50 research outputs found
Duality and Braiding in Twisted Quantum Field Theory
We re-examine various issues surrounding the definition of twisted quantum
field theories on flat noncommutative spaces. We propose an interpretation
based on nonlocal commutative field redefinitions which clarifies previously
observed properties such as the formal equivalence of Green's functions in the
noncommutative and commutative theories, causality, and the absence of UV/IR
mixing. We use these fields to define the functional integral formulation of
twisted quantum field theory. We exploit techniques from braided tensor algebra
to argue that the twisted Fock space states of these free fields obey
conventional statistics. We support our claims with a detailed analysis of the
modifications induced in the presence of background magnetic fields, which
induces additional twists by magnetic translation operators and alters the
effective noncommutative geometry seen by the twisted quantum fields. When two
such field theories are dual to one another, we demonstrate that only our
braided physical states are covariant under the duality.Comment: 35 pages; v2: Typos correcte
Fractional Spin for Quantum Hall Effect Quasiparticles
We investigate the issue of whether quasiparticles in the fractional quantum
Hall effect possess a fractional intrinsic spin. The presence of such a spin
is suggested by the spin-statistics relation , with
being the statistical angle, and, on a sphere, is required for consistent
quantization of one or more quasiparticles. By performing Berry-phase
calculations for quasiparticles on a sphere we find that there are two terms,
of different origin, that couple to the curvature and can be interpreted as
parts of the quasiparticle spin. One, due to self-interaction, has the same
value for both the quasihole and quasielectron, and fulfills the
spin-statistics relation. The other is a kinematical effect and has opposite
signs for the quasihole and quasielectron. The total spin thus agrees with a
generalized spin-statistics theorem . On the
plane, we do not find any corresponding terms.Comment: 15 pages, RevTeX-3.
The Spectrum of the Dirac Operator on Coset Spaces with Homogeneous Gauge Fields
The spectrum and degeneracies of the Dirac operator are analysed on compact
coset spaces when there is a non-zero homogeneous background gauge field which
is compatible with the symmetries of the space, in particular when the gauge
field is derived from the spin-connection. It is shown how the degeneracy of
the lowest Landau level in the recently proposed higher dimensional quantum
Hall effect is related to the Atiyah-Singer index theorem for the Dirac
operator on a compact coset space.Comment: 25 pages, typeset in LaTeX, uses youngtab.st
Noncommutativity and Lorentz Violation in Relativistic Heavy Ion Collisions
The experimental detection of the effects of noncommuting coordinates in
electrodynamic phenomena depends on the magnitude of |\theta B|, where \theta
is the noncommutativity parameter and B a background magnetic field. With the
present upper bound on \theta, given by \theta_{\rm bound} \simeq 1/(10 {\rm
TeV})^2, there was no large enough magnetic field in nature, including those
observed in magnetars, that could give visible effects or, conversely, that
could be used to further improve \theta_{\rm bound}. On the other hand,
recently it has been proposed that intense enough magnetic fields should be
produced at the beginning of relativistic heavy ion collisions. We discuss here
lepton pair production by free photons as one kind of signature of
noncommutativity and Lorentz violation that could occur at RHIC or LHC. This
allows us to obtain a more stringent bound on \theta, given by 10^{-3}
\theta_{\rm bound}, if such "exotic" events do not occur.Comment: Five pages, no figures
A Single-Tube, Functional Marker-Based Multiplex PCR Assay for Simultaneous Detection of Major Bacterial Blight Resistance Genes Xa21, xa13 and xa5 in Rice
AbstractIn marker-assisted breeding for bacterial blight (BB) resistance in rice, three major resistance genes, viz., Xa21, xa13 and xa5, are routinely deployed either singly or in combinations. As efficient and functional markers are yet to be developed for xa13 and xa5, we have developed simple PCR-based functional markers for both the genes. For xa13, we designed a functional PCR-based marker, xa13-prom targeting the InDel polymorphism in the promoter of candidate gene Os8N3 located on chromosome 8 of rice. With respect to xa5, a multiplex-PCR based functional marker system, named xa5FM, consisting of two sets of primer pairs targeting the 2-bp functional nucleotide polymorphism in the exon II of the gene TFIIAɤ5 (candidate for xa5), has been developed. Both xa13-prom and xa5FM can differentiate the resistant and susceptible alleles for xa13 and xa5, respectively, in a co-dominant fashion. Using these two functional markers along with the already reported functional PCR-based marker for Xa21 (pTA248), we designed a single-tube multiplex PCR based assay for simultaneous detection of all the three major resistance genes and demonstrated the utility of the multiplex marker system in a segregating population
Moments of inertia, nucleon axial-vector coupling, the {\bf 8}, {\bf 10}, and mass spectrums and the higher SU(3)_f representation mass splittings in the Skyrme model
The broad importance of a recent experimental discovery of pentaquarks
requires more theoretical insight into the structure of higher representation
multiplets. The nucleon axial-vector coupling, moments of inertia, the {\bf 8},
{\bf 10}, , and absolute mass spectra and the
higher SU(3) representation mass splittings for the multiplets ,
, , , , , and are computed in the framework of the minimal extended
Skyrme model by using only one free parameter, i.e., the Skyrme charge . The
analysis presented in this paper represents simple and clear theoretical
estimates, obtained without using any experimental results for higher
(,...) multiplets. The obtained results are in good agreement
with other chiral soliton model approaches that more extensively use
experimental results as inputs.Comment: 22 pages, 12 figures, 9 tables, version accepted in JHE
The Chiral Coupling Constants \lb{1} and \lb{2} from \pipi Phase Shifts
A Roy equation analysis of the available phase shift data is
performed with the S- wave scattering length in the range
predicted by the one-loop standard chiral perturbation theory. A suitable
dispersive framework is developed to extract the chiral coupling constants
\lb{1}, \lb{2} and yields \lb{1} and \lb{2}. We
remark on the implications of this determination to (combinations of) threshold
parameter predictions of the three lowest partial waves.Comment: 36 pages using latex with 1 figure embedded using eps
Particle-Vortex Duality and the Modular Group: Applications to the Quantum Hall Effect and Other 2-D Systems
We show how particle-vortex duality implies the existence of a large
non-abelian discrete symmetry group which relates the electromagnetic response
for dual two-dimensional systems in a magnetic field. For conductors with
charge carriers satisfying Fermi statistics (or those related to fermions by
the action of the group), the resulting group is known to imply many, if not
all, of the remarkable features of Quantum Hall systems. For conductors with
boson charge carriers (modulo group transformations) a different group is
predicted, implying equally striking implications for the conductivities of
these systems, including a super-universality of the critical exponents for
conductor/insulator and superconductor/insulator transitions in two dimensions
and a hierarchical structure, analogous to that of the quantum Hall effect but
different in its details. Our derivation shows how this symmetry emerges at low
energies, depending only weakly on the details of dynamics of the underlying
systems.Comment: 22 pages, LaTeX, 2 figures, uses revte
Quantum Gravity, Field Theory and Signatures of Noncommutative Spacetime
A pedagogical introduction to some of the main ideas and results of field
theories on quantized spacetimes is presented, with emphasis on what such field
theories may teach us about the problem of quantizing gravity. We examine to
what extent noncommutative gauge theories may be regarded as gauge theories of
gravity. UV/IR mixing is explained in detail and we describe its relations to
renormalization, to gravitational dynamics, and to deformed dispersion
relations in models of quantum spacetime of interest in string theory and in
doubly special relativity. We also discuss some potential experimental probes
of spacetime noncommutativity.Comment: 26 pages, 4 figures; v2: comments and references added; v3: typos
corrected, clarifying comments and references added; Based on Plenary Lecture
delivered at the XXIX Encontro Nacional de Fisica de Particulas e Campos, Sao
Lourenco, Brasil, September 22-26, 2008; Final version to be published in
General Relativity and Gravitatio