String theory seems to me . We just don't inhabit the mathematical construct that is AdS space. 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 . Rev. Since the determinant of the metric now plays a role in the physics, the allowed coordinate . In cosmology, the cosmological constant (usually denoted by the Greek capital letter lambda: ), 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. This would prove to be a mistake when, several years later . In quantum field theory, the vacuum is not really "empty," but is filled with fields that briefly appear because of quantum fluctuations. Regrettably, the sign of the vacuum energy is negative, and some supersymmetry remains unbroken. The corresponding equations resemble those of a Brans-Dicke theory . . 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. Conclusion. An old debate. The 2015 Gordon Research Conference on String Theory and Cosmology will be held in Hong Kong, 43 China. The String Theory Landscape rekindled the ashes of an old debate in physics, one that smolders to this day. The Cosmological Constant From The Viewpoint Of String Theory Edward Witten Dept. ABSTRACT. 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 = .This 'dark energy' can be equivalently described as a tensile material of tension that is locally Lorentz invariant (since g = in local inertial frames). Other configurations have different values of the cosmological constant, and are metastable but long-lived. 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. Apply today to reserve your spot. 7. would expect the cosmological constant to be around the Planck scale. 09 06 5v 1 [ he pth ] 1 9 Ju l 2 02 1 . A bstract Einstein originally posited a nonzero value for the cosmological constant, . If w = -1, the acceleration of the universe is constant and dark energy is the cosmological constant. String theory offers a concrete realization through its landscape of metastable vacua. . 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}. 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. 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 Energy Density Evil Clown 9129: Outpost 186, Cambridge MA 21 January 2017 In cosmology, the cosmological constant (usually denoted by the Greek capital letter lambda: ), 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. . 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. Cosmological Constants by String Theory, released 22 January 2017 1. Some would say that the value . If you start with a theory with no cosmological constant, these vacuum fluctuations . 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 . This enables the anthropic solution to the cosmological constant problem. Questions that were recently the stuff of speculation can .

ar X iv :2 10 7. The vacua are supersymmetric AdS_4 solutions in flux compactifications of type IIB string theory on orientifolds of Calabi-Yau hypersurfaces. In this paper, we study conditions on the string compactifications under which axion quintessence can happen. The proposal involves the metric determinant acting as a type of self-adjusting -field without a fine-tuned chemical potential. String theory has a large number of solutions for the extra dimensions. The fact that string theory landscape produces cosmological constant is a little bit unexpected result. The reason is that the Jacobi identities of the underlying algebra don't allow for one particular sign of the cosmological constant (corresponding to dS). String theory is the most promising candidate for a consistent quantum theory of gravitationally interacting matter fields. The cosmological constant and the string landscape. Other physicists, though, consider this . String Theory Research at UC Berkeley In classical general relativity there are almost no restrictions on spacetime and its matter content. In . Anthropic ideas can help answer other questions about . 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 = .This 'dark energy' can be equivalently described as a tensile material of tension that is locally Lorentz invariant (since g = in local inertial frames). String theory surely admits solutions with nonzero values of the cosmological constant. Abstract: We construct vacua of string theory in which all moduli are stabilized and the magnitude of the cosmological constant is exponentially small. 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 is considered. An essential part of the problem is achieving scale separation in cosmological solutions of quantum gravity: 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 We discuss the cosmological constant seesaw mechanism in the context of various models of current interest including chain inflation, inflatonless inflation, string theory, Universe entanglement . The cosmological constant was a problem, negative, zero, or positive values arrive at different universes . Followers. Much later it was revived and reinterpreted as the energy density of space, or vacuum energy, that arises . The cosmological constant drives the current accelerating expansion of the universe and what is most perplexing about it is its size. 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]. The meaning of STRING THEORY is a theory in physics: all elementary particles are manifestations of the vibrations of one-dimensional strings. | Find, read and cite all the research you need on . 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 . The equation is quite simple, with w being equal to the ideal gas constant R multiplied by temperature and divided by speed of light squared. String theory is one of the few mathematically consistent theories that can unify quantum physics and general relativity. [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. A new way is proposed to cancel the cosmological constant. It turns out that cosmological constant is conserved in .

The string theory landscape is an example of an adjustment mechanism. We discuss the status of this idea, and future directions. Some of these lead to the Standard Model eld content, but with a range of values for the cosmological constant and other constants of nature. 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. We construct a vacuum of string theory in which the magnitude of the vacuum energy is < 10123 in Planck units. 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. String theory attempts to link particle physics, the . String theory axions appear to be promising candidates for explaining cosmological constant via quintessence. energy density galactic halo effect field theory cold dark matter cosmological constant density functional several time string theory theory . The energy density of the vacuum, , is at least 60 orders of magnitude smaller than several known contributions to it. For each class we discuss key challenges. The physical as well as . The problem arises because in the standard framework of low energy physics, there appears to be no natural explanation for

. into a precision science as ground and space-based astronomical observations supply a wealth of unprecedently precise cosmological measurements. Several attempts have already been made to explain the vanishing cosmological constant in the framework of string theory [5]. 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. Membranes in such scenarios are thus surfaces across which the effective cosmological constant can jump. Anthropic ideas can help answer other questions about . Small cosmological constants in string theory. 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. dim. We suggest that a positive cosmological constant can be reconciled with string theory by considering wormholes in . Weinberg, S.: The cosmological constant problem. While observational studies have found that the constant is a really small number between 0 and 1, quantum mechanics predicts that . potential energy axion quintessence theory axions large number planck scale axion potential string compactifications nonzero cosmological constant unified model . The string theory landscape is an example of an adjustment mechanism. Now eliminate efrom (2.13) using the eequation of motion me= . It is well known that quantum field theory (QFT) induces a huge value of the cosmological constant (CC), , 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 vac may be mildly evolving . \gravity", with \cosmological constant" m2; in this interpretation eis the square root of the 1-dim. This value of is in excellent agreement with the measurements recently obtained by the High-Z Supernova Team and the Supernova Cosmology Project. 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. The Cosmological Constant Problem and the Multiverse of String Theory Raphael Bousso Berkeley Center for Theoretical Physics University of California, Berkeley . Small Cosmological Constants in String Theory We construct vacua of string theory in which all moduli are stabilized and the magnitude of the cosmological constant is exponentially small. The cosmological constant can be interpreted as the energy density of the vacuum, and can arise for at least two reasons. 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. . On one side are those who contend, as Albert Einstein once did, that the . 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. 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. Also, an effective cosmic-string-like solution of F-theory . Download Links [arxiv.org] . 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.

The vacua are supersymmetric AdS_4 solutions in flux compactifications of type IIB string theory on orientifolds of Calabi-Yau hypersurfaces. 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. Our approach provides a new angle on the cosmological . 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 is considered. We construct a supersymmetric vacuum of string theory in which the magnitude of the vacuum energy is <10^{-123} in Planck units. 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. The string theory landscape is an example of an adjustment mechanism. (2006), hep-th/0603249. The "cosmological constant problem" In string theory For fundamentally vanishing cc ("Witten's Dark Fantasy") For fundamentally non-vanishing cc 1. the \einbein". STRING THEORY Paul K. Townsend Department of Applied Mathematics and Theoretical Physics Centre for Mathematical Sciences, University of Cambridge . String Scale Cosmological Constant (2006) Cached. The article gives me this impression apparently using a negative cosmological constant. Some of these lead to the Standard Model eld content, but with a range of values for the cosmological constant and other constants of nature. If it is true string theory cannot accommodate stable dark energy, that may be a reason to doubt string theory. . String theory axions appear to be promising candidates for explaining cosmological constant via quintessence. . We discuss the status of this idea, and future directions. 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 . Before string theory, Albert Einstein was strongly influenced by the concept of an unchanging universe. de Sitter vacua of string theory with vac obsthus presents an obstruction to bringing the landscape argument for the cosmological constant problem into sharp focus in quantum gravity. The physical as well as . Susskind notes that string theory has some 10500 possible solutions, each of which could correspond to a separate universe within the multiverse. A special class of conformal gravity theories is proposed to solve the long standing problem of the fine-tuned cosmological constant.

String theory with its negative cosmological constant may provide the answer. If w < -1, which is called phantom dark energy, then the expansion is going to accelerate at such a . 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. History. 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! 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. I String theory:Unique theory, no adjustable parameters, many metastable solutions I Combine D-branes and their associated uxes to tie up 6 extra dimensions ! metric, i.e. String theory has a large number of solutions for the extra dimensions. Mod . 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 eld theory landscape, most observers see a much larger cosmological constant [Abbott 1985, Brown & Teitelboim 1987] 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) are to be determined dynamically at any local minimum solution in the string theory landscape. One example of such a duality [330] arises as follows: A particular kind of string theory in ten dimension (called type II Bstring theory) 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. DR. CRAIG: Here it's kind of like a teeter-totter. You can either deny string theory because it's . M. Demirtas, Manki Kim, L . 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 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 numerical value of the cosmological constant is calculated using a recently suggested cosmological model and found to be 35 s 2. Because string theory requires a multiverse, string theorists tend to regard the cosmological constant problem as essentially solved by this reasoning. 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. It also affects quantum mechanics and, in one way, string theory. One "solution" has been proposed by physicists working in string theory, who for 30 years have been earnestly seeking a complete and unique .

On the other hand, the number of vacuum states seems to be quite large, In this paper, we study conditions on the string compactifications under which axion quintessence can happen. 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. An extension of unimodular gravity and the cosmological constant. But to Vafa it is a reason to doubt dark energythat is, dark energy in its most popular form, called a cosmological constant. 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]. . We discuss the status of this idea, and future directions. It is well known that quantum field theory (QFT) induces a huge value of the cosmological constant (CC), , 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 vac may be mildly evolving . The vacua are supersymmetric AdS_4 solutions in flux compactifications of type IIB string theory on orientifolds of Calabi-Yau hypersurfaces. Idea In theories of gravity and cosmology a cosmological constant refers to an energy contribution associated with the vacuum itself. 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!

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. Cosmological constant and axions in string theory (2006) Cached. PDF | A bstract We construct supersymmetric AdS 4 vacua of type IIB string theory in compactifications on orientifolds of Calabi-Yau threefold. 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. 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. It is also interesting that we, for one special choice of background fields, after rescalling space-time metric, made a possible connection to the Conformal Cyclic Cosmology (CCC). Similarly, the observed vacuum energy, or cosmological constant, is some 120 orders of magnitude smaller than what is typically expected from string . Download Links [arxiv.org] [arxiv.org] . Here we consider a model that links the supersymmetric electroweak phenomenology (bottom . 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 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. Quanta Magazine, . This enables the anthropic solution to the cosmological constant problem.

CONCLUSION In this paper it is shown that the cosmological model for Takabayasi String with . The "cosmological constant'" of Einstein's general relativity equations is linearly related to the zero-point mass density.

The cosmological constant drives the current accelerating expansion of the universe and what is most perplexing about it is its size. Much later it was revived and reinterpreted as the energy density of space, or vacuum energy, that arises . For each class we discuss key challenges. In the proposed model time evolution of the inflaton field . 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. Some would say that the value . String theory seems to me to have failed to deliver what it had promised in the '80s, and is one of the . His general theory of relativity predicted a dynamic universe one that changed substantially over time so he introduced a term, called the cosmological constant, into the theory to make the universe static and eternal..

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. The mechanism that we introduce generates a well-controlled exponential hierarchy from an appropriate choice of the quantized parameters in the superpotential.