2,368 research outputs found
Self-dual solitons in N=2 supersymmetric semilocal Chern-Simons theory
We embed the semilocal Chern-Simons-Higgs theory into an N=2 supersymmetric
system. We construct the corresponding conserved supercharges and derive the
Bogomol'nyi equations of the model from supersymmetry considerations. We show
that these equations hold provided certain conditions on the coupling constants
as well as on the Higgs potential of the system, which are a consequence of the
huge symmetry of the theory, are satisfied. They admit string-like solutions
which break one half of the supersymmetries --BPS Chern-Simons semilocal cosmic
strings-- whose magnetic flux is concentrated at the center of the vortex. We
study such solutions and show that their stability is provided by supersymmetry
through the existence of a lower bound for the energy, even though the manifold
of the Higgs vacuum does not contain non-contractible loops.Comment: 12 pages, LaTeX, no figures, to appear in Modern Physics Letters
Dramatic robustness of a multiple delay dispersed interferometer to spectrograph errors: how mixing delays reduces or cancels wavelength drift
We describe demonstrations of remarkable robustness to instrumental noises by using a multiple delay externally dispersed interferometer (EDI) on stellar observations at the Hale telescope. Previous observatory EDI demonstrations used a single delay. The EDI (also called âTEDIâ) boosted the 2,700 resolution of the native TripleSpec NIR spectrograph (950-2450 nm) by as much as 10x to 27,000, using 7 overlapping delays up to 3 cm. We observed superb rejection of fixed pattern noises due to bad pixels, since the fringing signal responds only to changes in multiple exposures synchronous to the applied delay dithering. Remarkably, we observed a ~20x reduction of reaction in the output spectrum to PSF shifts of the native spectrograph along the dispersion direction, using our standard processing. This allowed high resolution observations under conditions of severe and irregular PSF drift otherwise not possible without the interferometer. Furthermore, we recently discovered an improved method of weighting and mixing data between pairs of delays that can theoretically further reduce the net reaction to PSF drift to zero. We demonstrate a 350x reduction in reaction to a native PSF shift using a simple simulation. This technique could similarly reduce radial velocity noise for future EDIâs that use two delays overlapped in delay space (or a single delay overlapping the native peak). Finally, we show an extremely high dynamic range EDI measurement of our ThAr lamp compared to a literature ThAr spectrum, observing weak features (~0.001x height of nearest strong line) that occur between the major lines. Because of individuality of each reference lamp, accurate knowledge of its spectrum between the (unfortunately) sparse major lines is important for precision radial velocimetry
Signature of superconducting states in cubic crystal without inversion symmetry
The effects of absence of inversion symmetry on superconducting states are
investigated theoretically. In particular we focus on the noncentrosymmetric
compounds which have the cubic symmetry like LiPtB. An appropriate
and isotropic spin-orbital interaction is added in the Hamiltonian and it acts
like a magnetic monopole in the momentum space. The consequent pairing
wavefunction has an additional triplet component in the pseudospin space, and a
Zeeman magnetic field can induce a collinear supercurrent
with a coefficient . The effects of anisotropy embedded in the cubic
symmetry and the nodal superconducting gap function on are also
considered. From the macroscopic perspectives, the pair of mutually induced
and magnetization can affect the distribution of magnetic
field in such noncentrosymmetric superconductors, which is studied through
solving the Maxwell equation in the Meissner geometry as well as the case of a
single vortex line. In both cases, magnetic fields perpendicular to the
external ones emerge as a signature of the broken symmetry.Comment: 16 pages in pre-print forma
Supersymmetric Electroweak Cosmic Strings
We study the connection between supersymmetry and a topological bound
in a two-Higgs-doublet system with an gauge group. We derive the Bogomol'nyi equations from
supersymmetry considerations showing that they hold provided certain conditions
on the coupling constants, which are a consequence of the huge symmetry of the
theory, are satisfied. Their solutions, which can be interpreted as electroweak
cosmic strings breaking one half of the supersymmetries of the theory, are
studied. Certain interesting limiting cases of our model which have recently
been considered in the literature are finally analyzed.Comment: 20 pages, RevTe
Phases of dual superconductivity and confinement in softly broken N=2 supersymmetric Yang-Mills theories
We study the electric flux tubes that undertake color confinement in N=2
supersymmetric Yang-Mills theories softly broken down to N=1 by perturbing with
the first two Casimir operators. The relevant Abelian Higgs model is not the
standard one due to the presence of an off-diagonal coupling among different
magnetic U(1) factors. We perform a preliminary study of this model at a
qualitative level. BPS vortices are explicitely obtained for particular values
of the soft breaking parameters. Generically however, even in the ultrastrong
scaling limit, vortices are not critical but live in a "hybrid" type II phase.
Also, ratios among string tensions are seen to follow no simple pattern. We
examine the situation at the half Higgsed vacua and find evidence for solutions
with the behaviour of superconducting strings. In some cases they are solutions
to BPS equations.Comment: 15 pages, 1 figure, revtex; v2: typos corrected, final versio
Holography and Unquenched Quark-Gluon Plasmas
We employ the string/gauge theory correspondence to study properties of
strongly coupled quark-gluon plasmas in thermal gauge theories with a large
number of colors and flavors. In particular, we analyze non-critical string
duals of conformal (S)QCD, as well as ten dimensional wrapped fivebrane duals
of SQCD-like theories. We study general properties of the dual plasmas,
including the drag force exerted on a probe quark and the jet quenching
parameter. We find that these plasma observables depend on the number of colors
and flavors in the ``QCD dual''; in particular, we find that the jet quenching
parameter increases linearly with N_f/N_c at leading order in the probe limit.
In the ten dimensional case we find a non trivial drag coefficient but a
vanishing jet quenching parameter. We comment on the relation of this result
with total screening and argue that the same features are shared by all known
plasmas dual to fivebranes in ten dimensions. We also construct new D5 black
hole solutions with spherical horizon and show that they exhibit the same
features.Comment: 30 pages. v2: Comments in section 2 and references updated, a typo
fixe
Externally Dispersed Interferometry for Precision Radial Velocimetry
Externally Dispersed Interferometry (EDI) is the series combination of a
fixed-delay field-widened Michelson interferometer with a dispersive
spectrograph. This combination boosts the spectrograph performance for both
Doppler velocimetry and high resolution spectroscopy. The interferometer
creates a periodic spectral comb that multiplies against the input spectrum to
create moire fringes, which are recorded in combination with the regular
spectrum. The moire pattern shifts in phase in response to a Doppler shift.
Moire patterns are broader than the underlying spectral features and more
easily survive spectrograph blurring and common distortions. Thus, the EDI
technique allows lower resolution spectrographs having relaxed optical
tolerances (and therefore higher throughput) to return high precision velocity
measurements, which otherwise would be imprecise for the spectrograph alone.Comment: 7 Pages, White paper submitted to the AAAC Exoplanet Task Forc
Magnetoelectric effects in heavy-fermion superconductors without inversion symmetry
We investigate effects of strong electron correlation on magnetoelectric
transport phenomena in noncentrosymmetric superconductors with particular
emphasis on its application to the recently discovered heavy-fermion
superconductor CePtSi. Taking into account electron correlation effects in
a formally exact way, we obtain the expression of the magnetoelectric
coefficient for the Zeeman-field-induced paramagnetic supercurrent, of which
the existence was predicted more than a decade ago. It is found that in
contrast to the usual Meissner current, which is much reduced by the mass
renormalization factor in the heavy-fermion state, the paramagnetic
supercurrent is not affected by the Fermi liquid effect. This result implies
that the experimental observation of the magnetoelectric effect is more
feasible in heavy-fermion systems than that in conventional metals with
moderate effective mass.Comment: 8 pages, 2 figures, minor correction
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