molecules. In string cosmology, this arises from the so-called dilaton field. CONCLUSION In this paper it is shown that the cosmological model for Takabayasi String with . This enables the anthropic solution to the cosmological constant problem. The "cosmological constant'" of Einstein's general relativity equations is linearly related to the zero-point mass density. For each class we discuss key challenges. 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. One example of such a duality [330] arises as follows: A particular kind of string theory in ten dimension (called type II Bstring theory) Now eliminate efrom (2.13) using the eequation of motion me= . String theory is one of the few mathematically consistent theories that can unify quantum physics and general relativity. Other physicists, though, consider this . Cosmological constant and axions in string theory (2006) Cached. String theory has no parameter except the string scale M S, so the Planck scale M Pl, the supersymmetry-breaking scale , the electroweak scale m EW as well as the vacuum energy density (cosmological constant) Λ are to be determined dynamically at any local minimum solution in the string theory landscape. The theory is defined in 10 or 11 space-time dimensions, which means we need to compactify the extra dimensions (for example, by curling them up into tiny circles) so as to be consistent with our four-dimensional Universe. . One "solution" has been proposed by physicists working in string theory, who for 30 years have been earnestly seeking a complete and unique . Here we consider a model that links the supersymmetric electroweak phenomenology (bottom . This value of Λ is in excellent agreement with the measurements recently obtained by the High-Z Supernova Team and the Supernova Cosmology Project. . of Physics, Cal Tech, Pasadena, CA 91125 and CIT-USC Center For Theoretical Physics, USC, Los Angeles CA The mystery of the cosmological constant is probably the most pressing obstacle to signi cantly improvingthe models ofelementaryparticle physics But to Vafa it is a reason to doubt dark energy—that is, dark energy in its most popular form, called a cosmological constant. I'm not up to date to all the stringy constructions of backgrounds, but I think the problem you're addressing is deeper: it has to do with supersymmetry. String theory is an attempt to describe the whole universe under a single "theory of everything" by adding extra dimensions of spacetime and thinking of particles as miniscule vibrating loops . The Cosmological Constant From The Viewpoint Of String Theory Edward Witten Dept. History. An old debate. This shows that the introduction by Einstein of a positive cosmological constant is equivalent to an assumption that the Universe is filled with an ideal fluid of negative pressure equal to its constant energy density: E = Λ.This 'dark energy' can be equivalently described as a tensile material of tension Λ that is locally Lorentz invariant (since g = η in local inertial frames). If you start with a theory with no cosmological constant, these vacuum fluctuations . Weinberg, S.: The cosmological constant problem. STRING THEORY Paul K. Townsend Department of Applied Mathematics and Theoretical Physics Centre for Mathematical Sciences, University of Cambridge . Some of these lead to the Standard Model field content, but with a range of values for the cosmological constant and other constants of nature. The string theory landscape is an example of an adjustment mechanism. A bstract An essential part of the problem is achieving scale separation in cosmological solutions of quantum gravity: The "cosmological constant problem" In string theory For fundamentally vanishing cc ("Witten's Dark Fantasy") For fundamentally non-vanishing cc 1. The string theory landscape is an example of an adjustment mechanism. The observed cosmological constant is a factor of 10 60 smaller than theoretical calculations would suggest: the largest mismatch between experiment and theory anywhere in physics! If it is true string theory cannot accommodate stable dark energy, that may be a reason to doubt string theory. The cosmological constant drives the current accelerating expansion of the universe and what is most perplexing about it is its size. Membranes in such scenarios are thus surfaces across which the effective cosmological constant can jump. This would prove to be a mistake when, several years later . Apply today to reserve your spot. Our approach provides a new angle on the cosmological . If w = -1, the acceleration of the universe is constant and dark energy is the cosmological constant. The cosmological constant and the string landscape. energy density galactic halo effect field theory cold dark matter cosmological constant density functional several time string theory theory . We discuss the status of this idea, and future directions. Questions that were recently the stuff of speculation can . The problem arises because in the standard framework of low energy physics, there appears to be no natural explanation for Anthropic ideas can help answer other questions about . Susskind notes that string theory has some 10500 possible solutions, each of which could correspond to a separate universe within the multiverse. The cosmological constant first appeared in a 1917 paper by Einstein entitled "Cosmological Considerations in the General Theory of Relativity" (Einstein 1917), in which he motivates its introduction into the field theory of general relativity by the need to stabilize the universe against the attractive effect of gravity: "The term is necessary only for the purpose of making possible . While observational studies have found that the constant is a really small number between 0 and 1, quantum mechanics predicts that . I String theory:Unique theory, no adjustable parameters, many metastable solutions I Combine D-branes and their associated fluxes to tie up 6 extra dimensions ! A special class of conformal gravity theories is proposed to solve the long standing problem of the fine-tuned cosmological constant. And a sufficient number of candidates that produce a cosmological constant of a random size is predicted and the emergence of life is a sufficient criterion to choose a solution that agrees with the real world. This enables the anthropic solution to the cosmological constant problem. Rev. Small cosmological constants in string theory Mehmet Demirtas , Manki Kim , Liam McAllister , Jakob Moritz & Andres Rios-Tascon Journal of High Energy Physics 2021, Article number: 136 ( 2021 ) Cite this article 61 Accesses 4 Citations 14 Altmetric Metrics A preprint version of the article is available at arXiv. The string theory landscape is an example of an adjustment mechanism. We suggest that a positive cosmological constant can be reconciled with string theory by considering wormholes in . M. Demirtas, Manki Kim, L . The physical as well as . the \einbein". Because string theory requires a multiverse, string theorists tend to regard the cosmological constant problem as essentially solved by this reasoning. Some of these lead to the Standard Model field content, but with a range of values for the cosmological constant and other constants of nature. For each class we discuss key challenges. The cosmological constant is a simple explanation of dark energy consistent with the observations; however, it is not the only possible explanation, and the value of the cosmological constant consistent with observation is over 60 orders of magnitude different from what theory predicts. The cosmological constant is a parameter measured very close to zero and it is a vintage theoretical problem to explain the smallness of which has eluded physicists for a long time [4]. Followers. We discuss the status of this idea, and future directions. The 2015 Gordon Research Conference on String Theory and Cosmology will be held in Hong Kong, 43 China. The Cosmological Constant - Sean M. Carroll 4.2 String theory Unlike supergravity, string theory appears to be a consistent and well-defined theory of quantum gravity, and therefore calculating the value of the cosmological constant should, at least in principle, be possible. For sufficiently large number of axions, cosmological constant can be accounted for as the potential energy of axions that have not yet relaxed to their minima. String theory axions appear to be promising candidates for explaining cosmological constant via quintessence. Energy Density Evil Clown 9129: Outpost 186, Cambridge MA 21 January 2017 String theory is the most promising candidate for a consistent quantum theory of gravitationally interacting matter fields. Download Links [arxiv.org] . [Submitted on 19 Jul 2021 ( v1 ), last revised 13 Aug 2021 (this version, v2)] Small Cosmological Constants in String Theory Mehmet Demirtas, Manki Kim, Liam McAllister, Jakob Moritz, Andres Rios-Tascon We construct supersymmetric vacua of type IIB string theory in compactifications on orientifolds of Calabi-Yau threefold hypersurfaces. Abstract: We construct vacua of string theory in which all moduli are stabilized and the magnitude of the cosmological constant is exponentially small. We just don't inhabit the mathematical construct that is AdS space. String theory surely admits solutions with nonzero values of the cosmological constant. The fact that string theory landscape produces cosmological constant is a little bit unexpected result. String theory with its negative cosmological constant may provide the answer. . Several attempts have already been made to explain the vanishing cosmological constant in the framework of string theory [5]. CERN-TH/95-36 DFTT 20/95 String Theory and Cosmology⋄ M. C. Bento∗ arXiv:gr-qc/9505038v1 22 May 1995 CERN, Theory Division CH-1211 Geneva 23 Switzerland and O. Bertolami∗† INFN-Sezione Torino Via Pietro Giuria 1 I-10125 Turin, Italy ABSTRACT We discuss the main cosmological implications of considering string-loop effects and . String theory seems to me . A new way is proposed to cancel the cosmological constant. PDF | A bstract We construct supersymmetric AdS 4 vacua of type IIB string theory in compactifications on orientifolds of Calabi-Yau threefold. 09 06 5v 1 [ he pth ] 1 9 Ju l 2 02 1 . If w < -1, which is called phantom dark energy, then the expansion is going to accelerate at such a . In . This shows that the introduction by Einstein of a positive cosmological constant is equivalent to an assumption that the Universe is filled with an ideal fluid of negative pressure equal to its constant energy density: E = Λ.This 'dark energy' can be equivalently described as a tensile material of tension Λ that is locally Lorentz invariant (since g = η in local inertial frames). Similarly, the observed vacuum energy, or cosmological constant, is some 120 orders of magnitude smaller than what is typically expected from string . In the proposed model time evolution of the inflaton field . Anti-de Sitter space-times have a negative cosmological constant (a number that describes the large-scale geometry of the universe); our universe has a positive one. into a precision science as ground and space-based astronomical observations supply a wealth of unprecedently precise cosmological measurements.
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