2,609 research outputs found
Perturbative Expansion in the Galilean Invariant Spin One-Half Chern-Simons Field Theory
A Galilean Chern-Simons field theory is formulated for the case of two
interacting spin-1/2 fields of distinct masses M and M'. A method for the
construction of states containing N particles of mass M and N' particles of
mass M' is given which is subsequently used to display equivalence to the
spin-1/2 Aharonov-Bohm effect in the N = N' =1 sector of the model. The latter
is then studied in perturbation theory to determine whether there are
divergences in the fourth order (one loop) diagram. It is found that the
contribution of that order is finite (and vanishing) for the case of parallel
spin projections while the antiparallel case displays divergences which are
known to characterize the spin zero case in field theory as well as in quantum
mechanics.Comment: 14 pages LaTeX, including 2 figures using eps
Color Variability of the Blazar AO 0235+16
Multicolor (UBVRIJHK) observations of the blazar AO 0235+16 are analyzed. The
light curves were compiled at the Turin Observatory from literature data and
the results of observations obtained in the framework of the WEBT program
(http://www.to.astro/blazars/webt/). The color variability of the blazar was
studied in eight time intervals with a sufficient number of multicolor optical
observations; JHK data are available for only one of these. The spectral energy
distribution (SED) of the variable component remained constant within each
interval, but varied strongly from one interval to another. After correction
for dust absorption, the SED can be represented by a power law in all cases,
providing evidence for a synchrotron nature of the variable component. We show
that the variability at both optical and IR wavelengths is associated with the
same variable source.Comment: 11 pages, 9 figures, 4 tables, accepted for publication in Astronomy
Report
Covariance systems
We introduce new definitions of states and of representations of covariance
systems. The GNS-construction is generalized to this context. It associates a
representation with each state of the covariance system. Next, states are
extended to states of an appropriate covariance algebra. Two applications are
given. We describe a nonrelativistic quantum particle, and we give a simple
description of the quantum spacetime model introduced by Doplicher et al.Comment: latex with ams-latex, 23 page
Chiral three-nucleon forces and bound excited states in neutron-rich oxygen isotopes
We study the spectra of neutron-rich oxygen isotopes based on chiral two- and
three-nucleon interactions. First, we benchmark our many-body approach by
comparing ground-state energies to coupled-cluster results for the same
two-nucleon interaction, with overall good agreement. We then calculate bound
excited states in 21,22,23O, focusing on the role of three-nucleon forces, in
the standard sd shell and an extended sdf7/2p3/2 valence space. Chiral
three-nucleon forces provide important one- and two-body contributions between
valence neutrons. We find that both these contributions and an extended valence
space are necessary to reproduce key signatures of novel shell evolution, such
as the N = 14 magic number and the low-lying states in 21O and 23O, which are
too compressed with two-nucleon interactions only. For the extended space
calculations, this presents first work based on nuclear forces without
adjustments. Future work is needed and open questions are discussed.Comment: 6 pages, 4 figures, published versio
Perturbative Analysis of Nonabelian Aharonov-Bohm Scattering
We perform a perturbative analysis of the nonabelian Aharonov-Bohm problem to
one loop in a field theoretic framework, and show the necessity of contact
interactions for renormalizability of perturbation theory. Moreover at critical
values of the contact interaction strength the theory is finite and preserves
classical conformal invariance.Comment: 12 pages in LaTeX, uses epsf.sty, 5 uuencoded Postscript figures sent
separately. MIT-CTP-228
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 the Nonabelian Aharonov Bohm Scattering of Spinless Particles
The Aharonov Bohm scattering for spinless, isospin 1/2, particles interacting
through a nonabelian Chern-Simons field is studied. Starting from the
relativistic quantum field theory and using a Coulomb gauge formulation, the
one loop renormalization program is implemented. Through the introduction of an
intermediary cutoff, separating the regions of high and low integration
momentum, the nonrelativistic limit is derived. The next to leading
relativistic approximation is also determined. In this approach quantum field
theory vacuum polarization effects are automatically incorporated.Comment: 20 pages, 8 figures, revtex. Misspelled reference corrected and new
references adde
Radiative Corrections to the Aharonov-Bohm Scattering
We consider the scattering of relativistic electrons from a thin magnetic
flux tube and perturbatively calculate the order , radiative
correction, to the first order Born approximation. We show also that the second
order Born amplitude vanishes, and obtain a finite inclusive cross section for
the one-body scattering which incorporates soft photon bremsstrahlung effects.
Moreover, we determine the radiatively corrected Aharonov-Bohm potential and,
in particular, verify that an induced magnetic field is generated outside of
the flux tube.Comment: 14 pages, revtex, 3 figure
The Path Integral Quantization And The Construction Of The S-matrix In The Abelian And Non-Abelian Chern-Simons Theories
The cvariant path integral quantization of the theory of the scalar and
spinor particles interacting through the abelian and non-Abelian Chern-Simons
gauge fields is carried out and is shown to be mathematically ill defined due
to the absence of the transverse components of these gauge fields. This is
remedied by the introduction of the Maxwell or the Maxwell-type (in the
non-Abelian case)term which makes the theory superrenormalizable and guarantees
its gauge-invariant regularization and renormalization. The generating
functionals are constructed and shown to be formally the same as those of QED
(or QCD) in 2+1 dimensions with the substitution of the Chern-Simons propagator
for the photon (gluon) propagator. By constructing the propagator in the
general case, the existence of two limits; pure Chern-Simons and QED (QCD)
after renormalization is demonstrated.
By carrying out carefully the path integral quantization of the non-Abelian
Chern-Simons theories using the De Witt-Fadeev-Popov and the Batalin-Fradkin-
Vilkovisky methods it is demonstrated that there is no need to quantize the
dimensionless charge of the theory. The main reason is that the action in the
exponent of the path integral is BRST-invariant which acquires a zero winding
number and guarantees the BRST renormalizability of the model.
The S-matrix operator is constructed, and starting from this S-matrix
operator novel topological unitarity identities are derived that demand the
vanishing of the gauge-invariant sum of the imaginary parts of the Feynman
diagrams with a given number of intermediate on-shell topological photon lines
in each order of perturbation theory. These identities are illustrated by an
explicit example.Comment: LaTex file, 31 pages, two figure
2D Spectroscopy of Candidate Polar-Ring Galaxies: I. The Pair of Galaxies UGC 5600/09
Observations of the pair of galaxies VV 330 with the SCORPIO multimode
instrument on the 6-m Special Astrophysical Observatory telescope are
presented. Large-scale velocity fields of the ionized gas in H-alfa and
brightness distributions in continuum and H-alfa have been constructed for both
galaxies with the help of a scanning Fabry Perot interferometer. Long-slit
spectroscopy is used to study the stellar kinematics. Analysis of the data
obtained has revealed a complex structure in each of the pair components. Three
kinematic subsystems have been identified in UGC 5600: a stellar disk, an inner
gas ring turned with respect to the disk through ~80degrees, and an outer gas
disk. The stellar and outer gas disks are noncoplanar. Possible scenarios for
the formation of the observed multicomponent kinematic galactic structure are
considered, including the case where the large-scale velocity field of the gas
is represented by the kinematic model of a disk with a warp. The velocity field
in the second galaxy of the pair, UGC 5609, is more regular. A joint analysis
of the data on the photometric structure and the velocity field has shown that
this is probably a late-type spiral galaxy whose shape is distorted by the
gravitational interaction, possibly, with UGC 5600.Comment: 18 pages, 6 figure
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