Excited states of 4He droplets

We study low-lying excited states of 4He clusters up to a cluster size of 40 atoms in a variational framework. The ansatz wave function combines two- and three-body correlations, coming from a translationally invariant configuration interaction description, and Jastrow-type short-range correlation. We have previously used this scheme to determine the ground-state energies of 4He and 3He clusters. Here we present an extension of this ansatz wave function having a good quantum angular momentum L. The variational procedure is applied independently to the cases with L = 0,2,4, and upper bounds for the corresponding energies are thus obtained. Moreover, centroid energies for L excitations are calculated through the use of sum rules. A comparison with previous calculations is also made.Fil: Guardiola, R.. Facultad de Física / Dpto de Física Atómica y Nuclear; EspañaFil: Navarro, J.. Csic - Univ. de Valencia / Inst. de Física Corpuscular; EspañaFil: Portesi, Mariela Adelina. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Departamento de Física; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Física La Plata. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Instituto de Física La Plata; Argentin

Radiación coherente y teoría de la información

El cuerpo de esta Tesis consta principalmente de dos partes y está organizado en cuatro capítulos, cuyo contenido detallamos en este sumario. La primera parte está dedicada al modelo de Dicke —que describe un conjunto de átomos interactuando con radiación electromagnética en una cavidad— y a la forma de caracterizar su dinámica por medio de la Teoría de la Información (TI). En este contexto informacional hacemos uso del concepto de entropía, que mediante maximización sujeta a ligaduras permite determinar el operador densidad que caracteriza al sistema cuántico en todo momento de su evolución. En la segunda parte de la Tesis, presentamos dos aplicaciones de una reciente generalización de la forma entròpica convencional de Boltzmann-Shannon. Una de ellas es el análisis de una formulación cuantitativa del Principio de Incerteza de la Mecánica Cuántica, en el espíritu de la TI. La otra aplicación se refiere a un estudio del tamaño aparente de un sistema físico en el contexto de la Mecánica Estadística no extensiva surgida de la entropía generalizada.Tesis digitalizada en SEDICI gracias a la Biblioteca de Física de la Facultad de Ciencias Exactas (UNLP).Facultad de Ciencias Exacta

Radiación coherente y teoría de la información

El cuerpo de esta Tesis consta principalmente de dos partes y está organizado en cuatro capítulos, cuyo contenido detallamos en este sumario. La primera parte está dedicada al modelo de Dicke —que describe un conjunto de átomos interactuando con radiación electromagnética en una cavidad— y a la forma de caracterizar su dinámica por medio de la Teoría de la Información (TI). En este contexto informacional hacemos uso del concepto de entropía, que mediante maximización sujeta a ligaduras permite determinar el operador densidad que caracteriza al sistema cuántico en todo momento de su evolución. En la segunda parte de la Tesis, presentamos dos aplicaciones de una reciente generalización de la forma entròpica convencional de Boltzmann-Shannon. Una de ellas es el análisis de una formulación cuantitativa del Principio de Incerteza de la Mecánica Cuántica, en el espíritu de la TI. La otra aplicación se refiere a un estudio del tamaño aparente de un sistema físico en el contexto de la Mecánica Estadística no extensiva surgida de la entropía generalizada.Tesis digitalizada en SEDICI gracias a la Biblioteca de Física de la Facultad de Ciencias Exactas (UNLP).Facultad de Ciencias Exacta

Ergodic statistical models: Entropic dynamics and chaos

We present an extension of the ergodic, mixing and Bernoulli levels of the ergodic hierarchy in dynamical systems, the information geometric ergodic hierarchy, making use of statistical models on curved manifolds in the context of information geometry. We discuss the 2×2 Gaussian Orthogonal Ensembles (GOE) within a 2D correlated model. For values of the correlation coefficient vanishingly small, we find that GOE belong to the information geometric (IG) mixing level having a maximum negative value of scalar curvature. Moreover, we propose a measure of distinguishability for the family of distributions of the 2D correlated model that results to be an upper bound of the IG correlation.Instituto de Física La PlataConsejo Nacional de Investigaciones Científicas y Técnica

Entropic Analysis of the Quantum Oscillator with a Minimal Length

The well-known Heisenberg-Robertson uncertainty relation for a pair of noncommuting observables, is expressed in terms of the product of variances and the commutator among the operators, computed for the quantum state of a system. Different modified commutation relations have been considered in the last years with the purpose of taking into account the effect of quantum gravity. Indeed it can be seen that letting [X,P]=iℏ(1+β P^2) implies the existence of a minimal length proportional to sqrt(β). The Bialynicki-Birula-Mycielski entropic uncertainty relation in terms of Shannon entropies is also seen to be deformed in the presence of a minimal length, corresponding to a strictly positive deformation parameter β. Generalized entropies can be implemented. Indeed, results for the sum of position and (auxiliary) momentum Rényi entropies with conjugated indices have been provided recently for the ground and first excited state. We present numerical findings for conjugated pairs of entropic indices, for the lowest lying levels of the deformed harmonic oscillator system in 1D, taking into account the position distribution for the wavefunction and the actual momentum.Fil: Puertas Centeno, David. Universidad Rey Juan Carlos; EspañaFil: Portesi, Mariela Adelina. Universidad Nacional de La Plata. Facultad de Ciencias Exactas; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Física La Plata. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Instituto de Física La Plata; Argentin

Gaussian ensembles distributions from mixing quantum systems

In the context of dynamical systems we present a derivation of the Gaussian ensembles distributions from quantum systems having a classical analogue that is mixing. We find that factorization property is satisfied for the mixing quantum systems expressed as a factorization of quantum mean values. For the case of the kicked rotator and in its fully chaotic regime, the factorization property links decoherence by dephasing with Gaussian ensembles in terms of the weak limit, interpreted as a decohered state. Moreover, a discussion about the connection between random matrix theory and quantum chaotic systems, based on some attempts made in previous works and from the viewpoint of the mixing quantum systems, is presented.Instituto de Física La Plat

Distinguishability notion based on Wootters statistical distance : Application to discrete maps

We study the distinguishability notion given by Wootters for states represented by probability density functions. This presents the particularity that it can also be used for defining a statistical distance in chaotic unidimensional maps. Based on that definition, we provide a metric d for an arbitrary discrete map. Moreover, from d, we associate a metric space with each invariant density of a given map, which results to be the set of all distinguished points when the number of iterations of the map tends to infinity. Also, we give a characterization of the wandering set of a map in terms of the metric d, which allows us to identify the dissipative regions in the phase space. We illustrate the results in the case of the logistic and the circle maps numerically and analytically, and we obtain d and the wandering set for some characteristic values of their parameters. Finally, an extension of the metric space associated for arbitrary probability distributions (not necessarily invariant densities) is given along with some consequences. The statistical properties of distributions given by histograms are characterized in terms of the cardinal of the associated metric space. For two conjugate variables, the uncertainty principle is expressed in terms of the diameters of the associated metric space with those variables.Instituto de Física La Plat

Entropic Analysis of the Quantum Oscillator with a Minimal Length

The well-known Heisenberg–Robertson uncertainty relation for a pair of noncommuting observables, is expressed in terms of the product of variances and the commutator among the operators, computed for the quantum state of a system. Different modified commutation relations have been considered in the last years with the purpose of taking into account the effect of quantum gravity. Indeed it can be seen that letting [X,P] = iℏ (1 + βP2) implies the existence of a minimal length proportional to β . The Bialynicki-Birula–Mycielski entropic uncertainty relation in terms of Shannon entropies is also seen to be deformed in the presence of a minimal length, corresponding to a strictly positive deformation parameter β . Generalized entropies can be implemented. Indeed, results for the sum of position and (auxiliary) momentum Renyi entropies with conjugated indices have been provided recently for the ground and first excited state. We present numerical findings for conjugated pairs of entropic indices, for the lowest lying levels of the deformed harmonic oscillator system in 1D, taking into account the position distribution for the wavefunction and the actual momentum.Instituto de Física La Plat

Natural metric for quantum information theory

We study in detail a very natural metric for quantum states. This new proposal has two basic ingredients: entropy and purification. The metric for two mixed states is defined as the square root of the entropy of the average of representative purifications of those states. Some basic properties are analyzed and its relation to other distances is investigated. As an illustrative application, the proposed metric is evaluated for one-qubit mixed states.Instituto de Física La Plat

Information measures based on Tsallis’ entropy and geometric considerations for thermodynamic systems

An analysis of the thermodynamic behavior of quantum systems can be performed from a geometrical perspective investigating the structure of the state space. We have developed such an analysis for nonextensive thermostatistical frameworks, making use of the q -divergence derived from Tsallis’ entropy. Generalized expressions for operator variance and covariance are considered, in terms of which the fundamental tensor is given.Facultad de Ciencias ExactasInstituto de Física La Plat