8,288 research outputs found
Standard Model Effective Field Theory: Integrating out a Generic Scalar
We consider renormalisable models extended in the scalar sector by a generic
scalar field in addition to the standard model Higgs boson field, and work out
the effective theory for the latter in the decoupling limit. We match the full
theory onto the effective theory at tree and one-loop levels, and concentrate
on dimension-6 operators of the Higgs and electroweak gauge fields induced from
such matching. The Wilson coefficients of these dimension-6 operators from
tree-level matching are further improved by renormalisation group running. For
specific representations of the scalar field, some "accidental"
couplings with the Higgs field are allowed and can lead to dimension-6
operators at tree and/or one-loop level. Otherwise, two types of interaction
terms are identified to have only one-loop contributions, for the Wilson
coefficients of which we have obtained a general formula. Using the obtained
results, we analyse constraints from electroweak oblique parameters and the
Higgs data on several phenomenological models.Comment: corrections on RGE improvemen
Terahertz Antiferromagnetic Spin Hall Nano-Oscillator
We consider the current-induced dynamics of insulating antiferromagnets in a
spin Hall geometry. Sufficiently large in-plane currents perpendicular to the
N\'{e}el order trigger spontaneous oscillations at frequencies between the
acoustic and the optical eigenmodes. The direction of the driving current
determines the chirality of the excitation. When the current exceeds a
threshold, the combined effect of spin pumping and current-induced torques
introduces a dynamic feedback that sustains steady-state oscillations with
amplitudes controllable via the applied current. The ac voltage output is
calculated numerically as a function of the dc current input for different
feedback strengths. Our findings open a route towards terahertz
antiferromagnetic spin-torque oscillators.Comment: 5+ pages, 4 figure
Electron Dynamics in Slowly Varying Antiferromagnetic Texture
Effective dynamics of conduction electrons in antiferromagnetic (AFM)
materials with slowly varying spin texture is developed via non-Abelian gauge
theory. Quite different from the ferromagnetic (FM) case, the spin of a
conduction electron does not follow the background texture even in the
adiabatic limit due to the accumulation of a SU(2) non-Abelian Berry phase.
Correspondingly, it is found that the orbital dynamics becomes spin-dependent
and is affected by two emergent gauge fields. While one of them is the
non-Abelian generalization of what has been discovered in FM systems, the other
leads to an anomalous velocity that has no FM counterpart. Two examples are
provided to illustrate the distinctive spin dynamics of a conduction electron.Comment: 4 pages, 3 figure
Quasi-Whittaker modules for the Schr\"odinger algebra
In this paper, we construct a new class of modules for the Schr\"{o}dinger
algebra \mS, called quasi-Whittaker module. Different from \cite{[ZC]}, the
quasi-Whittaker module is not induced by the Borel subalgebra of the
Schr\"{o}dinger algebra related with the triangular decomposition, but its
Heisenberg subalgebra \mH. We prove that, for a simple \mS-module ,
is a quasi-Whittaker module if and only if is a locally finite
\mH-module; Furthermore, we classify the simple quasi-Whittaker modules by
the elements with the action similar to the center elements in U(\mS) and
their quasi-Whittaker vectors. Finally, we characterize arbitrary
quasi-Whittaker modules.Comment: 17 page
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