19 research outputs found
Charged Scalar Pair Production in Strong-Field Photon-Photon Interaction
Following the pioneering work of H. Reiss [1], we provide a covariant
calculation of the charged scalar particle pair production. The calculation is
facilitated by the use of two-dimensional Bessel functions and light-font
coordinates.Comment: 8 page
Novel Edge States in Self-Dual Gravity
In contrast to the Einstein-Hilbert action, the action for self-dual gravity
contains vierbeins. They are eleminated at the level of observables by an
gauge condition implied by the action. We argue that despite
this condition, new "edge" or superselected state vectors corresponding to maps
of the spheres at infinity to arise. They
are characterised by new quantum numbers and they lead to mixed states. For
black holes, they arise both at the horizon and the spatial infinity and may be
relevant for the black hole information paradox. Similar comments can be made
about the Einstein-Palatini action which uses vierbeins.Comment: 15 pages, reference added, some minor notational changes - no changes
in conclusio
Anomalous Defects and Their Quantized Transverse Conductivities
Using a description of defects in solids in terms of three-dimensional
gravity, we study the propagation of electrons in the background of
disclinations and screw dislocations. We study the situations where there are
bound states that are effectively localized on the defect and hence can be
described in terms of an effective 1+1 dimensional field theory for the low
energy excitations. In the case of screw dislocations, we find that these
excitations are chiral and can be described by an effective field theory of
chiral fermions. Fermions of both chirality occur even for a given direction of
the magnetic field. The ``net'' chirality of the system however is not always
the same for a given direction of the magnetic field, but changes from one sign
of the chirality through zero to the other sign as the Fermi momentum or the
magnitude of the magnetic flux is varied. On coupling to an external
electromagnetic field, the latter becomes anomalous, and predicts novel
conduction properties for these materials.Comment: New material added. ReVTeX , 31 pgs., 4 figs.(uses epsf
decay from Infrared Lorentz Symmetry Violation
Lorentz symmetry forbids decays of massive spin-1 particle like the
into two massless photons, a result known as the Landau-Yang theorem. But it is
known that infrared effects can break Lorentz invariance. Employing the
construction of Mund et. al. \cite{MRS} which incorporated this Lorentz
violation, we propose an interaction leading to the decay and study the dependence of the decay on the parameter of this Lorentz
violation.Comment: 12 pages, 2 figure
Violation of the Landau-Yang theorem from infrared Lorentz symmetry breaking
Lorentz symmetry forbids decays of massive spin-1 particle like the Z0 into two massless photons, a result known as the Landau-Yang theorem. But it is known that infrared effects can break Lorentz invariance. Employing the construction of Mund et al. [1] which incorporated this Lorentz violation, we propose an interaction leading to the decay Z0â 2Îł and study the dependence of the decay on the parameter of this Lorentz violation
Morphological Classification of Radio Galaxies using Semi-Supervised Group Equivariant CNNs
Out of the estimated few trillion galaxies, only around a million have been
detected through radio frequencies, and only a tiny fraction, approximately a
thousand, have been manually classified. We have addressed this disparity
between labeled and unlabeled images of radio galaxies by employing a
semi-supervised learning approach to classify them into the known
Fanaroff-Riley Type I (FRI) and Type II (FRII) categories. A Group Equivariant
Convolutional Neural Network (G-CNN) was used as an encoder of the
state-of-the-art self-supervised methods SimCLR (A Simple Framework for
Contrastive Learning of Visual Representations) and BYOL (Bootstrap Your Own
Latent). The G-CNN preserves the equivariance for the Euclidean Group E(2),
enabling it to effectively learn the representation of globally oriented
feature maps. After representation learning, we trained a fully-connected
classifier and fine-tuned the trained encoder with labeled data. Our findings
demonstrate that our semi-supervised approach outperforms existing
state-of-the-art methods across several metrics, including cluster quality,
convergence rate, accuracy, precision, recall, and the F1-score. Moreover,
statistical significance testing via a t-test revealed that our method
surpasses the performance of a fully supervised G-CNN. This study emphasizes
the importance of semi-supervised learning in radio galaxy classification,
where labeled data are still scarce, but the prospects for discovery are
immense.Comment: 9 pages, 6 figures, accepted in INNS Deep Learning Innovations and
Applications (INNS DLIA 2023) workshop, IJCNN 2023, to be published in
Procedia Computer Scienc
Domain Formation in Finite-Time Quenches
We study the formation of domains in a continuous phase transition with a
finite-temperature quench. The model treated is the theory in two
spatial dimensions with global O(2) symmetry. We investigate this using
real-time thermal field theory, following Boyanovsky and collaborators, and
find that domain sizes appear to be smaller than those produced in an
instantaneous quench in the tree-level approximation. We also propose that a
more physical picture emerges by examining the two-point functions which do not
involve any cutoff on the short wavelength Goldstone modes.Comment: Revtex, 16 pages, 5 figures, Minor change
Heavy Quark Solitons
We investigate the heavy baryons which arise as solitonic excitations in a
``heavy meson" chiral Lagrangian which includes the light vector particles. It
is found that the effect of the light vectors may be substantial. We also
present a simple derivation which clearly shows the connection to the
Callan-Klebanov approach.Comment: 13 pages; LaTex; SU-4240-532; UR 1306/ER-40685-755 (Minor typos
corrected
Heavy Quark Solitons: Strangeness and Symmetry Breaking
We discuss the generalization of the Callan-Klebanov model to the case of
heavy quark baryons. The light flavor group is considered to be and the
limit of heavy spin symmetry is taken. The presence of the Wess-Zumino-Witten
term permits the neat development of a picture , at the collective level, of a
light diquark bound to a ``heavy" quark with decoupled spin degree of freedom.
The consequences of symmetry breaking are discussed in detail. We point
out that the mass splittings of the heavy baryons essentially measure
the ``low energy" physics once more and that the comparison with experiment is
satisfactory.Comment: 17 pages, RevTEX. Minor typos corrected and new references adde