Search results for "Observable"
showing 10 items of 634 documents
Quantum signatures in the dynamics of two dipole-dipole interacting soft dimers
2006
The quantum covariances of physically transparent pairs of observables relative to two dimers hosted in a solid matrix are exactly investigated in the temporal domain. Both dimers possess fermionic and bosonic degrees of freedom and are dipolarly coupled. We find out and describe clear signatures traceable back to the presence and persistence of quantum coherence in the time evolution of the system. Manifestations of a competition between intramolecular and intermolecular energy migration mechanisms are brought to light. The experimental relevance of our results is briefly commented.
Solitons and their observable signatures in quasi-one-dimensional systems
2005
We give an overview of the experimental signatures of nonlinear waves: notably topological and non topological solitons, in specific quasi-one-dimensional devices and condensed matter systems. Non topological solitons can be easily observed and manipulated, on a macroscopic scale, in optical fibers and electrical transmission lines. Topological solitons have been clearly identified as fluxons in Josephson transmission lines and as domain walls in condensed matter systems such as magnetic chains and synthetic polymers. By contrast, at the present time the observable signatures of nonlinear excitations such as pulse or envelope solitons and polarons, which are predicted to occur on a microsco…
Néel Transition of Lattice Fermions in a Harmonic Trap: A Real-Space Dynamic Mean-Field Study
2010
We study the magnetic ordering transition for a system of harmonically trapped ultracold fermions with repulsive interactions in a cubic optical lattice, within a real-space extension of dynamical mean-field theory. Using a quantum Monte Carlo impurity solver, we establish that antiferromagnetic correlations are signaled, at strong coupling, by an enhanced double occupancy. This signature is directly accessible experimentally and should be observable well above the critical temperature for long-range order. Dimensional aspects appear less relevant than naively expected.
Breaking of SU(4) symmetry and interplay between strongly correlated phases in the Hubbard model
2016
We study the thermodynamic properties of four-component fermionic mixtures described by the Hubbard model using the dynamical mean-field-theory approach. Special attention is given to the system with SU(4)-symmetric interactions at half filling, where we analyze equilibrium many-body phases and their coexistence regions at nonzero temperature for the case of simple cubic lattice geometry. We also determine the evolution of observables in low-temperature phases while lowering the symmetry of the Hamiltonian towards the two-band Hubbard model. This is achieved by varying interflavor interactions or by introducing the spin-flip term (Hund's coupling). By calculating the entropy for different s…
Coherent and squeezed vibrations for discrete variable harmonic oscillators
2009
In this work we study different types of coherent and squeezed states for the Charlier, Kravchuk and Meixner oscillators. We calculate the average values of different observables corresponding to the coherent states. We found that the coherent and squeezed states of the Kravchuk oscillator are unstable. There are also coherent and squeezed states that are similar to the coherent and squeezed states of the harmonic oscillator. We have introduced a discrete variable model for the biophoton coherent radiation, and the coherent thermal and squeezed thermal states. © 2009 Taylor & Francis.
Nonexponential 2H spin-lattice relaxation as a signature of the glassy state
1990
Abstract High-precision measurements of 2H spin-lattice relaxation on several molecular glass-forming liquids have been performed. As a general feature the following can be stated: At temperatures more than ten to twenty degrees above the calorimetric glass transition temperature Tg the 2H spin-lattice relaxation is exponential; below that temperature regime the relaxation is nonexponential. This crossover from exponential to nonexponential magnetization recovery implies that no common spin temperature caused by spin diffusion exists in a 2H glass. This contrasts 1H spin-lattice relaxation which is found to be strictly monoexponential throughout. The occurrence of nonexponential 2H relaxati…
Peltier’s and Thomson’s coefficients of thermoelectric phenomena in the observable formulation
2011
Four transport coefficients characterize the thermoelectric properties of materials. Three of them are widely measured and studied. But the number of references on the Peltier coefficient are very limited. This unequal result is a consequence of the Onsager reciprocal relation (ORR). A review on the preciseness and accuracy of Peltier coefficient measurements has been developed in this paper. Thus we can appreciate a low level in the experimental confirmation for the ORR. In order to describe the thermoelectric processes in an advantageous way, the observable formulation has been used. This is characterized by the electric potential measured at the probe terminals and for the heat flux whic…
Monte Carlo study of cluster-diameter distribution: An observable to estimate correlation lengths
1997
We report numerical simulations of two-dimensional $q$-state Potts models with emphasis on a new quantity for the computation of spatial correlation lengths. This quantity is the cluster-diameter distribution function $G_{diam}(x)$, which measures the distribution of the diameter of stochastically defined cluster. Theoretically it is predicted to fall off exponentially for large diameter $x$, $G_{diam} \propto \exp(-x/\xi)$, where $\xi$ is the correlation length as usually defined through the large-distance behavior of two-point correlation functions. The results of our extensive Monte Carlo study in the disordered phase of the models with $q=10$, 15, and $20$ on large square lattices of si…
High Precision Astrometry Over Large Angular Scales with Closure Constraints: The Triplet 1803+784/1928+738/2007+777
1996
The technique of differential astrometry using the phase-delay VLBI observable promises fractional precisions of ~2 × 10−9 in the determination of the separation of sources 5° or 6° apart on the sky (Guirado et al. 1995a; Lara et al. 1996). In our present research we seek further improvement in this technique through using triplets of radio sources, which provide a closure constraint in the determination of relative angular positions. This constraint not only eases the resolution of the phase-cycle ambiguities (a major problem in the least-squares approach to astrometry with phase delays), but it also strongly constrains the space of allowable parameter values.
Sensitivity analysis of consumption cycles
2018
We study the special case of a nonlinear stochastic consumption model taking the form of a 2-dimensional, non-invertible map with an additive stochastic component. Applying the concept of the stochastic sensitivity function and the related technique of confidence domains, we establish the conditions under which the system's complex consumption attractor is likely to become observable. It is shown that the level of noise intensities beyond which the complex consumption attractor is likely to be observed depends on the weight given to past consumption in an individual's preference adjustment.