2,512 research outputs found
Controllability of spin-boson systems
In this paper we study the so-called spin-boson system, namely {a two-level
system} in interaction with a distinguished mode of a quantized bosonic field.
We give a brief description of the controlled Rabi and Jaynes--Cummings models
and we discuss their appearance in the mathematics and physics literature. We
then study the controllability of the Rabi model when the control is an
external field acting on the bosonic part. Applying geometric control
techniques to the Galerkin approximation and using perturbation theory to
guarantee non-resonance of the spectrum of the drift operator, we prove
approximate controllability of the system, for almost every value of the
interaction parameter
The bound state Aharonov-Bohm effect around a cosmic string revisited
In this article we observe that the self-adjoint extension of the Hamiltonian
of a particle moving around a shielded cosmic string gives rise to a
gravitational analogue of the bound state Aharonov-Bohm effect.Comment: 2 pages, no figure
First Kepler results on compact pulsators VIII: Mode identifications via period spacings in mode pulsating Subdwarf B stars
We investigate the possibility of nearly-equally spaced periods in 13 hot
subdwarf B (sdB) stars observed with the Kepler spacecraft and one observed
with CoRoT. Asymptotic limits for gravity (g-)mode pulsations provide
relationships between equal period spacings of modes with differing degrees and
relationships between periods of the same radial order but differing degrees.
Period transforms, Kolmogorov-Smirnov tests, and linear least-squares fits have
been used to detect and determine the significance of equal period spacings. We
have also used Monte Carlo simulations to estimate the likelihood that the
detected spacings could be produced randomly.
Period transforms for nine of the Kepler stars indicate ell=1 period
spacings, with five also showing peaks for ell=2 modes. 12 stars indicate ell=1
modes using the Kolmogorov-Smirnov test while another shows solely ell=2 modes.
Monte Carlo results indicate that equal period spacings are significant in 10
stars above 99% confidence and 13 of the 14 are above 94% confidence. For 12
stars, the various methods find consistent regular period spacing values to
within the errors, two others show some inconsistencies, likely caused by
binarity, and the last has significant detections but the mode assignment
disagrees between methods.
We find a common ell=1 period spacing spanning a range from 231 to 272 s
allowing us to correlate pulsation modes with 222 periodicities and that the
ell=2 period spacings are related to the ell=1 spacings by the asymptotic
relationship . We briefly discuss the impact of equal period
spacings which indicate low-degree modes with a lack of significant mode
trappings.Comment: 27 pages, 4 figures, 17 tables. Accepted for publication in Monthly
Notices of the Royal Astronomical Societ
Functional evolution of quantum cylindrical waves
Kucha{\v{r}} showed that the quantum dynamics of (1 polarization) cylindrical
wave solutions to vacuum general relativity is determined by that of a free
axially-symmetric scalar field along arbitrary axially-symmetric foliations of
a fixed flat 2+1 dimensional spacetime. We investigate if such a dynamics can
be defined {\em unitarily} within the standard Fock space quantization of the
scalar field.
Evolution between two arbitrary slices of an arbitrary foliation of the flat
spacetime can be built out of a restricted class of evolutions (and their
inverses). The restricted evolution is from an initial flat slice to an
arbitrary (in general, curved) slice of the flat spacetime and can be
decomposed into (i) `time' evolution in which the spatial Minkowskian
coordinates serve as spatial coordinates on the initial and the final slice,
followed by (ii) the action of a spatial diffeomorphism of the final slice on
the data obtained from (i). We show that although the functional evolution of
(i) is unitarily implemented in the quantum theory, generic spatial
diffeomorphisms of (ii) are not. Our results imply that a Tomanaga-Schwinger
type functional evolution of quantum cylindrical waves is not a viable concept
even though, remarkably, the more limited notion of functional evolution in
Kucha{\v{r}}'s `half parametrized formalism' is well-defined.Comment: Replaced with published versio
On Petition for a Writ of Certiorari to The United States Court of Appeals for The Eighth Circuit, Brief of Law Professors Paul F. Rothstein, et. al., Office of the President v. Office of Independent Counsel
This Court should grant review not only because this is a case of national importance and prominence, but also because the decision below is a conspicuous departure from settled principles of evidence law. The panel majority concluded that communications between government lawyers and government officials are not protected by the attorney-client privilege, at least when those communications are sought by a federal grand jury. That conclusion conflicts with the predominant common-law understanding that the attorney-client privilege applies to government entities and that where the privilege applies, it is absolute (i.e., it protects against disclosure in all types of legal and investigative proceedings). In particular, the Court of Appeals\u27 decision rests on a fundamental misunderstanding of this Court\u27s decisions in Upjohn Co. v. United States, 449 U.S. 383 (1981), and United States v. Nixon, 418 U.s. 683 (1974).
Moreover, this case warrants further review because the decision below has profound implications beyond the parties to this dispute. The Court of Appeals\u27 ruling, if allowed to stand, will create widespread uncertainty among federal, state, and local officials concerning the extent to which their communications with their agency lawyers, for the purpose of seeking legal advice in the conduct of governmental affairs, are protected by the attorney-client privilege. Unless this Court grants review and resolves this uncertainty, the decision below will likely have an adverse effect on the current and future operation of not only the Office of the President of the United States, but also government at all levels. At the very least, a decision of such vast implications (as in the present case) should be made by the highest court in the land. We accordingly urge the Court to grant the petition for review
'Working out’ identity: distance runners and the management of disrupted identity
This article contributes fresh perspectives to the empirical literature on the sociology of the body, and of leisure and identity, by analysing the impact of long-term injury on the identities of two amateur but serious middle/long-distance runners. Employing a symbolic interactionist framework,and utilising data derived from a collaborative autoethnographic project, it explores the role
of ‘identity work’ in providing continuity of identity during the liminality of long-term injury and
rehabilitation, which poses a fundamental challenge to athletic identity. Specifically, the analysis
applies Snow and Anderson’s (1995) and Perinbanayagam’s (2000) theoretical conceptualisations
in order to examine the various forms of identity work undertaken by the injured participants, along
the dimensions of materialistic, associative and vocabularic identifications. Such identity work was
found to be crucial in sustaining a credible sporting identity in the face of disruption to the running
self, and in generating momentum towards the goal of restitution to full running fitness and reengagement
with a cherished form of leisure.
KEYWORDS: identity work, symbolic interactionism, distance running, disrupted identit
Priority sites for wildfowl conservation in Mexico
A set of priority sites for wildfowl conservation in Mexico was determined using contemporary count data (1991–2000) from the U.S. Fish & Wildlife Service mid-winter surveys. We used a complementarity approach implemented through linear integer programming that addresses particular conservation concerns for every species included in the analysis and large fluctuations in numbers through time.
A set of 31 priority sites was identified, which held more than 69% of the mid-winter count total in Mexico during all surveyed years. Six sites were in the northern highlands, 12 in the central highlands, six on the Gulf of Mexico coast and seven on the upper Pacific coast. Twenty-two sites from the priority set have previously been identified as qualifying for designation as wetlands of international importance under the Ramsar Convention and 20 sites are classified as Important Areas for Bird Conservation in Mexico. The information presented here provides an accountable, spatially-explicit, numerical basis for ongoing conservation planning efforts in Mexico, which can be used to improve existing wildfowl conservation networks in the country and can also be useful for conservation planning exercises elsewhere
Phase Space Reduction and Vortex Statistics: An Anyon Quantization Ambiguity
We examine the quantization of the motion of two charged vortices in a
Ginzburg--Landau theory for the fractional quantum Hall effect recently
proposed by the first two authors. The system has two second-class constraints
which can be implemented either in the reduced phase space or
Dirac-Gupta-Bleuler formalism. Using the intrinsic formulation of statistics,
we show that these two ways of implementing the constraints are inequivalent
unless the vortices are quantized with conventional statistics; either
fermionic or bosonic.Comment: 14 pages, PHYZZ
Seeing the way: visual sociology and the distance runner's perspective
Employing visual and autoethnographic data from a two‐year research project on distance runners, this article seeks to examine the activity of seeing in relation to the activity of distance running. One of its methodological aims is to develop the linkage between visual and autoethnographic data in combining an observation‐based narrative and sociological analysis with photographs. This combination aims to convey to the reader not only some of the specific subcultural knowledge and particular ways of seeing, but also something of the runner's embodied feelings and experience of momentum en route. Via the combination of narrative and photographs we seek a more effective way of communicating just how distance runners see and experience their training terrain. The importance of subjecting mundane everyday practices to detailed sociological analysis has been highlighted by many sociologists, including those of an ethnomethodological perspective. Indeed, without the competence of social actors in accomplishing these mundane, routine understandings and practices, it is argued, there would in fact be no social order
New OB star candidates in the Carina Arm around Westerlund 2 from VPHAS+
Date of Acceptance: 10/04/2015O and early B stars are at the apex of galactic ecology, but in the Milky Way, only a minority of them may yet have been identified. We present the results of a pilot study to select and parametrise OB star candidates in the Southern Galactic plane, down to a limiting magnitude of . A 2 square-degree field capturing the Carina Arm around the young massive star cluster, Westerlund 2, is examined. The confirmed OB stars in this cluster are used to validate our identification method, based on selection from the diagram for the region. Our Markov Chain Monte Carlo fitting method combines VPHAS+ with published photometry in order to derive posterior probability distributions of the stellar parameters and distance modulus, together with the reddening parameters and . The stellar parameters are sufficient to confirm OB status while the reddening parameters are determined to a precision of and . There are 489 objects that fit well as new OB candidates, earlier than B2. This total includes 74 probable massive O stars, 5 likely blue supergiants and 32 reddened subdwarfs. This increases the number of previously known and candidate OB stars in the region by nearly a factor of 10. Most of the new objects are likely to be at distances between 3 and 6 kpc. We have confirmed the results of previous studies that, at these longer distances, these sight lines require non-standard reddening laws with $3.5R_VPeer reviewe
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