arXiv subjects

K. Luz-Burgoa

Publications and source records attributed to K. Luz-Burgoa.

7 recordsLinked to original sources

arXiv2025

Thermodynamics and Bouncing Cosmology in Rastall-like Gravity

In this study, we explore the thermodynamic aspects of a modified version of Rastall's gravity theory and its implications for cosmological scenarios. We analyze the role of non-conserved energy-momentum tensor equations and investigate their influence on particle production within an irreversible thermodynamic framework. By introducing a novel Lagrangian, we derive modified field equations and establish their relationship with matter production, both with and without entropy generation. Our analysis focuses on ideal fluid models and extends to spatially flat LFRW cosmologies, providing key equations that govern energy density, pressure, and curvature dynamics. Furthermore, we propose a bouncing cosmological model, in which the universe undergoes cycles of contraction and expansion, avoiding the singularity associated with the Big Bang. Our results indicate that this bouncing scenario is feasible within the Rastall-like gravity framework, supported by particle production processes and stability conditions. The violation of energy conditions near the bounce point further confirms the consistency of this alternative cosmological model. The present work is focused on the theoretical foundations and internal consistency of the model; possible observational implications will be addressed in future investigations. We conclude that the proposed theory offers a coherent phenomenological approach to matter production and provides new insights into non-standard cosmological evolution.

gr-qc↗

arXiv2020

Quantization of the interior of the black hole

In this work we study the Schwarzschild metric in the context of canonical quantum gravity inside the horizon, close of horizon and near the black hole singularity. Using this standard quantization procedure, we show that the horizon is quantized and the black hole singularity disappears. For the first case, quantization of the Schwarzschild radius was obtained in terms of the Planck length $l_{Pl}$, a positive integer $n$ and the ordering factor of the operator $p$. From the quantization of the Schwarzschild radius it was possible to determine the area of the black hole event horizon, its mass and the quantum energy of the Hawking radiation as well as its frequency. For the solution close to the interior black hole singularity, the wave function was determined and applied the DeBroglie-Bohm interpretation. The Bohm's trajectory was found near to the singularity. It which describes how the spacetime evolves over time and depends on the ordering factor of the operator $p$. Thus, for the case where $|1-p|\neq0,3$, the Bohm's trajectory is finite and regular, that is, the singularity is removed. For the case where $|1-p|=3$, the Bohm's trajectory assumes an exponential behavior, never going to zero, avoiding the singularity.That result allows that spacetime be extended beyond the classical singularity.

gr-qc↗

arXiv2007

Computer simulations on the sympatric speciation modes for the Midas cichlid species complex

Cichlid fishes are one of the best model system for the study of evolution of the species. Inspired by them, in this paper we simulated the splitting of a single species into two separate ones via random mutations, with both populations living together in sympatry, sharing the same habitat. We study the ecological, mating and genetic conditions needed to reproduce the polychromatism and polymorphism of three species of the Midas Cichlid species complex. Our results show two scenarios for the A. Citrinellus speciation process, one with and the other without disruptive natural selection. In the first scenario, the ecological and genetic conditions are sufficient to create two new species, while in the second the mating and genetic conditions must be synchronized in order to control the velocity of genetic drift.

q-bio.PE↗

arXiv2006

Thermodynamic behavior of a phase transition in a model for sympatric speciation

We investigate the macroscopic effects of the ingredients that drive the origin of species through sympatric speciation. In our model, sympatric speciation is obtained as we tune up the strength of competition between individuals with different phenotypes. As a function of this control parameter, we can characterize, through the behavior of a macroscopic order parameter, a phase transition from a non-speciation to a speciation state of the system. The behavior of the first derivative of the order parameter with respect to the control parameter is consistent with a phase transition and exhibits a sharp peak at the transition point. For different resources distribution, the transition point is shifted, an effect similar to pressure in PVT system. The inverse of the parameter related to sexual selection strength behaves like an external field in the system and, as thus, is also a control parameter. The macroscopic effects of the biological parameters used in our model reveal thus fingerprints typical of thermodynamic quantities in a phase transition of an equilibrium physical system.

q-bio.PE↗

arXiv2005

Phase transition in a mean-field model for sympatric speciation

We introduce an analytical model for population dynamics with intra-specific competition, mutation and assortative mating as basic ingredients. The set of equations that describes the time evolution of population size in a mean-field approximation may be decoupled. We find a phase transition leading to sympatric speciation as a parameter that quantifies competition strength is varied. This transition, previously found in a computational model, occurs to be of first order.

q-bio.PE↗

arXiv2005

Computer Simulations to Study Sympatric Speciation Processes

We perform simulations based on the Penna model for biological ageing, now with the purpose of studying sympatric speciation, that is, the division of a single species into two or more populations, reproductively isolated, but without any physical barrier separating them. For that we introduce a new kind of competition among the individuals, using a modified Verhulst factor. The new competition depends on some specific phenotypic characteristic of each individual, which is represented by a pair of bitstrings. These strings are read in parallel and have no age structure. In this way, each individual genome consists of two parts. The first one has an age-structure and is related to the appearance of inherited diseases; the second part is not structured and takes into account the competition for the available resources. We also introduce sexual selection into the model, making use of another non-structured and independent pair of bitstrings. In this thesis we present three different models; two of them use, besides the competition, a sudden change in the ecology to obtain speciation. They were motivated by the speciation process observed in the Darwin finches, a family of birds that inhabits the Galapagos Islands, and also by that observed in the cichlids, a family of fish that lives in the Nicaragua Lakes and in the Vitoria Lake, in Africa. The third model does not use any ecological change: sympatric speciation is obtained depending only on the strength of competition among individuals with similar phenotypic characteristics.

q-bio.PE↗

arXiv2005

Sympatric Speciation in a Simple Food Web

Observations of the evolution of species groups in nature, such as well recognized Galapagos finches, have motivated much theoretical research aimed at understanding the processes associated with such radiations. The Penna model is one such model and has been widely used to study aging. In this paper we use the basic Penna model to investigate the process of sympatric speciation in a simple food web model. Initially our web consists of a primary food source and a single herbivore species that feeds on this resource. Subsequently we introduce a predator that feeds on the herbivore. In both instances we directly manipulate the food source, that is, its size distribution, and monitore the changes in the populations structures. Sympatric speciation is obtained for the consumer species in both webs, and our results confirm that the speciation velocity depends on how far up,in the food chain, the focus population is feeding. Simulations are done with three different sexual imprinting-like mechanisms, in order to discuss adaptation by natural selection.

q-bio.PE↗