9,907 research outputs found
On Extended Electroweak Symmetries
We discuss extensions of the Standard Model through extending the electroweak
gauge symmetry. An extended electroweak symmetry requires a list of extra
fermionic and scalar states. The former is necessary to maintain cancellation
of gauge anomalies, and largely fixed by the symmetry embedding itself. The
latter is usually considered quite arbitrary, so long as a vacuum structure
admitting the symmetry breaking is allowed. Anomaly cancellation may be used to
link the three families of quarks and leptons together, given a perspective on
flavor physics. It is illustrated lately that the kind of models may also have
the so-called little Higgs mechanism incorporated. This more or less fixes the
scalar sector and take care of the hierarchy problem, making such models of
extended electroweak symmetries quite appealing candidates as TeV scale
effective field theories.Comment: 1+8 pages of latex with ws-procs9x6.cls; talk presented at Coral
Gables Conference 200
EFFECT OF CONTACT ANGLE AND TANK GEOMETRY ON THE CONFIGURATION OF THE LIQUID-VAPOR INTERFACE DURING WEIGHTLESSNESS
Effect of contact angle and space vehicle tank geometry on configuration of rocket propellant liquid-vapor interface during weightlessnes
Static and dynamic behavior of the liquid- vapor interface during weightlessness
Static and dynamic behavior of liquid-vapor interface during weightlessnes
Quark Loop Contributions to Neutron, Deuteron, and Mercury EDMs from Supersymmetry without R parity
We present a detailed analysis of the neutron, deuteron and mercury electric
dipole moment from supersymmetry without R parity, focusing on the quark-scalar
loop contributions. Being proportional to top Yukawa and top mass, such
contributions are often large. Analytical expressions illustrating the explicit
role of the R-parity violating parameters are given following perturbative
diagonalization of mass-squared matrices for the scalars. Dominant
contributions come from the combinations for which
we obtain robust bounds. It turns out that neutron and deuteron EDMs receive
much stronger contributions than mercury EDM and any null result at the future
deuteron EDM experiment or Los Alamos neutron EDM experiment can lead to
extra-ordinary constraints on RPV parameter space. Even if R-parity violating
couplings are real, CKM phase does induce RPV contribution and for some cases
such a contribution is as strong as contribution from phases in the R-parity
violating couplings.Hence, we have bounds directly on even if the RPV parameters are all real.
Interestingly, even if slepton mass and/or is as high as 1 TeV, it
still leads to neutron EDM that is an order of magnitude larger than the
sensitivity at Los Alamos experiment. Since the results are not much sensitive
to , our constraints will survive even if other observables tighten
the constraints on .Comment: 16 pages, 10 figures, accepted for publication in Physical Review
Little Higgs Model Completed with a Chiral Fermionic Sector
The implementation of the little Higgs mechanism to solve the hierarchy
problem provides an interesting guiding principle to build particle physics
models beyond the electroweak scale. Most model building works, however, pay
not much attention to the fermionic sector. Through a case example, we
illustrate how a complete and consistent fermionic sector of the TeV effective
field theory may actually be largely dictated by the gauge structure of the
model. The completed fermionic sector has specific flavor physics structure,
and many phenomenological constraints on the model can thus be obtained beyond
gauge, Higgs, and top physics. We take a first look on some of the quark sector
constraints.Comment: 14 revtex pages with no figure, largely a re-written version of
hep-ph/0307250 with elaboration on flavor sector FCNC constraints; accepted
for publication in Phys.Rev.
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Effects of vibrational excitation on the F + H2O → HF + OH reaction: dissociative photodetachment of overtone-excited [F-H-OH].
The reaction F + H2O → HF + OH is a four-atom system that provides an important benchmark for reaction dynamics. Hydrogen atom transfer at the transition state for this reaction is expected to exhibit a strong dependence on reactant vibrational excitation. In the present study, the vibrational effects are examined by photodetachment of vibrationally excited F-(H2O) precursor anions using photoelectron-photofragment coincidence (PPC) spectroscopy and compared with full six-dimensional quantum dynamical calculations on ab initio potential energy surfaces. Prior to photodetachment at hνUV = 4.80 eV, the overtone of the ionic hydrogen bond mode in the precursor F-(H2O), 2νIHB at 2885 cm-1, was excited using a tunable IR laser. Experiment and theory show that vibrational energy in the anion can be effectively carried away by the photoelectron upon a Franck-Condon photodetachment, and also show evidence for an increase of branching into the F + H2O reactant channel. The experimental results suggest a greater role for product rotational excitation than theory. Improved potential energy surfaces and longer wavepacket propagation times would be helpful to further examine the nature of the discrepancy
Learning Bilinear Models of Actuated Koopman Generators from Partially-Observed Trajectories
Data-driven models for nonlinear dynamical systems based on approximating the
underlying Koopman operator or generator have proven to be successful tools for
forecasting, feature learning, state estimation, and control. It has become
well known that the Koopman generators for control-affine systems also have
affine dependence on the input, leading to convenient finite-dimensional
bilinear approximations of the dynamics. Yet there are still two main obstacles
that limit the scope of current approaches for approximating the Koopman
generators of systems with actuation. First, the performance of existing
methods depends heavily on the choice of basis functions over which the Koopman
generator is to be approximated; and there is currently no universal way to
choose them for systems that are not measure preserving. Secondly, if we do not
observe the full state, then it becomes necessary to account for the dependence
of the output time series on the sequence of supplied inputs when constructing
observables to approximate Koopman operators. To address these issues, we write
the dynamics of observables governed by the Koopman generator as a bilinear
hidden Markov model, and determine the model parameters using the
expectation-maximization (EM) algorithm. The E-step involves a standard Kalman
filter and smoother, while the M-step resembles control-affine dynamic mode
decomposition for the generator. We demonstrate the performance of this method
on three examples, including recovery of a finite-dimensional Koopman-invariant
subspace for an actuated system with a slow manifold; estimation of Koopman
eigenfunctions for the unforced Duffing equation; and model-predictive control
of a fluidic pinball system based only on noisy observations of lift and drag
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