1,039 research outputs found
The non-compact elliptic genus: mock or modular
We analyze various perspectives on the elliptic genus of non-compact
supersymmetric coset conformal field theories with central charge larger than
three. We calculate the holomorphic part of the elliptic genus via a free field
description of the model, and show that it agrees with algebraic expectations.
The holomorphic part of the elliptic genus is directly related to an
Appell-Lerch sum and behaves anomalously under modular transformation
properties. We analyze the origin of the anomaly by calculating the elliptic
genus through a path integral in a coset conformal field theory. The path
integral codes both the holomorphic part of the elliptic genus, and a
non-holomorphic remainder that finds its origin in the continuous spectrum of
the non-compact model. The remainder term can be shown to agree with a function
that mathematicians introduced to parameterize the difference between mock
theta functions and Jacobi forms. The holomorphic part of the elliptic genus
thus has a path integral completion which renders it non-holomorphic and
modular.Comment: 13 page
Gravitational Radiation from Travelling Waves on D-Strings
Boundary states that preserve supersymmetry are constructed for fractional
D-strings with travelling waves on a
orbifold. The gravitational radiation emitted between two D-strings with
antiparallel travelling waves is calculated.Comment: improvements and correction
Can Induced Theta Vacua be Created in Heavy Ion Collisions?
The development of the early Universe is a remarkable laboratory for the
study of most nontrivial properties of particle physics. What is more
remarkable is the fact that these phenomena at the QCD scale can be, in
principle, experimentally tested in heavy ion collisions. We expect that, in
general, an arbitrary theta-state would be created in the heavy ion collisions,
similar to the creation of the disoriented chiral condensate with an arbitrary
isospin direction. It should be a large domain with a wrong
orientation. We test this idea numerically in a simple model where we study the
evolution of the phases of the chiral condensates in QCD with two quark flavors
with non-zero theta-parameter. We see the formation of a non-zero theta-vacuum
with the formation time of the order of seconds. This result will
have important implications for a possible axion search experiment at RHIC.Comment: 4 pages, 3 figures, Latex, Discussion of experimental signatures
adde
Neutron electric dipole moment from lattice QCD
We carry out a feasibility study for the lattice QCD calculation of the
neutron electric dipole moment (NEDM) in the presence of the term. We
develop the strategy to obtain the nucleon EDM from the CP-odd electromagnetic
form factor at small , in which NEDM is given by where is the momentum transfer and is the
nucleon mass. We first derive a formula which relates , a matrix element
of the electromagnetic current between nucleon states, with vacuum expectation
values of nucleons and/or the current. In the expansion of , the
parity-odd part of the nucleon-current-nucleon three-point function contains
contributions not only from the parity-odd form factors but also from the
parity-even form factors multiplied by the parity-odd part of the nucleon
two-point function, and therefore the latter contribution must be subtracted to
extract . We then perform an explicit lattice calculation employing the
domain-wall quark action with the RG improved gauge action in quenched QCD at
GeV on a lattice. At the quark mass
, corresponding to , we accumulate 730
configurations, which allow us to extract the parity-odd part in both two- and
three-point functions. Employing two different Dirac matrix
projections, we show that a consistent value for cannot be obtained
without the subtraction described above. We obtain 0.024(5) fm for the neutron and
0.021(6) fm for the
proton.Comment: LaTeX2e, 43 pages, 42 eps figures, uses revtex4 and graphicx,
comments added and typos corrected, final version to appear in Phys. Rev.
Neutron electric dipole moment with external electric field method in lattice QCD
We discuss a possibility that the Neutron Electric Dipole Moment (NEDM) can
be calculated in lattice QCD simulations in the presence of the CP violating
term. In this paper we measure the energy difference between spin-up
and spin-down states of the neutron in the presence of an uniform and static
external electric field. We first test this method in quenched QCD with the RG
improved gauge action on a lattice at 2 GeV,
employing two different lattice fermion formulations, the domain-wall fermion
and the clover fermion for quarks, at relatively heavy quark mass . We obtain non-zero values of NEDM from calculations with both
fermion formulations. We next consider some systematic uncertainties of our
method for NEDM, using lattice at the same lattice spacing only
with the clover fermion. We finally investigate the quark mass dependence of
NEDM and observe a non-vanishing behavior of NEDM toward the chiral limit. We
interpret this behavior as a manifestation of the pathology in the quenched
approximation.Comment: LaTeX2e, 51 pages, 43 figures, uses revtex4 and graphicx, References
and comments added, typos corrected, accepted by PR
On the Zero-Slope Limit of the Compactified Closed Bosonic String
In the framework of the compactified closed bosonic string theory with the
extra spatial coordinates being circular with radius , we perform both the
zero-slope limit and the limit of the tree scattering
amplitude of four massless scalar particles. We explicitly show that this
double limit leads to amplitudes involving scalars which interact through the
exchange of a scalar, spin 1 and spin 2 particle. In particular, this latter
case reproduces the same result obtained in linearized quantum gravity.Comment: 10 pages, LaTex file, DSF-T-43/9
Possibility of spontaneous parity violation in hot QCD
We suggest that for QCD in the limit of a large number of colors, N, the
axial U(1) symmetry of massless quarks is effectively restored at the
deconfining=chiral phase transition. If the deconfining transition is of second
order, then the chiral transition is weakly first order. In this case,
metastable states in which parity is spontaneously broken appear at
temperatures below the phase transition. The production of these metastable
states would have dramatic signatures, including enhanced production of eta and
eta' mesons, which can decay through parity violating decay processes such as
eta -> pi^0 pi^0, and global parity odd asymmetries for charged pions. Using a
nonlinear sigma model, in QCD these metastable states only appear rather near
the phase transition.Comment: 4 pages, REVTe
D-branes and SQCD in Non-Critical Superstring Theory
Using exact boundary conformal field theory methods we analyze the D-brane
physics of a specific four-dimensional non-critical superstring theory which
involves the N=2 SL(2)/U(1) Kazama-Suzuki model at level 1. Via the holographic
duality of hep-th/9907178 our results are relevant for D-brane dynamics in the
background of NS5-branes and D-brane dynamics near a conifold singularity. We
pay special attention to a configuration of D3- and D5-branes that realizes N=1
supersymmetric QCD and discuss the massless spectrum and classical moduli of
this setup in detail. We also comment briefly on the implications of this
construction for the recently proposed generalization of the AdS/CFT
correspondence by Klebanov and Maldacena within the setting of non-critical
superstrings.Comment: harvmac, 47 pages, 6 figures; v4 same as v3 due to submission erro
Holonomy from wrapped branes
Compactifications of M-theory on manifolds with reduced holonomy arise as the
local eleven-dimensional description of D6-branes wrapped on supersymmetric
cycles in manifolds of lower dimension with a different holonomy group.
Whenever the isometry group SU(2) is present, eight-dimensional gauged
supergravity is a natural arena for such investigations. In this paper we use
this approach and review the eleven dimensional description of D6-branes
wrapped on coassociative 4-cycles, on deformed 3-cycles inside Calabi-Yau
threefolds and on Kahler 4-cycles.Comment: 1+8 pages, Latex. Proceedings of the Leuven workshop, 2002. v2:
Corrected typos in equations (4)-(8
Genus Two Partition and Correlation Functions for Fermionic Vertex Operator Superalgebras I
We define the partition and -point correlation functions for a vertex
operator superalgebra on a genus two Riemann surface formed by sewing two tori
together. For the free fermion vertex operator superalgebra we obtain a closed
formula for the genus two continuous orbifold partition function in terms of an
infinite dimensional determinant with entries arising from torus Szeg\"o
kernels. We prove that the partition function is holomorphic in the sewing
parameters on a given suitable domain and describe its modular properties.
Using the bosonized formalism, a new genus two Jacobi product identity is
described for the Riemann theta series. We compute and discuss the modular
properties of the generating function for all -point functions in terms of a
genus two Szeg\"o kernel determinant. We also show that the Virasoro vector one
point function satisfies a genus two Ward identity.Comment: A number of typos have been corrected, 39 pages. To appear in Commun.
Math. Phy
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