244 research outputs found
Laser modulation at the atomic level monthly report no. 7, 1-31 jan. 1965
Laser modulation at atomic level - yttrium- aluminum garnet emission and laser emission shift with homogeneous pulsed magnetic fiel
Laser modulation at the atomic level monthly report no. 8, 1 - 28 feb. 1965
Measurement of temperature dependence of energy levels involved in laser emissio
Expansion-Free Evolving Spheres Must Have Inhomogeneous Energy Density Distributions
In a recent paper a systematic study on shearing expansion-free spherically
symmetric distributions was presented. As a particular case of such systems,
the Skripkin model was mentioned, which corresponds to a nondissipative perfect
fluid with a constant energy density. Here we show that such a model is
inconsistent with junction conditions. It is shown that in general for any
nondissipative fluid distribution, the expansion-free condition requires the
energy density to be inhomogeneous. As an example we consider the case of dust,
which allows for a complete integration.Comment: 8 pages, Latex. To appear in Phys. Rev.D. Typos correcte
Rindler Particles and Classical Radiation
We describe the quantum and classical radiation by a uniformly accelerating
point source in terms of the elementary processes of absorption and emission of
Rindler scalar photons of the Fulling-Davies-Unruh bath observed by a
co-accelerating observer.To this end we compute the emission rate by a DeWitt
detector of a Minkowski scalar particle with defined transverse momentum per
unit of proper time of the source and we show that it corresponds to the
induced absorption or spontaneous and induced emission of Rindler photons from
the thermal bath. We then take what could be called the inert limit of the
DeWitt detector by considering the limit of zero gap energy. As suggested by
DeWitt, we identify in this limit the detector with a classical point source
and verify the consistency of our computation with the classical result.
Finally, we study the behavior of the emission rate in D space-time dimensions
in connection with the so called apparent statistics inversion.Comment: 8 pages, 2 figure
Non Abelian BF theories with sources and 2-D gravity
We study the interaction of non-Abelian topological theories defined on
two dimensional manifolds with point sources carrying non-Abelian charges. We
identify the most general solution for the field equations on simply and
multiply connected two-manifolds. Taking the particular choice of the so-called
extended Poincar\'e group as the gauge group we discuss how recent discussions
of two dimensional gravity models do fit in this formalism.Comment: 20 pages, Latex, To appear in Phys Rev D5
Homeostatic regulation of sleep in the white-crowned sparrow (Zonotrichia leucophrys gambelii)
<p>Abstract</p> <p>Background</p> <p>Sleep is regulated by both a circadian and a homeostatic process. The homeostatic process reflects the duration of prior wakefulness: the longer one stays awake, the longer and/or more intense is subsequent sleep. In mammals, the best marker of the homeostatic sleep drive is slow wave activity (SWA), the electroencephalographic (EEG) power spectrum in the 0.5–4 Hz frequency range during non-rapid eye movement (NREM) sleep. In mammals, NREM sleep SWA is high at sleep onset, when sleep pressure is high, and decreases progressively to reach low levels in late sleep. Moreover, SWA increases further with sleep deprivation, when sleep also becomes less fragmented (the duration of sleep episodes increases, and the number of brief awakenings decreases). Although avian and mammalian sleep share several features, the evidence of a clear homeostatic response to sleep loss has been conflicting in the few avian species studied so far. The aim of the current study was therefore to ascertain whether established markers of sleep homeostasis in mammals are also present in the white-crowned sparrow (<it>Zonotrichia leucophrys gambelii</it>), a migratory songbird of the order Passeriformes. To accomplish this goal, we investigated amount of sleep, sleep time course, and measures of sleep intensity in 6 birds during baseline sleep and during recovery sleep following 6 hours of sleep deprivation.</p> <p>Results</p> <p>Continuous (24 hours) EEG and video recordings were used to measure baseline sleep and recovery sleep following short-term sleep deprivation. Sleep stages were scored visually based on 4-sec epochs. EEG power spectra (0.5–25 Hz) were calculated on consecutive 4-sec epochs. Four vigilance states were reliably distinguished based on behavior, visual inspection of the EEG, and spectral EEG analysis: Wakefulness (W), Drowsiness (D), slow wave sleep (SWS) and rapid-eye movement (REM) sleep. During baseline, SWA during D, SWS, and NREM sleep (defined as D and SWS combined) was highest at the beginning of the major sleep period and declined thereafter. Moreover, peak SWA in both SWS and NREM sleep increased significantly immediately following sleep deprivation relative to baseline.</p> <p>Conclusion</p> <p>As in mammals, sleep deprivation in the white-crowned sparrow increases the intensity of sleep as measured by SWA.</p
Measuring multipole moments of Weyl metrics by means of gyroscopes
Using the technique of Rindler and Perlick we calculate the total precession
per revolution of a gyroscope circumventing the source of Weyl metrics. We
establish thereby a link between the multipole moments of the source and an
``observable'' quantity. Special attention deserves the case of the
gamma-metric. As an extension of this result we also present the corresponding
expressions for some stationary space-times.Comment: 18 pages Latex, To appear in J.Math.Phy
On the Squeezed Number States and their Phase Space Representations
We compute the photon number distribution, the Q distribution function and
the wave functions in the momentum and position representation for a single
mode squeezed number state using generating functions which allow to obtain any
matrix element in the squeezed number state representation from the matrix
elements in the squeezed coherent state representation. For highly squeezed
number states we discuss the previously unnoted oscillations which appear in
the Q function. We also note that these oscillations can be related to the
photon-number distribution oscillations and to the momentum representation of
the wave function.Comment: 16 pages, 9 figure
Husimi's function and quantum interference in phase space
We discuss a phase space description of the photon number distribution of non
classical states which is based on Husimi's function and does not
rely in the WKB approximation. We illustrate this approach using the examples
of displaced number states and two photon coherent states and show it to
provide an efficient method for computing and interpreting the photon number
distribution . This result is interesting in particular for the two photon
coherent states which, for high squeezing, have the probabilities of even and
odd photon numbers oscillating independently.Comment: 15 pages, 12 figures, typos correcte
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