3,285 research outputs found
Hydrodynamic Flow as Congruence of Geodesic Lines in Riemannian Space-Time
It is shown that small elements of perfect fluid in adiabatic processes move
along geodesic lines of a Riemannian space-time.Comment: 5 pages, Latex. Final versio
Do Present LEP Data Provide Evidence for Electroweak Corrections?
The Born approximation, based on instead of
, reproduces all electroweak precision measurements within their
accuracy. The low upper limits for the genuinely electroweak
corrections constitute one of the major achievements of LEP. The astonishing
smallness of these corrections results from the cancellation of a large
positive contribution from the heavy top quark and large negative contributions
from all other virtual particles. It is precisely the non-observation of
electroweak radiative corrections that places stringent upper and lower limits
on the top mass.Comment: 12 pages, preprint CERN-TH.6943/9
Mass of the higgs versus fourth generation masses
The predicted value of the higgs mass is analyzed assuming the
existence of the fourth generation of leptons () and quarks ().
The steep and flat directions are found in the five-dimensional parameter
space: , , , , . The LEPTOP fit of the precision
electroweak data is compatible (in particular) with GeV, GeV, GeV, GeV, and GeV. The quality of fits drastically improves when the data on b- and
c-quark asymmetries and new NuTeV data on deep inelastic scattering are
ignored.Comment: 8 pages, 4 figure
On the classification of scalar evolutionary integrable equations in dimensions
We consider evolutionary equations of the form where
is the nonlocality, and the right hand side is polynomial
in the derivatives of and . The recent paper \cite{FMN} provides a
complete list of integrable third order equations of this kind. Here we extend
the classification to fifth order equations. Besides the known examples of
Kadomtsev-Petviashvili (KP), Veselov-Novikov (VN) and Harry Dym (HD) equations,
as well as fifth order analogues and modifications thereof, our list contains a
number of equations which are apparently new. We conjecture that our examples
exhaust the list of scalar polynomial integrable equations with the nonlocality
. The classification procedure consists of two steps. First, we classify
quasilinear systems which may (potentially) occur as dispersionless limits of
integrable scalar evolutionary equations. After that we reconstruct dispersive
terms based on the requirement of the inheritance of hydrodynamic reductions of
the dispersionless limit by the full dispersive equation
Devil's staircase of incompressible electron states in a nanotube
It is shown that a periodic potential applied to a nanotube can lock
electrons into incompressible states. Depending on whether electrons are weakly
or tightly bound to the potential, excitation gaps open up either due to the
Bragg diffraction enhanced by the Tomonaga - Luttinger correlations, or via
pinning of the Wigner crystal. Incompressible states can be detected in a
Thouless pump setup, in which a slowly moving periodic potential induces
quantized current, with a possibility to pump on average a fraction of an
electron per cycle as a result of interactions.Comment: 4 pages, 1 figure, published versio
New global stability estimates for the Gel'fand-Calderon inverse problem
We prove new global stability estimates for the Gel'fand-Calderon inverse
problem in 3D. For sufficiently regular potentials this result of the present
work is a principal improvement of the result of [G. Alessandrini, Stable
determination of conductivity by boundary measurements, Appl. Anal. 27 (1988),
153-172]
Formulas and equations for finding scattering data from the Dirichlet-to-Neumann map with nonzero background potential
For the Schrodinger equation at fixed energy with a potential supported in a
bounded domain we give formulas and equations for finding scattering data from
the Dirichlet-to-Neumann map with nonzero background potential. For the case of
zero background potential these results were obtained in [R.G.Novikov,
Multidimensional inverse spectral problem for the equation
-\Delta\psi+(v(x)-Eu(x))\psi=0, Funkt. Anal. i Ego Prilozhen 22(4), pp.11-22,
(1988)]
Correlator of Topological Charge Densities in Instanton Model in QCD
The QCD sum rule for the correlator of topological charge densities and
related to it longitudinal part of the correlator of singlet axial currents is
considered in the framework of instanton model. The coupling constant of
eta'-meson with the singlet axial current is determined. Its value appears to
be in a good coincidence with the value determined recently from the connection
of the part of proton spin, carried by u,d,s quarks, with the derivative of QCD
topological susceptibility. From the same sum rule eta-eta' mixing angle is
found in the framework of two mixing angles model. Its value is close to that
found in the chiral effective theory. The correlator of topological charge
densities at large momenta is calculated.Comment: 14 pages, 2 figure
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