4,136 research outputs found
Letters between Elizabeth Rebekah Speer and William Kerr\u27s secretary
Letters concerning a position in the music department at the Agricultural College
Directing Brownian motion on a periodic surface
We consider an overdamped Brownian particle, exposed to a two-dimensional,
square lattice potential and a rectangular ac-drive. Depending on the driving
amplitude, the linear response to a weak dc-force along a lattice symmetry axis
consist in a mobility in basically any direction. In particular, motion exactly
opposite to the applied dc-force may arise. Upon changing the angle of the
dc-force relatively to the square lattice, the particle motion remains
predominantly opposite to the dc-force. The basic physical mechanism consists
in a spontaneous symmetry breaking of the unbiased deterministic particle
dynamics.Comment: 4 Pages, 4 figures, accepted for Phys. Rev. Let
Shuffle relations for regularised integrals of symbols
We prove shuffle relations which relate a product of regularised integrals of
classical symbols to regularised nested (Chen) iterated integrals, which hold
if all the symbols involved have non-vanishing residue. This is true in
particular for non-integer order symbols. In general the shuffle relations hold
up to finite parts of corrective terms arising from renormalisation on tensor
products of classical symbols, a procedure adapted from renormalisation
procedures on Feynman diagrams familiar to physicists. We relate the shuffle
relations for regularised integrals of symbols with shuffle relations for
multizeta functions adapting the above constructions to the case of symbols on
the unit circle.Comment: 40 pages,latex. Changes concern sections 4 and 5 : an error in
section 4 has been corrected, and the link between section 5 and the previous
ones has been precise
BIOMECHANICAL ANALYSIS OF THE DEADLIFT DURING THE 1999 SPECIAL OLYMPICS WORLD GAMES
Sumo and conventional deadlifts and high and low skilled lifters were compared during the 1999 Special Olympics World Games. Two video cameras collected 60 Hz data from 40 subjects, and parameters were quantified at barbell liftoff (LO) and barbell knee passing (KP). The sumo group had a more vertical trunk and horizontal thigh at LO, a less vertical shank at KP, and greater forefoot abduction. The sumo group generated ankle dorsiflexor, knee extensor, and hip extensor moments, while the conventional group produced ankle plantar flexor, knee flexor & extensor, and hip extensor moments. High skilled lifters had a 40% greater barbell load, greater knee flexion at LO and greater knee extension at KP, 15% less vertical bar distance, smaller plantar flexor and hip extensor moment arms at LO and KP, and greater knee extensor moment arms at LO
Algebraic Aspects of Abelian Sandpile Models
The abelian sandpile models feature a finite abelian group G generated by the
operators corresponding to particle addition at various sites. We study the
canonical decomposition of G as a product of cyclic groups G = Z_{d_1} X
Z_{d_2} X Z_{d_3}...X Z_{d_g}, where g is the least number of generators of G,
and d_i is a multiple of d_{i+1}. The structure of G is determined in terms of
toppling matrix. We construct scalar functions, linear in height variables of
the pile, that are invariant toppling at any site. These invariants provide
convenient coordinates to label the recurrent configurations of the sandpile.
For an L X L square lattice, we show that g = L. In this case, we observe that
the system has nontrivial symmetries coming from the action of the cyclotomic
Galois group of the (2L+2)th roots of unity which operates on the set of
eigenvalues of the toppling matrix. These eigenvalues are algebraic integers,
whose product is the order |G|. With the help of this Galois group, we obtain
an explicit factorizaration of |G|. We also use it to define other simpler,
though under-complete, sets of toppling invariants.Comment: 39 pages, TIFR/TH/94-3
Position Dependence of Charge Collection in Prototype Sensors for the CMS Pixel Detector
This paper reports on the sensor R&D activity for the CMS pixel detector.
Devices featuring several design and technology options have been irradiated up
to a proton fluencec of 1E15 n_eq/cm**2 at the CERN PS. Afterward they were
bump bonded to unirradiated readout chips and tested using high energy pions in
the H2 beam line of the CERN SPS. The readout chip allows a non zero suppressed
full analogue readout and therefore a good characterization of the sensors in
terms of noise and charge collection properties. The position dependence of
signal is presented and the differences between the two sensor options are
discussed.Comment: Contribution to the IEEE-NSS Oct. 2003, Portland, OR, USA, submitted
to IEEE-TNS 7 pages, 8 figures, 1 table. Revised, title change
The grand canonical ABC model: a reflection asymmetric mean field Potts model
We investigate the phase diagram of a three-component system of particles on
a one-dimensional filled lattice, or equivalently of a one-dimensional
three-state Potts model, with reflection asymmetric mean field interactions.
The three types of particles are designated as , , and . The system is
described by a grand canonical ensemble with temperature and chemical
potentials , , and . We find that for
the system undergoes a phase transition from a
uniform density to a continuum of phases at a critical temperature . For other values of the chemical potentials the system
has a unique equilibrium state. As is the case for the canonical ensemble for
this model, the grand canonical ensemble is the stationary measure
satisfying detailed balance for a natural dynamics. We note that , where is the critical temperature for a similar transition in
the canonical ensemble at fixed equal densities .Comment: 24 pages, 3 figure
Extraction of electric field in heavily irradiated silicon pixel sensors
A new method for the extraction of the electric field in the bulk of heavily
irradiated silicon pixel sensors is presented. It is based on the measurement
of the Lorentz deflection and mobility of electrons as a function of depth. The
measurements were made at the CERN H2 beam line, with the beam at a shallow
angle with respect to the pixel sensor surface. The extracted electric field is
used to simulate the charge collection and the Lorentz deflection in the pixel
sensor. The simulated charge collection and the Lorentz deflection is in good
agreement with the measurements both for non-irradiated and irradiated up to
1E15 neq/cm2 sensors.Comment: 6 pages, 11 figures, presented at the 13th International Workshop on
Vertex Detectors for High Energy Physics, September 13-18, 2004,
Menaggio-Como, Italy. Submitted to Nucl. Instr. Meth.
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