7,572 research outputs found
BFFT quantization with nonlinear constraints
We consider the method due to Batalin, Fradkin, Fradkina, and Tyutin (BFFT)
that makes the conversion of second-class constraints into first-class ones for
the case of nonlinear theories. We first present a general analysis of an
attempt to simplify the method, showing the conditions that must be fulfilled
in order to have first-class constraints for nonlinear theories but that are
linear in the auxiliary variables. There are cases where this simplification
cannot be done and the full BFFT method has to be used. However, in the way the
method is formulated, we show with details that it is not practicable to be
done. Finally, we speculate on a solution for these problems.Comment: 19 pages, Late
Hamiltonian embedding of the massive noncommutative U(1) theory
We show that the massive noncommutative U(1) can be embedded in a gauge
theory by using the BFFT Hamiltonian formalism. By virtue of the peculiar
non-Abelian algebraic structure of the noncommutative massive U(1) theory,
several specific identities involving Moyal commutators had to be used in order
to make the embedding possible. This leads to an infinite number of steps in
the iterative process of obtaining first-class constraints. We also shown that
the involutive Hamiltonian can be constructed.Comment: 8 pages, Revtex (multicol
Noncommutative Particles in Curved Spaces
We present a formulation in a curved background of noncommutative mechanics,
where the object of noncommutativity is considered as an
independent quantity having a canonical conjugate momentum. We introduced a
noncommutative first-order action in D=10 curved spacetime and the covariant
equations of motions were computed. This model, invariant under diffeomorphism,
generalizes recent relativistic results.Comment: 1+15 pages. Latex. New comments and results adde
Quantum complex scalar fields and noncommutativity
In this work we analyze complex scalar fields using a new framework where the
object of noncommutativity represents independent degrees of
freedom. In a first quantized formalism, and its canonical
momentum are seen as operators living in some Hilbert space.
This structure is compatible with the minimal canonical extension of the
Doplicher-Fredenhagen-Roberts (DFR) algebra and is invariant under an extended
Poincar\'e group of symmetry. In a second quantized formalism perspective, we
present an explicit form for the extended Poincar\'e generators and the same
algebra is generated via generalized Heisenberg relations. We also introduce a
source term and construct the general solution for the complex scalar fields
using the Green's function technique.Comment: 13 pages. Latex. Final version to appear in Physical Review
Thermodynamics of quantum crystalline membranes
We investigate the thermodynamic properties and the lattice stability of
two-dimensional crystalline membranes, such as graphene and related compounds,
in the low temperature quantum regime . A key role is played by
the anharmonic coupling between in-plane and out-of plane lattice modes that,
in the quantum limit, has very different consequences than in the classical
regime. The role of retardation, namely of the frequency dependence, in the
effective anharmonic interactions turns out to be crucial in the quantum
regime. We identify a crossover temperature, , between classical and
quantum regimes, which is K for graphene. Below , the
heat capacity and thermal expansion coefficient decrease as power laws with
decreasing temperature, tending to zero for as required by the
third law of thermodynamics.Comment: 13 pages, 1 figur
Reply to 'Comment on "Thermodynamics of quantum crystalline membranes"'
In this note, we reply to the comment made by E.I.Kats and V.V.Lebedev
[arXiv:1407.4298] on our recent work "Thermodynamics of quantum crystalline
membranes" [Phys. Rev. B 89, 224307 (2014)]. Kats and Lebedev question the
validity of the calculation presented in our work, in particular on the use of
a Debye momentum as a ultra-violet regulator for the theory. We address and
counter argue the criticisms made by Kats and Lebedev to our work.Comment: 5 pages, 4 figure
The Hamiltonian BRST quantization of a noncommutative nonabelian gauge theory and its Seiberg-Witten map
We consider the Hamiltonian BRST quantization of a noncommutative non abelian
gauge theory. The Seiberg-Witten map of all phase-space variables, including
multipliers, ghosts and their momenta, is given in first order in the
noncommutative parameter . We show that there exists a complete
consistence between the gauge structures of the original and of the mapped
theories, derived in a canonical way, once we appropriately choose the map
solutions.Comment: 10 pages, Latex. Address adde
HERA-B Framework for Online Calibration and Alignment
This paper describes the architecture and implementation of the HERA-B
framework for online calibration and alignment. At HERA-B the performance of
all trigger levels, including the online reconstruction, strongly depends on
using the appropriate calibration and alignment constants, which might change
during data taking. A system to monitor, recompute and distribute those
constants to online processes has been integrated in the data acquisition and
trigger systems.Comment: Submitted to NIM A. 4 figures, 15 page
Hamiltonian Embedding of SU(2) Higgs Model in the Unitary Gauge
Following systematically the generalized Hamiltonian approach of Batalin,
Fradkin and Tyutin (BFT), we embed the second-class non-abelian SU(2) Higgs
model in the unitary gauge into a gauge invariant theory. The strongly
involutive Hamiltonian and constraints are obtained as an infinite power series
in the auxiliary fields. Furthermore, comparing these results with those
obtained from the gauged second class Lagrangian, we arrive at a simple
interpretation for the first class Hamiltonian, constraints and observables.Comment: 13 pages, Latex, no figure
On Coulomb drag in double layer systems
We argue, for a wide class of systems including graphene, that in the low
temperature, high density, large separation and strong screening limits the
drag resistivity behaves as d^{-4}, where d is the separation between the two
layers. The results are independent of the energy dispersion relation, the
dependence on momentum of the transport time, and the wave function structure
factors. We discuss how a correct treatment of the electron-electron
interactions in an inhomogeneous dielectric background changes the theoretical
analysis of the experimental drag results of Ref. [1]. We find that a
quantitative understanding of the available experimental data [1] for drag in
graphene is lacking.Comment: http://iopscience.iop.org/0953-8984/24/33/335602
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