scholarly journals Constant-roll inflation in the generalized SU(2) Proca theory

2021 ◽  
Author(s):  
Juan Garnica Aguirre ◽  
Luis Gomez Diaz ◽  
Andres Navarro Leon ◽  
Yeinzon Rodriguez Garcia
Keyword(s):  
Vector Field ◽  
Degrees Of Freedom ◽  
Coupling Constants ◽  
Kinetic Term ◽  
De Sitter ◽  
Attraction Basin ◽  
Slow Roll ◽  
Dimensional Phase Space ◽  
Almost All ◽  
New Interactions

Abstract The generalized SU(2) Proca theory (GSU2P for short) is a variant of the well known generalized Proca theory (GP for short) where the vector field belongs to the Lie algebra of the SU(2) group of global transformations under which the action is made invariant. New interesting possibilities arise in this framework because of the existence of new interactions of purely non-Abelian character and new configurations of the vector field that result in spatial spherical symmetry and the cosmological dynamics being driven by the propagating degrees of freedom. We study the two-dimensional phase space of the system that results when the cosmic triad configuration is employed in the Friedmann-Lemaitre-Robertson-Walker background and find an attractor curve whose attraction basin covers almost all the allowed region. Such an attractor curve corresponds to a primordial inflationary solution that has the following characteristic properties: 1.) it is a de Sitter solution whose Hubble parameter is regulated by a generalized version of the SU(2) group coupling constant, 2.) it is constant-roll including, as opposite limiting cases, the slow-roll and ultra slow-roll varieties, 3.) a number of e-folds $N > 60$ is easily reached, 4.) it has a graceful exit into a radiation dominated period powered by the canonical kinetic term of the vector field and the Einstein-Hilbert term. The free parameters of the action are chosen such that the tensor sector of the theory is the same as that of general relativity at least up to second-order perturbations, thereby avoiding the presence of ghost and Laplacian instabilities in the tensor sector as well as making the gravity waves propagate at light speed. This is a proof of concept of the interesting properties we could find in this scenario when the coupling constants be replaced by general coupling functions.

scholarly journals Inflation driven by massive vector fields with derivative self-interactions

2019 ◽  
Vol 28 (04) ◽  
pp. 1950064 ◽  
Author(s):  
A. Oliveros ◽  
Marcos A. Jaraba
Keyword(s):  
Vector Field ◽  
Vector Fields ◽  
Kinetic Term ◽  
Model Parameters ◽  
Tensor Model ◽  
De Sitter ◽  
Frw Universe ◽  
Derivative Coupling ◽  
Massive Vector ◽  
Slow Roll

Inspired by the Generalized Proca Theory, we study a vector–tensor model of inflation with massive vector fields and derivative self-interactions. The action under consideration contains a usual Maxwell-like kinetic term, a general potential term and a term with nonminimal derivative coupling between the vector field and gravity, via the dual Riemann tensor. In this theory, the last term contains a free parameter, [Formula: see text], which quantifies the nonminimal derivative coupling. In this scenario, taking into account a spatially flat Friedmann–Robertson–Walker (FRW) universe and a general vector field, we obtain the general expressions for the equation of motion and the total energy–momentum tensor. Choosing a Proca-type potential, a suitable inflationary regimen driven by massive vector fields is studied. In this model, the isotropy of expansion is guaranteed by considering a triplet of orthogonal vector fields. In order to obtain an inflationary solution with this model, the quasi de Sitter expansion was considered. In this case, the vector field behaves as a constant. Finally, slow-roll analysis is performed and slow-roll conditions are defined for this model, which, for suitable constraints of the model parameters, can give the required number of e-folds for sufficient inflation.

Galileon inflation field with three dark eras of the universe

2020 ◽  
Vol 29 (10) ◽  
pp. 2050071
Author(s):  
A. I. Keskin
Keyword(s):  
Equations Of Motion ◽  
Vacuum State ◽  
Kinetic Term ◽  
Second Phase ◽  
De Sitter ◽  
Third Phase ◽  
Standard Cosmology ◽  
Slow Roll ◽  
Friction Term ◽  
The Universe

In this paper, we discuss possible three early eras of the universe in the theoretical context of the Galilean cosmology. The first phase is a slow-roll inflation phase in which the friction term in the equations of motion dominates over the kinetic term. This is the initial vacuum state leading to quasi-de Sitter expansion. The second phase is where the cosmological perturbations are supposed to be generated. In this phase, the friction term is supposed to be negligible which leads to the appearance of the Galileon inflation field. The third phase is the reheating phase in the standard cosmology, where the oscillations of a canonical scalar field in the model lead to this phase. These three eras for the early universe are shown by a single master equation of the theory. However, we compute observational indices (the scalar spectral index parameter and the tensor-to-scalar ratio) for the era where the era that the perturbations are produced. Finally, we compare viability of the theoretical findings with the latest Planck observational data.

scholarly journals Five dimensional Chern–Simons gravity for the expanded (anti)-de Sitter gauge group $${\hbox {C}}_5$$

2020 ◽  
Vol 80 (2) ◽  
Author(s):  
Matheus M. A. Paixão ◽  
Olivier Piguet
Keyword(s):  
Degrees Of Freedom ◽  
Hamiltonian Dynamics ◽  
Local Symmetry ◽  
Adjoint Representation ◽  
Coupling Constants ◽  
Simons Theory ◽  
De Sitter ◽  
Total Action ◽  
Form Field ◽  
Chern Simons

Abstract We study the Hamiltonian dynamics of a five-dimensional Chern–Simons theory for the gauge algebra $$C_5$$C5 of Izaurieta, Rodriguez and Salgado, the so-called $$\hbox {S}_H$$SH-expansão of the 5D (anti-)de Sitter algebra (a)ds, based on the cyclic group $${\mathbb {Z}}_4$$Z4. The theory consists of a 1-form field containing the (a)ds gravitation variables and 1-form field transforming in the adjoint representation of (a)ds. The gravitational part of the action necessarily contains a term quadratic in the curvature, beyond the Einstein–Hilbert and cosmological terms, for any choice of the two independent coupling constants. The total action is also invariant under a new local symmetry, called “crossed diffeomorphisms”, beyond the usual space-time diffeomorphisms. The number of physical degrees of freedom is computed. The theory is shown to be “generic” in the sense of Bañados, Garay and Henneaux, i.e., the constraint associated to the time diffeomorphisms is not independent from the other constraints.

scholarly journals VECTOR FIELD AND INFLATION

2011 ◽  
Vol 01 ◽  
pp. 120-125 ◽  
Author(s):  
SEOKTAE KOH
Keyword(s):  
Vector Field ◽  
Early Universe ◽  
Vector Potential ◽  
Field Potential ◽  
Kinetic Term ◽  
Small Field ◽  
Timelike Vector ◽  
Massive Vector ◽  
Slow Roll ◽  
Type Potential

We have investigated if the vector field can give rise to an accelerating phase in the early universe. We consider a timelike vector field with a general quadratic kinetic term in order to preserve an isotropic background spacetime. The vector field potential is required to satisfy the three minimal conditions for successful inflation: i) ρ > 0, ii) ρ + 3P < 0, and iii) the slow-roll conditions. As an example, we consider a massive vector potential and a small-field type potential as in scalar driven inflation.

scholarly journals Domestic corpuscular inflaton

2019 ◽  
Vol 16 (07) ◽  
pp. 1950108 ◽  
Author(s):  
Andrea Giugno ◽  
Andrea Giusti
Keyword(s):  
Degrees Of Freedom ◽  
Oscillatory Behavior ◽  
Particle Spectrum ◽  
De Sitter ◽  
Precise Description ◽  
Slow Roll ◽  
Inflationary Phase ◽  
Free Mode ◽  
Scalar Mode ◽  
Slow Roll Inflation

The aim of this paper is to provide a more precise description of the paradigm of corpuscular slow-roll inflation, which was previously introduced by Casadio et al. in [Corpuscular slow-roll inflation, Phys. Rev. D 97 (2018) 024041]. Specifically, we start by expanding the Starobinsky theory on a curved background and then infer the number and nature of the propagating degrees of freedom, both in the true inflationary phase and in a quasi-de Sitter approximation. We correctly find that the particle spectrum contains a transverse trace-free mode and a scalar one. The scalar mode displays a tachyonic nature during the slow-roll phase, due to the instability of the system, whereas it acquires the appropriate oscillatory behavior as the background approaches a critical value of the curvature. These results confirm the fact that the Einstein–Hilbert term acts as a perturbation to the quadratic one, and is responsible for driving the early Universe out of the inflationary phase, thus realizing the inflaton field in terms of pure (corpuscular) gravity.

scholarly journals Inflationary cosmology in unimodular F(T) gravity

2017 ◽  
Vol 32 (21) ◽  
pp. 1750114 ◽  
Author(s):  
Kazuharu Bamba ◽  
Sergei D. Odintsov ◽  
Emmanuel N. Saridakis
Keyword(s):  
Spectral Index ◽  
Teleparallel Gravity ◽  
Specific Model ◽  
Inflationary Cosmology ◽  
Model Parameters ◽  
De Sitter ◽  
Reconstruction Procedure ◽  
Additional Advantage ◽  
Slow Roll ◽  
Good Agreement

We investigate the inflationary realization in the context of unimodular F(T) gravity, which is based on the F(T) modification of teleparallel gravity, in which one imposes the unimodular condition through the use of Lagrange multipliers. We develop the general reconstruction procedure of the F(T) form that can give rise to a given scale-factor evolution, and then we apply it in the inflationary regime. We extract the Hubble slow-roll parameters that allow us to calculate various inflation-related observables, such as the scalar spectral index and its running, the tensor-to-scalar ratio, and the tensor spectral index. Then, we examine the particular cases of de Sitter and power-law inflation, of Starobinsky inflation, as well as inflation in a specific model of unimodular F(T) gravity. As we show, in all cases the predictions of our scenarios are in a very good agreement with Planck observational data. Finally, inflation in unimodular F(T) gravity has the additional advantage that it always allows for a graceful exit for specific regions of the model parameters.

scholarly journals ON THE QUANTUM CHROMODYNAMICS OF A MASSIVE VECTOR FIELD IN THE ADJOINT REPRESENTATION

2013 ◽  
Vol 28 (14) ◽  
pp. 1350054 ◽  
Author(s):  
ALFONSO R. ZERWEKH
Keyword(s):  
Vector Field ◽  
Quantum Chromodynamics ◽  
Extra Dimensions ◽  
Scalar Fields ◽  
Discrete Symmetry ◽  
Adjoint Representation ◽  
Coupling Constants ◽  
Gauge Symmetries ◽  
Gauge Fixing ◽  
Definition Of

In this paper, we explore the possibility of constructing the quantum chromodynamics of a massive color-octet vector field without introducing higher structures like extended gauge symmetries, extra dimensions or scalar fields. We show that gauge invariance is not enough to constraint the couplings. Nevertheless, the requirement of unitarity fixes the values of the coupling constants, which otherwise would be arbitrary. Additionally, it opens a new discrete symmetry which makes the coloron stable and avoid its resonant production at a collider. On the other hand, a judicious definition of the gauge fixing terms modifies the propagator of the massive field making it well-behaved in the ultraviolet limit. The relation between our model and the more general approach based on extended gauge symmetries is also discussed.

scholarly journals Torsion or not torsion, that is the question

2016 ◽  
Vol 25 (12) ◽  
pp. 1644013 ◽  
Author(s):  
Yuri Bonder
Keyword(s):  
General Relativity ◽  
Degrees Of Freedom ◽  
Empirical Support ◽  
Experimental Tests ◽  
Spin Polarized ◽  
Empirical Tests ◽  
New Interactions

A hypothesis of general relativity (GR) is that spacetime torsion vanishes identically. This assumption has no empirical support; in fact, a nonvanishing torsion is compatible with all the experimental tests of GR. The first part of this essay specifies the framework that is suitable to test the vanishing-torsion hypothesis, and an interesting relation with the gravitational degrees of freedom is suggested. In the second part, some original empirical tests are proposed based on the observation that torsion induces new interactions between different spin-polarized particles.

scholarly journals de Sitter vacua in N=8 supergravity and slow-roll conditions

2013 ◽  
Vol 718 (3) ◽  
pp. 1132-1136 ◽  
Author(s):  
G. DallʼAgata ◽  
G. Inverso
Keyword(s):  
De Sitter ◽  
Slow Roll ◽  
De Sitter Vacua

HOLOGRAPHIC SPACETIME

2012 ◽  
Vol 21 (11) ◽  
pp. 1241004 ◽  
Author(s):  
TOM BANKS
Keyword(s):  
String Theory ◽  
Degrees Of Freedom ◽  
Good Description ◽  
De Sitter ◽  
Finite Radius ◽  
Full Field ◽  
Mass Scaling ◽  
Finite Dimensional ◽  
Emergent Phenomena ◽  
Holographic Screen

The theory of holographic spacetime (HST) generalizes both string theory and quantum field theory (QFT). It provides a geometric rationale for supersymmetry (SUSY) and a formalism in which super-Poincare invariance follows from Poincare invariance. HST unifies particles and black holes, realizing both as excitations of noncommutative geometrical variables on a holographic screen. Compact extra dimensions are interpreted as finite-dimensional unitary representations of super-algebras, and have no moduli. Full field theoretic Fock spaces, and continuous moduli are both emergent phenomena of super-Poincare invariant limits in which the number of holographic degrees of freedom goes to infinity. Finite radius de Sitter (dS) spaces have no moduli, and break SUSY with a gravitino mass scaling like Λ1/4. In regimes where the Covariant Entropy Bound is saturated, QFT is not a good description in HST, and inflation is such a regime. Following ideas of Jacobson, the gravitational and inflaton fields are emergent classical variables, describing the geometry of an underlying HST model, rather than "fields associated with a microscopic string theory". The phrase in quotes is meaningless in the HST formalism, except in asymptotically flat and AdS spacetimes, and some relatives of these.

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