Search results for "Compact"
showing 10 items of 531 documents
From kinks to compactonlike kinks
1998
We show that, in the continuum limit, the generalized \ensuremath{\Phi}-four or double-well model with nonlinear coupling can exhibit compactonlike kink solutions for some specific velocity regimes and when the nonlinear coupling between pendulums is dominant. Our numerical simulations point out that the static compacton is stable and the dynamic compacton is unstable. Our study is extended to other topological systems where compacton solutions can also be found. A nice feature is that a mechanical analog of the double-well system can be constructed in the form of an experimental lattice of coupled pendulums, which, in the strong coupling limit, allows the observation of these entities.
Collimation for CLIC
2003
The collimation system of the Compact Linear Collider (CLIC) must fulfil a number of conflicting requirements, namely it should (1) remove beam halo to reduce the detector background, (2) provide a minimum distance between collimators and collision point for muon suppression, (3) ensure collimator survival and machine protection against errand beam pulses, (4) not be excessively long, and (5) not amplify incoming trajectory fluctuations via the collimator wake fields. Two optical systems have been designed — the first linear, the second non‐linear —, which promise to meet all these requirements for the design beam energy of 1.5 TeV. We decribe the various design criteria, a preliminary perf…
Computation of Amplitudes in the Discretized Approach to String Field Theory
1988
An approach to Witten string field theory based on the discretization of the world sheet is adopted. We use it to calculate tree amplitudes with the formulation of the theory based on string functionals. The results are evaluated numerically and turn out to be very accurate, giving, for a string approximated by 600 points, values within 0.02% of the prediction of the dual model. The method opens a way to calculate amplitudes in string field theory using nonflat backgrounds as well as compactified dimensions.
Micro-orbits in a many-brane model and deviations from Newton’s $$1/r^2$$ 1 / r 2 law
2016
We consider a 5-dimensional model with geometry ${\cal M} = {\cal M}_4 \times {\cal S}_1$, with compactification radius $R$. The Standard Model particles are localized onto a brane located at y=0, with identical branes localized at different points in the extra dimension. Objects located on our brane can orbit around objects located on a brane at a distance $d=y/R$, with an orbit and a period significantly different from the standard Newtonian ones. We study the kinematical properties of the orbits, finding that it is possible to distinguish one motion from the other in a large region of the initial conditions parameter space. This is a warm-up to study if a SM-like mass distribution on one…
Compact Topological Quantum Groups
1995
Using vector spaces topologies we unify the different models of quantum groups. Duality and reflexivity are built in. The Drinfeld deformation can be extended to the distributions on a simple compact Lie group and dually to the infinitely differentiable functions. The topological quantum double is similarly defined and a uniqueness result is obtained.
On the soft excess in the x-ray spectrum of circinus X-1: Revisitation of the distance to circinus X-1
2005
We report on a 300 ks BeppoSAX (0.12-200 keV) observation of Circinus X-1 (Cir X-1) at phases between 0.62 and 0.84 and on a 90 ks BeppoSAX observation of Cir X-1 at phases 0.11-0.16. Using the canonical model adopted until now to fit the energy spectrum of this source, large residuals appear below 1 keV. These are well fitted using an equivalent hydrogen column of 0.66¿1022 cm-2, adding absorption edges of O VII, O VIII, and Ne IX in the spectra extracted from the observation at phases 0.62-0.84 and adding absorption edges of O VII, O VIII, Mg XI, and Mg XII and absorption lines of O VIII and Mg XII in the spectra extracted from the observation at phases 0.11-0.16. During the observation a…
Gravitational radiation from the magnetic field of a strongly magnetized star
2003
We consider the electromagnetic (e.m.) field of a compact strongly magnetized star. The star is idealized as a perfect conducting sphere, rigidly rotating in a vacuum, with a magnetic moment not aligned with its rotation axis. Then we use the exterior e.m. solution, obtained by Deutsch (1955) in his classic paper, to calculate the gravitational waves emitted by the e.m. field when its wavelength is much longer than the radius of the star. In some astrophysical situations, this gravitational radiation can overcome the quadrupole one emitted by the matter of the star, and, for some magnetars, would be detectable in the near future, once the present detectors, planned or under construction, be…
Bose-Fermi equivalence and interacting string field theory
1995
Abstract We show that the bosonic and the fermionic realization of the ghost vertex in the Half-String (HS) Operator approach to Witten's String Field Theory (WSFT) are equivalent. In the process we discover that higher vertices (i.e., N > 3) can be eliminated in WSFT using only the overlap conditions defining the interaction vertex and ghost number counting.
B physics and extra dimensions
2003
We compute the dominant new physics contributions to the processes Z -> b b and B - B in the context of two representative models with extra dimensions. The main thrust of the calculations focuses on how to control the effects of the infinite tower of Kaluza-Klein modes inside the relevant one-loop diagrams. By comparing the results with the existing experimental data, most importantly those for Rb, we show that one may derive interesting lower bounds on the size of the compactification scale Mc.
The transverse structure of the QCD string
2010
The characterization of the transverse structure of the QCD string is discussed. We formulate a conjecture as to how the stress-energy tensor of the underlying gauge theory couples to the string degrees of freedom. A consequence of the conjecture is that the energy density and the longitudinal-stress operators measure the distribution of the transverse position of the string, to leading order in the string fluctuations, whereas the transverse-stress operator does not. We interpret recent numerical measurements of the transverse size of the confining string and show that the difference of the energy and longitudinal-stress operators is the appropriate probe to use when comparing with the nex…