SO(5) superconductor in a Zeeman magnetic field: Phase diagram and thermodynamic properties

In this paper we present calculations of the SO(5) quantum rotor theory of high-T$_{c}$ superconductivity in Zeeman magnetic field. We use the spherical approach for five-component quantum rotors in three-dimensional lattice to obtain formulas for critical lines, free energy, entropy and specific heat and present temperature dependences of these quantities for different values of magnetic field. Our results are in qualitative agreement with relevant experiments on high-T$_{c}$ cuprates.Comment: 4 pages, 2 figures, to appear in Phys. Rev. B, see http://prb.aps.or

Dependence of the superconducting critical temperature on the number of layers in homologous series of high-Tc cuprates

We study a model of $n$-layer high-temperature cuprates of homologous series like HgBa_2Ca_(n-1)Cu_nO_(2+2n+\delta) to explain the dependence of the critical temperature Tc(n) on the number $n$ of Cu-O planes in the elementary cell. Focusing on the description of the high-temperature superconducting system in terms of the collective phase variables, we have considered a semi-microscopic anisotropic three-dimensional vector XY model of stacked copper-oxide layers with adjustable parameters representing microscopic in-plane and out-of-plane phase stiffnesses. The model captures the layered composition along c-axis of homologous series and goes beyond the phenomenological Lawrence-Doniach model for layered superconductors. Implementing the spherical closure relation for vector variables we have solved the phase XY model exactly with the help of transfer matrix method and calculated Tc(n) for arbitrary block size $n$, elucidating the role of the c-axis anisotropy and its influence on the critical temperature. Furthermore, we accommodate inhomogeneous charge distribution among planes characterized by the charge imbalance coefficient $R$ being the function of number of layers $n$. By making a physically justified assumption regarding the doping dependence of the microscopic phase stiffnesses, we have calculated the values of parameter $R$ as a function of block size $n$ in good agreement with the nuclear magnetic resonance data of carrier distribution in multilayered high-Tc cuprates.Comment: 15 pages, 10 figures. Submitted to Physical Review

Collective patterns arising out of spatio-temporal chaos

We present a simple mathematical model in which a time averaged pattern emerges out of spatio-temporal chaos as a result of the collective action of chaotic fluctuations. Our evolution equation possesses spatial translational symmetry under a periodic boundary condition. Thus the spatial inhomogeneity of the statistical state arises through a spontaneous symmetry breaking. The transition from a state of homogeneous spatio-temporal chaos to one exhibiting spatial order is explained by introducing a collective viscosity which relates the averaged pattern with a correlation of the fluctuations.Comment: 11 pages (Revtex) + 5 figures (postscript

On the dynamics of a collapsing bubble in contact with a rigid wall

This work reveals that the dynamic response of a spherical cap bubble in contact with a rigid wall depends on the effective contact angle at the instant prior to collapse. This parameter allows us to discriminate between two regimes in which the mechanisms of interaction between the collapsing bubble and its surrounding medium differ significantly: When the contact angle is smaller than 90 degrees a classical jet directed towards the wall is observed whereas if the initial contact angle is larger than 90 degrees an annular re-entrant jet parallel to the wall appears. We show that this change of the behaviour can be explained using the impulse potential flow theory for small times which shows the presence of a singularity on the initial acceleration of the contact line when the contact angle is larger then 90 degrees. Direct Numerical Simulations show that although viscosity regularises the solution at $t > 0$, the solution remains singular at $t=0$. In these circumstances numerical and experimental results show that the collapse of flat bubbles can eventually lead to the formation of a vortex ring that unexpectedly induces long-range effects. The role of the bubble geometry at the instant of maximum expansion on the overall collapse process is shown to be well captured by the impulse potential flow theory, which can be easily generalised to other bubble shapes. These results may find direct application in the interpretation of geophysical flows as well as the control and design of bio-medical, naval, manufacturing and sonochemistry applications

Overview of the BlockNormal Event Trigger Generator

In the search for unmodeled gravitational wave bursts, there are a variety of methods that have been proposed to generate candidate events from time series data. Block Normal is a method of identifying candidate events by searching for places in the data stream where the characteristic statistics of the data change. These change-points divide the data into blocks in which the characteristics of the block are stationary. Blocks in which these characteristics are inconsistent with the long term characteristic statistics are marked as Event-Triggers which can then be investigated by a more computationally demanding multi-detector analysis.Comment: GWDAW-8 proceedings, 6 pages, 2 figure

AC losses and critical current density of superconducting GdBa2Cu3O7−x

Energy losses occurring in a cylindrical sample of Gd-Ba-Cu-O, subjected to an external AC magnetic field were examined. The loss dependence on the amplitude of the magnetic induction exhibits two stages of flux penetration into the superconductor. Critical current densitities for both stages of penetration were examined and an explanation for such behaviour is proposed. Support for this point of view is obtained by measurements on pulverized sample material. All measurements were performed at a temperature of 4.2 K and in absence of a background field.\ud \ud Analysis of the data provides two critical current densities: an inter-granular critical current density at weak alternating magnetic fields and an intra-granular critical current density at higher magnetic fields. The intra-granular critical current density is at least two orders of magnitude larger than the inter-granular one