13,808 research outputs found
Quark Potentials in the Higgs Phase of Large N Supersymmetric Yang-Mills Theories
We compute, in the large N limit, the quark potential for
supersymmetric SU(N) Yang-Mills theory broken to . At
short distances the quarks see only the unbroken gauge symmetry and have an
attractive potential that falls off as 1/L. At longer distances the interquark
interaction is sensitive to the symmetry breaking, and other QCD states appear.
These states correspond to combinations of the quark-antiquark pair with some
number of W-particles. If there is one or more W-particles then this state is
unstable because of the coulomb interaction between the W-particles and between
the W's and the quarks. As L is decreased the W-particles delocalize and these
coulomb branches merge onto a branch with a linear potential. The quarks on
this branch see the unbroken gauge group, but the flux tube is unstable to the
production of W-particles.Comment: 23 pages, 7 figures, harvmac (b
Investigating the BPS Spectrum of Non-Critical E_n Strings
We use the effective action of the non-critical strings to study its
BPS spectrum for . We show how to introduce mass parameters, or
Wilson lines, into the effective action, and then perform the appropriate
asymptotic expansions that yield the BPS spectrum. The result is the
character expansion of the spectrum, and is equivalent to performing the mirror
map on a Calabi-Yau with up to nine K\"ahler moduli. This enables a much more
detailed examination of the structure of the theory, and provides
extensive checks on the effective action description of the non-critical
string. We extract some universal ( independent) information concerning
the degeneracies of BPS excitations.Comment: 50 pages, harvmac (b
A Genuine Intermediate-Age Globular Cluster in M33
We present deep integrated-light spectroscopy of nine M33 globular clusters
taken with the Hectospec instrument at the MMT Observatory. Based on our
spectroscopy and previous deep color-magnitude diagrams obtained with
HST/WFPC2, we present evidence for the presence of a genuine intermediate-age
globular cluster in M33. The analysis of Lick line indices indicates that all
globular clusters are metal-poor ([Z/H] <~ -1.0) and that cluster M33-C38 is
about 5-8 Gyr younger than the rest of the sample M33 star clusters. We find no
evidence for a population of blue horizontal branch stars in the CMD of
M33-C38, which rules out the possibility of an artificially young spectroscopic
age due to the presence of hot stars. We infer a total mass of 5-9 x 10^4 M_sol
for M33-C38, which implies that M33-C38 has survived ~2-3 times longer than
some dynamical evolution model predictions for star clusters in M33, although
it is not yet clear to which dynamical component of M33 - thin disk, thick
disk, halo - the cluster is associated.Comment: 4 pages, 3 figures, accepted for publication in ApJ Letter
Imprinted Networks as Chiral Pumps
We investigate the interaction between a chirally imprinted network and a
solvent of chiral molecules. We find, a liquid crystalline polymer network is
preferentially swollen by one component of a racemic solvent. This ability to
separate is linked to the chiral order parameter of the network, and can be
reversibly controlled via temperature or a mechanical deformation. It is
maximal near the point at which the network loses its imprinted structure. One
possible practical application of this effect would be a mechanical device for
sorting mixed chiral molecules.Comment: 4 pages, 5 figure
Photoresponse of YBa2Cu3O(7-delta) granular and epitaxial superconducting thin films
The response is reported of thin films of YBa2Cu3O(7-delta) with either a very grainy or a smooth epitaxial morphology to visible radiation. SrTiO3 substrates were employed for both types of films. The grainy films were formed by sequential multi-layer electron beam evaporation while the epitaxial films were formed by laser ablation. Both films were patterned into H shaped detectors via a negative photolithographic process employing a Br/ethanol etchant. The bridge region of the H was 50 microns wide. The patterned films formed by laser ablation and sequential evaporation had critical temperatures of 74 K and 72 K respectively. The bridge was current biased and illuminated with chopped He-Ne laser radiation and the voltage developed in response to the illumination was measured. A signal was detected only above the critical temperature and the peak of the response coincided with the resistive transition for both types of films although the correspondence was less exact for the grainy film. The details of the responses and their analysis are presented
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