13,250 research outputs found
Gaugeon Formalism for Spin-3/2 Rarita-Schwinger Gauge Field
We provide a gauge covariant formalism of the canonically quantized theory of
spin-3/2 Rarita-Schwinger gauge field. The theory admits a quantum gauge
transformation by which we can shift the gauge fixing parameter. The quantum
gauge transformation does not change the BRST charge. Thus, the physical
Hilbert space is trivially independent of the gauge fixing parameter.Comment: 13 pages, no figures, LaTe
Fourier analyses of commensurability oscillations in Fibonacci lateral superlattices
Magnetotransport measurements have been performed on Fibonacci lateral
superlattices (FLSLs) -- two-dimensional electron gases subjected to a weak
potential modulation arranged in the Fibonacci sequence, LSLLSLS..., with
L/S=tau (the golden ratio). Complicated commensurability oscillation (CO) is
observed, which can be accounted for as a superposition of a series of COs each
arising from a sinusoidal modulation representing the characteristic length
scale of one of the self-similar generations in the Fibonacci sequence.
Individual CO components can be separated out from the magnetoresistance trace
by performing a numerical Fourier band-pass filter. From the analysis of the
amplitude of a single-component CO thus extracted, the magnitude of the
corresponding Fourier component in the potential modulation can be evaluated.
By examining all the Fourier contents observed in the magnetoresistance trace,
the profile of the modulated potential seen by the electrons can be
reconstructed with some remaining ambiguity about the interrelation of the
phase between different components.Comment: 11 pages, 10 figures, added references in Introduction, minor
revision
Structure and growth process of vapor-grown carbon fibers
The structure, effect of heat, and growth process of vapor-grown carbon fibers are investigated. The growth process of the carbon fibers could be divided into three stages; nucleation, elongation, and thickening processes. Also, a multi-layered structure can be produced as well as graphitization
Footprints of Supersymmetry on Higgs Decay
Motivated by future collider proposals that aim to measure the Higgs
properties precisely, we study the partial decay widths of the lightest Higgs
boson in the minimal supersymmetric standard model with an emphasis on the
parameter region where all superparticles and heavy Higgs bosons are not
accessible at the LHC. Taking account of phenomenological constraints such as
the Higgs mass, flavor constraints, vacuum stability, and perturbativity of
coupling constants up to the grand unification scale, we discuss how large the
deviations of the partial decay widths from the standard model predictions can
be. These constraints exclude large fraction of the parameter region where the
Higgs widths show significant deviation from the standard model predictions.
Nevertheless, even if superparticles and the heavy Higgses are out of the reach
of 14TeV LHC, the deviation may be large enough to be observed at future
collider experiments.Comment: 24 pages, 8 figures, version accepted in JHE
Universality of an impurity in a Bose-Einstein condensate
Universality is a powerful concept in physics, allowing one to construct
physical descriptions of systems that are independent of the precise
microscopic details or energy scales. A prime example is the Fermi gas with
unitarity limited interactions, whose universal properties are relevant to
systems ranging from atomic gases at microkelvin temperatures to the inner
crust of neutron stars. Here we address the question of whether unitary Bose
systems can possess a similar universality. We consider the simplest strongly
interacting Bose system, where we have an impurity particle ("polaron")
resonantly interacting with a Bose-Einstein condensate (BEC). Focusing on the
ground state of the equal-mass system, we use a variational wave function for
the polaron that includes up to three Bogoliubov excitations of the BEC, thus
allowing us to capture both Efimov trimers and associated tetramers. Unlike the
Fermi case, we find that the length scale associated with Efimov trimers (i.e.,
the three-body parameter) can strongly affect the polaron's behaviour, even at
boson densities where there are no well-defined Efimov states. However, by
comparing our results with recent quantum Monte Carlo calculations, we argue
that the polaron energy is a \emph{universal} function of the Efimov three-body
parameter for sufficiently low boson densities. We further support this
conclusion by showing that the energies of the deepest bound Efimov trimers and
tetramers at unitarity are universally related to one another, regardless of
the microscopic model. On the other hand, we find that the quasiparticle
residue and effective mass sensitively depend on the coherence length of
the BEC, with the residue tending to zero as diverges, in a manner akin
to the orthogonality catastrophe.Comment: 11 pages and 7 figures + supplemental materia
Renormalization-Scale Uncertainty in the Decay Rate of False Vacuum
We study radiative corrections to the decay rate of false vacua, paying
particular attention to the renormalization-scale dependence of the decay rate.
The decay rate exponentially depends on the bounce action. The bounce action
itself is renormalization scale dependent. To make the decay rate
scale-independent, radiative corrections, which are due to the field
fluctuations around the bounce, have to be included. We show quantitatively
that the inclusion of the fluctuations suppresses the scale dependence, and
hence is important for the precise calculation of the decay rate. We also apply
our analysis to a supersymmetric model and show that the radiative corrections
are important for the Higgs-stau system with charge breaking minima.Comment: 15 pages, 2 figures; added reference
On the Gauge Invariance of the Decay Rate of False Vacuum
We study the gauge invariance of the decay rate of the false vacuum for the
model in which the scalar field responsible for the false vacuum decay has
gauge quantum number. In order to calculate the decay rate, one should
integrate out the field fluctuations around the classical path connecting the
false and true vacua (i.e., so-called bounce). Concentrating on the case where
the gauge symmetry is broken in the false vacuum, we show a systematic way to
perform such an integration and present a manifestly gauge-invariant formula of
the decay rate of the false vacuum.Comment: 17 pages, published versio
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