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We generalize previous work by considering a novel gravitational model with an action given by an arbitrary function of the Ricci scalar, the matter Lagrangian density, a scalar field and a kinetic term constructed from the gradients of the…

General Relativity and Quantum Cosmology · Physics 2013-02-06 Tiberiu Harko , Francisco S. N. Lobo , Olivier Minazzoli

Different mechanisms which may possibly explain existence of magnetic fields on astronomically large scales are described. A recently suggested model of magnetic fields generation slightly before hydrogen recombination is discussed in more…

Astrophysics · Physics 2007-05-23 A. D. Dolgov

Field Theory on Event Symmetric space-time is constructed using the gauge group of discrete open strings. Models with invariant actions can be viewed as natural extensions of Matrix Models. The objective is to find a fundamental…

High Energy Physics - Theory · Physics 2007-05-23 P. E. Gibbs

In angular quantization approach a perturbation theory for the Massive Thirring Model (MTM) is developed, which allows us to calculate Vacuum Expectation Values of exponential fields in sin-Gordon theory near the free fermion point in first…

High Energy Physics - Theory · Physics 2009-10-31 R. H. Poghossian

The recently proposed non-Gaussian Mat\'{e}rn random field models, generated through Stochastic Partial differential equations (SPDEs), are extended by considering the class of Generalized Hyperbolic processes as noise forcings. The models…

Applications · Statistics 2013-07-25 David Bolin , Jonas Wallin

It has been speculated that gravity could be an emergent phenomenon, with classical general relativity as an effective, macroscopic theory, valid only for classical systems at large temporal and spatial scales. As in classical continuum…

General Relativity and Quantum Cosmology · Physics 2015-06-24 Huan Yang , Larry R. Price , Nicolas D. Smith , Rana X Adhikari , Haixing Miao , Yanbei Chen

We give a critical overview of various attempts to describe gravity as an emergent phenomenon, starting from examples of condensed matter physics, to arrive to more sophisticated pregeometric models. The common line of thought is to view…

General Relativity and Quantum Cosmology · Physics 2012-05-15 Lorenzo Sindoni

The Gaussian process state-space model (GPSSM) has attracted extensive attention for modeling complex nonlinear dynamical systems. However, the existing GPSSM employs separate Gaussian processes (GPs) for each latent state dimension,…

Machine Learning · Computer Science 2023-09-06 Zhidi Lin , Juan Maroñas , Ying Li , Feng Yin , Sergios Theodoridis

We develop an analytical forward model based on perturbation theory to predict the redshift-space galaxy overdensity at the field level given a realization of the initial conditions. We find that the residual noise between the model and…

Cosmology and Nongalactic Astrophysics · Physics 2021-06-02 Marcel Schmittfull , Marko Simonović , Mikhail M. Ivanov , Oliver H. E. Philcox , Matias Zaldarriaga

Large computer models are ubiquitous in the earth sciences. These models often have tens or hundreds of tuneable parameters and can take thousands of core-hours to run to completion while generating terabytes of output. It is becoming…

Atmospheric and Oceanic Physics · Physics 2022-03-21 Duncan Watson-Parris , Andrew Williams , Lucia Deaconu , Philip Stier

Expression for second post-Newtonian level gravitational deflection angle of massive particles is obtained in a model independent framework. Several of its important implications including the possibility of testing gravitational theories…

General Relativity and Quantum Cosmology · Physics 2008-11-26 A. Bhadra , K. Sarkar , K. K. Nandi

In this work, we analyze the possibility of gravitationally induced matter creation in the so-called Energy-Momentum-Squared gravity (EMSG), i.e. $f(R,T_{\mu\nu}T^{\mu\nu})$ gravity, in its dynamically equivalent scalar-tensor…

General Relativity and Quantum Cosmology · Physics 2024-03-15 Ricardo A. C. Cipriano , Tiberiu Harko , Francisco S. N. Lobo , Miguel A. S. Pinto , João Luís Rosa

Some models within the framework of Gauss-Bonnet gravities are considered in the presence of a non-minimally coupled scalar field. By imposing a particular constraint on the scalar field coupling, an extension of the called…

General Relativity and Quantum Cosmology · Physics 2022-07-19 Sergei D. Odintsov , Diego Saez-Chillon Gomez , German S. Sharov

We consider a DGP brane scenario where a scalar field is present on the brane through the introduction of a scalar potential, itself motivated by the notion of modified gravity. This theory predicts that the mass appearing in the…

General Relativity and Quantum Cosmology · Physics 2008-11-26 K. Atazadeh , H. R. Sepangi

Using the biquaternions algebra with involution and mutual quaternional gradients the equations of one model of electro-gravimagnetic (EGM) field are constructed on the base of Hamilton form of Maxwell equations. For this field the…

Mathematical Physics · Physics 2007-05-23 Lyudmila A. Alexeyeva

We present a novel scenario where a scalar field acquires a mass which depends on the local matter density: the field is massive on Earth, where the density is high, but is essentially free in the solar system, where the density is low. All…

Astrophysics · Physics 2009-11-10 Justin Khoury , Amanda Weltman

The origin of galactic and extra-galactic magnetic fields is an unsolved problem in modern cosmology. A possible scenario comes from the idea of these fields emerged from a small field, a seed, which was produced in the early universe…

Cosmology and Nongalactic Astrophysics · Physics 2013-06-14 Hector J. Hortua , Leonardo Castaneda , Juan M. Tejeiro

We examine an analytic variational inference scheme for the Gaussian Process State Space Model (GPSSM) - a probabilistic model for system identification and time-series modelling. Our approach performs variational inference over both the…

Machine Learning · Statistics 2018-12-11 Alessandro Davide Ialongo , Mark van der Wilk , Carl Edward Rasmussen

A modified theory of gravity, avoiding singularities in the standard theory of gravitation, has been developed by Hess & Greiner, known as the pseudo-complex theory of gravitation. The pc-GR theory shows remarkable observational differences…

Astrophysics of Galaxies · Physics 2019-03-06 Th. Boller , P. O. Hess , A. Mueller , H. Stoecker

Here, we analyze the primordial magnetic field transition between a radiative and a matter-dominated universe. The gravitational structure formation affects its evolution and energy spectrum. The structure excitation can trigger magnetic…

Astrophysics · Physics 2009-11-10 Grazyna Siemieniec-Ozieblo