8,094 research outputs found
Acoustics of tachyon Fermi gas
We consider a Fermi gas of free tachyons as a continuous medium and find
whether it satisfies the causality condition. There is no stable tachyon matter
with the particle density below critical value and the Fermi momentum
that depends on the tachyon mass . The pressure
and energy density cannot be arbitrary small, but the situation is
not forbidden. Existence of shock waves in tachyon gas is also discussed. At
low density the tachyon matter remains stable but no shock wave
do survive.Comment: 14 pages, 2 figures (color
Shock waves in superconducting cosmic strings: growth of current
Intrinsic equations of motion of superconducting cosmic string may admit
solutions in the shock-wave form that implies discontinuity of the current term
\chi. The hypersurface of discontinuity propagates at finite velocity
determined by finite increment \Delta \chi =\chi_+ -\chi_-. The current
increases \chi_+>\chi_- in stable shocks but transition between spacelike (\chi
>0) and timelike (\chi<0) currents is impossible.Comment: 13 pages, 3 figure
Interaction between superconducting vortices and Bloch wall in ferrite garnet film
Interaction between a Bloch wall in a ferrite-garnet film and a vortex in a
superconductor is analyzed in the London approximation. Equilibrium
distribution of vortices formed around the Bloch wall is calculated. The
results agree quantitatively with magneto-optical experiment where an in-plane
magnetized ferrite-garnet film placed on top of NbSe2 superconductor allows
observation of individual vortices. In particular, our model can reproduce a
counter-intuitive attraction observed between vortices and a Bloch wall having
the opposite polarity. It is explained by magnetic charges appearing due to
discontinuity of the in-plane magnetization across the wall.Comment: 4 pages, 5 figure
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