Macroscopic Expression Connecting the Rate of Energy Dissipation and Violation of the Fluctuation-Response Relation

A direct connection between the magnitude of the violation of the fluctuation-response relation (FRR) and the rate of energy dissipation is presented in terms of field variables of nonequilibrium systems. Here, we consider the density field of a colloidal suspension either in a relaxation process or in a nonequilibrium steady state driven by an external field. Using a path-integral representation of the temporal evolution of the density field, we find an equality that relates the magnitude of the violation of the FRR for scalar and vector potentials of the velocity field to the rate of energy dissipation for the entire system. Our result demonstrates that the violation of the FRR for field variables captures the entropic component of the dissipated free energy.Comment: 4 pages, a major reviso

Sublattice Asymmetric Reductions of Spin Values on Stacked Triangular Lattice Antiferromagnet CsCoBr3_3

We study the reductions of spin values of the ground state on a stacked triangular antiferromagnet using the spin-wave approach. We find that the spin reductions have sublattice asymmetry due to the cancellation of the molecular field. The sublattice asymmetry qualitatively analyzes the NMR results of CsCoBr$_3$.Comment: 5pages, 5figure

Sum rule for response function in nonequilibrium Langevin systems

We derive general properties of the linear response functions of nonequilibrium steady states in Langevin systems. These correspond to extension of the results which were recently found in Hamiltonian systems [A. Shimizu and T. Yuge, J. Phys. Soc. Jpn. {\bf 79}, 013002 (2010)]. We discuss one of the properties, the sum rule for the response function, in particular detail. We show that the sum rule for the response function of the velocity holds in the underdamped case, whereas it is violated in the overdamped case. This implies that the overdamped Langevin models should be used with great care. We also investigate the relation of the sum rule to an equality on the energy dissipation in nonequilibrium Langevin systems, which was derived by Harada and Sasa.Comment: 8 page

Super and Sub-Poissonian photon statistics for single molecule spectroscopy

We investigate the distribution of the number of photons emitted by a single molecule undergoing a spectral diffusion process and interacting with a continuous wave laser field. The spectral diffusion is modeled based on a stochastic approach, in the spirit of the Anderson-Kubo line shape theory. Using a generating function formalism we solve the generalized optical Bloch equations, and obtain an exact analytical formula for the line shape and Mandel's Q parameter. The line shape exhibits well known behaviors, including motional narrowing when the stochastic modulation is fast, and power broadening. The Mandel parameter, describing the line shape fluctuations, exhibits a transition from a Quantum sub-Poissonian behavior in the fast modulation limit, to a classical super-Poissonian behavior found in the slow modulation limit. Our result is applicable for weak and strong laser field, namely for arbitrary Rabi frequency. We show how to choose the Rabi frequency in such a way that the Quantum sub-Poissonian nature of the emission process becomes strongest. A lower bound on $Q$ is found, and simple limiting behaviors are investigated. A non-trivial behavior is obtained in the intermediate modulation limit, when the time scales for spectral diffusion and the life time of the excited state, become similar. A comparison is made between our results, and previous ones derived based on the semi-classical generalized Wiener--Khintchine theorem.Comment: 14 Phys. Rev style pages, 10 figure

Generating extremal neutrino mixing angles with Higgs family symmetries

The existence of maximal and minimal mixing angles in the neutrino mixing matrix motivates the search for extensions to the Standard Model that may explain these angles. A previous study (C.I.Low and R.R.Volkas, Phys.Rev.D68,033007(2003)), began a systematic search to find the minimal extension to the Standard Model that explains these mixing angles. It was found that in the minimal extensions to the Standard Model which allow neutrino oscillations, discrete unbroken lepton family symmetries only generate neutrino mixing matrices that are ruled out by experiment. This paper continues the search by investigating all models with two or more Higgs doublets, and an Abelian family symmetry. It is found that discrete Abelian family symmetries permit, but cannot explain, maximal atmospheric mixing, however these models can ensure theta_{13}=0.Comment: Minor modifications, references added, typos corrected. LaTeX, 16 page

Analysis of f-p model for octupole ordering in NpO2

In order to examine the origin of octupole ordering in NpO2, we propose a microscopic model constituted of neptunium 5f and oxygen 2p orbitals. To study multipole ordering, we derive effective multipole interactions from the f-p model by using the fourth-order perturbation theory in terms of p-f hopping integrals. Analyzing the effective model numerically, we find a tendency toward \Gamma_{5u} antiferro-octupole ordering.Comment: 4 pages, 3 figure

Incipient order in the t-J model at high temperatures

We analyze the high-temperature behavior of the susceptibilities towards a number of possible ordered states in the t-J-V model using the high-temperature series expansion. From all diagrams with up to ten edges, reliable results are obtained down to temperatures of order J, or (with some optimism) to J/2. In the unphysical regime, t<J, large superconducting susceptibilities are found, which moreover increase with decreasing temperatures, but for t>J, these susceptibilities are small and decreasing with decreasing temperature; this suggests that the t-J model does not support high-temperature superconductivity. We also find modest evidence of a tendency toward nematic and d-density wave orders. ERRATUM: Due to an error in the calculation, the series for d-wave supeconducting and extended s-wave superconducting orders were incorrect. We recalculate the series and give the replacement figures. In agreement with our earlier findings, we still find no evidence of any strong enhancement of the superconducting susceptibility with decreasing temperature. However, because different Pade approximants diverge from each other at somewhat higher temperatures than we originally found, it is less clear what this implies concerning the presence or absence of high-temperature superconductivity in the t-J model.Comment: 4 pages, 5 eps figures included; ERRATUM 2 pages, 3 eps figures correcting the error in the series for superconducting susceptibilitie

Granular Scale Magnetic Flux Cancellations in the Photosphere

We investigate the evolution of 5 granular-scale magnetic flux cancellations just outside the moat region of a sunspot by using accurate spectropolarimetric measurements and G-band images with the Solar Optical Telescope aboard Hinode. The opposite polarity magnetic elements approach a junction of the intergranular lanes and then they collide with each other there. The intergranular junction has strong red shifts, darker intensities than the regular intergranular lanes, and surface converging flows. This clearly confirms that the converging and downward convective motions are essential for the approaching process of the opposite-polarity magnetic elements. However, motion of the approaching magnetic elements does not always match with their surrounding surface flow patterns in our observations. This suggests that, in addition to the surface flows, subsurface downward convective motions and subsurface magnetic connectivities are important for understanding the approach and collision of the opposite polarity elements observed in the photosphere. We find that the horizontal magnetic field appears between the canceling opposite polarity elements in only one event. The horizontal fields are observed along the intergranular lanes with Doppler red shifts. This cancellation is most probably a result of the submergence (retraction) of low-lying photospheric magnetic flux. In the other 4 events, the horizontal field is not observed between the opposite polarity elements at any time when they approach and cancel each other. These approaching magnetic elements are more concentrated rather than gradually diffused, and they have nearly vertical fields even while they are in contact each other. We thus infer that the actual flux cancellation is highly time dependent events at scales less than a pixel of Hinode SOT (about 200 km) near the solar surface.Comment: Accepted for publication in the Astrophysical Journa

A statistical mechanics model for free-for-all airplane passenger boarding

I present and discuss a model for the free-for-all passenger boarding which is employed by some discount air carriers. The model is based on the principles of statistical mechanics where each seat in the aircraft has an associated energy which reflects the preferences of the population of air travelers. As each passenger enters the airplane they select their seats using Boltzmann statistics, proceed to that location, load their luggage, sit down, and the partition function seen by remaining passengers is modified to reflect this fact. I discuss the various model parameters and make qualitative comparisons of this passenger boarding model with models which involve assigned seats. This model can also be used to predict the probability that certain seats will be occupied at different times during the boarding process. These results may be of value to industry professionals as a useful description of this boarding method. However, it also has significant value as a pedagogical tool since it is a relatively unusual application of undergraduate level physics and it describes a situation with which many students and faculty may be familiar.Comment: version 1: 4 pages 2 figures version 2: 7 pages with 5 figure

Quantum scalar field in D-dimensional static black hole space-times

An Euclidean approach for investigating quantum aspects of a scalar field living on a class of D-dimensional static black hole space-times, including the extremal ones, is reviewed. The method makes use of a near horizon approximation of the metric and $\zeta$-function formalism for evaluating the partition function and the expectation value of the field fluctuations $$. After a review of the non-extreme black hole case, the extreme one is considered in some details. In this case, there is no conical singularity, but the finite imaginary time compactification introduces a cusp singularity. It is found that the $\zeta$-function regularized partition function can be defined, and the quantum fluctuations are finite on the horizon, as soon as the cusp singularity is absent, and the corresponding temperature is T=0.Comment: 9 pages, LaTe