921 research outputs found
Effect of the Haar measure on the finite temperature effective potential of Yang-Mills theory
Including the Haar measure we show that the effective potential of the
regularized SU(2) Yang-Mills theory has a minimum at vanishing Wilson-line
for strong coupling, whereas it develops two degenerate minima close to
for weak coupling. This suggests that the non-abelian character of
as contained in the Haar measure might be responsible for confinement.Comment: 3 pages, LATEX, 1 figure, figure available upon reques
Tracking serendipitous interactions: How individual cultures shape the office
In many work environments, serendipitous interactions between members of
different groups may lead to enhanced productivity, collaboration and knowledge
dissemination. Two factors that may have an influence on such interactions are
cultural differences between individuals in highly multicultural workplaces,
and the layout and physical spaces of the workplace itself. In this work, we
investigate how these two factors may facilitate or hinder inter-group
interactions in the workplace. We analyze traces collected using wearable
electronic badges to capture face-to-face interactions and mobility patterns of
employees in a research laboratory in the UK. We observe that those who
interact with people of different roles tend to come from collectivist cultures
that value relationships and where people tend to be comfortable with social
hierarchies, and that some locations in particular are more likely to host
serendipitous interactions, knowledge that could be used by organizations to
enhance communication and productivity.This work was supported by the Google Europe Fellowship in Mobile Computing.This is the author accepted manuscript. The final version is published in the Proceedings of the ACM Conference on Computer Supported Cooperative Work and Social Computing and can be found in the ACM digital library here: http://dl.acm.org/citation.cfm?doid=2531602.2531641
The visibility of IQHE at sharp edges: Experimental proposals based on interactions and edge electrostatics
The influence of the incompressible strips on the integer quantized Hall
effect (IQHE) is investigated, considering a cleaved-edge overgrown (CEO)
sample as an experimentally realizable sharp edge system. We propose a set of
experiments to clarify the distinction between the large-sample limit when bulk
disorder defines the IQHE plateau width and the small-sample limit smaller than
the disorder correlation length, when self-consistent edge electrostatics
define the IQHE plateau width. The large-sample or bulk QH regime is described
by the usual localization picture, whereas the small-sample or edge regime is
discussed within the compressible/incompressible strips picture, known as the
screening theory of QH edges. Utilizing the unusually sharp edge profiles of
the CEO samples, a Hall bar design is proposed to manipulate the edge potential
profile from smooth to extremely sharp. By making use of a side-gate
perpendicular to the two dimensional electron system, it is shown that the
plateau widths can be changed or even eliminated altogether. Hence, the
visibility of IQHE is strongly influenced when adjusting the edge potential
profile and/or changing the dc current direction under high currents in the
non-linear transport regime. As a second investigation, we consider two
different types of ohmic contacts, namely highly transmitting (ideal) and
highly reflecting (non-ideal) contacts. We show that if the injection contacts
are non-ideal, however still ohmic, it is possible to measure directly the
non-quantized transport taking place at the bulk of the CEO samples. The
results of the experiments we propose will clarify the influence of the edge
potential profile and the quality of the contacts, under quantized Hall
conditions.Comment: Substantially revised version of manuscript arXiv:0906.3796v1,
including new figures et
A detector module with highly efficient surface-alpha event rejection operated in CRESST-II Phase 2
The cryogenic dark matter experiment CRESST-II aims at the direct detection
of WIMPs via elastic scattering off nuclei in scintillating CaWO crystals.
We present a new, highly improved, detector design installed in the current run
of CRESST-II Phase 2 with an efficient active rejection of surface-alpha
backgrounds. Using CaWO sticks instead of metal clamps to hold the target
crystal, a detector housing with fully-scintillating inner surface could be
realized. The presented detector (TUM40) provides an excellent threshold of
keV and a resolution of keV (at
2.60keV). With significantly reduced background levels, TUM40 sets
stringent limits on the spin-independent WIMP-nucleon scattering cross section
and probes a new region of parameter space for WIMP masses below
3GeV/c. In this paper, we discuss the novel detector design and the
surface-alpha event rejection in detail.Comment: 9 pages, 6 figure
Results from 730 kg days of the CRESST-II Dark Matter Search
The CRESST-II cryogenic Dark Matter search, aiming at detection of WIMPs via
elastic scattering off nuclei in CaWO crystals, completed 730 kg days of
data taking in 2011. We present the data collected with eight detector modules,
each with a two-channel readout; one for a phonon signal and the other for
coincidently produced scintillation light. The former provides a precise
measure of the energy deposited by an interaction, and the ratio of
scintillation light to deposited energy can be used to discriminate different
types of interacting particles and thus to distinguish possible signal events
from the dominant backgrounds. Sixty-seven events are found in the acceptance
region where a WIMP signal in the form of low energy nuclear recoils would be
expected. We estimate background contributions to this observation from four
sources: 1) "leakage" from the e/\gamma-band 2) "leakage" from the
\alpha-particle band 3) neutrons and 4) Pb-206 recoils from Po-210 decay. Using
a maximum likelihood analysis, we find, at a high statistical significance,
that these sources alone are not sufficient to explain the data. The addition
of a signal due to scattering of relatively light WIMPs could account for this
discrepancy, and we determine the associated WIMP parameters.Comment: 17 pages, 13 figure
Measurement of shower development and its Moli\`ere radius with a four-plane LumiCal test set-up
A prototype of a luminometer, designed for a future e+e- collider detector,
and consisting at present of a four-plane module, was tested in the CERN PS
accelerator T9 beam. The objective of this beam test was to demonstrate a
multi-plane tungsten/silicon operation, to study the development of the
electromagnetic shower and to compare it with MC simulations. The Moli\`ere
radius has been determined to be 24.0 +/- 0.6 (stat.) +/- 1.5 (syst.) mm using
a parametrization of the shower shape. Very good agreement was found between
data and a detailed Geant4 simulation.Comment: Paper published in Eur. Phys. J., includes 25 figures and 3 Table
The CRESST II Dark Matter Search
Direct Dark Matter detection with cryodetectors is briefly discussed, with
particular mention of the possibility of the identification of the recoil
nucleus. Preliminary results from the CREEST II Dark Matter search, with 730
kg-days of data, are presented. Major backgrounds and methods of identifying
and dealing with them are indicated.Comment: Talk at DSU workshop, ITP Beijing, Oct. 2011. 9 figures, 2 table
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