Basic Thermodynamic Quantities Research Articles

THERMAL ENTANGLED QUANTUM REFRIGERATOR WORKING WITH THE TWO-QUBIT HEISENBERG XX MODEL

An entangled quantum refrigerator working with a two-qubit Heisenberg XX model in a constant external magnetic field is constructed in this paper. Based on the quantum first law of thermodynamics, the expressions for several basic thermodynamic quantities such as the heat transferred, the net work and the coefficient of performance are derived. Moreover, the influence of the thermal entanglement on the basic thermodynamic quantities is investigated. Several interesting features of the variation of the basic thermodynamic quantities with the thermal entanglement in zero and nonzero magnetic field are obtained. Lastly, we analyze the maximum coefficient of performance.

Low-energy theorems of QCD and bulk viscosity at finite temperature and baryon density in a magnetic field

The nonperturbative QCD vacuum at finite temperature and a finite baryon density in an external magnetic field is studied. Equations relating nonperturbative condensates to the thermodynamic pressure for $T\neq 0$, $\mu_q \neq 0$ and $H\neq 0$ are obtained, and low-energy theorems are derived. A bulk viscosity $\zeta(T, \mu, H)$ is expressed in terms of basic thermodynamical quantities describing the quark-gluon matter at $T\neq 0$, $\mu_q \neq 0$, and $H\neq 0$. Various limiting cases are also considered.

Dielectric pre-transitional behavior in the vicinity of isotropic–blue phase III transition

Pre-transitional effects have been observed from the study of static dielectric permittivity () and its temperature derivatives () near the isotropic to blue phase-III (I–BPIII) transition in a highly polar T-shaped liquid crystalline material having a stable BPIII phase which persists over a comparatively wide range of temperature (∼8°C). The pre-transitional behavior near I–BPIII transition is found to be very similar to that observed in isotropic–nematic (I–N) transition. Landau–de Genes and Maier–Saupe approaches, used earlier to describe anomalous behavior of εS near the I–N transition, have been implemented to investigate the present pre-transitional behavior near the I–BPIII transition. The value of critical exponent (α) for the I–BPIII transition is found to be close to that of the reported I–N transition. Temperature-dependent behavior of and have also been interpreted in terms of field-induced increments of basic thermodynamic quantities, namely internal energy, entropy, and Helmholtz free energy.

Thermal Entangled Quantum Refrigerator Working with Three-Qubit Heisenberg XX Model

An entangled quantum refrigerator working with a three-qubit one-dimensional isotropic Heisenberg XX model in a constant external magnetic field is constructed in this paper. Based on the quantum first law of thermodynamics, the expressions for several basic thermodynamic quantities such as the heat transferred, the net work and the coefficient of performance are derived. Moreover, the influence of the thermal entanglement on the basic thermodynamic quantities is investigated. Several interesting features of the variation of the basic thermodynamic quantities with the thermal entanglement in zero and nonzero magnetic field are obtained.

Toward a COSMO equation-of-state model of fluids and their mixtures

The basic objective of this work is the development of an approximate, yet coherent and consistent equation-of-state model of fluids, which will benefit from recent developments in the successful COnductor-like Screening MOdel (COSMO)-type group-contribution models with their quantum-mechanical description of fluids. The development is done within our recent non-random hydrogen-bonding (NRHB) equation-of-state framework. In contrast to NRHB, the new model will not need any new parameters for the strong specific interactions, such as hydrogen bonds, since they will be provided by its COSMO component and the associated quantum-chemistry calculations. The bridge between COSMO and NRHB is the non-randomness factors as calculated by the quasi-chemical treatment of the non-random distribution of molecular entities in the system. Analytical expressions are provided for all basic thermodynamic quantities, including expressions for the cavitation and charging components of the solvation Gibbs energy. The new equation-of-state model is tested against experimental data for vapor pressures, heats of vaporization, and liquid densities of pure fluids and on phase equilibria of mixtures. The strength and perspectives of the new model are critically discussed.

Effect of head group size, temperature and counterion specificity on cationic micelles

The critical micelle concentration (cmc) and ionisation degree ( α), of micelles of cetyltrimethylammonium bromide (CTABr), cetyltrimethylammonium chloride (CTACl), cetyltripropylammonium bromide (CTPABr) and cetyltripropylammonium chloride (CTPACl) have been measured over a narrow temperature range at 2 degree intervals using electrical conductivity. CTPACl and CTPABr are very soluble in water and were measured in the temperature range 275.15–323.15 K. The Krafft temperatures for CTABr and for CTACl are 293.15 K and 284.15 K, respectively and established a lower temperature limit for our studies on these two surfactants. The cmc vs temperature curves have a smooth minimum near room temperature and α linearly increases with temperature. The changes of cmc and α with temperature are smaller than those associated with the modification of head group size or counterion nature. Using these results, basic thermodynamic quantities associated with the phenomena of micellization have been evaluated. Thermodynamic properties of the surfactant solutions were discussed in terms of temperature dependence of the free energy, enthalpy and entropy of micellization. A close similarity between the effects of change in temperature on protein folding and micellization process appears from the data.

Dependence of the critical temperature on the Higgs field parametrization

We show that, despite the reparametrization symmetry of the Lagrangian describing the interaction between a scalar field and gauge vector bosons, the dynamics of the Higgs mechanism can be really affected by the representation gauge chosen for the Higgs field at temperatures T ≠ 0. This can be the case when the physical system described by the Higgs field chooses to undergo a condensation with a given degree of freedom rather than with other possible ones, as apparently observed in exotic superconductor systems. Actually, we study in detail such peculiar conditions and find that, varying the parametrization (without changing any physical parameter) for the two degrees of freedom of the complex scalar field, we obtain different expressions for the Higgs mass at T ≠ 0: in its turn this entails different expressions for the critical temperatures, ranging from zero to a maximum value, as well as different expressions for other basic thermodynamical quantities.

The superconducting state in metallic hydrogen under pressure at 2000 GPa

In this study, we have analysed the properties of the superconducting phase in metallic hydrogen under pressure at 2000 GPa. In particular, we have calculated the dependence of the basic thermodynamic quantities on the value of Coulomb pseudopotential ( μ ∗ ). The main results are the following: (i) The critical temperature ( T C ) is large even for high values of μ ∗ . (ii) The values of the ratios R 1 ≡ 2 Δ ( 0 ) / k B T C , R 2 ≡ Δ C ( k B T C ) / C N ( k B T C ) and R 3 ≡ T C C N ( k B T C ) / H C 2 ( 0 ) differ from the BCS values. (iii) The electron effective mass is large and reaches its maximum value for T = T C . Additionally, we have given the analytical formulas for T C , R 1 and R 2 which reproduce results originating from exact numerical calculations very well.

Critical point of the two-dimensional Bose gas: An S-matrix approach

A new treatment of the critical point of the two-dimensional interacting Bose gas is presented. In the lowest order approximation we obtain the critical temperature T c ≈ 2 π n / [ m log ( 2 π / m g ) ] , where n is the density, m the mass, and g the coupling. This result is based on a new formulation of interacting gases at finite density and temperature which is reminiscent of the thermodynamic Bethe ansatz in one dimension. In this formalism, the basic thermodynamic quantities are expressed in terms of a pseudo-energy. Consistent resummation of 2-body scattering leads to an integral equation for the pseudo-energy with a kernel based on the logarithm of the exact 2-body S-matrix.

Black hole evaporation within a momentum-dependent metric

We investigate the black hole thermodynamics in a ``deformed'' relativity framework where the energy-momentum dispersion law is Lorentz-violating and the Schwarzchild-like metric is momentum-dependent with a Planckian cutoff. We obtain net deviations of the basic thermodynamical quantities from the Hawking-Bekenstein predictions: actually, the black hole evaporation is expected to quit at a nonzero critical mass value (of the order of the Planck mass), leaving a zero temperature remnant, and avoiding a spacetime singularity. Quite surprisingly, the present semiclassical corrections to black hole temperature, entropy, and heat capacity turn out to be identical to the ones obtained within some quantum approaches.

Light-FrontQED1+1at Finite Temperature

We investigate the thermodynamic properties of quantum electrodynamics in 1+1 dimensions. We derive the partition function of the canonical ensemble in discrete light cone quantization and calculate the thermodynamical potential. This central quantity is evaluated for different system sizes and coupling strengths. We investigate the continuum limit and the thermodynamical limit and present basic thermodynamical quantities as a function of temperature for the interacting system. The results are compared to the idealized cases.

Entangled quantum heat engines based on two two-spin systems with Dzyaloshinski-Moriya anisotropic antisymmetric interaction

We construct an entangled quantum heat engine (EQHE) based on two two-spin systems with Dzyaloshinski-Moriya (DM) anisotropic antisymmetric interaction. By applying the explanations of heat transferred and work performed at the quantum level in Kieu's work [PRL, 93, 140403 (2004)], the basic thermodynamic quantities, i.e., heat transferred, net work done in a cycle and efficiency of EQHE are investigated in terms of DM interaction and concurrence. The validity of the second law of thermodynamics is confirmed in the entangled system. It is found that there is a same efficiency for both antiferromagnetic and ferromagnetic cases, and the efficiency can be controlled in two manners: 1. only by spin-spin interaction J and DM interaction D; 2. only by the temperature T and concurrence C. In order to obtain a positive net work, we need not entangle all qubits in two two-spin systems and we only require the entanglement between qubits in a two-spin system not be zero. As the ratio of entanglement between qubits in two two-spin systems increases, the efficiency will approach infinitely the classical Carnot one. An interesting phenomenon is an abrupt transition of the efficiency when the entanglements between qubits in two two-spin systems are equal.

Static dielectric pretransitional effects in thermotropic liquid crystals

AbstractThe paper presents a review of recent results on static dielectric behaviour in vicinity of weakly first order transition from isotropic liquid to a liquid crystalline nematic phase of compounds used in opto-electronic devices. Temperature behaviour of static permittivity and its derivative are interpreted in terms of a basic thermodynamic quantities increment (internal energy, entropy and Helmholtz free energy) induced by a probing electric field.

Second discontinuity in the specific heat of two-phase superconductors

The recently proposed theoretical model of superconductors endowed with two distinct superconducting phases and critical temperatures is further analyzed by introducing two distinct order parameters, described by two scalar fields which condensate at different temperatures. We find some deviations in basic thermodynamical quantities with respect to the Ginzburg–Landau one-phase superconductors. In particular, in contrast to the usual case where only one jump in specific heat takes place at the normal-superconductor transition temperature, we actually predict an additional discontinuity for CV when passing from a superconducting phase to the other one.

Four-level entangled quantum heat engines

Based on a two-qubit one-dimensional isotropic spin-$1∕2$ Heisenberg spin chain in a constant external magnetic field, we construct a four-level entangled quantum heat engine (QHE) and investigate the influence of entanglement between two qubits on basic thermodynamic quantities, i.e., the heat transferred and the work done in a cycle, and the efficiency of the QHE. The validity of the second law of thermodynamics is confirmed in the entangled system. We also find several interesting features of the variation of the efficiency with the entanglement of two different thermal equilibrium states in a work cycle in zero and finite magnetic field. An abrupt transition of efficiency is found in zero field.

Singular Pretransitional Behavior of the Electric Field-Dependent Part of the Thermodynamic Quantities of Strongly Polar Mesogenic Liquids in the Isotropic Phase

A new interpretation of the pretransitional temperature behavior of the static dielectric permittivity and its derivative in terms of the basic thermodynamic quantities: the internal energy, the entropy, and the Helmholtz free energy is presented. It was shown that in the case of strongly polar mesogenic compounds (as the homologous series of alkylcyanobiphenyls) the electric field-induced increments of both the internal energy and the entropy exhibit a critical-like temperature dependence in the vicinity of transition from the isotropic liquid to the nematic phase. As a most important pretransitional effect, it is shown that at a temperature of about 10 degrees before the phase transition, an electric field applied to the isotropic liquids induces an increase in the entropy (∆S > 0) instead of its decrease, as observed far from the phase transition or for the non-mesogenic dipolar liquids.

Computational study of the melting-freezing transition in the quantum hard-sphere system for intermediate densities. I. Thermodynamic results

The points where the fluid-solid (face-centered-cubic) transition takes place in the quantum hard-sphere system, for reduced densities 0.85>rhoN*>0.5 (reduced de Broglie wavelengths lambdaB*<or=0.8), have been determined via calculations of Helmholtz free energies. A number of complementary methods have been utilized, namely, path-integral Monte Carlo simulations for fixing the basic thermodynamic and structural quantities, Ornstein-Zernike computations of the fluid isothermal compressibilities using the centroid correlations, and applications of the Einstein crystal technique. Attention is paid to the evaluation of the statistical uncertainties in the isothermal compressibilities and also to the quantum implementation of the Einstein crystal technique by including explicitly the constraint of fixed center of mass. The equation of state along the fluid lambdaB* branches studied has been determined with two methods, one based on the isothermal compressibilities and the other on the usual virial estimator. Along the solid lambdaB* branches the equation of state has been fixed with the virial estimator. The results indicate that the phase transition investigated is governed by entropic effects and that the fluid-solid coexistence densities are arranged along a straight line rhoFCC*=rho(rhoF*), a behavior which at least holds even for lambdaB*<2, as revealed by completing the present analysis with data available in the literature.

Interactions and dynamics of mesogenic molecules in the vicinity of the isotropic to nematic phase transition

A role of the molecular structure and polarity in the dielectric behavior of nematogenic compounds in the vicinity of the isotropic to nematic phase transition is discussed. Temperature dependences of the static permittivity and its derivative, in relation to the basic thermodynamic quantities (internal energy, entropy and Helmholtz free energy), as well as an anomaly in the rotational diffusion of the mesogenic molecules and corresponding activation energy, are analyzed.

Prenematic Behavior of the Electric-Field-Induced Increment of the Basic Thermodynamic Quantities of Isotropic Mesogenic Liquids of Different Polarity

Temperature dependences of the static dielectric permittivity and its derivative, obtained for isotropic mesogenic liquids composed of the molecules of different polarity in relation to the basic thermodynamic quantities (internal energy, entropy, and Helmholtz free energy), are analyzed. A role of the molecular polarity in the dielectric behavior of the liquids in the vicinity of the isotropic to nematic phase transition is discussed.

An Alternative Approach to Nonrandomness in Solution Thermodynamics

An alternative formulation of the configurational partition function of mixtures is proposed, which leads to analytical expressions for the basic thermodynamic quantities, including the local compo...