26,046 research outputs found
E_11 and M Theory
We argue that eleven dimensional supergravity can be described by a
non-linear realisation based on the group E_{11}. This requires a formulation
of eleven dimensional supergravity in which the gravitational degrees of
freedom are described by two fields which are related by duality. We show the
existence of such a description of gravity.Comment: 21 pages, some typos corrected and two references adde
Anomalous isotopic predissociation in the F³Πu(v=1) state of O₂
Using a tunable, narrow-bandwidth vacuum-ultraviolet source based on third-harmonic generation from excimer-pumped dye-laser radiation, the F³Πu←X³Σg-(1,0)photoabsorption cross sections of ¹⁶O₂ and ¹⁸O₂ have been recorded in high resolution. Rotational analyses have been performed and the resultant F(v=1) term values fitted to the ³Π Hamiltonian of Brown and Merer [J. Mol. Spectrosc. 74, 488 (1979)]. A large rotationless isotope effect is observed in the F(v=1)predissociation, wherein the Lorentzian linewidth component for ¹⁸O₂ is a factor of ∼50 smaller than the corresponding ¹⁶O₂linewidth. This effect, a consequence of the nonadiabatic rotationless predissociation mechanism, is described using a coupled-channel treatment of the strongly Rydberg-valence-mixed 3Πu states. Significant J, e/f-parity, and sublevel dependencies observed in the isotopic F(v=1) rotational widths are found to derive from an indirect predissociation mechanism involving an accidental degeneracy with the E³Σ−u(v=3) level, itself strongly predissociated by ³Σ−u Rydberg-valence interactions, together with L-uncoupling (rotational) interactions between the Rydberg components of the F and E states. Transitions into the E(v=3) level are observed directly for the first time, specifically in the ¹⁸O₂ spectrumPartial support
was provided by an NSF International Opportunities for Scientists
and Engineers Program Grant No. INT-9513350, and
Visiting Fellowships for G.S. and J.B.W. at the Australian
National University
Accelerator dynamics of a fractional kicked rotor
It is shown that the Weyl fractional derivative can quantize an open system.
A fractional kicked rotor is studied in the framework of the fractional
Schrodinger equation. The system is described by the non-Hermitian Hamiltonian
by virtue of the Weyl fractional derivative. Violation of space symmetry leads
to acceleration of the orbital momentum. Quantum localization saturates this
acceleration, such that the average value of the orbital momentum can be a
direct current and the system behaves like a ratchet. The classical counterpart
is a nonlinear kicked rotor with absorbing boundary conditions.Comment: Submitted for publication in Phys. Rev.
On the relation between nuclear and nucleon Structure Functions and their moments
Calculations of nuclear Structure Functions (SF) F_k^A(x,Q^2) routinely
exploit a generalized convolution, involving the SF for nucleons F_k^N and the
linking SF f^{PN,A} of a fictitious nucleus, composed of point-particles, with
the latter usually expressed in terms of hadronic degrees of freedom. For
finite Q^2 the approach seemed to be lacking a solid justification and the same
is the case for recently proposed, effective nuclear parton distribution
functions (pdf), which exactly reproduce the above-mentioned hadronically
computed F_k^A. Many years ago Jaffe and West proved the above convolution in
the Plane Wave Impulse Approximation (PWIA) for the nuclear components in the
convolution. In the present note we extend the above proof to include classes
of nuclear Final State Interactions (FSI). One and the same function appears to
relate parton distribution functions (pdf) in nuclei and nucleons, and SF for
nuclear targets and for nucleons. That relation is the previously conjectured
one,with an entirely different interpretation of f^{PN,A}. We conclude with an
extensive analysis of moments of nuclear SF based on the generalized
convolution. Characteristics of those moments are shown to be quite similar to
the same for a nucleon. We conclude that the above evidences asymptotic freedom
of a nucleon in a medium and not of a composite nucleus.Comment: 18 pages, 9 figure
Remarks on E11 approach
We consider a few topics in approach to superstring/M-theory: even
subgroups ( orbifolds) of , n=11,10,9 and their connection to
Kac-Moody algebras; subgroup of and coincidence of one of
its weights with the weight of , known to contain brane charges;
possible form of supersymmetry relation in ; decomposition of
w.r.t. the and its square root at first few levels; particle orbit
of . Possible relevance of coadjoint orbits method is
noticed, based on a self-duality form of equations of motion in .Comment: Two references adde
DEKAS - An evolutionary case-based reasoning system to support protection scheme design
This paper describes a decision support system being developed in conjunction with two UK utility companies to aid the design of electrical power transmission protection systems. A brief overview of the application domain is provided, followed by a description of the work carried out to date concerning the development and deployment of the Design Engineering Knowledge Application System (DEKAS). The paper then discusses the provision of intelligent decision support to the design engineer through the application of case-based reasoning (CBR). The key benefits from this will be outlined in conjunction with a relevant case study
Tortuous ways to the extraction of neutron observables from inclusive lepton scattering
We analyze new JLAB data for inclusive electron scattering on various
targets. Computed and measured total inclusive cross sections in the range
show on a logarithmic scale reasonable agreement
for all targets. However, closer inspection of the Quasi-Elastic components
bares serious discrepancies. EMC ratios which may contain less systematic
errors fare the same. The above observations for the new data do not enable the
extraction of the magnetic form factor (FF) and the Structure Function
(SFs) of the neutron, although the application of exactly the same
analysis to older data had been successful. We add to the above analysis older
CLAS collaboration on . Removing some scattered points, it appears
possible to obtain the above mentioned neutron information. We compare our
results with others from alternative sources. Particular attention is paid to
the A=3 iso-doublet. Present data exist only for He, but the available
input and charge symmetry also enable computations for H. Their average is
the computed iso-scalar part and is compared with the empirical modification of
He towards a fictitious A=3 iso-singlet.Comment: 27 pages, 30 figure
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