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Carlos Leiva

Publications and source records attributed to Carlos Leiva.

17 recordsLinked to original sources
arXiv2026

Conformal Symmetry of Relativistic and Nonrelativistic Systems and AdS/CFT Correspondence

The nonlinear realization of conformal so(2,d) symmetry for relativistic systems and the dynamical conformal so(2,1) symmetry of nonrelativistic systems are investigated in the context of AdS/CFT correspondence. We show that the massless particle in d-dimensional Minkowski space can be treated as the system confined to the border of the AdS_{d+1} of infinite radius, while various nonrelativistic systems may be canonically related to a relativistic (massless, massive, or tachyon) particle on the AdS_2 X S^{d-1}. The list of nonrelativistic systems "unified" by such a correspondence comprises the conformal mechanics model, the planar charge-vortex and 3-dimensional charge-monopole systems, the particle in a planar gravitational field of a point massive source, and the conformal model associated with the charged particle propagating near the horizon of the extreme Reissner-Nordstrom black hole.

hep-th↗
arXiv2022

Inflation and Primordial Fluctuations in $F(T)$ Gravity's Rainbow

We study slow-roll inflation and the generation of primordial fluctuations in $F(T)$ gravity's rainbow. We obtain the second order action for scalar and tensor perturbations and then calculate the primordial power spectrum for them. Thus, after calculating the inflationary observables up to first order in slow-roll approximation, namely the scalar spectral index $n_{s}$ and the tensor-to scalar ratio $r$, we confront the predictions of the model with the current PLANCK and BICEP/Keck data.

gr-qc↗
arXiv2020

Shadow cast of non-commutative black holes in Rastall gravity

We study the shadow and energy emission rate of a spherically symmetric non-commutative black hole in Rastall gravity. Depending on the model parameters, the non-commutative black hole can reduce to the Schwarzschild black hole. Since the non-vanishing non-commutative parameter affects the formation of event horizon, the visibility of the resulting shadow depends on the non-commutative parameter in Rastall gravity. The obtained sectional shadows respect the unstable circular orbit condition, which is crucial for physical validity of the black hole image model.

hep-th↗
arXiv2017

Snyder Like Modified Gravity in Newton's Spacetime

This work is focused on searching a geodesic interpretation of the dynamics of a particle under the effects of a Snyder like deformation in the background of the Kepler problem. In order to accomplish that task, a newtonian spacetime is used. Newtonian spacetime is not a metric manifold, but allows to introduce a torsion free connection in order to interpret the dynamic equations of the deformed Kepler problem as geodesics in a curved spacetime. These geodesics and the curvature terms of the Riemann and Ricci tensors show a mass and a fundamental length dependence as expected, but are velocity independent. In this sense, the effect of introducing a deformed algebra is examinated and the corresponding curvature terms calculated, as well as the modifications of the integrals of motion.

physics.gen-ph↗
arXiv2017

Some features of a Schwarzchild Black Hole from a Snyder perspective

In this paper, the consequences of introducing a deformed Snyder-Kepler potential in the Schwarzchild metric are investigated. After this modification, it is obtained a dynamically depending horizon with different penetration radius for massive particles and light rays in radial orbits. In the case of circular orbits, they all remain untouched.

physics.gen-ph↗
arXiv2013

Thawing models in the presence of a generalized Chaplygin gas

In this paper we consider a cosmological model whose main components are a scalar field and a generalized Chaplygin gas. We obtain an exact solution for a flat arbitrary potential. This solution have the right dust limit when the Chaplygin parameter $A\rightarrow 0$. We use the dynamical systems approach in order to describe the cosmological evolution of the mixture for an exponential self-interacting scalar field potential. We study the scalar field with an arbitrary self-interacting potential using the "Method of $f$-devisers." Our results are illustrated for the special case of a coshlike potential. We find that usual scalar-field-dominated and scaling solutions cannot be late-time attractors in the presence of the Chaplygin gas (with $α>0$). We recover the standard results at the dust limit ($A\rightarrow 0$). In particular, for the exponential potential, the late-time attractor is a pure generalized Chaplygin solution mimicking an effective cosmological constant. In the case of arbitrary potentials, the late-time attractors are de Sitter solutions in the form of a cosmological constant, a pure generalized Chaplygin solution or a continuum of solutions, when the scalar field and the Chaplygin gas densities are of the same orders of magnitude. The different situations depend on the parameter choices.

astro-ph.CO↗
arXiv2012

The Kepler problem in the Snyder space

In this paper we study the Kepler problem in the non commutative Snyder scenario. We characterize the deformations in the Poisson bracket algebra under a mimic procedure from quantum standard formulations and taking into account a general recipe to build the noncommutative phase space coordinates (in the sense of Poisson brackets). We obtain an expression to the deformed potential, and then the consequences in the precession of the orbit of Mercury are calculated. This result allows us to find an estimated value for the non commutative deformation parameter introduced.

gr-qc↗
arXiv2009

Tachyonic Universes in Patch Cosmologies with $Ω>1$

In this article we study closed inflationary universe models by means of a tachyonic field. We described a general treatment for created a universe with $Ω>1$ in patch cosmology, which is able to represent General Relativity, Gauss-Bonnet or Randall-Sundrum patches. We use recent data from astronomical observations to constrain the parameters appearing in our model.

gr-qc↗
arXiv2008

Geodesic Structure of the Schwarzschild Black Hole in Rainbow Gravity

In this paper we study the geodesic structure of the Schwarzschild black hole in rainbow gravity analyzing the behavior of null and time-like geodesic. We find that the structure of the geodesics essentially does not change when the semi-classical effects are included. However, we can distinguish different scenarios if we take into account the effects of rainbow gravity. Depending on the type of rainbow functions under consideration, inertial and external observers see very different situations in radial and non radial motion of a test particles.

gr-qc↗
arXiv2008

1-D Harmonic Oscillator in Snyder Space, the Classic and the Quantum

The 1-D dimension harmonic oscillator in Snyder space is investigated in its classical and quantum versions. The classical trajectory is obtained and the semiclassical quantization from the phase space trajectories is discussed. In the meanwhile, an effective cutoff to high frequencies is found. The quantum version is developed and an equivalent usual harmonic oscillator is obtained through an effective mass and an effective frequency introduced in the model. This modified parameters give us an also modified energy spectra.

math-ph↗
arXiv2006

Generalized commutation relations and Non linear momenta theories, a close relationship

A revision of generalized commutation relations is performed, besides a description of Non linear momenta realization included in some DSR theories. It is shown that these propositions are closely related, specially we focus on Magueijo Smolin momenta and Kempf et al. and L.N. Chang generalized commutators. Due to this, a new algebra arises with its own features that is also analyzed.

hep-th↗
arXiv2004

Extended Non Linear Conformal Symmetry and DSR Velocities on the Physical Surface

The relation between Conformal generators and Magueijo Smolin Deformed Special Relativity term, added to Lorentz boosts, is achieved. The same is performed for Fock Lorentz transformations. Through a dimensional reduction procedure, it is demonstrated that a massless relativistic particle living in a $d$ dimensional space, is isomorphic to one living in a $d+2$ space with pure Lorentz invariance and to a particle living in a $AdS_{d+1}$ space. To accomplish these identifications, the Conformal Group is extended and a nonlinear algebra arises. Finally, because the relation between momenta and velocities is known, the problem of position space dynamics is solved.

hep-th↗
arXiv2004

Conformal Generators and Doubly Special Relativity Theories

In this paper, the relation between the modified Lorenz boosts, proposed in the doubly relativity theories and a linear combination of Conformal Group generators in $R^{1,d-1}$ is investigated. The introduction of a new generator is proposed in order to deform the Conformal Group to achieve the connection conjectured. The new generator is obtained trough a formal dimensional reduction from a free massless particle living in a $R^{2,d}$ space. Due this treatment it is possible to say that even DSR theories modify light cone structure in $R^{1,d-1}$, it could remains, in some cases, untouched in $R^{2,d}$.

gr-qc↗
arXiv2004

Nonlinear superconformal symmetry of a fermion in the field of a Dirac monopole

We study a longstanding problem of identification of the fermion-monopole symmetries. We show that the integrals of motion of the system generate a nonlinear classical Z_2-graded Poisson, or quantum super- algebra, which may be treated as a nonlinear generalization of the $osp(2|2)\oplus su(2)$. In the nonlinear superalgebra, the shifted square of the full angular momentum plays the role of the central charge. Its square root is the even osp(2|2) spin generating the u(1) rotations of the supercharges. Classically, the central charge's square root has an odd counterpart whose quantum analog is, in fact, the same osp(2|2) spin operator. As an odd integral, the osp(2|2) spin generates a nonlinear supersymmetry of De Jonghe, Macfarlane, Peeters and van Holten, and may be identified as a grading operator of the nonlinear superconformal algebra.

hep-th↗
arXiv2003

Superconformal mechanics and nonlinear supersymmetry

We show that a simple change of the classical boson-fermion coupling constant, $2α\to 2αn $, $n\in \N$, in the superconformal mechanics model gives rise to a radical change of a symmetry: the modified classical and quantum systems are characterized by the nonlinear superconformal symmetry. It is generated by the four bosonic integrals which form the so(1,2) x u(1) subalgebra, and by the 2(n+1) fermionic integrals constituting the two spin-n/2 so(1,2)-representations and anticommuting for the order n polynomials of the even generators. We find that the modified quantum system with an integer value of the parameter $α$ is described simultaneously by the two nonlinear superconformal symmetries of the orders relatively shifted in odd number. For the original quantum model with $|α|=p$, $p\in \N$, this means the presence of the order 2p nonlinear superconformal symmetry in addition to the osp(2|2) supersymmetry.

hep-th↗
arXiv2002

Algebra of chiral currents on the physical surface

Using a particular structure for the Lagrangian action in a one-dimensional Thirring model and performing the Dirac's procedure, we are able to obtain the algebra for chiral currents which is entirely defied on the constraint surface in the corresponding hamiltonian description of the theory.

hep-th↗