43 research outputs found
Calculation of the positron bound state with the copper atom
A new relativistic method for calculation of positron binding to atoms is
presented. The method combines a configuration interaction treatment of the
valence electron and the positron with a many-body perturbation theory
description of their interaction with the atomic core. We apply this method to
positron binding by the copper atom and obtain the binding energy of 170 meV (+
- 10%). To check the accuracy of the method we use a similar approach to
calculate the negative copper ion. The calculated electron affinity is 1.218
eV, in good agreement with the experimental value of 1.236 eV. The problem of
convergence of positron-atom bound state calculations is investigated, and
means to improve it are discussed. The relativistic character of the method and
its satisfactory convergence make it a suitable tool for heavier atoms.Comment: 15 pages, 5 figures, RevTe
Multipositronic systems
The stability of Coulombic systems containing positrons are investigated by
the stochastic variational method. The existence of several new exotic atoms
are predicted, including HPse+, LiPs2e+, or (H-,Ps2). Similar systems
(replacing the positrons by holes) might be observed in semiconductors.Comment: Phys. Rev. Lett., in pres
Nonlinear dynamics of a solid-state laser with injection
We analyze the dynamics of a solid-state laser driven by an injected
sinusoidal field. For this type of laser, the cavity round-trip time is much
shorter than its fluorescence time, yielding a dimensionless ratio of time
scales . Analytical criteria are derived for the existence,
stability, and bifurcations of phase-locked states. We find three distinct
unlocking mechanisms. First, if the dimensionless detuning and
injection strength are small in the sense that , unlocking occurs by a saddle-node infinite-period bifurcation.
This is the classic unlocking mechanism governed by the Adler equation: after
unlocking occurs, the phases of the drive and the laser drift apart
monotonically. The second mechanism occurs if the detuning and the drive
strength are large: . In this regime, unlocking
is caused instead by a supercritical Hopf bifurcation, leading first to phase
trapping and only then to phase drift as the drive is decreased. The third and
most interesting mechanism occurs in the distinguished intermediate regime . Here the system exhibits complicated, but
nonchaotic, behavior. Furthermore, as the drive decreases below the unlocking
threshold, numerical simulations predict a novel self-similar sequence of
bifurcations whose details are not yet understood.Comment: 29 pages in revtex + 8 figs in eps. To appear in Phys. Rev. E
(scheduled tentatively for the issue of 1 Oct 98
Monopoles near the Planck Scale and Unification
Considering our (3+1)-dimensional space-time as, in some way, discrete or l
attice with a parameter , where is the Planck length,
we have investigated the additional contributions of lattice artifact monopoles
to beta-functions of the renormalisation group equations for the running fine
structure constants (i=1,2,3 correspond to the U(1), SU(2) and
SU(3) gauge groups of the Standard Model) in the Family Replicated Gauge Group
Model (FRGGM) which is an extension of the Standard Model at high energies. It
was shown that monopoles have times smaller magnetic charge in FRGGM
than in SM ( is the number of families in FRGGM). We have estimated al
so the enlargement of a number of fermions in FRGGM leading to the suppression
of the asymptotic freedom in the non-Abelian theory. We have shown that, in
contrast to the case of AntiGUT when the FRGGM undergoes the breakdown at
GeV, we have the possibility of unification if the
FRGGM-breakdown occurs at GeV. By numerical calculations we
obtained an example of the unification of all gauge interactions (including
gravity) at the scale GeV. We discussed the
possibility of or (SUSY or not SUSY) unifications.Comment: 49 pages, 7 figure