43,933 research outputs found
Twisted Superconducting Semilocal Strings
A new class of twisted, current carrying, stationary, straight string
solutions having finite energy per unit length is constructed numerically in an
extended Abelian Higgs model with global SU(2) symmetry. The new solutions
correspond to deformations of the embedded Abrikosov-Nielsen-Olesen (ANO)
vortices by a twist -- a relative coordinate dependent phase between the two
Higgs fields. The twist induces a global current flowing through the string,
and the deformed solutions bifurcate with the ANO vortices in the limit of
vanishing current. For each value of the winding number (determining
the magnetic flux through the plane orthogonal to the string) there are
distinct, two-parametric families of solutions. One of the continuously varying
parameters is the twist, or the corresponding current, the other one can be
chosen to be the momentum of the string. For fixed values of the momentum and
twist, the distinct solutions have different energies and can be viewed as
a lowest energy ``fundamental'' string and its ``excitations''
characterized by different values of their ``polarization''. The latter is
defined as the ratio of the angular momentum of the vortex and its momentum. In
their rest frame the twisted vortices have lower energy than the embedded ANO
vortices and could be of considerable importance in various physical systems
(from condensed matter to cosmic strings).Comment: 39 pages, 20 figure
Superstrings on AdS_3 and Symmetric Products
Some properties of N=2 superstrings on AdS_3 x N are studied. Their spectrum
has the same pattern as 2-d CFTs in the moduli space of symmetric products
M^p/S_p, where p is associated with the number of long fundamental strings
required to construct the AdS_3 background, and M is the spacetime CFT
corresponding to short string excitations of a single long string. Worldsheet
operators associated with w long strings correspond to twisted sectors of
M^p/S_p.Comment: 43 pages, harvma
Unpaired Majorana modes on dislocations and string defects in Kitaev's honeycomb model
We study the gapped phase of Kitaev's honeycomb model (a spin liquid)
on a lattice with topological defects. We find that some dislocations and
string defects carry unpaired Majorana fermions. Physical excitations
associated with these defects are (complex) fermion modes made out of two
(real) Majorana fermions connected by a gauge string. The quantum state
of these modes is robust against local noise and can be changed by winding a
vortex around one of the dislocations. The exact solution respects gauge
invariance and reveals a crucial role of the gauge field in the physics of
Majorana modes. To facilitate these theoretical developments, we recast the
degenerate perturbation theory for spins in the language of Majorana fermions.Comment: 15 pages, 7 figures; added a brief history of twists, references, and
clarified the count of the topological degeneracy of the ground stat
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