1,900 research outputs found
The MSSM fine tuning problem: a way out
As is well known, electroweak breaking in the MSSM requires substantial
fine-tuning, mainly due to the smallness of the tree-level Higgs quartic
coupling, lambda_tree. Hence the fine tuning is efficiently reduced in
supersymmetric models with larger lambda_tree, as happens naturally when the
breaking of SUSY occurs at a low scale (not far from the TeV). We show, in
general and with specific examples, that a dramatic improvement of the fine
tuning (so that there is virtually no fine-tuning) is indeed a very common
feature of these scenarios for wide ranges of tan(beta) and the Higgs mass
(which can be as large as several hundred GeV if desired, but this is not
necessary). The supersymmetric flavour problems are also drastically improved
due to the absence of RG cross-talk between soft mass parameters.Comment: 28 pages, 9 PS figures, LaTeX Published versio
Nonsupersymmetric multibrane solutions
Gravity coupled to an arbitrary number of antisymmetric tensors and scalar
fields in arbitrary space-time dimensions is studied in a context of general,
static, spherically symmetric solutions with many orthogonally intersecting
branes. Neither supersymmetry nor harmonic gauge is assumed. It is shown that
the system reduces to a Toda-like system after an adequate redefinition of
transverse radial coordinate . Duality in the set of solutions
is observed
Conformal Scalar Propagation on the Schwarzschild Black-Hole Geometry
The vacuum activity generated by the curvature of the Schwarzschild
black-hole geometry close to the event horizon is studied for the case of a
massless, conformal scalar field. The associated approximation to the unknown,
exact propagator in the Hartle-Hawking vacuum state for small values of the
radial coordinate above results in an analytic expression which
manifestly features its dependence on the background space-time geometry. This
approximation to the Hartle-Hawking scalar propagator on the Schwarzschild
black-hole geometry is, for that matter, distinct from all other. It is shown
that the stated approximation is valid for physical distances which range from
the event horizon to values which are orders of magnitude above the scale
within which quantum and backreaction effects are comparatively pronounced. An
expression is obtained for the renormalised in the
Hartle-Hawking vacuum state which reproduces the established results on the
event horizon and in that segment of the exterior geometry within which the
approximation is valid. In contrast to previous results the stated expression
has the superior feature of being entirely analytic. The effect of the
manifold's causal structure to scalar propagation is also studied.Comment: 34 pages, 2 figures. Published on line on October 16, 2009 and due to
appear in print in Gen.Rel.Gra
Tannakian duality for Anderson-Drinfeld motives and algebraic independence of Carlitz logarithms
We develop a theory of Tannakian Galois groups for t-motives and relate this
to the theory of Frobenius semilinear difference equations. We show that the
transcendence degree of the period matrix associated to a given t-motive is
equal to the dimension of its Galois group. Using this result we prove that
Carlitz logarithms of algebraic functions that are linearly independent over
the rational function field are algebraically independent.Comment: 39 page
Contact symmetry of time-dependent Schr\"odinger equation for a two-particle system: symmetry classification of two-body central potentials
Symmetry classification of two-body central potentials in a two-particle
Schr\"{o}dinger equation in terms of contact transformations of the equation
has been investigated. Explicit calculation has shown that they are of the same
four different classes as for the point transformations. Thus in this problem
contact transformations are not essentially different from point
transformations. We have also obtained the detailed algebraic structures of the
corresponding Lie algebras and the functional bases of invariants for the
transformation groups in all the four classes
Dyson processes on the octonion algebra
We consider Brownian motion on symmetric matrices of octonions, and study the
law of the spectrum. Due to the fact that the octonion algebra is
nonassociative, the dimension of the matrices plays a special role. We provide
two specific models on octonions, which give some indication of the relation
between the multiplicity of eigenvalues and the exponent in the law of the
spectrum
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