Adjoint torelons, and the persistence of color electric flux tubes in the deconfined phase

It is argued that the adjoint torelon loop, i.e. a Polyakov loop in the adjoint representation running in a spatial, rather than temporal, direction, is an observable which is sensitive to the presence of long color electric flux tubes at high temperatures. We show via lattice Monte Carlo simulations that this observable has a sharp peak at the deconfinement transition, remains much larger than the vacuum value for some range of $T>T_c$, and falls below the vacuum value for $T > 2T_c$. This result suggests that long electric flux tubes may persist for a finite range of temperatures past the deconfinement transition, and at some stage disappear, presumably melting into a plasma of gluons. As a side remark, we point out that our results at $T<T_c$ imply that the eigenvalues of ordinary Polyakov loop holonomies in the confinement phase have a slight tendency to attract rather than repel, which may be relevant to certain models of confinement.Comment: 6 pages, 4 figure

Coulomb Confinement from the Yang-Mills Vacuum State in 2+1 Dimensions

The Coulomb-gauge ghost propagator, and the color-Coulomb potential, are computed in an ensemble of configurations derived from our recently proposed Yang-Mills vacuum wavefunctional in 2+1 dimensions. The results are compared to the corresponding values obtained by standard Monte Carlo simulations in three Euclidean dimensions. The agreement is quite striking for the Coulomb-gauge ghost propagator. The color-Coulomb potential rises linearly at large distances, but its determination suffers from rather large statistical fluctuations, due to configurations with very low values of $\mu_0$, the lowest eigenvalue of the Coulomb-gauge Faddeev-Popov operator. However, if one imposes cuts on the data, effectively leaving out configurations with very low $\mu_0$, the agreement of the potential in both sets of configurations is again satisfactory, although the errorbars grow systematically as the cutoff is eliminated.Comment: 8 pages, 5 figures (10 EPS files), RevTeX4.1. V2: original figs. 4 and 5 compressed into a new fig. 5; a new fig. 4; sec. IV.B slightly modified to reflect the changes. Version to appear in Phys. Rev. D. V3: a reference corrected

Design of a translation stage for focusing objective inside the LIBS interaction chamber

Diplomová práca popisuje návrh posuvu fokusačného objektívu vo vnútri interakčnej komory LIBS. Obsahuje popis základných vlastností a funkcií LIBS spektroskopie. Opisuje prehžad použitežných komponentov, hodnotí ich vlastnosti a vhodnosť použitia v konštrukcii posuvu do vákua. Ďalej uvádza výsledné konštrukčné riešenie lineárneho posuvu do vákua a hodnotí jeho výhody pre metódu LIBS.This diploma thesis describes the design of a translation stage for focusing objective inside the LIBS interaction chamber. It contains a description of the fundamentals and basic functions of LIBS spectroscopy. Moreover, in the thesis an overview of different translation stages as possible LIBS components is given. Their advantages and disadvantages for use in a vacuum translation stage construction are evaluated. The thesis describes the final solution of a linear translation stage for focusing objective, and his advantages for LIBS method

Dimensional Reduction and the Yang-Mills Vacuum State in 2+1 Dimensions

We propose an approximation to the ground state of Yang-Mills theory, quantized in temporal gauge and 2+1 dimensions, which satisfies the Yang-Mills Schrodinger equation in both the free-field limit, and in a strong-field zero mode limit. Our proposal contains a single parameter with dimensions of mass; confinement via dimensional reduction is obtained if this parameter is non-zero, and a non-zero value appears to be energetically preferred. A method for numerical simulation of this vacuum state is developed. It is shown that if the mass parameter is fixed from the known string tension in 2+1 dimensions, the resulting mass gap deduced from the vacuum state agrees, to within a few percent, with known results for the mass gap obtained by standard lattice Monte Carlo methods.Comment: 14 pages, 9 figures. v2: Typos corrected. v3: added a new section discussing alternative (new variables) approaches, and fixed a problem with the appearance of figures in the pdf version. Version to appear in Phys Rev

Graphical Demonstration of Selected Route Lookup Algorithm

V tejto práci je stručne popísaný princíp fungovania sietí, smerovacích protokolov, taktiež sú vysvetlené základy fungovania rôznych algoritmov pre vyhľadávanie najdlhších zhodných prefixov implementovaných v smerovačoch. Väčšia časť práce sa venuje algoritmu Tree Bitmap, ktorého demonštračný program bolo treba vytvoriť. Činnosť tohto algoritmu je zobrazovaná pomocou prehľadných animácií.This thesis briefly describes principe of networks, routing protocols and there are described basis of some existing longest prefix match algorithms, which are implemented in router's hardware. Main part of thesis deals with a Tree Bitmap algorithm, that demonstration program creating is an objective of this work. The principe of this algorithm is demonstrated by visual animations.

Asymptotic Scaling, Casimir Scaling, and Center Vortices

We report on two recent developments in the center vortex theory of confinement: (i) the asymptotic scaling of the vortex density, as measured in Monte Carlo simulations; and (ii) an explanation of Casimir scaling and the adjoint string tension, in terms of the center vortex mechanism.Comment: LATTICE98(confine), 3 pages, 3 figure

Color Screening, Casimir Scaling, and Domain Structure in G(2) and SU(N) Gauge Theories

We argue that screening of higher-representation color charges by gluons implies a domain structure in the vacuum state of non-abelian gauge theories, with the color magnetic flux in each domain quantized in units corresponding to the gauge group center. Casimir scaling of string tensions at intermediate distances results from random spatial variations in the color magnetic flux within each domain. The exceptional G(2) gauge group is an example rather than an exception to this picture, although for G(2) there is only one type of vacuum domain, corresponding to the single element of the gauge group center. We present some numerical results for G(2) intermediate string tensions and Polyakov lines, as well as results for certain gauge-dependent projected quantities. In this context, we discuss critically the idea of projecting link variables to a subgroup of the gauge group. It is argued that such projections are useful only when the representation-dependence of the string tension, at some distance scale, is given by the representation of the subgroup.Comment: 24 pages, 14 figures; v2: references added; v3: published version containing some additional introductory discussio