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O. Obregón

Publications and source records attributed to O. Obregón.

At least 19 recordsLinked to original sources

Entropy-Deformed Hamiltonian Dynamics of Schwarzschild Black Holes: A Superstatistical Approach

We study the effective dynamics of the Schwarzschild black hole interior by introducing entropic deformations derived from generalized superstatistical entropies $S_{+}$ and $S_{-}$. The resulting modified Hamiltonians $\bar{H}_{\pm}$, formulated in Ashtekar--Barbero variables, encode quantum gravity-inspired corrections that become significant near the Planck scale. Analytical solutions show that these corrections regularize the classical singularity, replacing it with a finite anisotropic core characterized by bounded canonical variables and a minimal internal area. For $S_{-}$ ($α_{-} > 0$), curvature invariants remain finite, yielding a completely regular interior, whereas $S_{+}$ ($α_{+} < 0$) leads to a localized region of high curvature associated with a cigar-like throat. The interior and exterior geometries are thus connected through this high-curvature region, indicating that the classical singularity is replaced by an entropic transition layer. These features reproduce loop quantum gravity phenomenology without invoking polymer discretization.

gr-qc

Thermodynamic geometry for a non-extensive ideal gas

A generalized entropy arising in the context of superstatistics is obtained for an ideal gas. The curvature scalar associated to the thermodynamic space generated by this modified entropy is calculated using two formalisms of the geometric approach to thermodynamics. Using the curvature/interaction hypothesis of the geometric approach to thermodynamic geometry it is found that as a consequence of considering a generalized statistics, an effective interaction arises but the interaction is not enough to give a phase transition. This generalized entropy seems to be relevant in confinement or in systems with not so many degrees of freedom, so it could be interesting to use such entropies to characterize the thermodynamics of small systems.

cond-mat.stat-mech

Towards Noncommutative Linking Numbers Via the Seiberg-Witten Map

In the present work some geometric and topological implications of noncommutative Wilson loops are explored via the Seiberg-Witten map. In the abelian Chern-Simons theory on a three dimensional manifold, it is shown that the effect of noncommutativity is the appearance of $6^n$ new knots at the $n$-th order of the Seiberg-Witten expansion. These knots are trivial homology cycles which are Poincaré dual to the high-order Seiberg-Witten potentials. Moreover the linking number of a standard 1-cycle with the Poincaré dual of the gauge field is shown to be written as an expansion of the linking number of this 1-cycle with the Poincaré dual of the Seiberg-Witten gauge fields. In the process we explicitly compute the noncommutative 'Jones-Witten' invariants up to first order in the noncommutative parameter. Finally in order to exhibit a physical example, we apply these ideas explicitly to the Aharonov-Bohm effect. It is explicitly displayed at first order in the noncommutative parameter, we also show the relation to the noncommutative Landau levels.

hep-th

A general procedure to find ground state solutions for finite $N$ M(atrix) theory. Reduced models and SUSY quantum cosmology

We propose a general method to find exact ground state solutions to the SU($N$) invariant matrix model arising from the quantization of the 11-dimensional supermembrane action in the light-cone gauge. We illustrate the method by applying it to lower dimensional models and for the SU(2) group. This approach can be used to find ground state solutions to the complete 9-dimensional model and for any SU($N$) group. The supercharges and the constraints related to the SU(2) symmetry are the relevant operators and they generate a multicomponent wave function. In the procedure, the fermionic degrees of freedom are represented by means of Dirac-like gamma matrices. We exhibit a relation between these finite $N$ matrix theory ground state solutions and SUSY quantum cosmology wave functions giving a possible physical significance to the theory even for finite $N$

hep-th

Toward Supergravity Spectral Action

A spectral action of Euclidean supergravity is proposed. We calculate up to $a_4$, the Seeley-Dewitt coefficients in the expansion of the spectral action associated to the supergravity Dirac operator. This is possible because in simple supergravity, as in pure gravity, a well defined and mathematically consistent Dirac operator can be constructed.

hep-th

A quantum cosmological model in Hořava-Lifshitz gravity

A Wheeler-DeWitt equation for the Kantowski-Sachs model is derived within the framework of the minimal quantum gravity theory proposed by Hořava. We study the solution to this equation in the ultraviolet limit for the specific case where the λ parameter of the theory takes its relativistic value λ = 1. It is observed that the minisuperspace variables switch their role compared with their usual infrared (General Relativity) behavior.

gr-qc

Quantum cosmology in Hořava-Lifshitz gravity

Quantum cosmology is studied within the framework of the minimal quantum gravity theory proposed by Hořava. For this purpose we choose the Kantowski-Sachs (KS) model and construct the corresponding Wheeler-DeWitt equation. We study the solution to this equation in the ultraviolet limit for different values of the running parameter λ of the theory. It is observed that the wave packet for this Universe changes completely compared with the one observed in the infrared (general relativity) regime. We also look at the classical solutions by means of a WKB semiclassical approximation. It is observed that if λ takes its relativistic value λ = 1 a generalized KS metric is obtained which differs from the usual KS solution in general relativity by an additional term arising from the higher-order curvature terms in the action and which dominates the behavior of the solution for very small values of the time parameter. We discuss the physical properties of this solution by comparing it with the usual KS solution in general relativity. The resulting solution has no horizons but singularities.

gr-qc

Generalized information entropies depending only on the probability distribution

Systems with a long-term stationary state that possess as a spatio-temporally fluctuation quantity $β$ can be described by a superposition of several statistics, a "super statistics". We consider first, the Gamma, log-normal and $F$-distributions of $β$. It is assumed that they depend only on $p_l$, the probability associated with the microscopic configuration of the system. For each of the three $β-$distributions we calculate the Boltzmann factors and show that they coincide for small variance of the fluctuations. For the Gamma distribution it is possible to calculate the entropy in a closed form, depending on $p_l$, and to obtain then an equation relating $p_l$ with $βE_l$. We also propose, as other examples, new entropies close related with the Kaniadakis and two possible Sharma-Mittal entropies. The entropies presented in this work do not depend on a constant parameter $q$ but on $p_l$. For the $p_l$-Gamma distribution and its corresponding $B_{p_l}(E)$ Boltzmann factor and the associated entropy, we show the validity of the saddle-point approximation. We also briefly discuss the generalization of one of the four Khinchin axioms to get this proposed entropy.

cond-mat.stat-mech

Towards a Supersymmetric Generalization of the Schwarzschild Black Hole

The Wheeler-DeWitt (WDW) equation for the Kantowski-Sachs model can also be understood as the WDW-equation corresponding to the Schwarzschild black hole due to the well known diffeomorphism between these two metrics. The WDW-equation and its solutions are ``ignorant'' of the coordinate patch one is using, only by imposing coordinate conditions we can differentiate between cosmological and black hole models. At that point, the foliation parameter $t$ or $r$ will appear in the solution of interest. In this work we supersymmetrize this WDW-equation obtaining an extra term in the potential with two possible signs. The WKB method is then applied, given rise to two classical equations. It is shown that the event horizon can never be reached because, very near to it the extra term in the potential, for each one of the equations, is more relevant than the one that corresponds to Schwarzschild. One can then study the asymptotic cases in which one of the two terms in the Hamiltonian dominates the behavior. One of them corresponds to the usual Schwarzschild black hole. We will study here the other two asymptotic regions; they provide three solutions. All of them have a singularity in $r=0$ and depending on an integration constant $C$ they can also present a singularity in $r=C^2$. Neither of these solutions have a Newtonian limit. The black hole solution we study is analyzed between the singularity $r=C^2$ and a maximum radius $r_m$. We find an associated mass, considering the related cosmological solution inside $r=C^2$, and based on the holographic principle an entropy can be assigned to this asymptotic solution.

hep-th

Is noncommutativity related with the smallness of $Λ$?

In this letter we study the effects of a noncommutative minisuperspace, including matter degrees of freedom on a FRW universe with cosmological constant. In this setting the vacuum energy density can be calculated to be of the same order as the observed energy density of the universe.

hep-th

Classical and quantum time dependent solutions in string theory

Using the ontological interpretation of quantum mechanics in a particular sense, we obtain the classical behaviour of the scale factor and two scalar fields, derived from a string effective action for the FRW time dependent model. Besides, the Wheeler-DeWitt equation is solved exactly. We speculate that the same procedure could also be applied to S-branes.

hep-th

The wave function of the universe and spontaneaus breaking of supersymmetry

In this work we define a scalar product ``weighted'' with the scalar factor $R$ and show how to find a normalized wave function for the supersymmetric quantum FRW cosmological model using the idea of supersymmetry breaking selection rules under local n=2 conformal supersymmetry. We also calculate the expectation value of the scalar factor R in this model and its corresponding behaviour.

hep-th

Supersymmetry of Demkov-Ostrovsky effective potentials in the R_0=0 sector

We present a supersymmetric analysis of the wave problem with a Demkov-Ostrovsky spherically symmetric class of focusing potentials at zero energy. Following a suggestion of Lévai, we work in the so-called R_0=0 sector in order to obtain the superpartner (fermionic) potentials within Witten's supersymmetric procedure. General solutions of the superpotential for the known physical cases are given explicitly.

quant-ph

Recurrence-shift relations for the polynomial functions of Aldaya, Bisquert, and Navarro-Salas

Using a simple factorization scheme we obtain the recurrence-shift relations of the polynomial functions of Aldaya, Bisquert and Navarro-Salas (ABNS), F_n^N(\fracωc\sqrtN x), i.e., one-step first-order differential relations referring to N, as follows. Firstly, we apply the scheme to the polynomial degree confirming the recurrence relations of Aldaya, Bisquert and Navarro-Salas, but also obtaining another slightly modified pair. Secondly, the factorization scheme is applied to the Gegenbauer polynomials to get the recurrence relations with respect to their parameter. Next, we make use of Nagel's result, showing the connection between Gegenbauer polynomials and the ABNS functions, to write down the recurrence-shift relations for the latter ones. Such relations may be used in the study of the spatial structure of pair-creation processes in an Anti-de Sitter gravitational background

quant-ph

Bistability for asymmetric discrete random walks

We show that asymmetric time-continuous discrete random walks can display bistability for equal values of Jauslin's shifting parameters. The bistability becomes more pronounced at increased asymmetry parameter

cond-mat

Supersymmetric features of the Maxwell fish-eye lens

We provide a supersymmetric analysis of the Maxwell fisheye (MF) wave problem at zero energy. Working in the so-called $R_{0}=0$ sector, we obtain the corresponding superpartner (fermionic) MF effective potential within Witten's one-dimensional (radial) supersymmetric procedure.

quant-ph

Two-dimensional Fokker-Planck solutions and Grassmann variables

After a short outline of the factorization and Grassmann picture of the one-dimensional (1D) Fokker-Planck (FP) equation, we consider a class of spatially-inhomogeneous solutions of the 2D FP equation with symmetric 2D (super)potentials. We show that the spatial inhomogeneities of that class of solutions can be attributed to underlying Grassmannian pseudo-degrees of freedom. Such an interpretation may also be applied to FP solutions in three and more dimensions.

cond-mat

Spin $3/2$ Fields Non-Minimal Coupling as Square Root of Linearized Gravity with Matter

A non-minimal coupling for spin $3/2$ fields is obtained. We use the fact that the Rarita-Schwinger field equations are the square root of the full linearized Einstein field equations in order to investigate the form of the interaction for the spin $3/2$ field with gauge fields. We deduce the form of the interaction terms for the electromagnetic and non-Abelian Yang-Mills fields by implementing appropiate energy momentum tensors on the linearized Einstein field equations. The interaction found for the electromagnetic case happens to coincide with the dipole term found by Ferrara {\it et al} by a very different procedure, namely by demanding $g=2$ at the tree level for the electromagnetic interaction of arbitrary spin particles. The same interaction is found by using the resource of linearized Supergravity N=2. For the case of the Yang-Mills field Supergravity N=4 is linearized, providing the already foreseen interaction.

hep-th