16,488 research outputs found
Fluctuations of the Casimir-Polder force between an atom and a conducting wall
We consider the quantum fluctuations of the Casimir-Polder force between a
neutral atom and a perfectly conducting wall in the ground state of the system.
In order to obtain the atom-wall force fluctuation we first define an operator
directly associated to the force experienced by the atom considered as a
polarizable body in an electromagnetic field, and we use a time-averaged force
operator in order to avoid ultraviolet divergences appearing in the fluctuation
of the force. This time-averaged force operator takes into account that any
measurement involves a finite time. We also calculate the Casimir-Polder force
fluctuation for an atom between two conducting walls. Experimental
observability of these Casimir-Polder force fluctuations is also discussed, as
well as the dependence of the relative force fluctuation on the duration of the
measurement.Comment: 6 page
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An assessment of the impact of lean interventions within the UK police service
The police service in England and Wales continues to face intense pressures to manage and reduce budgets while simultaneously maintaining and improving levels of service. In achieving reform, attention has been directed towards the implementation of proven operational improvement frameworks, such as 'lean thinking' taken from the automotive industry. This research draws on contemporary views of 'lean' as a knowledge creation process that is integrated into an absorptive capacity theoretical perspective. The work provides a new perspective on operational improvement within police forces and new insight into how such a reconceptualization may contribute to more successful police transformation
Experience and Assessment of the DOE/NASA Mod-1 2000 Kw Wind Turbine Generator at Boone, North Carolina
The Mod 1 program objectives are defined. The Mod 1 wind turbine is described. In addition to the steel blade operated on the wind turbine, a composite blade was designed and manufactured. During the early phase of the manufacturing cycle of Mod 1A configuration was designed that identified concepts such as partial span control, a soft tower, and upwind teetered rotors that were incorporated in second and third generation industry designs. The Mod 1 electrical system performed as designed, with voltage flicker characteristics within acceptable utility limits
Thin Films of 3He -- Implications on the Identification of 3 He -A
Recently the identification of 3He-A with the axial state has been
questioned. It is suggested that the A-phase can actually be in the axiplanar
state. We point out in the present paper that experiments in a film geometry
may be useful to distinguish the above two possibilities. In particular a
second order phase transition between an axial and an axiplanar state would
occur as a function of thickness or temperature.Comment: 3 pages, no figures latex- revtex aps accepted by J. of Low
Temperature Physic
Issues of Reggeization in Back-Angle Scattering
The Kirschner-Lipatov result for the DLLA of high-energy backward
scattering is re-derived without the use of integral equations. It is shown
that part of the inequalities between the variables in the
logarithmically-divergent integrals is inconsequential. The light-cone
wave-function interpretation under the conditions of backward scattering is
discussed. It is argued that for hadron-hadron scattering in the valence-quark
model the reggeization should manifest itself at full strength starting from
.Comment: 10 Pages, 2 Figures. To appear in Proc. of Int. Conf. "New Trends in
High Energy Physics", 27 Sept.-4 Oct. 2008, Yalta, Crimea, Ukrain
Effects of the Lattice Discreteness on a Soliton in the Su-Schrieffer-Heeger Model
In this paper we analytically study the effects of the lattice discreteness
on the electron band in the SSH model. We propose a modified version of the TLM
model which is derived from the SSH model using a continuum approximation. When
a soliton is induced in the electron-lattice system, the electron scattering
states both at the bottom of the valence band and the top of the conduction
band are attracted to the soliton. This attractive force induces weakly
localized electronic states at the band edges. Using the modified version of
the TLM model, we have succeeded in obtaining analytical solutions of the
weakly localized states and the extended states near the bottom of the valence
band and the top of the conduction band. This band structure does not modify
the order parameters. Our result coincides well with numerical simulation
works.Comment: to be appear in J.Phys.Soc.Jpn. Figures should be requested to the
author. They will be sent by the conventional airmai
Thermodynamic Scaling of the Viscosity of Van Der Waals, H-Bonded, and Ionic Liquids
Viscosities and their temperature, T, and volume, V, dependences are reported
for 7 molecular liquids and polymers. In combination with literature viscosity
data for 5 other liquids, we show that the superpositioning of relaxation times
for various glass-forming materials when expressed as a function of TV^g, where
the exponent g is a material constant, can be extended to the viscosity. The
latter is usually measured to higher temperatures than the corresponding
relaxation times, demonstrating the validity of the thermodynamic scaling
throughout the supercooled and higher T regimes. The value of g for a given
liquid principally reflects the magnitude of the intermolecular forces (e.g.,
steepness of the repulsive potential); thus, we find decreasing g in going from
van der Waals fluids to ionic liquids. For strongly H-bonded materials, such as
low molecular weight polypropylene glycol and water, the superpositioning
fails, due to the non-trivial change of chemical structure (degree of
H-bonding) with thermodynamic conditions.Comment: 16 pages 7 figure
Groups of two galaxies in SDSS: implications of colours on star formation quenching time-scales
We have devised a method to select galaxies that are isolated in their dark
matter halo (N=1 systems) and galaxies that reside in a group of exactly two
(N=2 systems). Our N=2 systems are widely-separated (up to
\,200\,\,kpc), where close galaxy-galaxy interactions are not
dominant. We apply our selection criteria to two volume-limited samples of
galaxies from SDSS DR6 with -19 and -20 to study the
effects of the environment of very sparse groups on galaxy colour. For
satellite galaxies in a group of two, we find a red excess attributed to star
formation quenching of 0.15\,\,0.01 and 0.14\,\,0.01 for the -19 and
-20 samples, respectively, relative to isolated galaxies of the same stellar
mass. Assuming N=1 systems are the progenitors of N=2 systems, an
immediate-rapid star formation quenching scenario is inconsistent with these
observations. A delayed-then-rapid star formation quenching scenario with a
delay time of 3.3 and 3.7\,Gyr for the -19 and -20 samples, respectively,
yields a red excess prediction in agreement with the observations. The
observations also reveal that central galaxies in a group of two have a slight
blue excess of 0.06\,\,0.02 and 0.02\,\,0.01 for the -19 and -20
samples, respectively, relative to N=1 populations of the same stellar mass.
Our results demonstrate that even the environment of very sparse groups of
luminous galaxies influence galaxy evolution and in-depth studies of these
simple systems are an essential step towards understanding galaxy evolution in
general.Comment: 17 pages, 11 figures, accepted to MNRA
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