1,838 research outputs found
Chaplygin Gravitodynamics
We consider a new approach for gravity theory coupled to Chaplygin matter in
which the {\it{relativistic}} formulation of the latter is of crucial
importance. We obtain a novel form of matter with dust like density and negative pressure. We explicitly show that our results are
compatible with a relativistic generalization of the energy conservation
principle, derived here.Comment: Title changed, Revised version,N o change in conclusions, Journal
ref.: MPL A21 (2006)1511-151
Metastable tight knots in a worm-like polymer
Based on an estimate of the knot entropy of a worm-like chain we predict that
the interplay of bending energy and confinement entropy will result in a
compact metastable configuration of the knot that will diffuse, without
spreading, along the contour of the semi-flexible polymer until it reaches one
of the chain ends. Our estimate of the size of the knot as a function of its
topological invariant (ideal aspect ratio) agrees with recent experimental
results of knotted dsDNA. Further experimental tests of our ideas are proposed.Comment: 4 pages, 3 figure
Aspects of Diffeomorphism and Conformal invariance in classical Liouville theory
The interplay between the diffeomorphism and conformal symmetries (a feature
common in quantum field theories) is shown to be exhibited for the case of
black holes in two dimensional classical Liouville theory. We show that
although the theory is conformally invariant in the near horizon limit, there
is a breaking of the diffeomorphism symmetry at the classical level. On the
other hand, in the region away from the horizon, the conformal symmetry of the
theory gets broken with the diffeomorphism symmetry remaining intact.Comment: Accepted in Euro. Phys. Letters., Title changed, abstract modified,
major modifications made in the pape
Enhancement by polydispersity of the biaxial nematic phase in a mixture of hard rods and plates
The phase diagram of a polydisperse mixture of uniaxial rod-like and
plate-like hard parallelepipeds is determined for aspect ratios and
15. All particles have equal volume and polydispersity is introduced in a
highly symmetric way. The corresponding binary mixture is known to have a
biaxial phase for , but to be unstable against demixing into two
uniaxial nematics for . We find that the phase diagram for
is qualitatively similar to that of the binary mixture, regardless
the amount of polydispersity, while for a sufficient amount of
polydispersity stabilizes the biaxial phase. This provides some clues for the
design of an experiment in which this long searched biaxial phase could be
observed.Comment: 4 pages, 5 eps figure files, uses RevTeX 4 styl
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