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We study the three dimensional Einstein gravity conformally coupled to a scalar field. Solutions of this theory are geometries with vanishing scalar curvature. We consider solutions with a constant scalar field which corresponds to an…

High Energy Physics - Theory · Physics 2012-11-08 M. Hasanpour , F. Loran , H. Razaghian

We construct the general four-dimensional N=2 supergravity theory coupled to vector and vector-tensor multiplets only. Consistency of the construction requires the introduction of the vector fields dual to those sitting in the same…

High Energy Physics - Theory · Physics 2011-07-06 Laura Andrianopoli , Riccardo D'Auria , Luca Sommovigo , Mario Trigiante

We propose a 3 + 1 dimensional model of gravity which results in inflation at early times, followed by radiation- and matter-dominated epochs and a subsequent acceleration at late times. Both the inflation and late time acceleration are…

High Energy Physics - Theory · Physics 2015-05-30 Carlos Herdeiro , Shinji Hirano

The Standard Model has three generations of fermions and although it does not contain any explicit reason for this, the existence of additional generations is now very constrained by experiment. Present measurements are saturating…

High Energy Physics - Phenomenology · Physics 2014-12-17 Alfredo Aranda , Jose A. R. Cembranos

The unified theory of string and two-dimensional quantum gravity is considered. The action for two-dimensional gravity is choosen in a well-known induced form and thus gravity posesses it's oun nontrivial dynamics even on the classical…

High Energy Physics - Theory · Physics 2007-05-23 I. L. Buchbinder , I. L. Shapiro , A. G. Sibiryakov

We consider the most general action for gravity which is quadratic in curvature. In this case first order and second order formalisms are not equivalent. This framework is a good candidate for a unitary and renormalizable theory of the…

High Energy Physics - Theory · Physics 2017-12-22 Enrique Alvarez , Jesus Anero , Sergio Gonzalez-Martin

Scalar-tensor theories of gravity modify General Relativity by introducing a scalar field that couples non-minimally to the metric tensor, while satisfying the weak-equivalence principle. These theories are interesting because they have the…

General Relativity and Quantum Cosmology · Physics 2017-09-27 David Anderson , Nicolas Yunes

The main obstacle in attempts to construct a consistent quantum gravity is the absence of independent flat time. This can in principle be cured by going out to higher dimensions. The modern paradigm assumes that the fundamental theory of…

High Energy Physics - Theory · Physics 2008-11-26 A. V. Smilga

Gravity cannot be quantized unless the quantized theory is cast on a manifold whose concomitant number of physical space dimensions and number of physical time dimensions correspond to physical reality, and not simply to the perception of…

General Physics · Physics 2014-06-09 Patrick L. Nash

Cosmic acceleration can be achieved not only with a sufficiently flat scalar field potential but through kinetic terms coupled to gravity. These derivative couplings impose a shift symmetry on the scalar field, aiding naturalness. We write…

Cosmology and Nongalactic Astrophysics · Physics 2011-11-29 Giulia Gubitosi , Eric V. Linder

We consider the supersymmetric vector multiplet in a purely quantum framework. We obtain some discrepancies with respect to the literature in the expression of the super-propagator and we prove that the model is consistent only for positive…

High Energy Physics - Theory · Physics 2009-11-07 Dan Radu Grigore , Günter Scharf

Gravitational instantons with NUT charge are magnetic monopoles upon dimensional reduction. We determine whether NUT charge can proliferate via the Polyakov mechanism and partially screen gravitational interactions. In semiclassical…

High Energy Physics - Theory · Physics 2015-06-18 Sean A. Hartnoll , David M. Ramirez

This study toward quantum gravity (QG) introduces an SU(N) gauge theory with the \Theta vacuum term for gravitational interactions, which leads to a group SU(2)_L x U(1)_Y x SU(3)_C for weak and strong interactions through dynamical…

General Relativity and Quantum Cosmology · Physics 2007-05-23 Heui-Seol Roh

We consider a discrete model of euclidean quantum gravity in four dimensions based on a summation over random simplicial manifolds. The action used is the Einstein-Hilbert action plus an $R^2$-term. The phase diagram as a function of the…

High Energy Physics - Theory · Physics 2009-10-22 J. Ambjorn , J. Jurkiewicz , C. F. Kristjansen

We establish Einstein-Hilbert gravity couplings in the effective action for Intersecting Brane Worlds. The four-dimensional induced Planck mass is determined by calculating graviton scattering amplitudes at one-loop in the string…

High Energy Physics - Theory · Physics 2008-11-26 Friedel Epple

Newton's gravitational constant $G$ has been measured to high accuracy in a number of independent experiments. For currently unresolved reasons, indicated values from different well-designed and thoroughly analyzed experiments differ by…

General Physics · Physics 2022-09-28 R. K. Nesbet

A self-interacting SU(2)-doublet of complex scalar fields, minimally coupled to Einstein-Gauss-Bonnet gravity is considered in five space-time dimensions. The classical equations admit two families of solitons corresponding to spinning and…

General Relativity and Quantum Cosmology · Physics 2014-06-11 Yves Brihaye , Jürgen Riedel

The Standard Model for electroweak interactions derives four vector gauge boson from an SU(2)xU(1) symmetry. A doublet of complex scalar (Higgs) bosons is added to generate masses by spontaneous symmetry breaking. Both, the four vector…

General Physics · Physics 2015-09-04 Martin A. Faessler

There are many theories of quantum gravity, depending on asymptotic boundary conditions, and the amount of supersymmetry. The cosmological constant is one of the fundamental parameters that characterize different theories. If it is…

High Energy Physics - Theory · Physics 2015-06-26 T. Banks

Within the extremal black hole attractors arising in ungauged $\mathcal{N}\geqslant 2$-extended Maxwell Einstein supergravity theories in $3+1$ space-time dimensions, we provide an overview of the stratification of the electric-magnetic…

High Energy Physics - Theory · Physics 2023-12-21 Alessio Marrani