31 research outputs found
Flux tubes and the type-I/type-II transition in a superconductor coupled to a superfluid
We analyze magnetic flux tubes at zero temperature in a superconductor that
is coupled to a superfluid via both density and gradient (``entrainment'')
interactions. The example we have in mind is high-density nuclear matter, which
is a proton superconductor and a neutron superfluid, but our treatment is
general and simple, modeling the interactions as a Ginzburg-Landau effective
theory with four-fermion couplings, including only s-wave pairing. We
numerically solve the field equations for flux tubes with an arbitrary number
of flux quanta, and compare their energies. This allows us to map the
type-I/type-II transition in the superconductor, which occurs at the
conventional kappa = 1/sqrt(2) if the condensates are uncoupled.
We find that a density coupling between the condensates raises the critical
kappa and, for a sufficiently high neutron density, resolves the type-I/type-II
transition line into an infinite number of bands corresponding to
``type-II(n)'' phases, in which n, the number of quanta in the favored flux
tube, steps from 1 to infinity. For lower neutron density, the coupling creates
spinodal regions around the type-I/type-II boundary, in which metastable flux
configurations are possible. We find that a gradient coupling between the
condensates lowers the critical kappa and creates spinodal regions. These
exotic phenomena may not occur in nuclear matter, which is thought to be deep
in the type-II region, but might be observed in condensed matter systems.Comment: 14 pages, improved discussion of the effects of varying the
neutron/proton condensate ratio; added reference
Giant vortices, vortex rings and reentrant behavior in type-1.5 superconductors
We predict that in a bulk type-1.5 superconductor the competing magnetic
responses of the two components of the order parameter can result in a vortex
interaction that generates group-stabilized giant vortices and unusual vortex
rings in the absence of any extrinsic pinning or confinement mechanism. We also
find within the Ginzburg-Landau theory a rich phase diagram with successions of
behaviors like type-1 -> type-1.5 -> type-2 -> type-1.5 as temperature
decreases.Comment: 5 pages, 4 figure
Interaction of vortices in superconductors with kappa close to 2^(-1/2)
Using a perturbative approach to the infinitely degenerate Bogomolnyi vortex
state for a superconductor with kappa = 2^(-1/2), T -> T_c, we calculate the
interaction of vortices in a superconductor with kappa close to 2^(-1/2). We
find, numerically and analytically, that depending on the material the
interaction potential between the vortices varies with decreasing kappa from
purely repulsive (as in a type-II superconductor) to purely attractive (as in a
type-I superconductor) in two different ways: either vortices form a bound
state and the distance between them changes gradually from infinity to zero, or
this transition occurs in a discontinuous way as a result of a competition
between minima at infinity and zero. We study the discontinuous transition
between the vortex and Meissner states caused by the non-monotonous vortex
interaction and calculate the corresponding magnetization jump.Comment: v1:original submit v2:changed formate of images (gave problems to
some) v3:corrected fig v4v6 (was -v4v6) orthographic corrections (and
U_lat/int) mismatch v4:more small orthographic corrections v5:converted to
revtex4 and bibTex v6:Renamed images to submit to pr
Symmetries within domain walls
The comparison of symmetries in the interior and the exterior of a domain
wall is relevant when discussing the correspondence between domain walls and
branes, and also when studying the interaction of walls and magnetic monopoles.
I discuss the symmetries in the context of an SU(N) times Z_2 model (for odd N)
with a single adjoint scalar field. Situations in which the wall interior has
less symmetry than the vacuum are easy to construct while the reverse situation
requires significant engineering of the scalar potential.Comment: 5 pages. Added reference
A q-analog of the ADHMN construction and axisymmetric multi-instantons
In the preceding paper (Phys. Lett. B463 (1999) 257), the authors presented a
q-analog of the ADHMN construction and obtained a family of anti-selfdual
configurations with a parameter q for classical SU(2) Yang-Mills theory in
four-dimensional Euclidean space. The family of solutions can be seen as a
q-analog of the single BPS monopole preserving (anti-)selfduality. Further
discussion is made on the relation to axisymmetric ansatz on anti-selfdual
equation given by Witten in the late seventies. It is found that the
q-exponential functions familiar in q-analysis appear as analytic functions
categorizing the anti-selfdual configurations yielded by axisymmetric ansatz.Comment: 11pages, Latex2e, to appear in Journal of Physics A: Mathematical and
General as a `Special Issue/Difference Equations
Non-Abelian Vortices without Dynamical Abelianization
Vortices carrying truly non-Abelian flux moduli, which do not dynamically
reduce to Abelian vortices, are found in the context of softly-broken supersymmetric chromodynamics (SQCD). By tuning the bare quark masses
appropriately we identify the vacuum in which the underlying SU(N) gauge group
is partially broken to SU(n) \times SU(r) \times U(1)/{\mathbbm Z}_{K}, where
is the least common multiple of , and with and
flavors of light quark multiplets. At much lower energies the
gauge group is broken completely by the squark VEVs, and vortices develop which
carry non-Abelian flux moduli . For we argue
that the SU(n) fluctuations become strongly coupled and Abelianize, while
leaving weakly fluctuating flux moduli. This allows us to recognize the
semi-classical origin of the light non-Abelian monopoles found earlier in the
fully quantum-mechanical treatment of 4D SQCD.Comment: 22 pages, 4 figures, One section (Section 2) added, and an extended
discussion added in Section
CPT violation and particle-antiparticle asymmetry in cosmology
General features of generation of the cosmological charge asymmetry in CPT
non-invariant world are discussed. If the effects of CPT violation manifest
themselves only in mass differences of particles and antiparticles, the baryon
asymmetry of the universe hardly can be explained solely by breaking of CPT
invariance. However, CPT non-invariant theories may lead to a new effect of
distorting the usual equilibrium distributions. If this takes place, CPT
violation may explain the baryon asymmetry of the universe.Comment: 7 pages, no figures. Submitted to a special issue of Yadernaya Fizika
(Physics of Atomic Nuclei) dedicated to 80th birthday of L.B. Okun. Three
references are adde
Cosmic strings in dilaton gravity
We examine the metric of an isolated self-gravitating abelian-Higgs vortex in
dilatonic gravity for arbitrary coupling of the vortex fields to the dilaton.
We look for solutions in both massless and massive dilaton gravity. We compare
our results to existing metrics for strings in Einstein and Jordan-Brans-Dicke
theory. We explore the generalization of Bogomolnyi arguments for our vortices
and comment on the effects on test particles.Comment: 24 pages plain TEX, 4 figures -- references amended, some additional
comments added, version to appear in journa
Abelian Higgs Hair for Black Holes
We find evidence for the existence of solutions of the Einstein and Abelian
Higgs field equations describing a black hole pierced by a Nielsen-Olesen
vortex. This situation falls outside the scope of the usual no-hair arguments
due to the non-trivial topology of the vortex configuration and the special
properties of its energy-momentum tensor. By a combination of numerical and
perturbative techniques we conclude that the black hole horizon has no
difficulty in supporting the long range fields of the Nielsen Olesen string.
Moreover, the effect of the vortex can in principle be measured from infinity,
thus justifying its characterization as black hole ``hair".Comment: 31 pages, plain tex, 7 figures included. minor corrections and
references adde
Supersymmetry breaking in noncommutative quantum mechanics
Supersymmetric quantum mechanics is formulated on a two dimensional
noncommutative plane and applied to the supersymmetric harmonic oscillator. We
find that the ordinary commutative supersymmetry is partially broken and only
half of the number of supercharges are conserved. It is argued that this
breaking is closely related to the breaking of time reversal symmetry arising
from noncommutativity