3,409 research outputs found
Mutants and SU(3)_q invariants
Details of quantum knot invariant calculations using a specific
SU(3)_q-module are given which distinguish the Conway and Kinoshita-Teresaka
pair of mutant knots. Features of Kuperberg's skein-theoretic techniques for
SU(3)_q invariants in the context of mutant knots are also discussed.Comment: 17 pages. Published copy, also available at
http://www.maths.warwick.ac.uk/gt/GTMon1/paper18.abs.htm
Invariants of genus 2 mutants
Pairs of genus 2 mutant knots can have different Homfly polynomials, for
example some 3-string satellites of Conway mutant pairs. We give examples which
have different Kauffman 3-variable polynomials, answering a question raised by
Dunfield et al in their study of genus 2 mutants. While pairs of genus 2 mutant
knots have the same Jones polynomial, given from the Homfly polynomial by
setting v=s^2, we give examples whose Homfly polynomials differ when v=s^3. We
also give examples which differ in a Vassiliev invariant of degree 7, in
contrast to satellites of Conway mutant knots.Comment: 16 pages, 20 figure
Prediction of unstable crack length in aluminium alloys
A method was set down for predicting the unstable length of a
crack in a flat sheet of aluminium alloy subjected to a steady tensile
stress.
The basis of the method was to take the work done to failure in
the 'neck' region of a tensile test specimen and apply it, with a
suitable constraint factor, to the flat sheet to give the work rate
required to propagate the crack.
Experimental evidence is produced in support of the method
Prediction of unstable crack length in aluminium alloys
A method was set down for predicting the unstable length of a
crack in a flat sheet of aluminium alloy subjected to a steady tensile
stress.
The basis of the method was to take the work done to failure in
the 'neck' region of a tensile test specimen and apply it, with a
suitable constraint factor, to the flat sheet to give the work rate
required to propagate the crack.
Experimental evidence is produced in support of the method
Superfluid Helium Orbital Resupply Coupling
The resupply of superfluid helium to satellites and other space-based experiment packages can increase the useful longevity of these devices far beyond their present life expectancies which are many times determined by the supply of helium coolant. The transfer of superfluid helium to spacecraft in space will require a reusable coupling that functions at 1.8 Kelvin with little heat leak and low pressure drop. Moog has designed the Helium Resupply Coupling to meet these operational requirements. Initially, the coupling manual mode operation will be demonstrated on orbit by an EVA crew member during the Space Shuttle borne Superfluid Helium On-Orbit Transfer (SHOOT) experiment. The ultimate application will use robotic (automatic) coupling operation to which the present design readily adapts. The utilization of Moog's exclusive Rotary Shut-Off (RSO) technology in the development of the Superfluid Helium Resupply Coupling is described. The coupling not only performs the function of a flow control valve and disconnect but also provides adequate safety features for a shuttle launched man-rated payload. In addition, the coupling incorporates the necessary features to provide the high thermal isolation of the internal flow path from the external environment
Treating some solid state problems with the Dirac equation
The ambiguity involved in the definition of effective-mass Hamiltonians for
nonrelativistic models is resolved using the Dirac equation. The multistep
approximation is extended for relativistic cases allowing the treatment of
arbitrary potential and effective-mass profiles without ordering problems. On
the other hand, if the Schrodinger equation is supposed to be used, our
relativistic approach demonstrate that both results are coincidents if the
BenDaniel and Duke prescription for the kinetic-energy operator is implemented.
Applications for semiconductor heterostructures are discussed.Comment: 06 pages, 5 figure
Families of stable and metastable solitons in coupled system of scalar fields
In this paper, we obtain stable and metastable soliton solutions of a coupled
system of two real scalar fields with five five discrete points of vacua. These
solutions have definite topological charges and rest energies and show
classical dynamical stability. From a quantum point of view, however, the
V-type solutions are expected to be unstable and decay to D-type solutions. The
induced decay of a V-type soliton into two D-type ones is calculated
numerically, and shown to be chiral, in the sense that the decay products do
not respect left-right symmetry.Comment: 9 pages and 5 figure
Weak-localization and rectification current in non-diffusive quantum wires
We show that electron transport in disordered quantum wires can be described
by a modified Cooperon equation, which coincides in form with the Dirac
equation for the massive fermions in a 1+1 dimensional system. In this new
formalism, we calculate the DC electric current induced by electromagnetic
fields in quasi-one-dimensional rings. This current changes sign, from
diamagnetic to paramagnetic, depending on the amplitude and frequency of the
time-dependent external electromagnetic field.Comment: changed title, added more detail, to appear in J. Phys.: Condens.
Matte
Relations between Kauffman and Homfly satellite invariants
We extend a mod 2 relation between the Kauffman and Homfly polynomials, first
observed by Rudolph in 1987, to the general Kauffman and Homfly satellite
invariants.Comment: 9 page
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