41,446 research outputs found
Quantum Determinism from Quantum General Covariance
The requirement of general covariance of quantum field theory (QFT) naturally
leads to quantization based on the manifestly covariant De Donder-Weyl
formalism. To recover the standard noncovariant formalism without violating
covariance, fields need to depend on time in a specific deterministic manner.
This deterministic evolution of quantum fields is recognized as a covariant
version of the Bohmian hidden-variable interpretation of QFT.Comment: 6 pages, revised, new references, Honorable Mention of the Gravity
Research Foundation 2006 Essay Competition, version to appear in Int. J. Mod.
Phys.
Health monitoring of federated future internet experimentation facilities
The federation of Future Internet testbeds as envisaged by the Fed4FIRE project is a complex undertaking. It combines a large number of existing, independent testbeds in a single federation, and presents them to the experimenter as if it were a single infrastructure. Operating and using such an infrastructure requires a profound knowledge of the status of the health of the underlying independent systems. Inspired by network monitoring techniques used to operate the Internet today, this paper considers how a centralized health monitoring system can be set up in a federated environment of Future Internet Experimentation Facilities. We show why it is a vital tool for experimenters and First Level Support in the federation, which health monitoring information must be captured, and how this information can be displayed most appropriately
New Cosmological Structures on Medium Angular Scales Detected with the Tenerife Experiments
We present observations at 10 and 15 GHz taken with the Tenerife experiments
in a band of the sky at Dec.=+35 degrees. These experiments are sensitive to
multipoles in the range l=10-30. The sensitivity per beam is 56 and 20 microK
for the 10 and the 15 GHz data, respectively. After subtraction of the
prediction of known radio-sources, the analysis of the data at 15 GHz at high
Galactic latitude shows the presence of a signal with amplitude Delta Trms ~ 32
microK. In the case of a Harrison-Zeldovich spectrum for the primordial
fluctuations, a likelihood analysis shows that this signal corresponds to a
quadrupole amplitude Q_rms-ps=20.1+7.1-5.4 microK, in agreement with our
previous results at Dec.+=40 degrees and with the results of the COBE DMR.
There is clear evidence for the presence of individual features in the RA range
190 degrees to 250 degrees with a peak to peak amplitude of ~110 microK. A
preliminary comparison between our results and COBE DMR predictions for the
Tenerife experiments clearly indicates the presence of individual features
common to both. The constancy in amplitude over such a large range in frequency
(10-90 GHz) is strongly indicative of an intrinsic cosmological origin for
these structures.Comment: ApJ Letters accepted, 13 pages Latex (uses AASTEX) and 4 encapsulated
postscript figures
The Energy-Momentum Tensor in Fulling-Rindler Vacuum
The energy density in Fulling-Rindler vacuum, which is known to be negative
"everywhere" is shown to be positive and singular on the horizons in such a
fashion as to guarantee the positivity of the total energy. The mechanism of
compensation is displayed in detail.Comment: 9 pages, ULB-TH-15/9
Spectral gap of segments of periodic waveguides
We consider a periodic strip in the plane and the associated quantum
waveguide with Dirichlet boundary conditions. We analyse finite segments of the
waveguide consisting of periodicity cells, equipped with periodic boundary
conditions at the ``new'' boundaries. Our main result is that the distance
between the first and second eigenvalue of such a finite segment behaves like
.Comment: 3 page
Coral symbiodinium community composition across the Belize Mesoamerican barrier reef system is influenced by host species and thermal variability
Accepted manuscrip
The Tenerife Cosmic Microwave Background Maps: Observations and First Analysis
The results of the Tenerife Cosmic Microwave Background (CMB) experiments are
presented. These observations cover 5000 and 6500 square degrees on the sky at
10 and 15 GHz respectively centred around Dec.~ +35 degrees. The experiments
are sensitive to multipoles l=10-30 which corresponds to the Sachs-Wolfe
plateau of the CMB power spectra. The sensitivity of the results are ~31 and
\~12 microK at 10 and 15 GHz respectively in a beam-size region (5 degrees
FWHM). The data at 15 GHz show clear detection of structure at high Galactic
latitude; the results at 10 GHz are compatible with these, but at lower
significance. A likelihood analysis of the 10 and 15 GHz data at high Galactic
latitude, assuming a flat CMB band power spectra gives a signal Delta
T_l=30+10-8 microK (68 % C.L.). Including the possible contaminating effect due
to the diffuse Galactic component, the CMB signal is Delta T_l=30+15-11 microK.
These values are highly stable against the Galactic cut chosen. Assuming a
Harrison-Zeldovich spectrum for the primordial fluctuations, the above values
imply an expected quadrupole Q_RMS-PS=20+10-7 microK which confirms previous
results from these experiments, and which are compatible with the COBE DMR.Comment: 17 pages, 7 figures. Submitted to Ap
- …