34 research outputs found
Normal ordering and boundary conditions for fermionic string coordinates
We build up normal ordered products for fermionic open string coordinates
consistent with boundary conditions. The results are obtained considering the
presence of antisymmetric tensor fields. We find a discontinuity of the normal
ordered products at string endpoints even in the absence of the background. We
discuss how the energy momentum tensor also changes at the world-sheet boundary
in such a way that the central charge keeps the standard value at string end
points.Comment: In this revised version we clarify the issue of consistency between
supersymmetry and boundary conditions and stress the fact that we are
considering flat space. we also add two more reference
Fermionic anticommutators for open superstrings in the presence of antisymmetric tensor field
We build up the anticommutator algebra for the fermionic coordinates of open
superstrings attached to branes with antisymmetric tensor fields. We use both
Dirac quantization and the symplectic Faddeev Jackiw approach. In the
symplectic case we find a way of generating the boundary conditions as zero
modes of the symplectic matrix by taking a discretized form of the action and
adding terms that vanish in the continuous limit. This way boundary conditions
can be handled as constraints.Comment: Revision: passage from discrete to continuous clarified, comment on
previous results using Dirac quantization included, typos corrected. Version
to appear in Phys. Lett.
Canonical Transformations and Gauge Fixing in the Triplectic Quantization
We show that the generators of canonical transformations in the triplectic
manifold must satisfy constraints that have no parallel in the usual field
antifield quantization. A general form for these transformations is presented.
Then we consider gauge fixing by means of canonical transformations in this
Sp(2) covariant scheme, finding a relation between generators and gauge fixing
functions. The existence of a wide class of solutions to this relation nicely
reflects the large freedom of the gauge fixing process in the triplectic
quantization. Some solutions for the generators are discussed. Our results are
then illustrated by the example of Yang Mills theory.Comment: A new section about the cohomological approach to the extended BRST
quantization has been included. Some new references were added too. Final
version to appear in Nucl. Phys.B. 12 pages, LATE
A superspace formulation of the BV action
We show that the BV (Batalin Vilkovisky) action, formulated with an extended
BRST symmetry (including the shift symmetry), is also invariant under an
extended anti-BRST transformation (where the antifields are the parameters of
the transformation), when the gauge fixing Lagrangian is both BRST and
anti-BRST invariant. We show that for a general gauge fixing Lagrangian, the BV
action can be written in a manifestly extended BRST invariant manner in a
superspace with one Grassmann coordinate whereas it can be expressed in a
manifestly extended BRST and anti-BRST invariant manner in a superspace with
two Grassmann coordinates when the gauge fixing Lagrangian is invariant under
both BRST and anti-BRST transformations.Comment: 20 page
Deep Inelastic Scattering in Holographic AdS/QCD Models
We review the description of deep inelastic scattering using some AdS/QCD
phenomenological models.Comment: Talk presented by NRFB at Light Cone 2009: Relativistic Hadronic and
Particle Physics, 8-13 Jul 2009, Sao Jose dos Campos, Brazi
Black-hole quasinormal modes and scalar glueballs in a finite-temperature AdS/QCD model
We use the holographic AdS/QCD soft-wall model to investigate the spectrum of
scalar glueballs in a finite temperature plasma. In this model, glueballs are
described by a massless scalar field in an AdS_5 black hole with a dilaton
soft-wall background. Using AdS/CFT prescriptions, we compute the boundary
retarded Green's function. The corresponding thermal spectral function shows
quasiparticle peaks at low temperatures. We also compute the quasinormal modes
of the scalar field in the soft-wall black hole geometry. The temperature and
momentum dependences of these modes are analyzed. The positions and widths of
the peaks of the spectral function are related to the frequencies of the
quasinormal modes. Our numerical results are found employing the power series
method and the computation of Breit-Wigner resonances.Comment: Revision: Results unchanged. More discussions on the model and on the
results. References added. 28 pages, 7 figures, 5 table
Highly-parallelized simulation of a pixelated LArTPC on a GPU
The rapid development of general-purpose computing on graphics processing units (GPGPU) is allowing the implementation of highly-parallelized Monte Carlo simulation chains for particle physics experiments. This technique is particularly suitable for the simulation of a pixelated charge readout for time projection chambers, given the large number of channels that this technology employs. Here we present the first implementation of a full microphysical simulator of a liquid argon time projection chamber (LArTPC) equipped with light readout and pixelated charge readout, developed for the DUNE Near Detector. The software is implemented with an end-to-end set of GPU-optimized algorithms. The algorithms have been written in Python and translated into CUDA kernels using Numba, a just-in-time compiler for a subset of Python and NumPy instructions. The GPU implementation achieves a speed up of four orders of magnitude compared with the equivalent CPU version. The simulation of the current induced on 10^3 pixels takes around 1 ms on the GPU, compared with approximately 10 s on the CPU. The results of the simulation are compared against data from a pixel-readout LArTPC prototype