5,714 research outputs found
String-- and Brane--Localized Causal Fields in a Strongly Nonlocal Model
We study a weakly local, but nonlocal model in spacetime dimension
and prove that it is maximally nonlocal in a certain specific quantitative
sense. Nevertheless, depending on the number of dimensions , it has
string--localized or brane--localized operators which commute at spatial
distances. In two spacetime dimensions, the model even comprises a covariant
and local subnet of operators localized in bounded subsets of Minkowski space
which has a nontrivial scattering matrix. The model thus exemplifies the
algebraic construction of local observables from algebras associated with
nonlocal fields.Comment: paper re-written with a change of emphasis and new result
On the equivalence of two deformation schemes in quantum field theory
Two recent deformation schemes for quantum field theories on the
two-dimensional Minkowski space, making use of deformed field operators and
Longo-Witten endomorphisms, respectively, are shown to be equivalent.Comment: 14 pages, no figure. The final version is available under Open
Access. CC-B
Yang–Baxter endomorphisms
Every unitary solution of the Yang–Baxter equation (R-matrix) in dimension (Formula presented.) can be viewed as a unitary element of the Cuntz algebra (Formula presented.) and as such defines an endomorphism of (Formula presented.). These Yang–Baxter endomorphisms restrict and extend to several other (Formula presented.) - and von Neumann algebras, and furthermore define a II (Formula presented.) factor associated with an extremal character of the infinite braid group. This paper is devoted to a detailed study of such Yang–Baxter endomorphisms. We discuss the relative commutants of the subfactors induced by Yang–Baxter endomorphisms, a new perspective on algebraic operations on R-matrices such as tensor products and cabling powers, the characters of the infinite braid group defined by R-matrices, and ergodicity properties. This also yields new concrete information on partial traces and spectra of R-matrices
Radiation reaction and four-momentum conservation for point-like dyons
We construct for a system of point-like dyons a conserved energy-momentum
tensor entailing finite momentum integrals, that takes the radiation reaction
into account.Comment: 12 pages, no figure
An operator expansion for integrable quantum field theories
A large class of quantum field theories on 1+1 dimensional Minkowski space,
namely, certain integrable models, has recently been constructed rigorously by
Lechner. However, the construction is very abstract and the concrete form of
local observables in these models remains largely unknown. Aiming for more
insight into their structure, we establish a series expansion for observables,
similar but not identical to the well-known form factor expansion. This
expansion will be the basis for a characterization and explicit construction of
local observables, to be discussed elsewhere. Here, we establish the expansion
independent of the localization aspect, and analyze its behavior under
space-time symmetries. We also clarify relations with deformation methods in
quantum field theory, specifically, with the warped convolution in the sense of
Buchholz and Summers.Comment: minor corrections and clarifications, as published in J. Phys A; 24
page
Development of Silicon Strip Detectors for a Medium Energy Gamma-ray Telescope
We report on the design, production, and testing of advanced double-sided
silicon strip detectors under development at the Max-Planck-Institute as part
of the Medium Energy Gamma-ray Astronomy (MEGA) project. The detectors are
designed to form a stack, the "tracker," with the goal of recording the paths
of energetic electrons produced by Compton-scatter and pair-production
interactions. Each layer of the tracker is composed of a 3 x 3 array of 500
micron thick silicon wafers, each 6 cm x 6 cm and fitted with 128 orthogonal p
and n strips on opposite sides (470 micron pitch). The strips are biased using
the punch-through principle and AC-coupled via metal strips separated from the
strip implant by an insulating oxide/nitride layer. The strips from adjacent
wafers in the 3 x 3 array are wire-bonded in series and read out by 128-channel
TA1.1 ASICs, creating a total 19 cm x 19 cm position-sensitive area. At 20
degrees C a typical energy resolution of 15-20 keV FWHM, a position resolution
of 290 microns, and a time resolution of ~1 microsec is observed.Comment: 9 pages, 13 figures, to appear in NIM-A (Proceedings of the 9th
European Symposium on Semiconductor Detectors
Test Results on the Silicon Pixel Detector for the TTF-FEL Beam Trajectory Monitor
Test measurements on the silicon pixel detector for the beam trajectory
monitor at the free electron laser of the TESLA test facility are presented. To
determine the electronic noise of detector and read-out and to calibrate the
signal amplitude of different pixels the 6 keV photons of the manganese K line
are used. Two different methods determine the spatial accuracy of the detector:
In one setup a laser beam is focused to a straight line and moved across the
pixel structure. In the other the detector is scanned using a low-intensity
electron beam of an electron microscope. Both methods show that the symmetry
axis of the detector defines a straight line within 0.4 microns. The
sensitivity of the detector to low energy X-rays is measured using a vacuum
ultraviolet beam at the synchrotron light source HASYLAB. Additionally, the
electron microscope is used to study the radiation hardness of the detector.Comment: 14 pages (Latex), 13 figures (Postscript), submitted to Nuclear
Instruments and Methods
Deformations of Fermionic Quantum Field Theories and Integrable Models
Considering the model of a scalar massive Fermion, it is shown that by means
of deformation techniques it is possible to obtain all integrable quantum field
theoretic models on two-dimensional Minkowski space which have factorizing
S-matrices corresponding to two-particle scattering functions S_2 satisfying
S_2(0) = -1. Among these models there is for example the Sinh-Gordon model. Our
analysis provides a complement to recent developments regarding deformations of
quantum field theories. The deformed model is investigated also in higher
dimensions. In particular, locality and covariance properties are analyzed.Comment: 20 page
EIT ground-state cooling of long ion strings
Electromagnetically-induced-transparency (EIT) cooling is a ground-state
cooling technique for trapped particles. EIT offers a broader cooling range in
frequency space compared to more established methods. In this work, we
experimentally investigate EIT cooling in strings of trapped atomic ions. In
strings of up to 18 ions, we demonstrate simultaneous ground state cooling of
all radial modes in under 1 ms. This is a particularly important capability in
view of emerging quantum simulation experiments with large numbers of trapped
ions. Our analysis of the EIT cooling dynamics is based on a novel technique
enabling single-shot measurements of phonon numbers, by rapid adiabatic passage
on a vibrational sideband of a narrow transition
An excited state coupled-cluster study on indigo dyes
In the present study, the domain-based pair natural orbital implementation of the similarity-transformed equation of motion method is employed to reproduce the vibrationally resolved absorption spectra of indigo dyes. After an initial investigation of multireference, basis set and implicit solvent effects, our calculated 0–0 transition energies are compared to a benchmark set of experimental absorption band maxima. It is established that the agreement between our method and experimental results is well below the desired 0.1 eV threshold in virtually all cases and that the shift in excitation energies upon chemical substitution is also well reproduced. Finally, the entire spectra of some of the main components of the Tyrian purple dye mixture are reproduced and it is found that our computed spectra match the experimental ones without an empirical shift
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