Search results for "Quantum"
showing 10 items of 9714 documents
Space-Efficient 1.5-Way Quantum Turing Machine
2001
1.5QTM is a sort of QTM (Quantum Turing Machine) where the head cannot move left (it can stay where it is and move right). For computations is used other - work tape. In this paper will be studied possibilities to economize work tape space more than the same deterministic Turing Machine can do (for some of the languages). As an example language (0i1i|i ≥ 0) is chosen, and is proved that this language could be recognized by deterministic Turing machine using log(i) cells on work tape , and 1.5QTM can recognize it using constant cells quantity.
Refrigeration of an array of cylindrical nanosystems by superfluid helium counterflow
2017
Abstract Motivated by the challenge of computer refrigeration, we study the limits set by the transition to quantum turbulence on the cooling of an array of heat-producing cylindrical nanosystems by means of superfluid-helium counterflow. The effective thermal conductivity in laminar counterflow superfluid helium is obtained in channels with rectangular cross section, through arrays of mutually parallel cylinders and in the combined situation of arrays of orthogonal cylinders inside the rectangular channel. The maximum cooling capacity is analyzed on the condition that turbulence is avoided and that the highest temperature does not exceed the lambda temperature.
Competition of Direct and Indirect Sources of Thermal Entanglement in a spin star network
2017
A spin star system consisting of three peripheral two-state systems and a central one is considered, with the peripheral spins assumed to interact with each other, as well as with the central one. It is shown that such two couplings, each one being a thermal entanglement source, can significantly compete in the formation of quantum correlations in the thermal state, to the point that they can destroy any thermal entanglement of the peripheral spins.
Quantum dynamics of the intensity-dependent Tavis-Cummings model
1999
An exactly solvable generalization of the intensity-dependent Jaynes-Cummings model to the case of N0 atoms is introduced together with its solution. The quantum dynamics of the model including the squeezing properties of the su(1,1) Perelomov and Glauber coherent states is investigated. The cases of one and two atoms present in the cavity are analysed in detail. These two cases are compared in the situation when the atomic subsystem is initially prepared in the ground state, the Dicke state and the state of thermal equilibrium.
A quantum model of Schwarzschild black hole evaporation
1996
We construct a one-loop effective metric describing the evaporation phase of a Schwarzschild black hole in a spherically symmetric null-dust model. This is achieved by quantising the Vaidya solution and by chosing a time dependent quantum state. This state describes a black hole which is initially in thermal equilibrium and then the equilibrium is switched off, so that the black hole starts to evaporate, shrinking to a zero radius in a finite proper time. The naked singularity appears, and the Hawking flux diverges at the end-point. However, a static metric can be imposed in the future of the end-point. Although this end-state metric cannot be determined within our construction, we show tha…
Symmetries and solvable models for evaporating 2D black holes
1997
We study the evaporation process of a 2D black hole in thermal equilibrium when the ingoing radiation is suddenly switched off. We also introduce global symmetries of generic 2D dilaton gravity models which generalize the extra symmetry of the CGHS model. © Elsevier Science B.V
Relativistic kinematic approach to the classical ideal gas
2019
he necessary and sufficient conditions for a unit time-like vector field to be the unit velocity of a classical ideal gas are obtained. In a recent paper [Coll, Ferrando and S\'aez, Phys. Rev D {\bf 99} (2019)] we have offered a purely hydrodynamic description of a classical ideal gas. Here we take one more step in reducing the number of variables necessary to characterize these media by showing that a plainly kinematic description can be obtained. We apply the results to obtain test solutions to the hydrodynamic equation that model the evolution in local thermal equilibrium of a classical ideal gas. \end{abstract}
Thermodynamic class II Szekeres-Szafron solutions. Singular models
2019
A family of parabolic Szekeres-Szafron class II solutions in local thermal equilibrium is studied and their associated thermodynamics are obtained. The subfamily with the hydrodynamic behavior of a generic ideal gas (defined by the equation of state $p = k n \Theta$) results to be an inhomogeneous generalization of flat FLRW $\gamma$-law models. Three significative interpretations that follow on from the choice of three specific thermodynamic schemes are analyzed in depth. First, the generic ideal gas in local thermal equilibrium; this interpretation leads to an inhomogeneous temperature $\Theta$. Second, the thermodynamics with homogeneous temperature considered by Lima and Tiomno (CQG 6 1…
Local thermal equilibrium and ideal gas Stephani universes
2005
The Stephani universes that can be interpreted as an ideal gas evolving in local thermal equilibrium are determined. Five classes of thermodynamic schemes are admissible, which give rise to five classes of regular models and three classes of singular models. No Stephani universes exist representing an exact solution to a classical ideal gas (one for which the internal energy is proportional to the temperature). But some Stephani universes may approximate a classical ideal gas at first order in the temperature: all of them are obtained. Finally, some features about the physical behavior of the models are pointed out.
Oxide growth and tunneling characteristics of Sn-SnO x -Sn junctions
1979
Sn—SnOx—Sn tunneling junctions were prepared by thermal oxidation of vacuum deposited Sn-films. The thickness growth of the oxide was followed by ellipsometric measurements. From logarithmic conductivity measurements the barrier heights were determined. The tunneling characteristic could be well described by the two-band-tunneling model using a value of 0.14 for the ratio of the effective masses in the oxide and the metal.