32 research outputs found
Generalized quantum field theory: perturbative computation and perspectives
We analyze some consequences of two possible interpretations of the action of
the ladder operators emerging from generalized Heisenberg algebras in the
framework of the second quantized formalism. Within the first interpretation we
construct a quantum field theory that creates at any space-time point particles
described by a q-deformed Heisenberg algebra and we compute the propagator and
a specific first order scattering process. Concerning the second one, we draw
attention to the possibility of constructing this theory where each state of a
generalized Heisenberg algebra is interpreted as a particle with different
mass.Comment: 19 page
Non-linear generalization of the sl(2) algebra
We present a generalization of the sl(2) algebra where the algebraic
relations are constructed with the help of a general function of one of the
generators. When this function is linear this algebra is a deformed sl(2)
algebra. In the non-linear case, the finite dimensional representations are
constructed in two different ways. In the first case, which provides finite
dimensional representations only for the non-linear case, these representations
come from solutions to a dynamical equation and we show how to construct
explicitly these representations for a general quadratic non-linear function.
The other type of finite dimensional representation comes from solutions to a
cut condition equation. We give examples of solutions of this type in the
non-linear case as well.Comment: 13 pages, 3 EPS figures, Late
Generating statistical distributions without maximizing the entropy
We show here how to use pieces of thermodynamics' first law to generate
probability distributions for generalized ensembles when only level-population
changes are involved. Such microstate occupation modifications, if properly
constrained via first law ingredients, can be associated not exclusively to
heat and acquire a more general meaning.Comment: 6 pages, no figures, Conferenc
Nonextensive Entropies derived from Form Invariance of Pseudoadditivity
The form invariance of pseudoadditivity is shown to determine the structure
of nonextensive entropies. Nonextensive entropy is defined as the appropriate
expectation value of nonextensive information content, similar to the
definition of Shannon entropy. Information content in a nonextensive system is
obtained uniquely from generalized axioms by replacing the usual additivity
with pseudoadditivity. The satisfaction of the form invariance of the
pseudoadditivity of nonextensive entropy and its information content is found
to require the normalization of nonextensive entropies. The proposed principle
requires the same normalization as that derived in [A.K. Rajagopal and S. Abe,
Phys. Rev. Lett. {\bf 83}, 1711 (1999)], but is simpler and establishes a basis
for the systematic definition of various entropies in nonextensive systems.Comment: 16 pages, accepted for publication in Physical Review
Generating statistical distributions without maximizing the entropy
We show here how to use pieces of thermodynamics’ first law to generate probability distributions for generalized ensembles when only level-population changes are involved. Such microstate occupation modifications, if properly constrained via first law ingredients, can be associated not exclusively to heat and acquire a more general meaning.Instituto de Física La Plat
Short Range Ising Spin Glasses: a critical exponent study
The critical properties of short-range Ising spin-glass models, defined on a
diamond hierarchical lattice of graph fractal dimension , 3, and 4,
and scaling factor 2 are studied via a method based on the Migdal-Kadanoff
renormalization-group scheme. The order parameter critical exponent is
directly estimated from the data of the local Edwards- Anderson (EA) order
parameter, obtained through an exact recursion procedure. The scaling of the EA
order parameter, leading to estimates of the exponent of the correlation
length is also performed. Four distinct initial distributions of the quenched
coupling constants (Gaussian, bimodal, uniform and exponential) are considered.
Deviations from a universal behaviour are observed and analysed in the
framework of the renormalized flow in a two dimensional appropriate parameter
space.Comment: 9 pages, 01 figure (ps
Universality in short-range Ising spin glasses
The role of the distribution of coupling constants on the critical exponents
of the short-range Ising spin-glass model is investigated via real space
renormalization group. A saddle-point spin glass critical point characterized
by a fixed-point distribution is found in an appropriated parameter space. The
critical exponents and are directly estimated from the data of
the local Edwards-Anderson order parameters for the model defined on a diamond
hierarchical lattice of fractal dimension . Four distinct initial
distributions of coupling constants (Gaussian, bimodal, uniform and
exponential) are considered; the results clearly indicate a universal behavior.Comment: 11 pages, 4 figures, to published in Physica A 199
On a generalization of the binomial distribution and its Poisson-like limit
We examine a generalization of the binomial distribution associated with a
strictly increasing sequence of numbers and we prove its Poisson-like limit.
Such generalizations might be found in quantum optics with imperfect detection.
We discuss under which conditions this distribution can have a probabilistic
interpretation.Comment: 17 pages, 6 figure
Limit cycle induced by multiplicative noise in a system of coupled Brownian motors
We study a model consisting of nonlinear oscillators with {\em global
periodic} coupling and {\em local multiplicative} and additive noises. The
model was shown to undergo a nonequilibrium phase transition towards a
broken-symmetry phase exhibiting noise-induced "ratchet" behavior. A previous
study \cite{[7]} focused on the relationship between the character of
thehysteresis loop, the number of ``homogeneous'' mean-field solutions and the
shape of the stationary mean-field probability distribution function. Here we
show --as suggested by the absence of stable solutions when the load force is
beyond a critical value-- the existence of a limit cycle induced by
both:multiplicative noise and {\em global periodic} coupling.Comment: Submitted to Phys. Rev. E, RevTex, 18 pgs, 5 figure
Anomalous diffusion with absorption: Exact time-dependent solutions
Recently, analytical solutions of a nonlinear Fokker-Planck equation
describing anomalous diffusion with an external linear force were found using a
non extensive thermostatistical Ansatz. We have extended these solutions to the
case when an homogeneous absorption process is also present. Some peculiar
aspects of the interrelation between the deterministic force, the nonlinear
diffusion and the absorption process are discussed.Comment: RevTex, 16 pgs, 4 figures. Accepted in Physical Review