3,069 research outputs found
Skewed distributions fixed by diagonal partons at small x,\xi and at HERA
We show that the skewed parton distributions are completely determined at
small x and \xi by the conventional diagonal partons. We study the application
to diffractive vector meson production at HERA.Comment: 3 pages, LATeX, no figures, uses npb.sty, presented at the DIS99
Workshop, Zeuthen, Germany, April 19-23, 1999, to appear in the proceeding
The CantiClever: a dedicated probe for magnetic force microscopy
We present a new cantilever for magnetic-force microscopy (MFM), the CantiClever, which is not derived from atomic-force microscopy (AFM) probes but optimized for MFM. Our design integrates the cantilever and the magnetic tip in a single manufacturing process with the use of silicon micromachining techniques, which allows for batch fabrication of the probes. This manufacturing process enables precise control on all dimensions of the magnetic tip, resulting in a very thin magnetic element with a very high aspect ratio. Using. the CantiClever, magnetic features down to 30 nm could be observed in a CAMST reference sample
Wave scattering by small bodies and creating materials with a desired refraction coefficient
Asymptotic solution to many-body wave scattering problem is given in the case
of many small scatterers. The small scatterers can be particles whose physical
properties are described by the boundary impedances, or they can be small
inhomogeneities, whose physical properties are described by their refraction
coefficients. Equations for the effective field in the limiting medium are
derived. The limit is considered as the size of the particles or
inhomogeneities tends to zero while their number tends to infinity.
These results are applied to the problem of creating materials with a desired
refraction coefficient. For example, the refraction coefficient may have
wave-focusing property, or it may have negative refraction, i.e., the group
velocity may be directed opposite to the phase velocity. This paper is a review
of the author's results presented in MR2442305 (2009g:78016), MR2354140
(2008g:82123), MR2317263 (2008a:35040), MR2362884 (2008j:78010), and contains
new results.Comment: In this paper the author's invited plenary talk at the 7-th PACOM
(PanAfrican Congress of Mathematicians), is presente
Searching for a light Fermiophobic Higgs Boson at the Tevatron
We propose new production mechanisms for light fermiophobic Higgs bosons
() with suppressed couplings to vector bosons () at the Fermilab
Tevatron. These mechanisms (e.g. ) are complementary to the
conventional process , which suffers from a strong suppression of
in realistic models with a . The new mechanisms extend the
coverage at the Tevatron Run II to the larger region, and offer the
possibility of observing new event topologies with up to 4 photons.Comment: 15 pages, including 5 eps-figure
A class of quasicontractive semigroups acting on Hardy and Dirichlet space
This paper provides a complete characterization of quasicontractive C0-semigroups on Hardy and Dirichlet space with a prescribed generator of the form Af = Gf ′. We show that such semigroups are semigroups of composition operators, and we give simple sufficient and necessary condition on G. Our techniques are based on ideas from semigroup theory, such as the use of numerical ranges
Scattering of electromagnetic waves by many thin cylinders: theory and computational modeling
Electromagnetic (EM) wave scattering by many parallel infinite cylinders is
studied asymptotically as a tends to 0, where a is the radius of the cylinders.
It is assumed that the centres of the cylinders are distributed so that their
numbers is determined by some positive function N(x). The function N(x) >= 0 is
a given continuous function. An equation for the self-consistent (limiting)
field is derived as a tends to 0. The cylinders are assumed perfectly
conducting. Formula for the effective refraction coefficient of the new medium,
obtained by embedding many thin cylinders into a given region, is derived. The
numerical results presented demonstrate the validity of the proposed approach
and its efficiency for solving the many-body scattering problems, as well as
the possibility to create media with negative refraction coefficients.Comment: 21 pages, 13 figure
- …