20,290 research outputs found
Stability Criteria for Breached Pair Superfluidity
We present simple, concrete, two-fermion models that exhibit
thermodynamically stable isotropic translationally-invariant gapless superfluid
states (breached pair superfluidity). The mass ratio between the components and
the momentum structure of the interaction are crucial for determining the
stability of such states: Idealized, momentum-independent (``contact'')
interactions are insufficient.Comment: 5 pages, REVTeX4. Minor updates in response to comments. References
adde
The Resonance Overlap and Hill Stability Criteria Revisited
We review the orbital stability of the planar circular restricted three-body
problem, in the case of massless particles initially located between both
massive bodies. We present new estimates of the resonance overlap criterion and
the Hill stability limit, and compare their predictions with detailed dynamical
maps constructed with N-body simulations. We show that the boundary between
(Hill) stable and unstable orbits is not smooth but characterized by a rich
structure generated by the superposition of different mean-motion resonances
which does not allow for a simple global expression for stability.
We propose that, for a given perturbing mass and initial eccentricity
, there are actually two critical values of the semimajor axis. All values
are
unstable in the Hill sense. The first limit is given by the Hill-stability
criterion and is a function of the eccentricity. The second limit is virtually
insensitive to the initial eccentricity, and closely resembles a new resonance
overlap condition (for circular orbits) developed in terms of the intersection
between first and second-order mean-motion resonances.Comment: 33 pages, 14 figures, accepte
Gravitational Fragmentation in Galaxy Mergers: A Stability Criteria
We study the gravitational stability of gaseous streams in the complex
environment of a galaxy merger, because mergers are known to be places of
ongoing massive cluster formation and bursts of star formation. We find an
analytic stability parameter for case of gaseous streams orbiting around the
merger remnant. We test our stability criteria using hydrodynamical simulations
of galaxy mergers, obtaining satisfactory results. We find that our criteria
successfully predicts the streams that will be gravitationally unstable to
fragment into clumps.Comment: 10 pages, 2 figures. After 2nd referee repor
Necessary and Sufficient Elastic Stability Conditions in Various Crystal Systems
While the Born elastic stability criteria are well-known for cubic crystals,
there is some confusion in the literature about the form it should take for
lower symmetry crystal classes. We present here closed form necessary and
sufficient conditions for elastic stability in all crystal classes, as a
concise and pedagogical reference to stability criteria in non-cubic materials
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