Charged Black Hole in a Canonical Ensemble

We consider the thermodynamics of a charged black hole enclosed in a cavity. The charge in the cavity and the temperature at the walls are fixed so that we have a canonical ensemble. We derive the phase structure and stability of black hole equilibrium states. We compare our results to that of other work which uses asymptotically anti-de Sitter boundary conditions to define the thermodynamics. The thermodynamic properties have extensive similarities which suggest that the idea of AdS holography is more dependent on the existence of the boundary than on the exact details of asymptotically AdS metrics.Comment: 9 pages; 4 multipart figure

On correlation between protein secondary structure, backbone bond angles, and side-chain orientations

We investigate the fine structure of the sp3 hybridized covalent bond geometry that governs the tetrahedral architecture around the central C$_\alpha$ carbon of a protein backbone, and for this we develop new visualization techniques to analyze high resolution X-ray structures in Protein Data Bank. We observe that there is a correlation between the deformations of the ideal tetrahedral symmetry and the local secondary structure of the protein. We propose a universal coarse grained energy function to describe the ensuing side-chain geometry in terms of the C$_\beta$ carbon orientations. The energy function can model the side-chain geometry with a sub-atomic precision. As an example we construct the C$_\alpha$-C$_\beta$ structure of HP35 chicken villin headpiece. We obtain a configuration that deviates less than 0.4 \.A in root-mean-square distance from the experimental X-ray structure

Parameter space metric for 3.5 post-Newtonian gravitational-waves from compact binary inspirals

We derive the metric on the parameter space of 3.5 post-Newtonian (3.5PN) stationary phase compact binary inspiral waveforms for a single detector, neglecting spin, eccentricity, and finite-body effects. We demonstrate that this leads to better template placement than the current practice of using the 2PN metric to place 3.5PN templates: The recovered event rate is improved by about 10% at a cost of nearly doubling the number of templates. The cross-correlations between mass parameters are also more accurate, which will result in better coincidence tests.Comment: 10 pages, 7 figure

Elastic Energy and Phase Structure in a Continuous Spin Ising Chain with Applications to the Protein Folding Problem

We present a numerical Monte Carlo analysis of a continuos spin Ising chain that can describe the statistical proterties of folded proteins. We find that depending on the value of the Metropolis temperature, the model displays the three known nontrivial phases of polymers: At low temperatures the model is in a collapsed phase, at medium temperatures it is in a random walk phase, and at high temperatures it enters the self-avoiding random walk phase. By investigating the temperature dependence of the specific energy we confirm that the transition between the collapsed phase and the random walk phase is a phase transition, while the random walk phase and self-avoiding random walk phase are separated from each other by a cross-over transition. We also compare the predictions of the model to a phenomenological elastic energy formula, proposed by Huang and Lei to describe folded proteins.Comment: 12 pages, 23 figures, RevTeX 4.

Finite Mirror Effects in Advanced Interferometric Gravitational Wave Detectors

Thermal noise is expected to be the dominant source of noise in the most sensitive frequency band of second generation ground based gravitational wave detectors. Reshaping the beam to a flatter wider profile which probes more of the mirror surface reduces this noise. The "Mesa" beam shape has been proposed for this purpose and was subsequently generalized to a family of hyperboloidal beams with two parameters: twist angle alpha and beam width D. Varying alpha allows a continuous transition from the nearly-flat to the nearly-concentric Mesa beam configurations. We analytically prove that in the limit of infinite D hyperboloidal beams become Gaussians. The Advanced LIGO diffraction loss design constraint is 1 ppm per bounce. In the past the diffraction loss has often been calculated using the clipping approximation that, in general, underestimates the diffraction loss. We develop a code using pseudo-spectral methods to compute the diffraction loss directly from the propagator. We find that the diffraction loss is not a strictly monotonic function of beam width, but has local minima that occur due to finite mirror effects and leads to natural choices of D. For the Mesa beam a local minimum occurs at D = 10.67 cm and leads to a diffraction loss of 1.4 ppm. We find that if one requires a diffraction loss of strictly 1 ppm, the alpha = 0.91 pi hyperboloidal beam is optimal, leading to the coating thermal noise being lower by about 10% than for a Mesa beam while other types of thermal noise decrease as well. We then develop an iterative process that reconstructs the mirror to specifically account for finite mirror effects. This allows us to increase the D parameter and lower the coating noise by about 30% compared to the original Mesa configuration.Comment: 13 pages, 12 figures, 4 tables. Referee input included and typos fixed. Accepted by Phys. Rev.

Improving the Sensitivity of Advanced LIGO Using Noise Subtraction

This paper presents an adaptable, parallelizable method for subtracting linearly coupled noise from Advanced LIGO data. We explain the features developed to ensure that the process is robust enough to handle the variability present in Advanced LIGO data. In this work, we target subtraction of noise due to beam jitter, detector calibration lines, and mains power lines. We demonstrate noise subtraction over the entirety of the second observing run, resulting in increases in sensitivity comparable to those reported in previous targeted efforts. Over the course of the second observing run, we see a 30% increase in Advanced LIGO sensitivity to gravitational waves from a broad range of compact binary systems. We expect the use of this method to result in a higher rate of detected gravitational-wave signals in Advanced LIGO data.Comment: 15 pages, 6 figure

Memory and superposition in a spin glass

Non-equilibrium dynamics in a Ag(Mn) spin glass are investigated by measurements of the temperature dependence of the remanent magnetisation. Using specific cooling protocols before recording the thermo- or isothermal remanent magnetisations on re-heating, it is found that the measured curves effectively disclose non-equilibrium spin glass characteristics such as ageing and memory phenomena as well as an extended validity of the superposition principle for the relaxation. The usefulness of this "simple" dc-method is discussed, as well as its applicability to other disordered magnetic systems.Comment: REVTeX style; 8 pages, 4 figure

Scaling Law and Aging Phenomena in the Random Energy Model

We study the effect of temperature shift on aging phenomena in the Random Energy Model (REM). From calculation on the correlation function and simulation on the Zero-Field-Cooled magnetization, we find that the REM satisfies a scaling relation even if temperature is shifted. Furthermore, this scaling property naturally leads to results obtained in experiment and the droplet theory.Comment: 8 pages, 7 figures, to be submitted to J. Phys. Soc. Jp

Short range ferromagnetism and spin glass state in Y0.7Ca0.3MnO3\mathrm{Y_{0.7}Ca_{0.3}MnO_{3}}

Dynamic magnetic properties of $\mathrm{Y_{0.7}Ca_{0.3}MnO_{3}}$ are reported. The system appears to attain local ferromagnetic order at $T_{\mathrm{SRF}} \approx 70$ K. Below this temperature the low field magnetization becomes history dependent, i.e. the zero field cooled (ZFC) and field cooled (FC) magnetization deviate from each other and closely logarithmic relaxation appears at our experimental time scales (0.3-$10^{4}$ sec). The zero field cooled magnetization has a maximum at $T_{\mathrm{f}}\approx 30$ K, whereas the field cooled magnetization continues to increase, although less sharply, also below this temperature. Surprisingly, the dynamics of the system shows non-equilibrium spin glass (SG) features not only below the maximum in the ZFC magnetization, but also in the temperature region between this maximum and $T_{\mathrm{SRF}}$. The aging and temperature cycling experiments show only quantitative differences in the dynamic behavior above and below the maximum in the ZFC-magnetization; similarly, memory effects are observed in both temperature regions. We attribute the high temperature behavior to the existence of clusters of short range ferromagnetic order below $T_{\mathrm{SRF}}$; the configuration evolves into a conventional spin glass state at temperatures below $T_{\mathrm{f}}$.Comment: REVTeX style; 8 pages, 8 figure

Brown-York Energy and Radial Geodesics

We compare the Brown-York (BY) and the standard Misner-Sharp (MS) quasilocal energies for round spheres in spherically symmetric space-times from the point of view of radial geodesics. In particular, we show that the relation between the BY and MS energies is precisely analogous to that between the (relativistic) energy E of a geodesic and the effective (Newtonian) energy E_{eff} appearing in the geodesic equation, thus shedding some light on the relation between the two. Moreover, for Schwarzschild-like metrics we establish a general relationship between the BY energy and the geodesic effective potential which explains and generalises the recently observed connection between negative BY energy and the repulsive behaviour of geodesics in the Reissner-Nordstrom metric. We also comment on the extension of this connection between geodesics and the quasilocal BY energy to regions inside a horizon.Comment: v3: 7 pages, shortened and revised version to appear in CQ