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Gravity
Presents the basic principles of gravity, a history of how the theory was developed, the revisions made by Albert Einstein, and descriptions of how gravity works in space, with examples from America's space program.
Book
Rapidly rotating neutron stars in Formula omitted gravity
In this work, we study the influence of f(R, T) gravity on rapidly rotating neutron stars. First we discuss the main aspects of this modified theory of gravity where the gravitational Lagrangian is an arbitrary function of the Ricci scalar R and of the trace of the energy-momentum tensor T. Then we present the basic equations for neutron stars including the equations of state used in the present work to describe the hadronic matter. Some physical quantities of interest are calculated such as mass-radius relations, moments of inertia, angular momentum, and compactness. By considering four different rotation regimes, we obtain results that indicate substantial modifications in the physical properties of neutron stars in f(R, T) gravity when compared to those in the context of general relativity. In particular, the mass-radius relation for sequences of stars indicates that f(R, T) gravity increases the mass and the equatorial radius of the neutron stars for stars rotating with an angular velocity smaller than Kepler limit.
Journal Article
Gravity
\"What keeps objects from floating out of your hand? What if your feet drifted away from the ground? What stops everything from floating into space? Gravity ... Jason Chin has taken a complex subject and made it brilliantly accessible to young readers in this unusual, innovative, and very beautiful book.
Book
The trouble with gravity : solving the mystery beneath our feet
\"[A] ... science writer traces our millennia-long effort to understand the phenomenon of gravity--the greatest mystery in physics, and a force that has shaped our universe and our minds in ways we have never fully understood until now\"-- Provided by publisher.
Book
Gödel-type solutions in Formula omitted) gravity
In this paper, [Formula omitted]) gravity is considered. It is a modified theory of gravity that exhibits a strong coupling of gravitational and matter fields. Therefore, if gravity is governed by this model a number of issues must be re-examined. In this context, the question of causality and its violation is studied. Such analysis is carried out using the Gödel-type solutions. It is shown that this model allows both causal and non-causal solutions. These solutions depend directly on the content of matter present in the universe. For the non-causal solution, a critical radius is calculated, beyond which causality is violated. Taking different matter contents, an infinite critical radius emerges that leads to a causal solution. In this causal solution, a natural relationship emerges between the parameters that determine the matter considered.
Journal Article
Gravity : investigating the force, mass, and attraction of physical bodies
A look at various theories throughout history about gravity.
Book
Noncommutative Formula omitted Chern-Simons gravity: Kaluza-Klein reduction and chiral gravitational anomaly
Actions for noncommutative (NC) gauge field theories can be expanded perturbatively in powers of the noncommutativity parameter [Formula omitted] using the Seiberg-Witten map between ordinary classical fields and their NC counterparts. The leading order term represents classical ( [Formula omitted]) action while higher-order terms give us [Formula omitted]-dependent NC corrections that ought to capture some aspects of quantum gravity. Building on previous work of Aschieri and Castellani on NC Chern-Simons (CS) gauge and gravity theories, showing that non-trivial [Formula omitted]-dependence exists only for spacetime dimensions [Formula omitted], we investigate a correlated effect of these extra spatial dimensions and noncommutativity on four-dimensional physics, up to first-order in [Formula omitted]. Assuming that one spatial dimension is compactified into a circle, we apply the Kaluza-Klein reduction procedure on the NC [Formula omitted] CS theory for the conformal gauge group SO(4, 2), to obtain an effective, [Formula omitted]-dependent four-dimensional theory of gravity that has Einstein-Hilbert gravity with negative cosmological constant as its commutative limit. We derive field equations for this modified theory of gravity and study the effect of NC interactions on some classical geometries, such as the AdS-Schwarzschild black hole. We find that this NC background spacetime gives rise to chiral gravitational anomaly due to the nonvanishing [Formula omitted]-dependent Pontryagin density.
Journal Article
