7,327 research outputs found
Phase Transitions in liquid Helium 3
The phase transitions of liquid Helium 3 are described by truncations of an
exact nonperturbative renormalization group equation. The location of the first
order transition lines and the jump in the order parameter are computed
quantitatively. At the triple point we find indications for partially universal
behaviour. We suggest experiments that could help to determine the effective
interactions between fermion pairs.Comment: 4 pages, 6 figures, LaTe
Polarization of the fermionic vacuum by a global monopole with finite core
We study the vacuum polarization effects associated with a massive fermionic
field in a spacetime produced by a global monopole considering a nontrivial
inner structure for it. In the general case of the spherically symmetric static
core with finite support we evaluate the vacuum expectation values of the
energy-momentum tensor and the fermionic condensate in the region outside the
core. These quantities are presented as the sum of point-like global monopole
and core-induced contributions. The asymptotic behavior of the core-induced
vacuum densities are investigated at large distances from the core, near the
core and for small values of the solid angle corresponding to strong
gravitational fields. As an application of general results the flower-pot model
for the monopole's core is considered and the expectation values inside the
core are evaluated.Comment: 22 pages, 4 figure
Periods of activity cycles in late-type stars
The mean magnetic field dynamo theory is utilized to obtain the qualitative dependence of the period of activity on the angular velocity of rotation for stars with sufficiently extensive convective shells. The dependence of the cycle period on the spectral class is also discussed
Model tests of cluster separability in relativistic quantum mechanics
A relativistically invariant quantum theory first advanced by Bakamjian and
Thomas has proven very useful in modeling few-body systems. For three particles
or more, this approach is known formally to fail the constraint of cluster
separability, whereby symmetries and conservation laws that hold for a system
of particles also hold for isolated subsystems. Cluster separability can be
restored by means of a recursive construction using unitary transformations,
but implementation is difficult in practice, and the quantitative extent to
which the Bakamjian-Thomas approach violates cluster separability has never
been tested. This paper provides such a test by means of a model of a scalar
probe in a three-particle system for which (1) it is simple enough that there
is a straightforward solution that satisfies Poincar\'e invariance and cluster
separability, and (2) one can also apply the Bakamjian-Thomas approach. The
difference between these calculations provides a measure of the size of the
corrections from the Sokolov construction that are needed to restore cluster
properties. Our estimates suggest that, in models based on nucleon degrees of
freedom, the corrections that restore cluster properties are too small to
effect calculations of observables.Comment: 13 pages, 15 figure
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