2,087 research outputs found
Problems and strategy of the first flight to the comets
Substantiation is given for the urgency of using space equipment to study comets in order to work out the basic problem of the origin and evolution of the solar system. The potentialities and advantages of selecting ballistically-accessible objects among the newly discovered comets are shown (as a preliminary study). The technique of early detection of such objects is discussed
On the Question of Polygonality and Irregularities of the Shape of Certain Craters on the Moon
Evaluation of moon crater polygonality, and irregular shape
Penetrators (penetrating sondes) and new possibilities for study of the planets
The fields of possible use of penetrators in space research are considered. A survey of the condition of development and plans for use of penetrators abroad is presented and an analysis is given of the significance of scientific problems when probing planets
Yang-Mills condensates in cosmology
We discuss homogeneous and isotropic cosmological models driven by SU(2)
gauge fields in the framework of Einstein gravity. There exists a Yang-Mills
field configuration, parametrized by a single scalar function, which consists
of parallel electric and magnetic fields and has the stress tensor mimicking an
homogeneous and isotropic fluid. The unique SU(2) gauge theory with spontaneous
symmetry breaking sharing the same property is the Yang-Mills coupled to the
complex doublet Higgs, this exists only in the case of the closed universe.
This model contains an intrinsic mechanism for inflation due to the Higgs
potential. Our second goal is to show that a successful inflation can be
achieved also within the pure Yang-Mills theory adding an appropriate
theta-term.Comment: Submitted to Proceedings of "Quantum field theory under the influence
of external conditions", Benasque, Spain, September 18-24, 2011 2011, Sep 18
-- Sep 2
Cylindrically symmetric solitons in Einstein-Yang-Mills theory
Recently new Einstein-Yang-Mills (EYM) soliton solutions were presented which
describe superconducting strings with Kasner asymptotic (hep-th/0610183). Here
we study the static cylindrically symmetric SU(2) EYM system in more detail.
The ansatz for the gauge field corresponds to superposition of the azimuthal
and the longitudinal components of the color magnetic field. We
derive sum rules relating data on the symmetry axis to asymptotic data and show
that generic asymptotic structure of regular solutions is Kasner. Solutions
starting with vacuum data on the axis generically are divergent. Regular
solutions correspond to some bifurcation manifold in the space of parameters
which has the low-energy limiting point corresponding to string solutions in
flat space (with the divergent total energy) and the high-curvature point where
gravity is crucial. Some analytical results are presented for the low energy
limit, and numerical bifurcation curves are constructed in the gravitating
case. Depending on the parameters, the solution looks like a straight string or
a pair of straight and circular strings. The existence of such non-linear
superposition of two strings becomes possible due to self-interaction terms in
the Yang-Mills action which suppress contribution of the circular string near
the polar axis.Comment: 21 pages, 11 figure
Microscopic derivation of Frenkel excitons in second quantization
Starting from the microscopic hamiltonian describing free electrons in a
periodic lattice, we derive the hamiltonian appropriate to Frenkel excitons.
This is done through a grouping of terms different from the one leading to
Wannier excitons. This grouping makes appearing the atomic states as a relevant
basis to describe Frenkel excitons in the second quantization. Using them, we
derive the Frenkel exciton creation operators as well as the commutators which
rule these operators and which make the Frenkel excitons differing from
elementary bosons. The main goal of the present paper is to provide the
necessary grounds for future works on Frenkel exciton many-body effects, with
the composite nature of these particles treated exactly through a procedure
similar to the one we have recently developed for Wannier excitons.Comment: 16 pages, 4 figure
A Note on Stress-Energy Tensor and Variational Principle for Null Strings
A straightforward application of the variational principle to null strings
meets difficulties since string's world-sheets are degenerate. It is known that
the variational principle in this case can be formulted with the help of
two-vector density on the string world-sheet which plays a role of Lagrange
multipliers. It is shown that recently suggested stress-energy tensor of null
strings can be derived by variation over the background metric of the action
used to describe tensionless limit in the string theory. One of the Lagrange
multipliers is related to the energy of the null string.Comment: 4 page
Theory of a Narrow roton Absorption Line in the Spectrum of a Disk-Shaped SHF Resonator
We calculate the probability of the birth of a circular phonon (c-phonon) in
He II by a c-photon of the resonator. It is shown that this probability has
sharp maxima at frequencies, where the effective group velocity of the c-phonon
is equal to zero; the density of states of c-phonons strongly grows at such
frequencies. For He II, these frequencies correspond to a roton and a maxon.
From the probability of the c-roton birth, we calculate the roto line width
which is found to approximately agree with the experimental one. We conclude
that the roton line observed in the super-high-frequency (SHF) absorption
spectrum of helium is related to the birth of c-rotons. A possible
interpretation of the Stark effect observed for the roton line is also
proposed.Comment: 13 pages, 1 figure, v2: journal variant, several minor correction
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