11,476 research outputs found
Weak-triplet, color-octet scalars and the CDF dijet excess
We extend the standard model to include a weak-triplet and color-octet
scalar. This `octo-triplet' field consists of three particles, two charged and
one neutral, whose masses and renormalizable interactions depend only on two
new parameters. The charged octo-triplet decay into a W boson and a gluon is
suppressed by a loop factor and an accidental cancellation. Thus, the main
decays of the charged octo-triplet may occur through higher-dimensional
operators, mediated by a heavy vectorlike fermion, into quark pairs. For an
octo-triplet mass below the t\bar{b} threshold, the decay into Wb\bar{b} or
Wb\bar{s} through an off-shell top quark has a width comparable to that into
c\bar{s} or c\bar{b}. Pair production with one octo-triplet decaying into two
jets and the other decaying into a W and two soft b jets may explain the
dijet-plus-W excess reported by the CDF Collaboration. Using a few kinematic
distributions, we compare two mechanisms of octo-triplet pair production:
through an s-channel coloron and through the coupling to gluons. The
higher-dimensional operators that allow dijet decays also lead to CP violation
in B_s - \bar B_s mixing.Comment: 18 pages. New CDF kinematic distributions using 7.3 fb^{-1} compared
to both resonant and gluon-induced pair production of octets. Corrections in
Section 3.1. Comment on the D0 Wjj result included in Section 3.3.
Implications for LHC expanded in Section 3.
Expanded mixed multiscale finite element methods and their applications for flows in porous media
We develop a family of expanded mixed Multiscale Finite Element Methods
(MsFEMs) and their hybridizations for second-order elliptic equations. This
formulation expands the standard mixed Multiscale Finite Element formulation in
the sense that four unknowns (hybrid formulation) are solved simultaneously:
pressure, gradient of pressure, velocity and Lagrange multipliers. We use
multiscale basis functions for the both velocity and gradient of pressure. In
the expanded mixed MsFEM framework, we consider both cases of separable-scale
and non-separable spatial scales. We specifically analyze the methods in three
categories: periodic separable scales, - convergence separable scales, and
continuum scales. When there is no scale separation, using some global
information can improve accuracy for the expanded mixed MsFEMs. We present
rigorous convergence analysis for expanded mixed MsFEMs. The analysis includes
both conforming and nonconforming expanded mixed MsFEM. Numerical results are
presented for various multiscale models and flows in porous media with shales
to illustrate the efficiency of the expanded mixed MsFEMs.Comment: 33 page
Evidence of slow-light effects from rotary drag of structured beams
Self-pumped slow light, typically observed within laser gain media, is created by an intense pump field. By observing the rotation of a structured laser beam upon transmission through a spinning ruby window, we show that the slowing effect applies equally to both the dark and bright regions of the incident beam. This result is incompatible with slow-light models based on simple pulse-reshaping arising from optical bleaching. Instead, the slow-light effect arises from the long upper-state lifetime of the ruby and a saturation of the absorption, from which the Kramers–Kronig relation gives a highly dispersive phase index and a correspondingly high group index
Fermi acceleration in time-dependent rectangular billiards due to multiple passages through resonances
We consider a slowly rotating rectangular billiard with moving boundaries and
use the canonical perturbation theory to describe the dynamics of a billiard
particle. In the process of slow evolution certain resonance conditions can be
satisfied. Correspondingly, phenomena of scattering on a resonance and capture
into a resonance happen in the system. These phenomena lead to destruction of
adiabatic invariance and to unlimited acceleration of the particle.Comment: 20 pages. Presented on School-Conference "Mathematics and Physics of
Billiard-Like Systems" (Ubatuba, 2011). Accepted to Chao
Global action-angle coordinates for completely integrable systems with noncompact invariant submanifolds
The obstruction to the existence of global action-angle coordinates of
Abelian and noncommutative (non-Abelian) completely integrable systems with
compact invariant submanifolds has been studied. We extend this analysis to the
case of noncompact invariant submanifolds.Comment: 13 pages, to be published in J. Math. Phys. (2007
Gauge Invariant Treatment of the Electroweak Phase Transition
We evaluate the gauge invariant effective potential for the composite field
in the SU(2)-Higgs model at finite temperature.
Symmetric and broken phases correspond to the domains and
, respectively. The effective potential increases very steeply
at small values of . Predictions for several observables, derived from
the ordinary and the gauge invariant effective potential, are compared. Good
agreement is found for the critical temperature and the jump in the order
parameter. The results for the latent heat differ significantly for large Higgs
masses.Comment: 8 pages latex, DESY-94-043, 4 figures can be obtained via e-mail from
[email protected]
Instabilities in complex mixtures with a large number of components
Inside living cells are complex mixtures of thousands of components. It is
hopeless to try to characterise all the individual interactions in these
mixtures. Thus, we develop a statistical approach to approximating them, and
examine the conditions under which the mixtures phase separate. The approach
approximates the matrix of second virial coefficients of the mixture by a
random matrix, and determines the stability of the mixture from the spectrum of
such random matrices.Comment: 4 pages, uses RevTeX 4.
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