8,015 research outputs found
Magnetic Gaps related to Spin Glass Order in Fermionic Systems
We provide evidence for spin glass related magnetic gaps in the fermionic
density of states below the freezing temperature. Model calculations are
presented and proposed to be relevant for explaining resistivity measurements
which observe a crossover from variable-range- to activated behavior. The
magnetic field dependence of a hardgap and the low temperature decay of the
density of states are given. In models with fermion transport a new
metal-insulator transition is predicted to occur due to the spin-glass gap,
anteceding the spin glass to quantum paramagnet transition at smaller spin
density. Important fluctuation effects due to finite range frustrated
interactions are estimated and discussed.Comment: 4 pages, 1 Postscript figure, revised version accepted for
publication in Physical Review Letter
Burst statistics in Alcator C-Mod SOL turbulence
Bursty fluctuations in the scrape-off layer (SOL) of Alcator C-Mod have been
analyzed using gas puff imaging data. This reveals many of the same fluctuation
properties as Langmuir probe measurements, including normal distributed
fluctuations in the near SOL region while the far SOL plasma is dominated by
large amplitude bursts due to radial motion of blob-like structures.
Conditional averaging reveals burst wave forms with a fast rise and slow decay
and exponentially distributed waiting times. Based on this, a stochastic model
of burst dynamics is constructed. The model predicts that fluctuation
amplitudes should follow a Gamma distribution. This is shown to be a good
description of the gas puff imaging data, validating this aspect of the model.Comment: 8 pages, 6 figure
Effects of synchronous music on treadmill running among elite triathletes
This is the post-print version of the final paper published in Journal of Science and Medicine in Sport. The published article is available from the link below. Changes resulting from the publishing process, such as peer review, editing, corrections, structural formatting, and other quality control mechanisms may not be reflected in this document. Changes may have been made to this work since it was submitted for publication. Copyright @ 2011 Elsevier B.V.Objectives: Music can provide ergogenic, psychological, and psychophysical benefits during physical activity, especially when movements are performed synchronously with music. The present study developed the train of research on synchronous music and extended it to elite athletes. Design: Repeated-measures laboratory experiment. Method: Elite triathletes (n = 11) ran in time to self-selected motivational music, a neutral equivalent and a no-music control during submaximal and exhaustive treadmill running. Measured variables were time-to-exhaustion, mood responses, feeling states, RPE, blood lactate concentration, oxygen consumption and running economy. Results: Time-to-exhaustion was 18.1% and 19.7% longer, respectively, when running in time to motivational and neutral music, compared to no music. Mood responses and feeling states were more positive with motivational music compared to either neutral music or no music. RPE was lowest for neutral music and highest for the no-music control. Blood lactate concentrations were lowest for motivational music. Oxygen consumption was lower with music by 1.0%–2.7%. Both music conditions were associated with better running economy than the no-music control. Conclusions: Although neutral music did not produce the same level of psychological benefits as motivational music, it proved equally beneficial in terms of time-to-exhaustion and oxygen consumption. In functional terms, the motivational qualities of music may be less important than the prominence of its beat and the degree to which participants are able to synchronise their movements to its tempo. Music provided ergogenic, psychological and physiological benefits in a laboratory study and its judicious use during triathlon training should be considered.QAS Centre of Excellence for Applied Sport
Science Researc
Can a Lattice String Have a Vanishing Cosmological Constant?
We prove that a class of one-loop partition functions found by Dienes, giving
rise to a vanishing cosmological constant to one-loop, cannot be realized by a
consistent lattice string. The construction of non-supersymmetric string with a
vanishing cosmological constant therefore remains as elusive as ever. We also
discuss a new test that any one-loop partition function for a lattice string
must satisfy.Comment: 14 page
A Possible Selves Intervention to Enhance School Involvement
Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/89945/1/oyserman__terry__bybee__2002.pd
Wave function-dependent mobility and suppression of interface roughness scattering in a strained SiGe p-channel field-effect structure
The 4 K Hall mobility has been measured in a top-gated, inverted, modulation-doped Si/Si0.8Ge0.2 structure having a Si:B doping layer beneath the alloy. From comparisons with theoretical calculations, we argue that, unlike an ordinary enhancement-mode SiGe p-channel metal–oxide–semiconductor structure, this configuration leads to a decrease of interface roughness scattering with increasing sheet carrier density. We also speculate on the nature of the interface charge observed in these structures at low temperature
Improved estimation of hidden Markov model parameters from multiple observation sequences
The huge popularity of Hidden Markov models in pattern recognition is due to the ability to 'learn' model parameters from an observation sequence through Baum-Welch and other re-estimation procedures. In the case of HMM parameter estimation from an ensemble of observation sequences, rather than a single sequence, we require techniques for finding the parameters which maximize the likelihood of the estimated model given the entire set of observation sequences. The importance of this study is that HMMs with parameters estimated from multiple observations are shown to be many orders of magnitude more probable than HMM models learned from any single observation sequence - thus the effectiveness of HMM 'learning' is greatly enhanced. In this paper, we present techniques that usually find models significantly more likely than Rabiner's well-known method on both seen and unseen sequences
The WAY theorem and the quantum resource theory of asymmetry
The WAY theorem establishes an important constraint that conservation laws
impose on quantum mechanical measurements. We formulate the WAY theorem in the
broader context of resource theories, where one is constrained to a subset of
quantum mechanical operations described by a symmetry group. Establishing
connections with the theory of quantum state discrimination we obtain optimal
unitaries describing the measurement of arbitrary observables, explain how
prior information can permit perfect measurements that circumvent the WAY
constraint, and provide a framework that establishes a natural ordering on
measurement apparatuses through a decomposition into asymmetry and charge
subsystems.Comment: 11 pages, 3 figure
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