1,372 research outputs found
Locally covariant quantum field theory with external sources
We provide a detailed analysis of the classical and quantized theory of a
multiplet of inhomogeneous Klein-Gordon fields, which couple to the spacetime
metric and also to an external source term; thus the solutions form an affine
space. Following the formulation of affine field theories in terms of
presymplectic vector spaces as proposed in [Annales Henri Poincare 15, 171
(2014)], we determine the relative Cauchy evolution induced by metric as well
as source term perturbations and compute the automorphism group of natural
isomorphisms of the presymplectic vector space functor. Two pathological
features of this formulation are revealed: the automorphism group contains
elements that cannot be interpreted as global gauge transformations of the
theory; moreover, the presymplectic formulation does not respect a natural
requirement on composition of subsystems. We therefore propose a systematic
strategy to improve the original description of affine field theories at the
classical and quantized level, first passing to a Poisson algebra description
in the classical case. The idea is to consider state spaces on the classical
and quantum algebras suggested by the physics of the theory (in the classical
case, we use the affine solution space). The state spaces are not separating
for the algebras, indicating a redundancy in the description. Removing this
redundancy by a quotient, a functorial theory is obtained that is free of the
above mentioned pathologies. These techniques are applicable to general affine
field theories and Abelian gauge theories. The resulting quantized theory is
shown to be dynamically local.Comment: v2: 42 pages; Appendix C on deformation quantization and references
added. v3: 47 pages; compatible with version to appear in Annales Henri
Poincar
Working with Nonassociative Geometry and Field Theory
We review aspects of our formalism for differential geometry on
noncommutative and nonassociative spaces which arise from cochain twist
deformation quantization of manifolds. We work in the simplest setting of
trivial vector bundles and flush out the details of our approach providing
explicit expressions for all bimodule operations, and for connections and
curvature. As applications, we describe the constructions of physically viable
action functionals for Yang-Mills theory and Einstein-Cartan gravity on
noncommutative and nonassociative spaces, as first steps towards more elaborate
models relevant to non-geometric flux deformations of geometry in closed string
theory.Comment: 20 pages; v2: Reference added; Contribution to the proceedings of the
Corfu Summer Institute on Elementary Particle Physics and Gravity, September
1-26, 2015, Corfu, Greece; Final version published in Proceedings of Scienc
Cheeger-Simons differential characters with compact support and Pontryagin duality
By adapting the Cheeger-Simons approach to differential cohomology, we
establish a notion of differential cohomology with compact support. We show
that it is functorial with respect to open embeddings and that it fits into a
natural diagram of exact sequences which compare it to compactly supported
singular cohomology and differential forms with compact support, in full
analogy to ordinary differential cohomology. We prove an excision theorem for
differential cohomology using a suitable relative version. Furthermore, we use
our model to give an independent proof of Pontryagin duality for differential
cohomology recovering a result of [Harvey, Lawson, Zweck - Amer. J. Math. 125
(2003) 791]: On any oriented manifold, ordinary differential cohomology is
isomorphic to the smooth Pontryagin dual of compactly supported differential
cohomology. For manifolds of finite-type, a similar result is obtained
interchanging ordinary with compactly supported differential cohomology.Comment: 33 pages, no figures - v3: Final version to be published in
Communications in Analysis and Geometr
Processing Issues in Top-Down Approaches to Quantum Computer Development in Silicon
We describe critical processing issues in our development of single atom
devices for solid-state quantum information processing. Integration of single
31P atoms with control gates and single electron transistor (SET) readout
structures is addressed in a silicon-based approach. Results on electrical
activation of low energy (15 keV) P implants in silicon show a strong dose
effect on the electrical activation fractions. We identify dopant segregation
to the SiO2/Si interface during rapid thermal annealing as a dopant loss
channel and discuss measures of minimizing it. Silicon nanowire SET pairs with
nanowire width of 10 to 20 nm are formed by electron beam lithography in SOI.
We present first results from Coulomb blockade experiments and discuss issues
of control gate integration for sub-40nm gate pitch levels
Detection of low energy single ion impacts in micron scale transistors at room temperature
We report the detection of single ion impacts through monitoring of changes
in the source-drain currents of field effect transistors (FET) at room
temperature. Implant apertures are formed in the interlayer dielectrics and
gate electrodes of planar, micro-scale FETs by electron beam assisted etching.
FET currents increase due to the generation of positively charged defects in
gate oxides when ions (121Sb12+, 14+, Xe6+; 50 to 70 keV) impinge into channel
regions. Implant damage is repaired by rapid thermal annealing, enabling
iterative cycles of device doping and electrical characterization for
development of single atom devices and studies of dopant fluctuation effects
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