29,357 research outputs found
Spherically symmetric monopoles in noncommutative space
We construct a spherically symmetric noncommutative space in three dimensions
by foliating the space with concentric fuzzy spheres. We show how to construct
a gauge theory in this space and in particular we derive the noncommutative
version of a Yang-Mills-Higgs theory. We find numerical monopole solutions of
the equations of motion.Comment: 13 pages, 3 figure
Noncommutative fermions and Morita equivalence
We study the Morita equivalence for fermion theories on noncommutative
two-tori. For rational values of the parameter (in appropriate units)
we show the equivalence between an abelian noncommutative fermion theory and a
nonabelian theory of twisted fermions on ordinary space. We study the chiral
anomaly and compute the determinant of the Dirac operator in the dual theories
showing that the Morita equivalence also holds at this level.Comment: 12 pages, LaTex file, no figures. Minor corrections, version to
appear in Phys. Lett.
Self-dual Chern-Simons solitons in noncommutative space
We construct exact soliton solutions to the Chern-Simons-Higgs system in
noncommutative space, for non-relativistic and relativistic models. In both
cases we find regular vortex-like solutions to the BPS equations which approach
the ordinary selfdual non-topological and topological solitons when the
noncommutative parameter goes to zero.Comment: 15 pages, 4 figure
String solutions in Chern-Simons-Higgs model coupled to an axion
We study a d=2+1 dimensional Chern-Simons gauge theory coupled to a Higgs
scalar and an axion field, finding the form of the potential that allows the
existence of selfdual equations and the corresponding Bogomolny bound for the
energy of static configurations. We show that the same conditions allow for the
N=2 supersymmetric extension of the model, reobtaining the BPS equations from
the supersymmetry requirement. Explicit electrically charged vortex-like
solutions to these equations are presented.Comment: 11 pages, 3 figure
Solar Fe abundance and magnetic fields - Towards a consistent reference metallicity
We investigate the impact on Fe abundance determination of including magnetic
flux in series of 3D radiation-MHD simulations of solar convection which we
used to synthesize spectral intensity profiles corresponding to disc centre. A
differential approach is used to quantify the changes in theoretical equivalent
width of a set of 28 iron spectral lines spanning a wide range in lambda,
excitation potential, oscillator strength, Land\'e factor, and formation
height. The lines were computed in LTE using the spectral synthesis code LILIA.
We used input magnetoconvection snapshots covering 50 minutes of solar
evolution and belonging to series having an average vertical magnetic flux
density of 0, 50, 100 and 200 G. For the relevant calculations we used the
Copenhagen Stagger code. The presence of magnetic fields causes both a direct
(Zeeman-broadening) effect on spectral lines with non-zero Land\'e factor and
an indirect effect on temperature-sensitive lines via a change in the
photospheric T-tau stratification. The corresponding correction in the
estimated atomic abundance ranges from a few hundredths of a dex up to |Delta
log(Fe)| ~ 0.15 dex, depending on the spectral line and on the amount of
average magnetic flux within the range of values we considered. The
Zeeman-broadening effect gains relatively more importance in the IR. The
largest modification to previous solar abundance determinations based on
visible spectral lines is instead due to the indirect effect, i.e., the
line-weakening caused by a warmer stratification on an optical depth scale. Our
results indicate that the average solar iron abundance obtained when using
magnetoconvection models can be 0.03-0.11 dex higher than when using the
simpler HD convection approach. We demonstrate that accounting for magnetic
flux is important in state-of-the-art solar photospheric abundance
determinations based on 3D simulations.Comment: 12 pages, 7 figures, A&A in pres
Particle-vortex dynamics in noncommutative space
We study the problem of a charged particle in the presence of a uniform
magnetic field plus a vortex in noncommutative planar space considering the two
possible non-commutative extensions of the corresponding Hamiltonian, namely
the ``fundamental'' and the ``antifundamental'' representations. Using a Fock
space formalism we construct eigenfunctions and eigenvalues finding in each
case half of the states existing in the ordinary space case. In the limit of
we recover the two classes of states found in ordinary space,
relevant for the study of anyon physics.Comment: 13 pages, no figures, plain LaTeX. References adde
Structure of the Vacuum in Deformed Supersymmetric Chiral Models
We analyze the vacuum structure of N=1/2 chiral supersymmetric theories in
deformed superspace. In particular we study O'Raifeartaigh models with
C-deformed superpotentials and canonical and non-canonical deformed Kahler
potentials. We find conditions under which the vacuum configurations are
affected by the deformations.Comment: 15 pages, minor corrections. Version to appear in JHE
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