5,769 research outputs found
Hidden Higgs Particle
A modification of the standard model of electroweak interactions with the
nonlocal Higgs sector is proposed. Proper form of nonlocality makes Higgs
particles unobservable after the electroweak symmetry breaking. They appear
only as a virtual state because their propagator is an entire function. We
discuss some specific consequences of this approach comparing it with the
conventional standard model.Comment: 15 pages, LaTeX, no figure
Lepton number, black hole entropy and 10 to the 32 copies of the Standard Model
Lepton number violating processes are a typical problem in theories with a
low quantum gravity scale. In this paper we examine lepton number violation
(LNV) in theories with a saturated black hole bound on a large number of
species. Such theories have been advocated recently as a possible solution to
the hierarchy problem and an explanation of the smallness of neutrino masses.
Naively one would expect black holes to introduce TeV scale LNV operators, thus
generating unacceptably large rates of LNV processes. We show, however, that
this does not happen in this scenario due to a complicated compensation
mechanism between contributions of different Majorana neutrino states to these
processes. As a result rates of LNV processes are extremely small and far
beyond experimental reach, at least for the left-handed neutrino states.Comment: 6 pages, 3 figures, to appear in Proc. PASCOS 2010, Valencia, Spai
Ideas of I. M. Sechenov in aviation and space medicine
The contributions I. M. Sechenov (19th century) made to modern physiology are described, including his studies on gases in the blood (O2 and CO2), and how these studies were the basic building blocks of current efforts in aviation and space medicine. Sechenov also studied hypokinesia, which is becoming important in long duration space flights
Leptoquarks: Neutrino masses and accelerator phenomenology
Leptoquark-Higgs interactions induce mixing between leptoquark states with
different chiralities once the electro-weak symmetry is broken. In such LQ
models Majorana neutrino masses are generated at 1-loop order. Here we
calculate the neutrino mass matrix and explore the constraints on the parameter
space enforced by the assumption that LQ-loops explain current neutrino
oscillation data. LQs will be produced at the LHC, if their masses are at or
below the TeV scale. Since the fermionic decays of LQs are governed by the same
Yukawa couplings, which are responsible for the non-trivial neutrino mass
matrix, several decay branching ratios of LQ states can be predicted from
measured neutrino data. Especially interesting is that large lepton flavour
violating rates in muon and tau final states are expected. In addition, the
model predicts that, if kinematically possible, heavier LQs decay into lighter
ones plus either a standard model Higgs boson or a gauge boson.
Thus, experiments at the LHC might be able to exclude the LQ mechanism as
explanation of neutrino data.Comment: 28 pages, 10 figure
Wavelength limits on isobaricity of perturbations in a thermally unstable radiatively cooling medium
Nonlinear evolution of one-dimensional planar perturbations in an optically
thin radiatively cooling medium in the long-wavelength limit is studied
numerically. The accepted cooling function generates in thermal equilibrium a
bistable equation of state . The unperturbed state is taken close to
the upper (low-density) unstable state with infinite compressibility
(). The evolution is shown to proceed in three different stages.
At first stage, pressure and density set in the equilibrium equation of state,
and velocity profile steepens gradually as in case of pressure-free flows. At
second stage, those regions of the flow where anomalous pressure (i.e. with
negative compressibility) holds, create velocity profile more sharp than in
pressure-free case, which in turn results in formation of a very narrow
(short-wavelength) region where gas separates the equilibrium equation of state
and pressure equilibrium sets in rapidly. On this stage, variation in pressure
between narrow dense region and extended environment does not exceed more than
0.01 of the unperturbed value. On third stage, gas in the short-wavelength
region reaches the second (high-density) stable state, and pressure balance
establishes through the flow with pressure equal to the one in the unperturbed
state. In external (long-wavelength) regions, gas forms slow isobaric inflow
toward the short-wavelength layer. The duration of these stages decreases when
the ratio of the acoustic time to the radiative cooling time increases. Limits
in which nonlinear evolution of thermally unstable long-wavelength
perturbations develops in isobaric regime are obtained.Comment: 21 pages with 7 figures, Revtex, accepted in Physics of Plasma
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