8,181 research outputs found
A Bilocal Field Theory in Four Dimensions
A bilocal field theory having M\"{o}bius gauge invariance is proposed. In
four dimensions there exists a zero momentum state of the first quantized
model, which belongs to a non-trivial BRS cohomology class. A field theory
lagrangian having a gauge invariance only in four dimensions is constructed.Comment: 13 pages, TEP-9R, LaTe
Non-compact Mirror Bundles and (0,2) Liouville Theories
We study (0,2) deformations of N=2 Liouville field theory and its mirror
duality. A gauged linear sigma model construction of the ultraviolet theory
connects (0,2) deformations of Liouville field theory and (0,2) deformations of
N=2 SL(2,R)/U(1) coset model as a mirror duality. Our duality proposal from the
gauged linear sigma model completely agrees with the exact CFT analysis. In the
context of heterotic string compactifications, the deformation corresponds to
the introduction of a non-trivial gauge bundle. This non-compact
Landau-Ginzburg construction yields a novel way to study the gauge bundle
moduli for non-compact Calabi-Yau manifolds.Comment: 34 page
Diameter dependence of ferromagnetic spin moment in Au nanocrystals
Au nanoparticles exhibit ferromagnetic spin polarization and show diameter
dependence in magnetization. The magnetic moment per Au atom in the particle
attains its maximum value at a diameter of about 3 nanometer (nm) in the
Magnetization-Diameter curve. Because Au metal is a typical diamagnetic
material, its ferromagnetic polarization mechanism is thought to be quite
different from the ferromagnetism observed in transition metals. The size
effect strongly suggests the existence of some spin correlation effect at the
nanoscale. The so-called ``Fermi hole effect'' is the most probable one given
in the free electron gas system. Ferromagnetism in Au nanoparticles is
discussed using this model.Comment: 5 pages, 6 figures, to appear in Phys. Rev.
Dipole trap model for the metallic state in gated silicon-inversion layers
In order to investigate the metallic state in high-mobility Si-MOS
structures, we have further developed and precised the dipole trap model which
was originally proposed by B.L. Altshuler and D.L. Maslov [Phys. Rev. Lett.\
82, 145 (1999)]. Our additional numerical treatment enables us to drop several
approximations and to introduce a limited spatial depth of the trap states
inside the oxide as well as to include a distribution of trap energies. It
turns out that a pronounced metallic state can be caused by such trap states at
appropriate energies whose behavior is in good agreement with experimental
observations.Comment: 16 pages, 10 figures, submitte
N=2 Supersymmetric Sigma Models and D-branes
We study D-branes of N=2 supersymmetric sigma models. Supersymmetric
nonlinear sigma models with 2-dimensional target space have D0,D1,D2-branes,
which are realized as A-,B-type supersymmetric boundary conditions on the
worldsheet. When we embed the models in the string theory, the Kahler potential
is restricted and leads to a 2-dim black hole metric with a dilaton background.
The D-branes in this model are susy cycles and consistent with the analysis of
conjugacy classes. The generalized metrics with U(n) isometry is proposed and
dynamics on them are realized by linear sigma models. We investigate D-branes
of the linear sigma models and compare the results with those in the nonlinear
sigma models.Comment: 23 pages, 5 figure
Preliminary Results from Recent Measurements of the Antiprotonic Helium Hyperfine Structure
We report on preliminary results from a systematic study of the hyperfine
(HF) structure of antiprotonic helium. This precise measurement which was
commenced in 2006, has now been completed. Our initial analysis shows no
apparent density or power dependence and therefore the results can be averaged.
The statistical error of the observable M1 transitions is a factor of 60
smaller than that of three body quantum electrodynamic (QED) calculations,
while their difference has been resolved to a precision comparable to theory (a
factor of 10 better than our first measurement). This difference is sensitive
to the antiproton magnetic moment and agreement between theory and experiment
would lead to an increased precision of this parameter, thus providing a test
of CPT invariance.Comment: 6 pages, 4 figure
N=2 Liouville Theory with Boundary
We study N=2 Liouville theory with arbitrary central charge in the presence
of boundaries. After reviewing the theory on the sphere and deriving some
important structure constants, we investigate the boundary states of the theory
from two approaches, one using the modular transformation property of annulus
amplitudes and the other using the bootstrap of disc two-point functions
containing degenerate bulk operators. The boundary interactions describing the
boundary states are also proposed, based on which the precise correspondence
between boundary states and boundary interactions is obtained. The open string
spectrum between D-branes is studied from the modular bootstrap approach and
also from the reflection relation of boundary operators, providing a
consistency check for the proposal.Comment: 1+48 pages, no figure. typos corrected and references added. the
version to appear in JHE
D-brane Categories for Orientifolds -- The Landau-Ginzburg Case
We construct and classify categories of D-branes in orientifolds based on
Landau-Ginzburg models and their orbifolds. Consistency of the worldsheet
parity action on the matrix factorizations plays the key role. This provides
all the requisite data for an orientifold construction after embedding in
string theory. One of our main results is a computation of topological field
theory correlators on unoriented worldsheets, generalizing the formulas of Vafa
and Kapustin-Li for oriented worldsheets, as well as the extension of these
results to orbifolds. We also find a doubling of Knoerrer periodicity in the
orientifold context.Comment: 45 pages, 6 figure
Non-Supersymmetric Seiberg Duality, Orientifold QCD and Non-Critical Strings
We propose an electric-magnetic duality and conjecture an exact conformal
window for a class of non-supersymmetric U(N_c) gauge theories with fermions in
the (anti)symmetric representation of the gauge group and N_f additional scalar
and fermion flavors. The duality exchanges N_c with N_f -N_c \mp 4 leaving N_f
invariant, and has common features with Seiberg duality in N=1 SQCD with SU or
SO/Sp gauge group. At large N the duality holds due to planar equivalence with
N=1 SQCD. At finite N we embed these gauge theories in a setup with D-branes
and orientifolds in a non-supersymmetric, but tachyon-free, non-critical type
0B string theory and argue in favor of the duality in terms of boundary and
crosscap state monodromies as in analogous supersymmetric situations. One can
verify explicitly that the resulting duals have matching global anomalies.
Finally, we comment on the moduli space of these gauge theories and discuss
other potential non-supersymmetric examples that could exhibit similar
dualities.Comment: 45 pages, 1 figur
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