8,546 research outputs found
Calculation of transition probabilities and ac Stark shifts in two-photon laser transitions of antiprotonic helium
Numerical ab initio variational calculations of the transition probabilities
and ac Stark shifts in two-photon transitions of antiprotonic helium atoms
driven by two counter-propagating laser beams are presented. We found that
sub-Doppler spectroscopy is in principle possible by exciting transitions of
the type (n,L)->(n-2,L-2) between antiprotonic states of principal and angular
momentum quantum numbers n~L-1~35, first by using highly monochromatic,
nanosecond laser beams of intensities 10^4-10^5 W/cm^2, and then by tuning the
virtual intermediate state close (e.g., within 10-20 GHz) to the real state
(n-1,L-1) to enhance the nonlinear transition probability. We expect that ac
Stark shifts of a few MHz or more will become an important source of systematic
error at fractional precisions of better than a few parts in 10^9. These shifts
can in principle be minimized and even canceled by selecting an optimum
combination of laser intensities and frequencies. We simulated the resonance
profiles of some two-photon transitions in the regions n=30-40 of the
\bar{p}^4He^+ and \bar{p} ^3He^+ isotopes to find the best conditions that
would allow this.Comment: 18 pages 2 tables 12 figures, submitted to Phys. Rev.
Electroweak Sudakov at two loop level
We investigate the Sudakov double logarithmic corrections to the form factor
of fermion in the SU(2)XU(1) electroweak theory. We adopt the familiar Feynman
gauge and present explicit calculations at the two loop level. We show that the
leading logarithmic corrections coming from the infrared singularities are
consistent with the "postulated" exponentiated electroweak Sudakov form factor.
The similarities and differences in the "soft" physics between the electroweak
theory and the unbroken non-abelian gauge theory (QCD) will be clarified.Comment: 8 pages, 14 figure
Non-compact Mirror Bundles and (0,2) Liouville Theories
We study (0,2) deformations of N=2 Liouville field theory and its mirror
duality. A gauged linear sigma model construction of the ultraviolet theory
connects (0,2) deformations of Liouville field theory and (0,2) deformations of
N=2 SL(2,R)/U(1) coset model as a mirror duality. Our duality proposal from the
gauged linear sigma model completely agrees with the exact CFT analysis. In the
context of heterotic string compactifications, the deformation corresponds to
the introduction of a non-trivial gauge bundle. This non-compact
Landau-Ginzburg construction yields a novel way to study the gauge bundle
moduli for non-compact Calabi-Yau manifolds.Comment: 34 page
D-brane Categories for Orientifolds -- The Landau-Ginzburg Case
We construct and classify categories of D-branes in orientifolds based on
Landau-Ginzburg models and their orbifolds. Consistency of the worldsheet
parity action on the matrix factorizations plays the key role. This provides
all the requisite data for an orientifold construction after embedding in
string theory. One of our main results is a computation of topological field
theory correlators on unoriented worldsheets, generalizing the formulas of Vafa
and Kapustin-Li for oriented worldsheets, as well as the extension of these
results to orbifolds. We also find a doubling of Knoerrer periodicity in the
orientifold context.Comment: 45 pages, 6 figure
Collective oscillation period of inter-coupled biological negative cyclic feedback oscillators
A number of biological rhythms originate from networks comprised of multiple
cellular oscillators. But analytical results are still lacking on the
collective oscillation period of inter-coupled gene regulatory oscillators,
which, as has been reported, may be different from that of an autonomous
oscillator. Based on cyclic feedback oscillators, we analyze the collective
oscillation pattern of coupled cellular oscillators. First we give a condition
under which the oscillator network exhibits oscillatory and synchronized
behavior. Then we estimate the collective oscillation period based on a novel
multivariable harmonic balance technique. Analytical results are derived in
terms of biochemical parameters, thus giving insight into the basic mechanism
of biological oscillation and providing guidance in synthetic biology design.Comment: arXiv admin note: substantial text overlap with arXiv:1203.125
Strings on pp-waves and massive two dimensional field theories
We find a general class of pp-wave solutions of type IIB string theory such
that the light cone gauge worldsheet lagrangian is that of an interacting
massive field theory. When the light cone Lagrangian has (2,2) supersymmetry we
can find backgrounds that lead to arbitrary superpotentials on the worldsheet.
We consider situations with both flat and curved transverse spaces. We describe
in some detail the background giving rise to the N=2 sine Gordon theory on the
worldsheet. Massive mirror symmetry relates it to the deformed model (or
sausage model) which seems to elude a purely supergravity target space
interpretation.Comment: harvmac, 26 pages, v2,3: references added, typos correcte
Dipole trap model for the metallic state in gated silicon-inversion layers
In order to investigate the metallic state in high-mobility Si-MOS
structures, we have further developed and precised the dipole trap model which
was originally proposed by B.L. Altshuler and D.L. Maslov [Phys. Rev. Lett.\
82, 145 (1999)]. Our additional numerical treatment enables us to drop several
approximations and to introduce a limited spatial depth of the trap states
inside the oxide as well as to include a distribution of trap energies. It
turns out that a pronounced metallic state can be caused by such trap states at
appropriate energies whose behavior is in good agreement with experimental
observations.Comment: 16 pages, 10 figures, submitte
Leaf spring made of fiber-reinforced resin
A leaf spring made of a matrix reinforced by at least two types of reinforcing fibers with different Young's modulus is described in this Japanese patent. At least two layers of reinforcing fibers are formed by partially arranging the reinforcing fibers toward the direction of the thickness of the leaf spring. A mixture of different types of reinforced fibers is used at the area of boundary between the two layers of reinforced fibers. The ratio of blending of each type of reinforced fiber is frequently changed to eliminate the parts where discontinuous stress may be applied to the leaf spring. The objective of this invention is to prevent the rapid change in Young's modulus at the boundary area between each layer of reinforced fibers in the leaf spring
Physics at CERN's Antiproton Decelerator
The Antiproton Decelerator of CERN began operation in 1999 to serve
experiments for studies of CPT invariance by precision laser and microwave
spectroscopy of antihydrogen () and antiprotonic helium
(). The first 12 years of operation saw cold
synthesized by overlapping clouds of positrons () and antiprotons
() confined in magnetic Penning traps. Cold was also
produced in collisions between Rydberg positronium atoms and .
Ground-state was later trapped for up to s in a
magnetic bottle trap, and microwave transitions excited between its hyperfine
levels. In the atom, UV transitions were measured to a
precision of (2.3-5) by sub-Doppler two-photon laser
spectroscopy. From this the antiproton-to-electron mass ratio was determined as
1836.1526736(23), which agrees with the p value. Microwave
spectroscopy of yielded a measurement of the
magnetic moment with a precision of 0.3%. More recently the magnetic moment of
a single confined in a Penning trap was measured with a higher
precision, as in nuclear
magnetons. Other measurements include the energy loss of 1-100 keV
traversing conductor and insulator targets; the cross sections of <10 keV
ionizing gas targets; and the cross sections of 5-MeV
annihilating on target foils via nuclear collisions. The biological
effectiveness of beams destroying cancer cells was measured as a
possible method for radiological therapy. New experiments under preparation
attempt to measure the gravitational acceleration of or
synthesize \obar{\rm H}^+.Comment: To be published in Progress in Particle and Nuclear Physic
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