1,448 research outputs found
Nonlinear field-dependence and f-wave interactions in superfluid 3He
We present results of transverse acoustics studies in superfluid ^{3}He-B at
fields up to 0.11 T. Using acoustic cavity interferometry, we observe the
Acoustic Faraday Effect for a transverse sound wave propagating along the
magnetic field, and we measure Faraday rotations of the polarization as large
as 1710^{\circ}. We use these results to determine the Zeeman splitting of the
Imaginary Squashing mode, an order parameter collective mode with total angular
momentum J=2. We show that the pairing interaction in the f-wave channel is
attractive at a pressure of P=6 bar. We also report nonlinear field dependence
of the Faraday rotation at frequencies substantially above the mode frequency
not accounted for in the theory of the transverse acoustic dispersion relation
formulated for frequencies near the mode. Consequently, we have identified the
region of validity of the theory allowing us to make corrections to the
analysis of Faraday rotation experiments performed in earlier work.Comment: 7 pages, 5 figure
Charges of Exceptionally Twisted Branes
The charges of the exceptionally twisted (D4 with triality and E6 with charge
conjugation) D-branes of WZW models are determined from the microscopic/CFT
point of view. The branes are labeled by twisted representations of the affine
algebra, and their charge is determined to be the ground state multiplicity of
the twisted representation. It is explicitly shown using Lie theory that the
charge groups of these twisted branes are the same as those of the untwisted
ones, confirming the macroscopic K-theoretic calculation. A key ingredient in
our proof is that, surprisingly, the G2 and F4 Weyl dimensions see the simple
currents of A2 and D4, respectively.Comment: 19 pages, 2 figures, LaTex2e, complete proofs of all statements,
updated bibliograph
Spin Susceptibility of the Topological Superconductor UPt3 from Polarized Neutron Diffraction
Experiment and theory indicate that UPt3 is a topological superconductor in
an odd-parity state, based in part from temperature independence of the NMR
Knight shift. However, quasiparticle spin-flip scattering near a surface, where
the Knight shift is measured, might be responsible. We use polarized neutron
scattering to measure the bulk susceptibility with H||c, finding consistency
with the Knight shift but inconsistent with theory for this field orientation.
We infer that neither spin susceptibility nor Knight shift are a reliable
indication of odd-parity
Can a Lattice String Have a Vanishing Cosmological Constant?
We prove that a class of one-loop partition functions found by Dienes, giving
rise to a vanishing cosmological constant to one-loop, cannot be realized by a
consistent lattice string. The construction of non-supersymmetric string with a
vanishing cosmological constant therefore remains as elusive as ever. We also
discuss a new test that any one-loop partition function for a lattice string
must satisfy.Comment: 14 page
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