arXiv subjects

A. Maia Jr

Publications and source records attributed to A. Maia Jr.

5 recordsLinked to original sources

arXiv2008

Small Fluctuations in $λϕ^{n+1}$ Theory in a Finite Domain: An Hirota's Method Approach

We present a method to calculate small stationary fluctuations around static solutions describing bound states in a $(1+1)$-dimensional $λϕ^{n+1}$ theory in a finite domain. We also calculate explicitly fluctuations for the $λϕ^4$. These solutions are written in terms of Jacobi Elliptic functions and are obtained from both linear and nonlinear equations. For the linear case we get eingenvalues of a Lamé type Equation and the nonlinear one relies on Hirota's Method.

hep-th↗

arXiv2005

Lightning Stars: Anomalous Photoproduction in Neutron Stars via Parametric Resonance Mechanism

In this work we propose a new mechanism for photoproduction inside a neutron star based on Parametric Resonance phenomenon as firstly applied to Inflationary Cosmology. Our assumptions are based on the pion condensation model by Harrington and Shepard. We show that a huge number of photons are created which, on turns, reheats the matter in the star's core. Thus, we argue that Parametric Resonance can be effective during a brief period out of an neutron star lifetime leading to an anomalous uprising variation of its brightness departing from the black body radiation at regularly spaced frequencies. In adition, a time periodic signal is obtained in moderate (not exponential) regimes. We argue also that our PR mechanism offers a simple and feasible explanation for some recent observations of giant flares from neutron stars.

astro-ph↗

arXiv1999

Energy Levels of Classical Interacting Fields in a Finite Domain in 1+1 Dimension

We study the behavior of bound energy levels for the case of two classical interacting fields $ϕ$ and $χ$ in a finite domain (box) in (1 + 1) dimension on which we impose Dirichlet boundary conditions (DBC). The total Lagrangian contain a $\fracλ{4}ϕ^4$ self-interaction and an interaction term given by $g ϕ^2 χ^2$. We calculate the energy eigenfunctions and its correspondent eigenvalues and study their dependence on the size of the box (L) as well on the free parameters of the Lagrangian: mass ratio $β= \frac{M^{2}_χ}{M^{2}_ϕ}$, and interaction coupling constants $λ$ and $g$. We show that for some configurations of the above parameters, there exists critical sizes of the box for which instability points of the field $χ$ appear.

hep-th↗

arXiv1999

Spectrum of $γ$-Fluids: A Statistical Derivation

The spectrum of massless bosonic and fermionic fluids satisfying the equation of state $p=(γ-1)ρ$ is derived using elementary statistical methods. As a limiting case, the Lorentz invariant spectrum of the vacuum ($γ=0, p=-ρ$) is deduced. These results are in agreement with our earlier derivation for bosons using thermodynamics and semiclassical considerations.

hep-th↗

arXiv1999

Energy Levels of Interacting Fields in a Box

We study the influence of boundary conditions on energy levels of interacting fields in a box and discuss some consequences when we change the size of the box. In order to do this we calculate the energy levels of bound states of a scalar massive field $χ$ interacting with another scalar field $ϕ$ through the lagrangian ${\cal L}_{int} = 3/2 gϕ^{2}χ^{2}$ in an one-dimensional box, on which we impose Dirichlet boundary conditions. We have found that the gap between the bound states changes with the size of the box in a non-trivial way. For the case the masses of the two fields are equal and for large box the energy levels of Dashen-Hasslacher-Neveu (DHN model) (Dashen et al, 1974) are recovered and we have a kind of boson condensate for the ground state. Below to a critical box size $L\sim 2.93 2\sqrt{2}/M$ the ground state level splits, which we interpret as particle-antiparticle production under small perturbations of box size. Below another critical sizes $(L\sim 6/10 2\sqrt{2}/M)$ and $(L\sim 1.71 2\sqrt{2}/M)$ of the box, the ground state and first excited state merge in the continuum part of the spectrum.

hep-th↗