3,798 research outputs found
Suppressing sensorimotor activity modulates the discrimination of auditory emotions but not speaker identity
Our ability to recognize the emotions of others is a crucial feature of human social cognition. Functional neuroimaging studies indicate that activity in sensorimotor cortices is evoked during the perception of emotion. In the visual domain, right somatosensory cortex activity has been shown to be critical for facial emotion recognition. However, the importance of sensorimotor representations in modalities outside of vision remains unknown. Here we use continuous theta-burst transcranial magnetic stimulation (cTBS) to investigate whether neural activity in the right postcentral gyrus (rPoG) and right lateral premotor cortex (rPM) is involved in nonverbal auditory emotion recognition. Three groups of participants completed same-different tasks on auditory stimuli, discriminating between the emotion expressed and the speakers' identities, before and following cTBS targeted at rPoG, rPM, or the vertex (control site). A task-selective deficit in auditory emotion discrimination was observed. Stimulation to rPoG and rPM resulted in a disruption of participants' abilities to discriminate emotion, but not identity, from vocal signals. These findings suggest that sensorimotor activity may be a modality-independent mechanism which aids emotion discrimination. Copyright © 2010 the authors
Temperature dependence of the band gap of 28Si:P at very low temperatures measured via time-resolved optical spectroscopy
We measure the temperature dependence of the indirect band gap of isotopically purified 28Si:P in the regime from 0.1 K to 3 K by high-resolution absorption spectroscopy of the donor bound exciton transition. The measurements increase the up-to-date precision of the temperature-dependent band gap change by more than one order of magnitude and reveal a T4 dependence which is about a factor of two less than observed in previous measurements. Such a T4 dependence is predicted by theory, but the absolute values differ between our experiment and the most up-to-date calculations by a factor of 30, corroborating that the electron-phonon interaction at low temperatures is still not correctly included into theory. What is more, the ability of such very high-precision band-gap measurements facilitates the use of time- and spatially resolved 28Si:P absorption as a contactless, local thermometer and electric field sensor with a demonstrated time resolution of milliseconds
Low Temperature Relaxation of Donor Bound Electron Spins in 28Si:P
We measure the spin-lattice relaxation of donor bound electrons in ultrapure, isotopically enriched, phosphorus-doped 28Si:P. The optical pump-probe experiments reveal at low temperatures extremely long spin relaxation times which exceed 20 h. The 28Si:P spin relaxation rate increases linearly with temperature in the regime below 1 K and shows a distinct transition to a T9 dependence which dominates the spin relaxation between 2 and 4 K at low magnetic fields. The T7 dependence reported for natural silicon is absent. At high magnetic fields, the spin relaxation is dominated by the magnetic field dependent single phonon spin relaxation process. This process is well documented for natural silicon at finite temperatures but the 28Si:P measurements validate additionally that the bosonic phonon distribution leads at very low temperatures to a deviation from the linear temperature dependence of Γ as predicted by theory
Low Temperature Relaxation of Donor Bound Electron Spins in Si 28: P
We measure the spin-lattice relaxation of donor bound electrons in ultrapure, isotopically enriched, phosphorus-doped Si28:P. The optical pump-probe experiments reveal at low temperatures extremely long spin relaxation times which exceed 20 h. The Si28:P spin relaxation rate increases linearly with temperature in the regime below 1 K and shows a distinct transition to a T9 dependence which dominates the spin relaxation between 2 and 4 K at low magnetic fields. The T7 dependence reported for natural silicon is absent. At high magnetic fields, the spin relaxation is dominated by the magnetic field dependent single phonon spin relaxation process. This process is well documented for natural silicon at finite temperatures but the Si28:P measurements validate additionally that the bosonic phonon distribution leads at very low temperatures to a deviation from the linear temperature dependence of Γ as predicted by theory
Fluorescence during Doppler cooling of a single trapped atom
We investigate the temporal dynamics of Doppler cooling of an initially hot
single trapped atom in the weak binding regime using a semiclassical approach.
We develop an analytical model for the simplest case of a single vibrational
mode for a harmonic trap, and show how this model allows us to estimate the
initial energy of the trapped particle by observing the fluorescence rate
during the cooling process. The experimental implementation of this temperature
measurement provides a way to measure atom heating rates by observing the
temperature rise in the absence of cooling. This method is technically
relatively simple compared to conventional sideband detection methods, and the
two methods are in reasonable agreement. We also discuss the effects of RF
micromotion, relevant for a trapped atomic ion, and the effect of coupling
between the vibrational modes on the cooling dynamics.Comment: 12 pages, 11 figures, Submitted to Phys. Rev.
Diffractive photoproduction at large momentum transfer in coherent hadron - hadron interactions at CERN LHC
The vector meson production in coherent hadron-hadron interactions at LHC
energies is studied assuming that the color singlet -channel exchange
carries large momentum transfer. We consider the non-forward solution of the
BFKL equation at high energy and large momentum transfer and estimate the
rapidity distribution and total cross section for the process , where can be a proton or a nucleus. We predict large rates,
which implies that the experimental identification can be feasible at the LHC.Comment: 10 pages, 5 figures, 1 table. Version to be published in Physical
Review
Double diffractive meson production and the BFKL Pomeron at colliders
In this Letter we study the double diffractive vector meson production in
collisions assuming the dominance of the BFKL pomeron exchange. We
consider the non-forward solution of the BFKL equation at high energy and large
momentum transfer and estimate the total cross section for the process with antitagged and , where and can
be any two vector mesons (). The
event rates for the future linear colliders are given.Comment: 8 pages, 1 figure, Version to be published in Physical Review
Symmetric qubits from cavity states
Two-mode cavities can be prepared in quantum states which represent symmetric
multi-qubit states. However, the qubits are impossible to address individually
and as such cannot be independently measured or otherwise manipulated. We
propose two related schemes to coherently transfer the qubits which the cavity
state represents onto individual atoms, so that the qubits can then be
processed individually. In particular, our scheme can be combined with the
quantum cloning scheme of Simon and coworkers [C. Simon et al, PRL 84, 2993
(2000)] to allow the optimal clones which their scheme produces to be spatially
separated and individually utilized.Comment: 8 pages, 4 figures, minor typographical errors correcte
Oscillatory Energy Exchange Between Waves Coupled by a Dynamic Artificial Crystal
We describe a general mechanism of controllable energy exchange between waves
propagating in a dynamic artificial crystal. We show that if a spatial
periodicity is temporarily imposed on the transmission properties of a
wave-carrying medium whilst a wave is inside, this wave is coupled to a
secondary counter-propagating wave and energy oscillates between the two. The
oscillation frequency is determined by the width of the spectral band gap
created by the periodicity and the frequency difference between the coupled
waves. The effect is demonstrated with spin waves in a dynamic magnonic
crystal.Comment: 5 pages, 4 figure
Back-Reaction In Lightcone QED
We consider the back-reaction of quantum electrodynamics upon an electric
field E(x_+) = - A'_-(x_+) which is parallel to x^3 and depends only on the
lightcone coordinate x_+ = (x^0 + x^3)/\sqrt{2}. Novel features are that the
mode functions have simple expressions for arbitrary A_-(x_+), and that one
cannot ignore the usual lightcone ambiguity at zero + momentum. Each mode of
definite canonical momenta k_+ experiences pair creation at the instant when
its kinetic momentum p_+=k_+ - e A_-(x_+) vanishes, at which point operators
from the surface at x_- =-\infty play a crucial role. Our formalism permits a
more explicit and complete derivation of the rate of particle production than
is usually given. We show that the system can be understood as the infinite
boost limit of the analogous problem of an electric field which is homogeneous
on surfaces of constant x^0.Comment: 37 pages, 2 figures, LaTeX 2 epsilo
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