408,608 research outputs found
Symmetry Principles for String Theory
The gauge symmetries that underlie string theory arise from inner
automorphisms of the algebra of observables of the associated conformal field
theory. In this way it is possible to study broken and unbroken symmetries on
the same footing, and exhibit an infinite-dimensional supersymmetry algebra
that includes space-time diffeomorphisms and an infinite number of
spontaneously broken level-mixing symmetries. We review progress in this area,
culminating in the identification of a weighted tensor algebra as a subalgebra
of the full symmetry. We also briefly describe outstanding problems. Talk
presented at the Gursey memorial conference, Istanbul, Turkey, June, 1994.Comment: 5 pages, Plain TeX, no figure
RF circulator structures via offset lithography
Further developments are reported of the conductive lithographic film (CLF) process in which components of radio-frequency circulators are fabricated economically via offset lithography. The performance of centre conductor elements printed from silver-loaded inks on polymer substrates is compared with that of conventional solid copper structures
Second cohomology groups and finite covers
For D an infinite set, k>1 and W the set of k-sets from D, there is a natural
closed permutation group G_k which is a non-split extension of \mathbb{Z}_2^W
by \Sym(D). We classify the closed subgroups of G_k which project onto
\Sym(D)$. The question arises in model theory as a problem about finite covers,
but here we formulate and solve it in algebraic terms.Comment: Typos corrected; change of title to 'Second cohomology groups and
finite covers of infinite symmetric groups' in published versio
O(d,d,Z) Transformations as Automorphisms of the Operator Algebra
We implement the O(d,d,Z) transformations of T-duality as automorphisms of
the operator algebras of Conformal Field Theories. This extends these
transformations to arbitrary field configurations in the deformation class.Comment: 9 pages, Plain Te
The fluctuation theorem and Lyapunov weights
The Fluctuation Theorem (FT) is a generalisation of the Second Law of
Thermodynamics that applies to small systems observed for short times. For
thermostatted systems it gives the probability ratio that entropy will be
consumed rather than produced. In this paper we derive the Transient and Steady
State Fluctuation Theorems using Lyapunov weights rather than the usual Gibbs
weights. At long times the Fluctuation Theorems so derived are identical to
those derived using the more standard Gibbs weights.Comment: 26 pages; to appear in Physica
Printed analogue filter structures
The authors report progress in conductive lithographic film (CLF) technology, which uses the offset lithographic printing process to form electrically conductive patterns on flexible substrates. Networks of planar passive components and interconnects fabricated simultaneously via the CLF process form notch filter networks at 85 kHz
Quark Condensates in Non-Supersymmetric MQCD
A set of non-supersymmetric minimal area embeddings of an M-theory 5-brane
are considered. The field theories on the surface of the 5-brane have the field
content of N=2 SQCD with fundamental representation matter fields. By suitable
choice of curve parameters the N=2 and N=1 superpartners may be decoupled
leaving a semi-classical approximation to QCD with massive quarks. As
supersymmetry breaking is introduced a quark condensate grows breaking the low
energy flavour symmetry. At (odd) spontaneous CP
violation is observed consistent with that of the QCD chiral lagrangian.Comment: 16 pages, 1 ps figure, corrected some typos, updated reference
Controlled Soft Breaking of N=1 SQCD
We discuss the introduction of soft breaking terms into the exact solutions
of N=1 SQCD using a spurion analysis. The spurion symmetries are not sufficient
to determine the behavior of models in which squark or gaugino masses alone are
introduced. However, a controlled approximation is obtained in some cases if a
supersymmetric mass is first introduced for the matter fields. We present
low-energy solutions for two models with perturbing soft breaking terms, one
with a gaugino mass and one with squark mixing. These models have non-trivial
theta angle dependence and exhibit phase transitions at non-zero theta angle
analogous to those found in the chiral Lagrangian description of QCD.Comment: 10 pages, Latex, one eps figur
The geometry of Hrushovski constructions, I. The uncollapsed case
An intermediate stage in Hrushovski's construction of flat strongly minimal
structures in a relational language L produces omega-stable structures of rank
omega. We analyze the pregeometries given by forking on the regular type of
rank omega in these structures. We show that varying L can affect the (local)
isomorphism type of the pregeometry, but not its finite subpregeometries. A
sequel will compare these to the pregeometries of the strongly minimal
structures.Comment: 31 page
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