Static quark anti-quark pair in SU(2) gauge theory

We study singlet and triplet correlation functions of static quark anti-quark pair defined through gauge invariant time-like Wilson loops and Polyakov loop correlators in finite temperature SU(2) gauge theory. We use the Luescher-Weisz multilevel algorithm, which allows to calculate these correlators at very low temperatures. We observe that the naive separation of singlet and triplet states in general does not hold non-perturbatively, however, is recovered in the limit of small separation and the temperature dependence of the corresponding correlators is indeed very different.Comment: ReVTeX, 11 pages, 5 figure

Dielectric properties characterization of La- and Dy-doped BiFeO3 thin films

The dielectric response of La- and Dy- doped BiFeO3 thin films at microwave frequencies (up to 12 GHz) has been monitored as a function of frequency, direct current (dc) electric field, and magnetic field in a temperature range from 25 to 300 °C. Both the real and imaginary parts of the response have been found to be non-monotonic (oscillating) functions of measuring frequency. These oscillations are not particularly sensitive to a dc electric field; however, they are substantially dampened by a magnetic field. The same effect has been observed when the volume of the characterized sample is increased. This phenomenon is attributed to the presence of a limited number of structural features with a resonance type response. The exact origin of these features is unknown at present. Leakage current investigations were performed on the whole set of films. The films were highly resistive with low leakage current, thereby giving us confidence in the microwave measurements. These typically revealed ‘N'-type I-V characteristic

The Study of Dielectric Properties of Biological Tissue under Thermal Modification in vitro

The aim of this paper is to study the dynamics of the dielectric properties of the tissue in the experimental controlled thermal modification. Material and methods: the experiment was performed on equal in volume and mass samples of intraoperatively removed tissue of Palmar aponeurosis (n=8). The thermal effect was simulated by placing tissue fragments in a thermostat (processing time – 5 min., temperature – 60 C). Duration of exposure after thermal modification was 5 min. Dielectric properties of tissues was determined using an original hardware-software complex for near-field resonant microwave sensing. Results: the study made it possible to verify the shifts in dielectric properties of the tissue that occur under short-term exposure to high temperature in vitro. It is shown that the dielectric permeability and conductivity of the biological object are significantly reduced under the influence of this factor, which is primarily due to a decrease of its hydration degree

Multiple filamentation of laser beams with different diameters in the air at a 100-meter path

Results of experiments on controlling the position and length of the filamentation zone of femtosecond laser pulses in atmospheric path length 110 m using different initial spatial focusing and defocusing. The obtained distribution of filaments along the filamentation zone, measured dependence the length of the filamentation zone of the numerical aperture of the beam, its initial radius and pulse power

Multiple filamentation of laser beams with different diameters in the air at a 150-meter path

Results of experiments on controlling the position and length of the filamentation zone of femtosecond laser pulses in atmospheric path length 150 m using different initial spatial focusing and defocusing. The obtained distribution of filaments along the filamentation zone, measured dependence the length of the filamentation zone of the numerical aperture of the beam, its initial radius and pulse power

Filamentation of terawatt laser pulses along hundred-meter atmospheric paths

Results of the experimental study of filamentation of terawatt femtosecond pulses of a Ti:Sapphire laser along an atmospheric path 106 m long using different spatial focusing and pulse power are presented. The control of filamentation region position and length by means of changing the initial laser beam focusing is shown to be highly effective. Dependencies are derived of filamentation region position and length on the initial degree of focusing, pulse power, and the number of filaments along the filamentation region. The obtained data on the filamentation region length and the number of filaments are compared with the results of our previous experiments and data from other authors

Global self-focusing and features of multiple filamentation of radiation of a subterawatt Ti:sapphire laser with a centimeter output aperture along a 150-m path

The formation and propagation of postfilamentation channels along a controllable path 150 m long are studied experimentally for collimated beams of different diameters. During multiple filamentation, a laser beam is compressed into a global focus, after passing which its angular divergence is much greater than the divergence of postfilamentation channels generated during the filamentation. It is shown that the intensity of the postfilamentation channels is sufficient for starting multiple filamentation in optical elements at distances much longer than the filamentation region length

Modeling of multiple filamentation of terawatt laser pulses on a hundred-meter air path

The results of numerical simulation of multiple filamentation of terawatt femtosecond pulse Ti:Sapphire laser performed on the experimental data obtained in the airway of a length of 106 m when changing the initial spatial focusing and laser power