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

Identifying derivations through the spectra of their values

We consider the relationship between derivations $d$ and $g$ of a Banach algebra $B$ that satisfy \s(g(x)) \subseteq \s(d(x)) for every $x\in B$, where \s(\, . \,) stands for the spectrum. It turns out that in some basic situations, say if $B=B(X)$, the only possibilities are that $g=d$, $g=0$, and, if $d$ is an inner derivation implemented by an algebraic element of degree 2, also $g=-d$. The conclusions in more complex classes of algebras are not so simple, but are of a similar spirit. A rather definitive result is obtained for von Neumann algebras. In general $C^*$-algebras we have to make some adjustments, in particular we restrict our attention to inner derivations implemented by selfadjoint elements. We also consider a related condition $\|[b,x]\|\leq M\|[a,x]\|$ for all selfadjoint elements $x$ from a $C^*$-algebra $B$, where $a,b\in B$ and $a$ is normal.Comment: 12 page

Optical equipment for measuring deformation of machine tool components

This paper describes the possibilities of measuring deformation of machine tool components based on monitoring change in the optical beam path. Deformation is evaluated relatively between an optical beam source and a sensing element. The great advantage lies in the fact that an active sensing element can be replaced by a passive optical element. No electronics needs to be installed in the measured place. Thus there is no necessity to protect electronic elements in a harsh environment. Another advantage is no need for statically arranged cables when measuring deformation on moving components. The measuring equipment presented in this paper consists of a measuring part and a part for measuring the motion of the reference beam. The position of a stiff body in space is clearly defined by 6 coordinates. The described optical equipment enables measurement of 4 coordinates, or 5 coordinates if an interferometer is used. The unmeasured coordinate describes the rotation of the measured body around the axis parallel with the optical beam

Numerical simulation of the detection of crack in reinforced concrete structures of NPP due to expansion of reinforcing corrosive products using Impact-Echo method

Nuclear energy boom is starting nowadays. But also current nuclear power plants (NPP) are duty to certify their security for regular renewal of their operating licenses. NPP security can be significantly affected by defects of large amount of ageing reinforced concrete structures. Advanced Impact-Echo method seams to be very hopeful to cooperate at performing in-service inspections such structures. Just these in-service inspections are included in the first priority group of specific technical issues according to the recommendations of OECD-Nuclear Energy Agency, Commission on Safety of Nuclear Installation in the field of ageing management.This paper continues of extensive project dealing with Impact-Echo method application. It will present method description and main results of numerical modeling of detection and localization of crack caused by corrosive product expansion. Steel reinforcing rods are subjected to corrosion due to diffusion of corrosive agents from structure surface. Corrosive products have up to 7-times larger volume than pure steel. Raised strain can cad lead up to concrete failure and crack development. We investigate whether it is possible to detect these growing cracks by Impact-Echo method in time.Experimental verification of our numerical predictions is prepared on Civil Faculty in Brno

Lie Superautomorphisms on Associative Algebras, II

Lie superautomorphisms of prime associative superalgebras are considered. A definitive result is obtained for central simple superalgebras: their Lie superautomorphisms are of standard forms, except when the dimension of the superalgebra in question is 2 or 4.Comment: 19 pages, accepted for publication in Algebr. Represent. Theor

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