scholarly journals Topological Gravity Motivated by Renormalization Group

Symmetry ◽  
2018 ◽  
Vol 10 (9) ◽  
pp. 396 ◽  
Author(s):  
Taisaku Mori ◽  
Shin’ichi Nojiri
Keyword(s):  
Fixed Point ◽  
Renormalization Group ◽  
Cosmological Constant ◽  
Coupling Constants ◽  
Late Time ◽  
De Sitter ◽  
Topological Field ◽  
Lagrangian Densities ◽  
Topological Theories ◽  
The Universe

Recently, we have proposed models of topological field theory including gravity in Mod. Phys. Lett. A 2016, 31, 1650213 and Phys. Rev. D 2017, 96, 024009, in order to solve the problem of the cosmological constant. The Lagrangian densities of the models are BRS (Becchi-Rouet-Stora) exact and therefore the models can be regarded as topological theories. In the models, the coupling constants, including the cosmological constant, look as if they run with the scale of the universe and its behavior is very similar to the renormalization group. Motivated by these models, we propose new models with an the infrared fixed point, which may correspond to the late time universe, and an ultraviolet fixed point, which may correspond to the early universe. In particular, we construct a model with the solutions corresponding to the de Sitter space-time both in the ultraviolet and the infrared fixed points.

scholarly journals Towards the Structure of Black Holes in Asymptotically Safe Gravity

2018 ◽  
Author(s):  
Adémólá Adéìféoba
Keyword(s):  
Black Holes ◽  
Fixed Point ◽  
Renormalization Group ◽  
Cosmological Constant ◽  
Critical Exponents ◽  
De Sitter ◽  
Renormalization Group Flow ◽  
Spacetime Singularity ◽  
Singularity Resolution ◽  
Group Flow

Asymptotically safe quantum gravity suggests a resolution to the classical spacetime singularity of Schwarzschild-(A)dS black holes. In particular, this is realizable only for a vanishing microscopic value of the dimensionless cosmological constant at the asymptotically safe fixed point. To accommodate a nonzero infrared value of the cosmological constant, we consider the linearized Renormalization Group flow away from the fixed point, which is characterized by two critical exponents in the Einstein-Hilbert truncation. In this study, we show that the realization of a regular de-Sitter core places a bound on the universal gravitational critical exponents. Accordingly, our study hints at the possibility of singularity resolution in black holes, as explicit estimates of the critical exponents in the literature point towards a realization of our bound.

scholarly journals THE CASE OF ASYMPTOTIC SUPERSYMMETRY

2013 ◽  
Vol 28 (14) ◽  
pp. 1350053 ◽  
Author(s):  
BRUCE L. SÁNCHEZ-VEGA ◽  
ILYA L. SHAPIRO
Keyword(s):  
Fixed Point ◽  
Renormalization Group ◽  
Gauge Coupling ◽  
High Energy ◽  
Systematic Investigation ◽  
Coupling Constants ◽  
Scalar Coupling ◽  
Asymptotic State ◽  
Stable Fixed Point ◽  
Scalar Couplings

We start systematic investigation for the possibility to have supersymmetry (SUSY) as an asymptotic state of the gauge theory in the high energy (UV) limit, due to the renormalization group running of coupling constants of the theory. The answer on whether this situation takes place or not, can be resolved by dealing with the running of the ratios between Yukawa and scalar couplings to the gauge coupling. The behavior of these ratios does not depend too much on whether gauge coupling is asymptotically free (AF) or not. It can be shown that the UV stable fixed point for the Yukawa coupling is not supersymmetric. Taking this into account, one can break down SUSY only in the scalar coupling sector. We consider two simplest examples of such breaking, namely N = 1 supersymmetric QED and QCD. In one of the cases one can construct an example of SUSY being restored in the UV regime.

Cosmic acceleration with tachyon field

2018 ◽  
Vol 33 (34) ◽  
pp. 1850199 ◽  
Author(s):  
A. I. Keskin
Keyword(s):  
Scalar Field ◽  
Energy Momentum Tensor ◽  
Momentum Tensor ◽  
Cosmic Acceleration ◽  
Late Time ◽  
De Sitter ◽  
Tachyon Field ◽  
Minimal Coupling ◽  
Acceleration Of The Universe ◽  
The Universe

In this study, we examine two models of the scalar field, that is, a normal scalar field and a tachyon scalar field in [Formula: see text] gravity to describe cosmic acceleration of the universe, where [Formula: see text], [Formula: see text] and [Formula: see text] are Ricci curvature scalar, trace of energy–momentum tensor and kinetic energy of scalar field [Formula: see text], respectively. Using the minimal-coupling Lagrangian [Formula: see text], for both the scalar models we obtain a viable cosmological system, where [Formula: see text] and [Formula: see text] are real constants. While a normal scalar field gives a system describing expansion from the deceleration to the late-time acceleration, tachyon field together with [Formula: see text] in the system produces a quintessential expansion which is very close to de Sitter point, where we find a new condition [Formula: see text] for inflation.

A DYNAMICAL SYSTEM APPROACH TO THE GBIG COSMOLOGY

2011 ◽  
Vol 08 (06) ◽  
pp. 1179-1188 ◽  
Author(s):  
KOUROSH NOZARI ◽  
F. KIANI
Keyword(s):  
Dynamical System ◽  
Phase Space ◽  
Cosmological Constant ◽  
System Approach ◽  
Stable Solution ◽  
Late Time ◽  
Curvature Effect ◽  
De Sitter ◽  
Dynamical System Approach ◽  
Bonnet Term

We study the phase space of an extension of the normal DGP cosmology with a cosmological constant on the brane and curvature effect that is incorporated via the Gauss–Bonnet term in the bulk action. We study late-time cosmological dynamics of this scenario within a dynamical system approach. We show that the stable solution of the cosmological dynamics in this model is a de Sitter phase.

BLACK HOLE QUANTIZATION, THERMODYNAMICS AND COSMOLOGICAL CONSTANT

2004 ◽  
Vol 13 (05) ◽  
pp. 885-898
Author(s):  
LI XIANG
Keyword(s):  
Black Hole ◽  
Cosmological Constant ◽  
Vacuum Energy ◽  
Planck Scale ◽  
Additional Term ◽  
Logarithmic Correction ◽  
De Sitter ◽  
Horizon Area ◽  
Constant Distance ◽  
The Universe

Bekenstein argues that the horizon area of a black hole has a constant distance spectrum. We investigate the effects of such a discrete spectrum on the thermodynamics of a Schwarzchild black hole (SBH) and a Schwarzchild–de Sitter black hole (SdBH), in terms of the time-energy uncertainty relation and Stefan–Boltzman law. For the massive SBH, a negative and logarithmic correction to the Bekenstein–Hawking entropy is obtained, as well as other authors by using other methods. As to the minimal hole near the Planck scale, its entropy is no longer proportional to the horizon area, but is of order of the mass of the hole. This is similar to an excited stringy state. The vanishing heat capacity of such a minimal black hole implies that it may be a remnant as the ground state of the evaporating hole. The properties of a SdBH are similar to the SBH, except for an additional term of square area associated with the cosmological constant. In order to maintain the validity of the Bekenstein–Hawking formula, the cosmological constant is strongly limited by the size of the biggest black hole in the universe. A relation associated with the cosmological constant, Planck area and the Stefan–Boltzman constant is obtained. The cosmological constant is not only related to the vacuum energy, but is also related to the thermodynamics.

scholarly journals Cosmological constant from the emergent gravity perspective

2014 ◽  
Vol 23 (06) ◽  
pp. 1430011 ◽  
Author(s):  
T. Padmanabhan ◽  
Hamsa Padmanabhan
Keyword(s):  
Cosmological Constant ◽  
Sufficient Conditions ◽  
Integration Constant ◽  
Dimensionless Number ◽  
Late Time ◽  
Field Equations ◽  
Cosmological Constant Problem ◽  
Emergent Gravity ◽  
Background Material ◽  
The Universe

Observations indicate that our universe is characterized by a late-time accelerating phase, possibly driven by a cosmological constant Λ, with the dimensionless parameter [Formula: see text], where LP= (Għ/c3)1/2is the Planck length. In this review, we describe how the emergent gravity paradigm provides a new insight and a possible solution to the cosmological constant problem. After reviewing the necessary background material, we identify the necessary and sufficient conditions for solving the cosmological constant problem. We show that these conditions are naturally satisfied in the emergent gravity paradigm in which (i) the field equations of gravity are invariant under the addition of a constant to the matter Lagrangian and (ii) the cosmological constant appears as an integration constant in the solution. The numerical value of this integration constant can be related to another dimensionless number (called CosMIn) that counts the number of modes inside a Hubble volume that cross the Hubble radius during the radiation and the matter-dominated epochs of the universe. The emergent gravity paradigm suggests that CosMIn has the numerical value 4π, which, in turn, leads to the correct, observed value of the cosmological constant. Further, the emergent gravity paradigm provides an alternative perspective on cosmology and interprets the expansion of the universe itself as a quest towards holographic equipartition. We discuss the implications of this novel and alternate description of cosmology.

scholarly journals Chaotic inflation in spatially homogeneous Bianchi type V space–time

2017 ◽  
Vol 95 (12) ◽  
pp. 1267-1270
Author(s):  
Raj Bali ◽  
P. Kumari
Keyword(s):  
Bianchi Type ◽  
Space Time ◽  
Late Time ◽  
De Sitter ◽  
Spatially Homogeneous ◽  
Inflationary Parameters ◽  
Type V ◽  
The Universe ◽  
Anisotropic Phase ◽  
Bianchi Type V

Chaotic inflationary scenario in spatially homogeneous Bianchi type V space–time following Linde (Phys. Lett. B, 129, 177 (1983). doi: 10.1016/0370-2693(83)90837-7 ) and the condition [Formula: see text] based on theory of super cooling during the cosmological phase transition proposed by Kirzhnits and Linde (Ann. Phys. 101, 195 (1976). doi: 10.1016/0003-4916(76)90279-7 ), is discussed. It has been found that the model represents anisotropic phase of the Universe in general but at late time, it isotropizes. The deceleration parameter q = −1 indicates that the model leads to de Sitter space–time. It is found that inflationary parameters, namely, slow roll parameters, and anisotropic parameters are in excellent agreement with the Planck Collaboration’s 2013 results (Astron. Astrophys. 571, A22 (2014). doi: 10.1051/0004-6361/201321569 ).

scholarly journals LATE-TIME PHANTOM UNIVERSE IN SO(1, 1) DARK ENERGY MODEL WITH EXPONENTIAL POTENTIAL

2005 ◽  
Vol 20 (15) ◽  
pp. 1147-1154 ◽  
Author(s):  
YI-HUAN WEI
Keyword(s):  
Dark Energy ◽  
Dark Energy Model ◽  
Energy Model ◽  
Late Time ◽  
De Sitter ◽  
Exponential Potential ◽  
Coupling Energy ◽  
Expansion Phase ◽  
Perturbation Field ◽  
The Universe

We discuss the late-time property of universe and phantom field in the SO(1, 1) dark energy model for the potential V = V0e-βΦα with α and β two positive constants. We assume in advance some conditions satisfied by the late-time field to simplify equations, which are confirmed to be correct from the eventual results. For α < 2, the field falls exponentially off and the phantom equation of state rapidly approaches -1. When α = 2, the kinetic energy ρk and the coupling energy ρc become comparable but there is always ρk < -ρc so that the phantom property of field proceeds to hold. The analysis on the perturbation to the late-time field Φ illustrates the square effective mass of the perturbation field is always positive and thus the phantom is stable. The universe considered currently may evade the future sudden singularity and will evolve to de Sitter expansion phase.

scholarly journals A novel teleparallel dark energy model

2016 ◽  
Vol 25 (02) ◽  
pp. 1650025 ◽  
Author(s):  
Giovanni Otalora
Keyword(s):  
Dark Energy ◽  
Scalar Field ◽  
Teleparallel Gravity ◽  
Accelerated Expansion ◽  
Late Time ◽  
De Sitter ◽  
Sitter Group ◽  
Current State ◽  
Expansion Of The Universe ◽  
The Universe

Although equivalent to general relativity, teleparallel gravity (TG) is conceptually speaking a completely different theory. In this theory, the gravitational field is described by torsion, not by curvature. By working in this context, a new model is proposed in which the four-derivative of a canonical scalar field representing dark energy is nonminimally coupled to the “vector torsion”. This type of coupling is motivated by the fact that a scalar field couples to torsion through its four-derivative, which is consistent with local spacetime kinematics regulated by the de Sitter group [Formula: see text]. It is found that the current state of accelerated expansion of the universe corresponds to a late-time attractor that can be (i) a dark energy-dominated de Sitter solution ([Formula: see text]), (ii) a quintessence-type solution with [Formula: see text], or (iii) a phantom-type [Formula: see text] dark energy.

scholarly journals Cold dark matter: Bose-Einstein condensation of gluons in Anti-de Sitter space time

2021 ◽  
Author(s):  
Gilles Cohen-Tannoudji ◽  
Jean-Pierre Gazeau
Keyword(s):  
Dark Matter ◽  
Dark Energy ◽  
Standard Model ◽  
Cosmological Constant ◽  
Cold Dark Matter ◽  
Hidden Variables ◽  
Einstein Condensation ◽  
De Sitter ◽  
Bose Einstein ◽  
The Universe

In the same way as the realization of some of the famous gedanken experiments imagined by the founding fathers of quantum mechanics has recently led to the current renewal of the interpretation of quantum physics, it seems that the most recent progresses of observational astrophysics can be interpreted as the realization of some cosmological gedanken experiments such as the removal from the universe of the whole visible matter or the cosmic time travel leading to a new cosmological standard model. This standard model involves two dark components of the universe, dark energy and dark matter. Whereas dark energy is usually associated with the positive cosmological constant, we propose to explain dark matter as a pure QCD effect. This effect is due to the trace anomaly viewed as a negative cosmological constant accompanying baryonic matter at the hadronization transition from the quark gluon plasma phase to the colorless hadronic phase. Our approach not only yields a ratio Dark/Visible equal to 11/2 but also provides gluons and (anti-)quarks with an extra mass of vibrational nature. Currently observed dark matter is thus interpreted as a gluon Bose Einstein condensate that is a relic of the quark period. Such an interpretation would comfort the idea that, apart from the violation of the matter/antimatter symmetry satisfying the Sakharov&rsquo;s conditions, the reconciliation of particle physics and cosmology needs not the recourse to any ad hoc fields, particles or hidden variables.

Sign in / Sign up

Export Citation Format

Share Document