E.V. Corrêa Silva

Quantization of Friedmann-Robertson-Walker spacetimes in the presence of a negative cosmological constant and radiation

The quantization of the Friedmann-Robertson-Walker spacetime in the presence of a negative cosmological constant was used in a recent paper to conclude that there are solutions that avoid singularities (big bang-big crunch) at the quantum level. We show that a proper study of their model does not indicate that it prevents the occurrence of singularities at the quantum level, in fact the quantum probability of such event is larger than the classical one. Our numerical simulations based on the powerful variational sinc collocation method (VSCM) also show that the precision of the results of that paper is much lower than the 20 significant digits reported by the authors.

Tunneling probability for the birth of an asymptotically de Sitter universe

In the present work, we quantize a closed Friedmann-Robertson-Walker model in the presence of a positive cosmological constant and radiation. It gives rise to a Wheeler-DeWitt equation for the scale factor which has the form of a Schrodinger equation for a potential with a barrier. We solve it numerically and determine the tunneling probability for the birth of a asymptotically DeSitter, inflationary universe, initially, as a function of the mean energy of the initial wave-function. Then, we verify that the tunneling probability increases with the cosmological constant, for a fixed value of the mean energy of the initial wave-function.

Symplectic method in quantum cosmology

E. V. Corrêa Silva∗,1 G. A. Monerat†,1 G. Oliveira-Neto‡,1 C. Neves§,1 and L. G. Ferreira Filho¶2 Departamento de Matemática e Computação, Faculdade de Tecnologia, Universidade do Estado do Rio de Janeiro, Rodovia Presidente Dutra, Km 298, Pólo Industrial, CEP 27537-000, Resende-RJ, Brazil. Departamento de Mecânica e Energia, Faculdade de Tecnologia, Universidade do Estado do Rio de Janeiro, Rodovia Presidente Dutra, Km 298, Pólo Industrial, CEP 27537-000, Resende-RJ, Brazil. (Dated: March 24, 2009)

AN EARLY UNIVERSE MODEL WITH STIFF MATTER AND A COSMOLOGICAL CONSTANT

In the present work, we study the quantum cosmology description of a Friedmann-Robertson-Walker model in the presence of a stiff matter perfect fluid and a negative cosmological constant. We work in the Schutzs variational formalism and the spatial sections have constant negative curvature. We quantize the model and obtain the appropriate Wheeler-DeWitt equation. In this model the states are bounded therefore we compute the discrete energy spectrum and the corresponding eigenfunctions. In the present work, we consider only the negative eigenvalues and their corresponding eigenfunctions. This choice implies that the energy density of the perfect fluid is negative. A stiff matter perfect fluid with this property produces a model with a bouncing solution, at the classical level, free from an initial singularity. After that, we use the eigenfunctions in order to construct wave packets and evaluate the time-dependent expectation value of the scale factor. We find that it oscillates between maximum and minimum values. Since the expectation value of the scale factor never vanishes, we confirm that this model is free from an initial singularity, also, at the quantum level.

High-temperature series expansion of the Helmholtz free energy of the quantum spin- S X Y Z chain

We consider the

Spectral: Solving Schroedinger and Wheeler–DeWitt equations in the positive semi-axis by the spectral method

XYZ

Probing singularities in quantum cosmology with curvature scalars

chain model of arbitrary spin

The high temperature expansion of the classical XYZ chain

S

Explorando sistemas hamiltonianos: estudo analítico

in the high temperature region, with external magnetic field and single-ion anisotropy term. Our high-temperature expansion of the Helmholtz free energy is analytic in the parameters of the model for

Notes on the quantization of FRW model in the presence of a cosmological constant and radiation

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