93 research outputs found
Relativistic corrections to the long range interaction between closed shell atoms
The complete correction to the long range interaction between
neutral closed shell atoms is obtained, the relation to the asymptotic
expansion of the known short range interaction at the atomic scale is presented
and a general interaction potential which is valid in the whole range of the
inter atomic distances is constructed.Comment: 9 pages, accepted for Phys. Rev.
Dipole Excitation of Dipositronium
The energy interval between the ground and the P-wave excited states of the
recently discovered positronium molecule Ps_2 is evaluated, including the
relativistic and the leading logarithmic radiative corrections, E_P-E_S = 0.181
586 7(8) a.u. The P-state, decaying usually via annihilation, is found to decay
into the ground state by an electric dipole transition 19 percent of the time.
Anticipated observation of this transition will provide insight into this
exotic system.Comment: 5 page
Dispersion representations and anomalous singularities of the triangle diagram
We discuss dispersion representations for the triangle diagram
, the single dispersion representation in and the
double dispersion representation in and , with special emphasis
on the appearance of the anomalous singularities and the anomalous cuts in
these representations. For the double dispersion representation in and
, the appearance of the anomalous cut in the region is
demonstrated, and a new derivation of the anomalous double spectral density is
given. We point out that the double spectral representation is particularly
suitable for applications in the region of and/or above the
two-particle thresholds. The dispersion representations for the triangle
diagram in the nonrelativistic limit are studied and compared with the triangle
diagram of the nonrelativistic field theory.Comment: 10 pages, revtex, added a reference, version to be published in Phys.
Rev.
Quadrupolar contact terms and Hyperfine Structure
In the interaction of two electric quadrupoles, there is at short distances a
contact term proportional to the second derivative of a delta function. This
contact term contributes to the hyperfine splitting of bound states of two
particles with spin one or higher-for example the bound states of Omega minus
and a nucleus of spin one.The contact hyperfine splitting occurs in states with
orbital angular momentum one(p-wave), in contrast to the Fermi contact
interaction which is in s-states.We find that these contact splittings will be
observable with Omega minus atoms and help measure the quadrupole moment and
charge radius of the hyperon.Comment: 19 pages; two sentences deleted from first versio
Synchrotron radiation by fast fermions in heavy-ion collisions
We study the synchrotron radiation of gluons by fast quarks in strong
magnetic field produced by colliding relativistic heavy-ions. We argue that due
to high electric conductivity of plasma, time variation of the magnetic field
is slow and estimate its relaxation time. We calculate the energy loss due to
synchrotron radiation of gluons by fast quarks. We find that the typical energy
loss per unit length for a light quark at LHC is a few GeV per fm. This effect
alone predicts quenching of jets with up to about 20 GeV. We also show
that the spin-flip transition effect accompanying the synchrotron radiation
leads to a strong polarization of quarks and leptons with respect to the
direction of the magnetic field. Observation of the lepton polarization may
provide a direct evidence of existence of strong magnetic field in heavy-ion
collisions.Comment: 10 pages, 6 figures; v3: estimate of the relaxation time of magnetic
field is revised, acknowledgment adde
Coulomb problem for vector bosons versus Standard Model
The Coulomb problem for vector bosons W(+/-) propagating in an attractive
Coulomb field incorporates a known difficulty, i.e. the total charge of the
boson localized on the Coulomb center turns out infinite. This fact contradicts
the renormalizability of the Standard model, which presumes that at small
distances all physical quantities are well defined. The paradox is shown to be
resolved by the QED vacuum polarization, which brings in a strong effective
repulsion and eradicates the infinite charge of the boson on the Coulomb
center. The effect makes the Coulomb problem for vector bosons well defined and
consistent with the Standard Model.Comment: 4 page
Classical Noncommutative Electrodynamics with External Source
In a -noncommutative (NC) gauge field theory we extend the
Seiberg-Witten (SW) map to include the (gauge-invariance-violating) external
current and formulate - to the first order in the NC parameter -
gauge-covariant classical field equations. We find solutions to these equations
in the vacuum and in an external magnetic field, when the 4-current is a static
electric charge of a finite size , restricted from below by the elementary
length. We impose extra boundary conditions, which we use to rule out all
singularities, included, from the solutions. The static charge proves to
be a magnetic dipole, with its magnetic moment being inversely proportional to
its size . The external magnetic field modifies the long-range Coulomb field
and some electromagnetic form-factors. We also analyze the ambiguity in the SW
map and show that at least to the order studied here it is equivalent to the
ambiguity of adding a homogeneous solution to the current-conservation
equation
Quantum Theory and Galois Fields
We discuss the motivation and main results of a quantum theory over a Galois
field (GFQT). The goal of the paper is to describe main ideas of GFQT in a
simplest possible way and to give clear and simple arguments that GFQT is a
more natural quantum theory than the standard one. The paper has been prepared
as a presentation to the ICSSUR' 2005 conference (Besancon, France, May 2-6,
2005).Comment: Latex, 24 pages, 1 figur
Non-Linear Compton Scattering of Ultrashort and Ultraintense Laser Pulses
The scattering of temporally shaped intense laser pulses off electrons is
discussed by means of manifestly covariant quantum electrodynamics. We employ a
framework based on Volkov states with a time dependent laser envelope in
light-cone coordinates within the Furry picture. An expression for the cross
section is constructed, which is independent of the considered pulse shape and
pulse length. A broad distribution of scatted photons with a rich pattern of
subpeaks like that obtained in Thomson scattering is found. These broad peaks
may overlap at sufficiently high laser intensity, rendering inappropriate the
notion of individual harmonics. The limit of monochromatic plane waves as well
as the classical limit of Thomson scattering are discussed. As a main result, a
scaling law is presented connecting the Thomson limit with the general result
for arbitrary kinematics. In the overlapping regions of the spectral density,
the classical and quantum calculations give different results, even in the
Thomson limit. Thus, a phase space region is identified where the differential
photon distribution is strongly modified by quantum effects.Comment: 31 pages, 10 figure
Relativistic Coulomb problem for particles with arbitrary half-integer spin
Using relativistic tensor-bispinorial equations proposed in hep-th/0412213 we
solve the Kepler problem for a charged particle with arbitrary half-integer
spin interacting with the Coulomb potential.Comment: Misprints are correcte
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