2,271 research outputs found

### The gravitational energy

We present the expression $t_{\mu\nu}$ of the energy-momentum tensor of the
gravitational field in the framework of the recent proposal of the Geometric
Scalar theory of gravity (GSG). From the conservation of $t_{\mu\nu}$ it
follows the dynamics of the gravitational field. As an example of this
expression for $t_{\mu\nu}$ we calculate the gravitational energy of a compact
object.Comment: 8 page

### Dragged Metrics

We show that the path of any accelerated body in an arbitrary space-time
geometry $g_{\mu\nu}$ can be described as geodesics in a dragged metric
$\hat{q}_{\mu\nu}$ that depends only on the background metric and on the motion
of the body. Such procedure allows the interpretation of all kind of
non-gravitational forces as modifications of the metric of space-time. This
method of effective elimination of the forces by a change of the metric of the
substratum can be understood as a generalization of the d'Alembert principle
applied to all relativistic processes

### The gravitational mechanism to generate mass II

With the eminent confirmation or disproof of the existence of Higgs boson by
experiments on the LHC it is time to analyze in a non-dogmatic way the
suggestions to understand the origin of the mass. Here we analyze the recent
proposal according to which gravity is what is really responsible for the
generation of mass of all bodies. The great novelty of such mechanism is that
the gravitational field acts merely as a catalyst, once the final expression of
the mass does not depend either on the intensity or on the particular
characteristics of the gravitational field.Comment: This is the further development of previous article (The
gravitational mechanism to generate mass, arXiv:1008.2371) which appeared in
Classical and Quantum Gravity 28 (2011) 03500

### What is the origin of the mass of the Higgs boson?

The purpose of this paper is to present a unified description of mass
generation mechanisms that have been investigated so far and that are called
the Mach and Higgs proposals. In our mechanism, gravity acts merely as a
catalyst and the final expression of the mass depends neither on the intensity
nor on the particular properties of the gravitational field. We shall see that
these two strategies to provide mass for all bodies that operate independently
and competitively can be combined into a single unified theoretical framework.
As a consequence of this new formulation we are able to present an answer to
the question: what is the origin of the mass of the Higgs boson?Comment: 7 pages. arXiv admin note: substantial text overlap with
arXiv:1111.4228, arXiv:1008.237

### Friedmann-like solutions with a non-vanishing Weyl tensor

We have solved the Einstein equations of general relativity for a class of
metrics with constant spatial curvature and found a non-vanishing Weyl tensor
in the presence of an energy-momentum tensor with an anisotropic pressure
component. The time evolution of the spacetime is guided by the usual Friedmann
equations and the constraints on the hypersurface comprise a separated system
of equations that can be independently solved. Contrary to the apparent
behavior induced by some choices of coordinates, the metric we have obtained is
completely regular everywhere and is free of singularities (except the
well-known Friedmann singularity at $t=0$). The physical features of this
solution are elucidated by using the Quasi-Maxwellian equations (a set of third
order differential equations describing the dynamics of the gravitational field
in terms of the Weyl tensor). The motion of test particles is also analyzed in
order to confirm the maximal extension of the manifold under consideration.
These results indicate that the anisotropic pressure could mimic dark matter
effects on certain geodesic congruences keeping the cosmic flow unchanged.Comment: We did a proof-reading of the previous version and now we include a
more detailed discussion of our result

### The Quasi-Maxwellian Equations of General Relativity: Applications to the Perturbation Theory

A comprehensive review of the equations of general relativity in the
quasi-Maxwellian (QM) formalism introduced by Jordan, Ehlers and Kundt is made.
Our main interest concerns its applications to the analysis of the perturbation
of standard cosmology in the Friedman-Lema\^itre-Robertson-Walker framework.
The major achievement of the QM scheme is its use of completely gauge
independent quantities. We shall see that in the QM-scheme we deal directly
with observable quantities. This reveals its advantage over the old method
introduced by Lifshitz et al that deals with perturbation in the standard
Einstein framework. For completeness, we compare the QM-scheme to the
gauge-independent method of Bardeen, a procedure consisting on particular
choices of the perturbed variables as a combination of gauge dependent
quantities.Comment: The main goal of this review is to make a little more popular the use
of the JEK frame in the realm of perturbation theory of Friedman universes.
Indeed, the Lifshitz-Bardeen method and the JEK frame give the same results
for the perturbations in the linear regime. The main interest on JEK rests on
its unambiguous way to deal with perturbation within the cosmological FLRW
scenari

### Dynamical Wormhole Definitions Confronted

Crude comparison between four alternative proposals for the very definition
of a wormhole is provided, all of which were intended to apply to the dynamical
cases. An interesting dynamical solution, based upon large scale magnetic
fields, is used for the comparisons. Such solution goes beyond the perfect
fluid approximation due to an anisotropic pressure component, bringing to the
fore some unsuspected features of those definitions. Certain notions as
reversible traversability are claimed as a way to select among those
definitions the best suited one to represent our intuition of what a wormhole
solution is expected to be.Comment: 14 pages, 21 figure

### Lattice-layer entanglement in Bernal-stacked bilayer graphene

The complete lattice-layer entanglement structure of Bernal stacked bilayer
graphene is obtained for the quantum system described by a tight-binding
Hamiltonian which includes mass and bias voltage terms. Through a suitable
correspondence with the parity-spin $SU(2)\otimes SU(2)$ structure of a Dirac
Hamiltonian, when it brings up tensor and pseudovector external field
interactions, the lattice-layer degrees of freedom can be mapped into such a
parity-spin two-qubit basis which supports the interpretation of the bilayer
graphene eigenstates as entangled ones in a lattice-layer basis. The Dirac
Hamiltonian mapping structure simply provides the tools for the manipulation of
the corresponding eigenstates and eigenenergies of the Bernal-stacked graphene
quantum system. The quantum correlational content is then quantified by means
of quantum concurrence, in order to have the influence of mass and bias voltage
terms quantified, and in order to identify the role of the trigonal warping of
energy in the intrinsic entanglement. Our results show that while the mass term
actively suppresses the intrinsic quantum entanglement of bilayer eigenstates,
the bias voltage term spreads the entanglement in the Brillouin zone around the
Dirac points. In addition, the interlayer coupling modifies the symmetry of the
lattice-layer quantum concurrence around a given Dirac point. It produces some
distortion on the quantum entanglement profile which follows the same pattern
of the isoenergy line distortion in the Bernal-stacked bilayer graphene.Comment: 24 pages, 8 figure

### The C$\nu$B energy density through the quantum measurement theory

We apply concepts from the quantum measurement theory to obtain some
cosmological neutrino background (C$\nu$B) properties and discuss their
relevance in defining theoretical bounds on cosmological neutrino energy
density. Describing three neutrino generations as a composite quantum system
through the generalized theory of quantum measurement provides us with the
probabilistic correlation between observable energies and neutrino flavor
eigenstates. By observing that flavor-averaged and flavor-weighted energies are
the quantum observables respectively generated by selective and non-selective
quantum measurement schemes, it is possible to identify the constraints on the
effective mass value expression that determines the neutrino contribution to
the energy density of the cosmic inventory. Our results agree with the quantum
mechanics viewpoint that asserts that the cosmological neutrino energy density
is obtained from a coherent sum of mass eigenstate energies, for normal and
inverted mass hierarchies.Comment: 19 pages, 5 figures, for completeness, in the Appendix, we have added
the contents related to Quantum Measurement schemes reproduced from
arXiv:1104.3120 of one of the authors of this manuscript (Alex E.
Bernardini). The credits/quotations are consistent and accurately given to
arXiv:1104.3120. The authors suggest the reading of arXiv:1104.3120 as a
background for the present manuscrip

### Entanglement of Dirac bi-spinor states driven by Poincar\'e classes of \mbox{SU}(2) \otimes \mbox{SU}(2) coupling potentials

A generalized description of entanglement and quantum correlation properties
constraining internal degrees of freedom of Dirac(-like) structures driven by
arbitrary Poincar\'e classes of external field potentials is proposed. The role
of (pseudo)scalar, (pseudo)vector and tensor interactions in
producing/destroying intrinsic quantum correlations for \mbox{SU}(2) \otimes
\mbox{SU}(2) bi-spinor structures is discussed in terms of generic coupling
constants. By using a suitable ansatz to obtain the Dirac Hamiltonian
eigenspinor structure of time-independent solutions of the associated Liouville
equation, the quantum entanglement, via concurrence, and quantum correlations,
via geometric discord, are computed for several combinations of well-defined
Poincar\'e classes of Dirac potentials. Besides its inherent formal structure,
our results setup a framework which can be enlarged as to include localization
effects and to map quantum correlation effects into Dirac-like systems which
describe low-energy excitations of graphene and trapped ions.Comment: 29 pages, 8 figure

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