12,324 research outputs found
Dipoles in thin sheets
A flat elastic sheet may contain pointlike conical singularities that carry a
metrical "charge" of Gaussian curvature. Adding such elementary defects to a
sheet allows one to make many shapes, in a manner broadly analogous to the
familiar multipole construction in electrostatics. However, here the underlying
field theory is non-linear, and superposition of intrinsic defects is
non-trivial as it must respect the immersion of the resulting surface in three
dimensions. We consider a "charge-neutral" dipole composed of two conical
singularities of opposite sign. Unlike the relatively simple electrostatic
case, here there are two distinct stable minima and an infinity of unstable
equilibria. We determine the shapes of the minima and evaluate their energies
in the thin-sheet regime where bending dominates over stretching. Our
predictions are in surprisingly good agreement with experiments on paper
sheets.Comment: 20 pages, 5 figures, 2 table
Physics at Low x
The QCD expectations concerning the deep inelastic lepton - hadron scattering
at low and their phenomenological implications for HERA are summarised.
Theoretical predictions for the structure function based on the
leading log resummation are presented and compared with the results
obtained from the Altarelli-Parisi equations. Theoretical predictions are
confronted with the recent data from HERA. The role of studying the final
states in deep inelastic scattering for revealing the dynamics at low is
emphasised and some dedicated measurements like deep inelastic plus jet events,
transverse energy flow and dijet production in deep inelastic scattering are
discussed.Comment: 16 pages, 8 figures, review talk presented at the Workshop "QCD94",
7-13 July 1994, Montpellier, France (to appear in the Proceedings of the
Workshop), Krak\'ow INP report N0 1681/PH, hard copies of the figures
available on request from the author at [email protected]
Fusion of aerial images and sensor data from a ground vehicle for improved semantic mapping
This work investigates the use of semantic information to link ground level occupancy maps and aerial images. A ground level semantic map, which shows open ground and indicates the probability of cells being occupied by walls of buildings, is obtained by a mobile robot equipped with an omnidirectional camera, GPS and a laser range finder. This semantic information is used for local and global segmentation of an aerial image. The result is a map where the semantic information has been extended beyond the range of the robot sensors and predicts where the mobile robot can find buildings and potentially driveable ground
Deep inelastic events containing a forward photon as a probe of small dynamics
We calculate the rate of producing deep inelastic events containing an
energetic isolated forward photon at HERA. We quantify the enhancement arising
from the leading gluon emissions with a view to using such events to
identify the underlying dynamics.Comment: 11 pages, Latex, 7 ps figure
Azimuthal decorrelation of forward and backward jets at the Tevatron
We analyse the azimuthal decorrelation of Mueller-Navelet dijets produced in
the collisions at Tevatron energies using a BFKL framework which incorporates
dominant subleading effects. We show that these effects significantly reduce
the decorrelation yet they are still insufficient to give satisfactory
description of experimental data. However a good description of the data is
obtained after incorporating within formalism the effective rapidity defined by
Del Duca and Schmidt.Comment: 1+9 pages, 6 eps figures; the final version to appear in Phys. Lett.
B; one reference added, the use of effective rapidity and the need for BFKL
resummmation for small azimuthal angles better motivate
Gluon shadowing in the low x region probed by the LHC
Starting from an unintegrated gluon distribution which satisfies a `unified'
equation which embodies both BFKL and DGLAP behaviour, we compute the shadowing
corrections to the integrated gluon in the small x domain that will be
accessible at the LHC. The corrections are calculated via the Korchegov
equation, which incorporates the leading ln(1/x) triple-Pomeron vertex, and are
approximately resummed using a simple Pade technique. We find that the
shadowing corrections to xg(x,Q^2) are rather small in the HERA domain, but
lead to a factor of 2 suppression in the region x \sim 10^-6, Q^2 \sim 4 GeV^2
accessible to experiments at the LHC.Comment: LaTeX, 8 pages including 1 figure, second version with extra comments
and references, accepted by Physics Letters
On dynamically generated parton distribution functions and their properties
The idea of ``dynamically'' generated parton distribution functions, based on
regular initial conditions at low momentum scale, is reanalyzed with particular
emphasize paid to its compatibility with the factorization mechanism. Basic
consequences of this approach are discussed and compared to those of the
conventional approach, employing singular initial distribution functions.Comment: 15 pages, Latex, 5 figures in PS format attache
Small optic suspensions for Advanced LIGO input optics and other precision optical experiments
We report on the design and performance of small optic suspensions developed
to suppress seismic motion of out-of-cavity optics in the Input Optics
subsystem of the Advanced LIGO interferometric gravitational wave detector.
These compact single stage suspensions provide isolation in all six degrees of
freedom of the optic, local sensing and actuation in three of them, and passive
damping for the other three
Unitarization of the BFKL Pomeron on a Nucleus
We analyze the evolution equation describing all multiple hard pomeron
exchanges in a hadronic or nuclear structure functions that was proposed
earlier. We construct a perturbation series providing us with an exact solution
to the equation outside of the saturation region. The series demonstrates how
at moderately high energies the corrections to the single BFKL pomeron exchange
contribution which are due to the multiple pomeron exchanges start unitarizing
total deep inelastic scattering cross section. We show that as energy increases
the scattering cross section of the quark-antiquark pair of a fixed transverse
separation on a hadron or nucleus given by the solution of our equation inside
of the saturation region unitarizes and becomes independent of energy. The
corresponding F_2 structure function also unitarizes and becomes linearly
proportional to ln s. We also discuss possible applications of the developed
technique to diffraction.Comment: REVTeX, 20 pages, 6 figure
A terrestrial search for dark contents of the vacuum, such as dark energy, using atom interferometry
We describe the theory and first experimental work on our concept for
searching on earth for the presence of dark content of the vacuum (DCV) using
atom interferometry. Specifically, we have in mind any DCV that has not yet
been detected on a laboratory scale, but might manifest itself as dark energy
on the cosmological scale. The experimental method uses two atom
interferometers to cancel the effect of earth's gravity and diverse noise
sources. It depends upon two assumptions: first, that the DCV possesses some
space inhomogeneity in density, and second that it exerts a sufficiently strong
non-gravitational force on matter. The motion of the apparatus through the DCV
should then lead to an irregular variation in the detected matter-wave phase
shift. We discuss the nature of this signal and note the problem of
distinguishing it from instrumental noise. We also discuss the relation of our
experiment to what might be learned by studying the noise in gravitational wave
detectors such as LIGO.The paper concludes with a projection that a future
search of this nature might be carried out using an atom interferometer in an
orbiting satellite. The apparatus is now being constructed
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