110 research outputs found
Second central extension in Galilean covariant field theory
The second central extension of the planar Galilei group has been alleged to
have its origin in the spin variable. This idea is explored here by considering
local Galilean covariant field theory for free fields of arbitrary spin. It is
shown that such systems generally display only a trivial realization of the
second central extension. While it is possible to realize any desired value of
the extension parameter by suitable redefinition of the boost operator, such an
approach has no necessary connection to the spin of the basic underlying field.Comment: 6 pgs., late
Casimir effect for the sphere revisited
In a recent work Brevik \emph{et al.} have offered formal proofs of two
results which figure prominently in calculations of the Casimir pressure on a
sphere. It is shown by means of simple counterexamples that each of those
proofs is necessarily incorrect.Comment: 4 pages, no figures, to be published in Physics Letters
Path Integral Solubility of a General Two-Dimensional Model
The solubility of a general two dimensional model, which reduces to various
models in different limits, is studied within the path integral formalism.
Various subtleties and interesting features are pointed out.Comment: 7 pages, UR1386, ER40685-83
Reply to Hagen & Sudarshan's Comment
We show that the argument in Phys Rev Lett 70 (1993) 1360 is correct and
consistent, and that Hagen & Sudarshan's solution has inconsistency leading to
non-vanishing commutators of and even in physical
states. This proves that many of HS's statements in their Comment are based
merely on incorrect guess, but not on careful algebra.Comment: one page, UMN-TH-1245/9
Equivalence of Several Chern-Simons Matter Models
Not only does Chern-Simons (CS) coupling characterize statistics, but also
spin and scaling dimension of matter fields. We demonstrate spin transmutation
in relativistic CS matter theory, and moreover show equivalence of several
models. We study CS vector model in some details, which provide consistent
check to the assertion of the equivalence.Comment: latex, 7page, IFT-478-UNC/NUP-A-93-15 A version within the length
limit for Phys. Rev. Letts (in press
Injury and illness profiles during the 2014 South African Ironman triathlon
Background: There is a need for ongoing scrutiny of injury and illness profiles of ultra-distance athletes. This study aimed to record the medical history, illness and injuries of athletes receiving medical attention during the 2014 Ironman South Africa (IMSA) triathlon, and to investigate the temporal presentation of medical encounters.Methods: This was a retrospective, cross-sectional study. All athletes who required medical attention at the main medical tent and all of the medical posts or mobile units along the route were included in this study A total of 2 331 athletes started the race. Data included age, gender, time and stage of the race when medical attention was required, pre-race medical history and medication use, illness and injuries treated, special investigations performed, and weather conditions.Results: Overall, 179 athletes (7.7%) required medical attention. The incidence of medical encounters was 7.8%. A significantly higher percentage of younger participants encountered medical problems (P = 0.04). Most patient encounters (80.1%) occurred after the race. The median duration of treatment was 26 minutes. Medication was used by 35.1% of patients during the race. The most common medical encounters were exertion-related (71.2%), gastro-intestinal (16.4%), dermatological (11.9%), musculoskeletal (9.6%) and cardiorespiratory conditions (2.4%).Conclusion: Medical encounters occurred more frequently in later stages of the race. Most medical conditions were exertion-related. Potential higher risk may be associated with medication use, recent illness, and in younger participants. Temporal stacking of medical personnel, planning of resources according to expected conditions, preventative measures for high-risk behaviour, and on-going data collection with comparable methodology are recommended.Keywords: triathletes, medical encounters, medication use, treatment, event medical managemen
On spin-1 massive particles coupled to a Chern-Simons field
We study spin one particles interacting through a Chern-Simons field. In the
Born approximation, we calculate the two body scattering amplitude considering
three possible ways to introduce the interaction: (a) a Proca like model
minimally coupled to a Chern-Simons field, (b) the model obtained from (a) by
replacing the Proca's mass by a Chern-Simons term and (c) a complex
Maxwell-Chern-Simons model minimally coupled to a Chern-Simons field. In the
low energy regime the results show similarities with the Aharonov-Bohm
scattering for spin 1/2 particles. We discuss the one loop renormalization
program for the Proca's model. In spite of the bad ultraviolet behavior of the
matter field propagator, we show that, up to one loop the model is power
counting renormalizable thanks to the Ward identities satisfied by the
interaction vertices.Comment: 14 pages, 5 figures, revte
On Aharonov-Casher bound states
In this work bound states for the Aharonov-Casher problem are considered.
According to Hagen's work on the exact equivalence between spin-1/2
Aharonov-Bohm and Aharonov-Casher effects, is known that the
term cannot be neglected in the
Hamiltonian if the spin of particle is considered. This term leads to the
existence of a singular potential at the origin. By modeling the problem by
boundary conditions at the origin which arises by the self-adjoint extension of
the Hamiltonian, we derive for the first time an expression for the bound state
energy of the Aharonov-Casher problem. As an application, we consider the
Aharonov-Casher plus a two-dimensional harmonic oscillator. We derive the
expression for the harmonic oscillator energies and compare it with the
expression obtained in the case without singularity. At the end, an approach
for determination of the self-adjoint extension parameter is given. In our
approach, the parameter is obtained essentially in terms of physics of the
problem.Comment: 11 pages, matches published versio
Aharonov-Bohm scattering of charged particles and neutral atoms: the role of absorption
The Aharonov-Bohm scattering of charged particles by the magnetic field of an
infinitely long and infinitely thin solenoid (magnetic string) in an absorbing
medium is studied. We discuss the partial-wave approach to this problem and
show that standard partial-wave method can be adjusted to this case. The effect
of absorption leads to oscillations of the AB cross section.
Based on this we investigate the scattering of neutral atoms with induced
electric dipole moments by a charge wire of finite radius which is placed in an
uniform magnetic field. The physical realistic and practically important case
that all atoms which collide with the wire are totally absorbed at its surface,
is studied in detail. The dominating terms of the scattering amplitude are
evaluated analytically for different physical constellations. The rest terms
are written in a form suitable for a numerical computation. We show that if the
magnetic field is absent, the absorbing charged wire causes oscillations of the
cross section. In the presence of the magnetic field the cross section
increases and the dominating Aharonov--Bohm peak appears in the forward
direction, suppressing the oscillations.Comment: 15 pages, LaTeXfile, 2 figure
Thermodynamics of Relativistic Fermions with Chern-Simons Coupling
We study the thermodynamics of the relativistic Quantum Field Theory of
massive fermions in three space-time dimensions coupled to an Abelian
Maxwell-Chern-Simons gauge field. We evaluate the specific heat at finite
temperature and density and find that the variation with the statistical angle
is consistent with the non-relativistic ideas on generalized statistics.Comment: 12 pages, REVTe
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