Possible solution to the horizon problem: Modified aging in massless scalar theories of gravity

1993 ◽  
Vol 47 (10) ◽  
pp. 4282-4291 ◽  
Author(s):  
Janna J. Levin ◽  
Katherine Freese
Keyword(s):  
Massless Scalar ◽  
Horizon Problem ◽  
Theories Of Gravity ◽  
Scalar Theories

scholarly journals Cosmological constraints on post-Newtonian parameters in effectively massless scalar-tensor theories of gravity

2019 ◽  
Vol 100 (10) ◽  
Author(s):  
Massimo Rossi ◽  
Mario Ballardini ◽  
Matteo Braglia ◽  
Fabio Finelli ◽  
Daniela Paoletti ◽  
...  
Keyword(s):  
Massless Scalar ◽  
Cosmological Constraints ◽  
Theories Of Gravity

scholarly journals ON BOUNDARY TERMS AND CONFORMAL TRANSFORMATIONS IN CURVED SPACETIMES

2002 ◽  
Vol 11 (05) ◽  
pp. 703-714 ◽  
Author(s):  
R. CASADIO ◽  
A. GRUPPUSO
Keyword(s):  
Hamiltonian Formalism ◽  
Massless Scalar ◽  
Massless Scalar Field ◽  
Conformal Transformations ◽  
Five Dimensions ◽  
Four Dimensions ◽  
Boundary Terms ◽  
Pure Gravity ◽  
Theories Of Gravity ◽  
Flat Spacetimes

We intend to clarify the interplay between boundary terms and conformal transformations in scalar-tensor theories of gravity. We first consider the action for pure gravity in five dimensions and show that, on compactifing a la Kaluza–Klein to four dimensions, one obtains the correct boundary terms in the Jordan (or String) Frame form of the Brans–Dicke action. Further, we analyze how the boundary terms change under the conformal transformations which lead to the Pauli (or Einstein) frame and to the nonminimally coupled massless scalar field. In particular, we study the behaviour of the total energy in asymptotically flat spacetimes as it results from surface terms in the Hamiltonian formalism.

ON STABILITY OF SIMPLEST NONSINGULAR INFLATIONARY COSMOLOGICAL MODELS WITHIN GENERAL RELATIVITY AND GAUGE THEORIES OF GRAVITY

2004 ◽  
Vol 13 (04) ◽  
pp. 695-707 ◽  
Author(s):  
G. V. VERESHCHAGIN
Keyword(s):  
General Relativity ◽  
Scalar Field ◽  
Gauge Theories ◽  
Initial Conditions ◽  
Solvable Model ◽  
Cosmological Models ◽  
Massless Scalar ◽  
Massless Scalar Field ◽  
Theories Of Gravity ◽  
Analysis Of Stability

In this paper we provide approximate analytical analysis of stability of nonsingular inflationary chaotic-type cosmological models. Initial conditions for nonsingular solutions at the bounce correspond to dominance of potential part of the energy density of the scalar field over its kinetic part both within general relativity and gauge theories of gravity. Moreover, scalar field at the bounce exceeds the Planckian value and on expansion stage these models correspond to chaotic inflation. Such solutions can be well approximated by explicitly solvable model with constant effective potential (cosmological term) and massless scalar field during the bounce and on stages of quasi-exponential contraction and expansion. Perturbative analysis shows that nonsingular inflationary solutions are exponentially unstable during contraction stage. This result is compared with numerical calculations.

scholarly journals Weights, recursion relations and projective triangulations for positive geometry of scalar theories

2020 ◽  
Vol 2020 (10) ◽  
Author(s):  
Renjan Rajan John ◽  
Ryota Kojima ◽  
Sujoy Mahato
Keyword(s):  
Scattering Amplitudes ◽  
Detailed Analysis ◽  
Tree Level ◽  
Massless Scalar ◽  
Weighted Sum ◽  
Canonical Forms ◽  
Factorization Property ◽  
Scalar Theory ◽  
Recursion Relations ◽  
Scalar Theories

Abstract The story of positive geometry of massless scalar theories was pioneered in [1] in the context of bi-adjoint ϕ3 theories. Further study proposed that the positive geometry for a generic massless scalar theory with polynomial interaction is a class of polytopes called accordiohedra [2]. Tree-level planar scattering amplitudes of the theory can be obtained from a weighted sum of the canonical forms of the accordiohedra. In this paper, using results of the recent work [3], we show that in theories with polynomial interactions all the weights can be determined from the factorization property of the accordiohedron. We also extend the projective recursion relations introduced in [4, 5] to these theories. We then give a detailed analysis of how the recursion relations in ϕp theories and theories with polynomial interaction correspond to projective triangulations of accordiohedra. Following the very recent development [6] we also extend our analysis to one-loop integrands in the quartic theory.

scholarly journals Slowly rotating topological neutron stars: universal relations and epicyclic frequencies

2020 ◽  
Vol 80 (9) ◽  
Author(s):  
Victor I. Danchev ◽  
Daniela D. Doneva ◽  
Stoytcho S. Yazadjiev
Keyword(s):  
General Relativity ◽  
Neutron Stars ◽  
Strong Field ◽  
Compact Objects ◽  
X Ray ◽  
Tests Of General Relativity ◽  
New Type ◽  
Theories Of Gravity ◽  
Scalar Theories ◽  
The Moment

AbstractIn the modern era of abundant X-ray detections and the increasing momentum of gravitational waves astronomy, tests of general relativity in strong field regime become increasingly feasible and their importance for probing gravity cannot be understated. To this end, we study the characteristics of slowly rotating topological neutron stars in the tensor-multi-scalar theories of gravity following the static study of this new type of compact objects by two of the authors. We explore the moment of inertia and verify that universal relations known from general relativity hold for this new class of compact objects. Furthermore, we study the properties of their innermost stable circular orbits and the epicyclic frequencies due to the latter’s hinted link to observational quantities such as quasi-periodic X-ray spectrum features.

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