24,073 research outputs found
The Lyttleton-Bondi Universe and Charge Equality
Theoretical arguments on electron and proton charge magnitude equalit
Test of CPT and Lorentz invariance from muonium spectroscopy
Following a suggestion of Kostelecky et al. we have evaluated a test of CPT
and Lorentz invariance from the microwave spectroscopy of muonium. Hamiltonian
terms beyond the standard model violating CPT and Lorentz invariance would
contribute frequency shifts and to
and , the two transitions involving muon spin flip, which were
precisely measured in ground state muonium in a strong magnetic field of 1.7 T.
The shifts would be indicated by anti-correlated oscillations in and
at the earth's sidereal frequency. No time dependence was found in
or at the level of 20 Hz, limiting the size of some CPT
and Lorentz violating parameters at the level of GeV,
representing Planck scale sensitivity and an order of magnitude improvement in
sensitivity over previous limits for the muon.Comment: 4 pages, 4 figures, uses REVTeX and epsf, submitted to Phys. Rev.
Let
Sensitivity to new physics: a_e vs. a_mu
At present it is generally believed that ``new physics'' effects contribute
to leptonic anomalous magnetic moment, a_l, via quantum loops only and they are
proportional to the squared lepton mass, (m_l)^2. An alternative mechanism for
a contribution by new physics is proposed. It occurs at the tree level and
exhibits a linear rather than quadratic dependence on m_l. This leads to a much
larger sensitivity of a_e to the new physics than was expected so far.Comment: 4 pages, 2 figure
Variational Two Fermion Wave Equations in QED: Muonium Like Systems
We consider a reformulation of QED in which covariant Green functions are
used to solve for the electromagnetic field in terms of the fermion fields. The
resulting modified Hamiltonian contains the photon propagator directly. A
simple Fock-state variational trial function is used to derive relativistic
two-fermion equations variationally from the expectation value of the
Hamiltonian of the field theory. The interaction kernel of the equation is
shown to be, in essence, the invariant M-matrix in lowest order. Solutions of
the two-body equations are presented for muonium like system for small coupling
strengths. The results compare well with the observed muonium spectrum, as well
as that for hydrogen and muonic hydrogen. Anomalous magnetic moment effects are
discussed
The effects of disturbance threat on leaf-cutting ant colonies: a laboratory study
The flexibility of organisms to respond plastically to their environment is fundamental to their fitness and evolutionary success. Social insects provide some of the most impressive examples of plasticity, with individuals exhibiting behavioural and sometimes morphological adaptations for their specific roles in the colony, such as large soldiers for nest defence. However, with the exception of the honey bee model organism, there has been little investigation of the nature and effects of environmental stimuli thought to instigate alternative phenotypes in social insects. Here we investigate the effect of repeated threat disturbance over a prolonged (17 month) period on both behavioural and morphological phenotypes, using phenotypically plastic leaf-cutting ants (Atta colombica) as a model system. We found a rapid impact of threat disturbance on the behavioural phenotype of individuals within threat-disturbed colonies becoming more aggressive, threat-responsive and phototactic within as little as two weeks. We found no effect of threat disturbance on morphological phenotypes, potentially because constraints such as resource limitation outweighed the benefit for colonies of producing larger individuals. The results suggest that plasticity in behavioural phenotypes can enable insect societies to respond to threats even when constraints prevent alteration of morphological phenotypes
Anomalous biased diffusion in a randomly layered medium
We present analytical results for the biased diffusion of particles moving
under a constant force in a randomly layered medium. The influence of this
medium on the particle dynamics is modeled by a piecewise constant random
force. The long-time behavior of the particle position is studied in the frame
of a continuous-time random walk on a semi-infinite one-dimensional lattice. We
formulate the conditions for anomalous diffusion, derive the diffusion laws and
analyze their dependence on the particle mass and the distribution of the
random force.Comment: 19 pages, 1 figur
Atomic beam source of polarized electrons
Polarized electrons produced by atomic beam apparatus - hyperfine structure intervals of alkali atom
Celestial mechanics in Kerr spacetime
The dynamical parameters conventionally used to specify the orbit of a test
particle in Kerr spacetime are the energy , the axial component of the
angular momentum, , and Carter's constant . These parameters are
obtained by solving the Hamilton-Jacobi equation for the dynamical problem of
geodesic motion. Employing the action-angle variable formalism, on the other
hand, yields a different set of constants of motion, namely, the fundamental
frequencies , and associated with
the radial, polar and azimuthal components of orbital motion. These
frequencies, naturally, determine the time scales of orbital motion and,
furthermore, the instantaneous gravitational wave spectrum in the adiabatic
approximation. In this article, it is shown that the fundamental frequencies
are geometric invariants and explicit formulas in terms of quadratures are
derived. The numerical evaluation of these formulas in the case of a rapidly
rotating black hole illustrates the behaviour of the fundamental frequencies as
orbital parameters such as the semi-latus rectum , the eccentricity or
the inclination parameter are varied. The limiting cases of
circular, equatorial and Keplerian motion are investigated as well and it is
shown that known results are recovered from the general formulas.Comment: 25 pages (LaTeX), 5 figures, submitted to Class. Quantum Gra
Supersymmetry and LHC
The motivation for introduction of supersymmetry in high energy physics as
well as a possibility for supersymmetry discovery at LHC (Large Hadronic
Collider) are discussed. The main notions of the Minimal Supersymmetric
Standard Model (MSSM) are introduced. Different regions of parameter space are
analyzed and their phenomenological properties are compared. Discovery
potential of LHC for the planned luminosity is shown for different channels.
The properties of SUSY Higgs bosons are studied and perspectives of their
observation at LHC are briefly outlined.Comment: Lectures given at the 9th Moscow International School of Physics
(XXXIV ITEP Winter School of Physics
The integral of the spin-dependent structure function g1p and the Ellis-Jaffe sum rule
Hughes VW, Papavassiliou V, Piegaia R, Schüler KP, Baum G. The integral of the spin-dependent structure function g1p and the Ellis-Jaffe sum rule. Phys.Lett. B. 1988;212(4):511-514
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