7,772 research outputs found
Symmetry as a sufficient condition for a finite flex
We show that if the joints of a bar and joint framework are
positioned as `generically' as possible subject to given symmetry constraints
and possesses a `fully-symmetric' infinitesimal flex (i.e., the
velocity vectors of the infinitesimal flex remain unaltered under all symmetry
operations of ), then also possesses a finite flex which
preserves the symmetry of throughout the path. This and other related
results are obtained by symmetrizing techniques described by L. Asimov and B.
Roth in their paper `The Rigidity Of Graphs' from 1978 and by using the fact
that the rigidity matrix of a symmetric framework can be transformed into a
block-diagonalized form by means of group representation theory. The finite
flexes that can be detected with these symmetry-based methods can in general
not be found with the analogous non-symmetric methods.Comment: 26 pages, 10 figure
QCD sum rules for D mesons in dense and hot nuclear matter
Open charm mesons (pseudo-scalar and scalar as well as axial-vector and
vector) propagating or resting in nuclear matter display an enhanced
sensitivity to the chiral condensate. This offers new prospects to seek for
signals of chiral restoration, in particular in p-A and p-bar-A reactions as
envisaged in first-round experiments by the CBM and PANDA collaborations at
FAIR. Weinberg type sum rules for charming chiral partners are presented, and
the distinct in-medium modifications of open-charm mesons are discussed. We
also address the gluon condensates near Tc and their impact on QCD sum rules.Comment: 6 pages, 7 figures, conference proceeding
Plasmons, plasminos and Landau damping in a quasiparticle model of the quark-gluon plasma
A phenomenological quasiparticle model is surveyed for 2+1 quark flavors and
compared with recent lattice QCD results. Emphasis is devoted to the effects of
plasmons, plasminos and Landau damping. It is shown that thermodynamic bulk
quantities, known at zero chemical potential, can uniquely be mapped towards
nonzero chemical potential by means of a thermodynamic consistency condition
and a stationarity condition.Comment: Sep. 2007. 13 pp. Invited talk given at Zimanyi 75 Memorial Workshop
on Hadronic and Quark Matter, Budapest, Hungary, 2-4 Jul. 2007; reviewed and
published versio
Plasmons, plasminos and Landau damping in a quasiparticle model of the quark-gluon plasma
A phenomenological quasiparticle model is surveyed for 2+1 quark flavors and
compared with recent lattice QCD results. Emphasis is devoted to the effects of
plasmons, plasminos and Landau damping. It is shown that thermodynamic bulk
quantities, known at zero chemical potential, can uniquely be mapped towards
nonzero chemical potential by means of a thermodynamic consistency condition
and a stationarity condition.Comment: Sep. 2007. 13 pp. Invited talk given at Zimanyi 75 Memorial Workshop
on Hadronic and Quark Matter, Budapest, Hungary, 2-4 Jul. 2007; reviewed and
published versio
Operation of a haynes alloy no. 25 forced circulation loop to study the effects of hydrogen in a simulated sunflower system
Haynes alloy forced circulation mercury loop for studying hydrogen effects in working fluid of Rankine cycle Sunflower solar power syste
Equation of state for QCD matter in a quasiparticle model
A phenomenological QCD quasiparticle model provides a means to map lattice
QCD results to regions relevant for a variety of heavy-ion collision
experiments at larger baryon density. We report on effects of collectives modes
and damping on the equation of state.Comment: Oct. 2008. 2 p
The orbit rigidity matrix of a symmetric framework
A number of recent papers have studied when symmetry causes frameworks on a
graph to become infinitesimally flexible, or stressed, and when it has no
impact. A number of other recent papers have studied special classes of
frameworks on generically rigid graphs which are finite mechanisms. Here we
introduce a new tool, the orbit matrix, which connects these two areas and
provides a matrix representation for fully symmetric infinitesimal flexes, and
fully symmetric stresses of symmetric frameworks. The orbit matrix is a true
analog of the standard rigidity matrix for general frameworks, and its analysis
gives important insights into questions about the flexibility and rigidity of
classes of symmetric frameworks, in all dimensions.
With this narrower focus on fully symmetric infinitesimal motions, comes the
power to predict symmetry-preserving finite mechanisms - giving a simplified
analysis which covers a wide range of the known mechanisms, and generalizes the
classes of known mechanisms. This initial exploration of the properties of the
orbit matrix also opens up a number of new questions and possible extensions of
the previous results, including transfer of symmetry based results from
Euclidean space to spherical, hyperbolic, and some other metrics with shared
symmetry groups and underlying projective geometry.Comment: 41 pages, 12 figure
- …