1,126,575 research outputs found

### Furry picture transition rates in the intense fields at a lepton collider interaction point

The effect on particle physics processes by intense electromagnetic fields in
the charge bunch collisions at future lepton colliders is considered. Since the
charge bunch fields are tied to massive sources (the $e^{+}e^{-}$ charges), a
reference frame is chosen in which the fields appear to be co-propagating.
Solutions of the Dirac equation minimally coupled to the electromagnetic fields
reasonably associated with two intense overlapping charge bunches are obtained
and found to be a Volkov solution with respect to a null 4-vector whose
3-vector part lies in the common propagation direction. These solutions are
used within the Furry interaction picture to calculate the beamstrahlung
transition rate for electron radiation due to interaction with the
electromagnetic fields of two colliding charge bunches. New analytic
expressions are obtained and compared numerically with the beamstrahlung in the
electromagnetic field of one charge bunch. The techniques developed will be
applied to other collider physics processes in due course.Comment: 7 pages, 5 figures, Phys Lett B preprin

### An Informal Summary of a New Formalism for Classifying Spin-Orbit Systems Using Tools Distilled from the Theory of Bundles

We give an informal summary of ongoing work which uses tools distilled from
the theory of fibre bundles to classify and connect invariant fields associated
with spin motion in storage rings. We mention four major theorems. One ties
invariant fields with the notion of normal form, the second allows comparison
of different invariant fields and the two others tie the existence of invariant
fields to the existence of certain invariant sets. We explain how the theorems
apply to the spin dynamics of spin-$1/2$ and spin-$1$ particles. Our approach
elegantly unifies the spin-vector dynamics from the T-BMT equation with the
spin-tensor dynamics and other dynamics and suggests an avenue for addressing
the question of the existence of the invariant spin field.Comment: Based on a presentation at Spin2014, The 21st International Symposium
on Spin Physics, Beijing, China, October 2014. To be published in the
International Journal of Modern Physics, Conference Serie

### A New Principle in Physics: the Principle of "Finiteness", and Some Consequences

In this paper I propose a new principle in physics: the principle of
"finiteness". It stems from the definition of physics as a science that deals
(among other things) with measurable dimensional physical quantities. Since
measurement results, including their errors, are always finite, the principle
of finiteness postulates that the mathematical formulation of "legitimate" laws
of physics should prevent exactly zero or infinite solutions. Some consequences
of the principle of finiteness are discussed, in general, and then more
specifically in the fields of special relativity, quantum mechanics, and
quantum gravity. The consequences are derived independently of any other theory
or principle in physics. I propose "finiteness" as a postulate (like the
constancy of the speed of light in vacuum, "c"), as opposed to a notion whose
validity has to be corroborated by, or derived theoretically or experimentally
from other facts, theories, or principles.Comment: 13 pages, 0 figure

### Frontiers of Astrophysics - Workshop Summary

We summarize recent results presented in the astrophysics session during a
conference on ``Frontiers of Contemporary Physics''. We will discuss three main
fields (High-Energy Astrophysics, Relativistic Astrophysics, and Cosmology),
where Astrophysicists are pushing the limits of our knowledge of the physics of
the universe to new frontiers. Since the highlights of early 1997 were the
first detection of a redshift and the optical and X-ray afterglows of gamma-ray
bursts, as well as the first well-documented flares of TeV-Blazars across a
large fraction of the electromagnetic spectrum, we will concentrate on these
topics. Other topics covered are black holes and relativistic jets, high-energy
cosmic rays, Neutrino-Astronomy, extragalactic magnetic fields, and
cosmological models.Comment: Proceedings of the Workshop "Frontiers in Contemporary Physics",
Nashville, May 11-16, 1997, AIP-conference series, Ed. T. Weiler & R.
Panvini, LaTex(aip2col), 13 pages, preprint also available at
http://www.astro.umd.edu/~hfalcke/publications.html#frontier

### Few-Body Problems in Hadron Spectroscopy

Some rigorous results can be derived using a very simple approach to hadron
spectroscopy, in which a static potential is associated with non-relativistic
kinematics. Several regularities of the experimental spectrum are explained by
such models. It is underlined that certain methods developed for hadronic
physics have found applications in other fields, in particular atomic physics.
A few results can be extended to cases involving spin-dependent forces or
relativistic kinematics.Comment: Latex with espcrc1, Invited Talk at the 17th European Conference on
Few-Body Physics, 11--16 September 2000, Evora, Portugal, to appear in
Nuclear Physics A. Misprint corrected p.2, thanks to A. Ga

### Spin-3 Chromium Bose-Einstein Condensates

We analyze the physics of spin-3 Bose-Einstein condensates, and in particular
the new physics expected in on-going experiments with condensates of Chromium
atoms. We first discuss the ground-state properties, which, depending on still
unknown Chromium parameters, and for low magnetic fields can present various
types of phases. We also discuss the spinor-dynamics in Chromium spinor
condensates, which present significant qualitative differences when compared to
other spinor condensates. In particular, dipole-induced spin relaxation may
lead for low magnetic fields to transfer of spin into angular momentum similar
to the well-known Einstein-de Haas effect. Additionally, a rapid large
transference of population between distant magnetic states becomes also
possible.Comment: 4 pages, 3 eps figures. Error in the previous version correcte

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