29 research outputs found
Heun Functions and the energy spectrum of a charged particle on a sphere under magnetic field and Coulomb force
We study the competitive action of magnetic field, Coulomb repulsion and
space curvature on the motion of a charged particle. The three types of
interaction are characterized by three basic lengths: l_{B} the magnetic
length, l_{0} the Bohr radius and R the radius of the sphere. The energy
spectrum of the particle is found by solving a Schr\"odinger equation of the
Heun type, using the technique of continued fractions. It displays a rich set
of functioning regimes where ratios \frac{R}{l_{B}} and \frac{R}{l_{0}} take
definite values.Comment: 12 pages, 5 figures, accepted to JOPA, november 200
Structure of Higher Spin Gauge Interactions
In a previous paper, higher spin gauge field theory was formulated in an
abstract way, essentially only keeping enough machinery to discuss "gauge
invariance" of an "action". The approach could be thought of as providing an
interface (or syntax) towards an implementation (or semantics) yet to be
constructed. The structure then revealed turns out to be that of a strongly
homotopy Lie algebra.
In the present paper, the framework will be connected to more conventional
field theoretic concepts. The Fock complex vertex operator implementation of
the interactions in the BRST-BV formulation of the theory will be elaborated.
The relation between the vertex order expansion and homological perturbation
theory will be clarified. A formal non-obstruction argument is reviewed. The
syntactically derived sh-Lie algebra structure is semantically mapped to the
Fock complex implementation and it is shown that the recursive equations
governing the higher order vertices are reproduced.
Global symmetries and subsidiary conditions are discussed and as a result the
tracelessness constraints are discarded. Thus all equations needed to compute
the vertices to any order are collected. The framework is general enough to
encompass all possible interaction terms.
Finally, the abstract framework itself will be strengthened by showing that
it can be naturally phrased in terms of the theory of categories.Comment: A few changes and additions made in the Introduction. Three
references added. Typos corrected. Text agrees with published version in J.
Math. Phys. except for minor journal specific proof-reading changes. 61 page
Top quark physics in hadron collisions
The top quark is the heaviest elementary particle observed to date. Its large
mass makes the top quark an ideal laboratory to test predictions of
perturbation theory concerning heavy quark production at hadron colliders. The
top quark is also a powerful probe for new phenomena beyond the Standard Model
of particle physics. In addition, the top quark mass is a crucial parameter for
scrutinizing the Standard Model in electroweak precision tests and for
predicting the mass of the yet unobserved Higgs boson. Ten years after the
discovery of the top quark at the Fermilab Tevatron top quark physics has
entered an era where detailed measurements of top quark properties are
undertaken. In this review article an introduction to the phenomenology of top
quark production in hadron collisions is given, the lessons learned in Tevatron
Run I are summarized, and first Run II results are discussed. A brief outlook
to the possibilities of top quark research a the Large Hadron Collider,
currently under construction at CERN, is included.Comment: 84 pages, 32 figures, accepted for publication by Reports on Progress
in Physic
A Pedagogical Review of Electroweak Symmetry Breaking Scenarios
We review different avenues of electroweak symmetry breaking explored over
the years. This constitutes a timely exercise as the world's largest and the
highest energy particle accelerator, namely, the Large Hadron Collider (LHC) at
CERN near Geneva, has started running whose primary mission is to find the
Higgs or some phenomena that mimic the effects of the Higgs, i.e. to unravel
the mysteries of electroweak phase transition. In the beginning, we discuss the
Standard Model Higgs mechanism. After that we review the Higgs sector of the
Minimal Supersymmetric Standard Model. Then we take up three relatively recent
ideas: Little Higgs, Gauge-Higgs Unification, and Higgsless scenarios. For the
latter three cases, we first present the basic ideas and restrict our
illustration to some instructive toy models to provide an intuitive feel of the
underlying dynamics, and then discuss, for each of the three cases, how more
realistic scenarios are constructed and how to decipher their experimental
signatures. Wherever possible, we provide enough pedagogical details, which the
beginners might find useful.Comment: 45 pages, Review based on a series of lectures; v2: 63 pages,
substantially expanded, references added, to appear in `Reports on Progress
in Physics