448 research outputs found
Tetraquark particle in the string model
We discuss possibility of the existence of tetraquark states made of four
quarks in the string (flux tube) model. The new particle is composed of a
diquark and an anti-diquark which are connected by a color flux. It is shown
that the vibrational and rotational excited states of the string explain some
non- mesons observed experimentally. Moreover we discuss the decay
widths of such tetraquarks with the use of the Schwinger mechanism.Comment: 5 pages, 6 figure
Extended Supersymmetric sigma-Model Based on the SO(2N+1) Lie Algebra of the Fermion Operators
Extended supersymmetric sigma-model is given, standing on the SO(2N+1) Lie
algebra of fermion operators composed of annihilation-creation operators and
pair operators. Canonical transformation, the extension of the SO(2N)
Bogoliubov transformation to the SO(2N+1) group, is introduced. Embedding the
SO(2N+1) group into an SO(2N+2) group and using SO(2N+2)/U(N+1) coset
variables, we investigate a new aspect of the supersymmetric sigma-model on the
Kaehler manifold of the symmetric space SO(2N+2)/U(N+1). We construct a Killing
potential which is just the extension of the Killing potential in the
SO(2N)/U(N) coset space given by van Holten et al. to that in the
SO(2N+2)/U(N+1) coset space. To our great surprise, the Killing potential is
equivalent with the generalized density matrix. Its diagonal-block matrix is
related to a reduced scalar potential with a Fayet-Ilipoulos term. The reduced
scalar potential is optimized in order to see the behaviour of the vacuum
expectation value of the sigma-model fields and a proper solution for one of
the SO(2N+1) group parameters is obtained. We give bosonization of the SO(2N+2)
Lie operators, vacuum functions and differential forms for their bosons
expressed in terms of the SO(2N+2)/U(N+1) coset variables, a U(1) phase and the
corresponding Kaehler potential.Comment: 28 pages, submitted to Nucl. Phys.
Shear viscosity of the quark matter
We discuss shear viscosity of the quark matter by using Kubo formula. The
shear viscosity is calculated in the framework of the quasi-particle RPA for
the Nambu-Jona-Lasinio model. We obtain a formula that the shear viscosity is
expressed by the quadratic form of the quark spectral function in the chiral
symmetric phase. The magnitude of the shear viscosity is discussed assuming the
Breit-Wigner type for the spectral function.Comment: 5 pages, 6 figure
Experimental isovalthinuria. I. Induction by isovaleric acid
In order to see whether isovalthinuria can be induced in animals other than the cat, that was found to excrete isovalthine in normal urine as previously reported³, using rat, guinea pig, rabbit and dog as test animals, isovaleric acid was adminstered either orally or parenterally and their urine was analyzed for the presence of isovalthine. As the result it was found that the rat, guinea pig, rabbit and dog administered with isovaleric acid orally or parenterally all excreted isovalthine in their urine, which normally does not contain it.</p
Effect of fatigue on fascicle behavior of human biceps femoris in eccentric knee flexions in vivo
The role of soil states in medium-range weather predictability
International audienceCurrent day operational ensemble weather prediction systems generally rely upon perturbed atmospheric initial states, thereby neglecting the eventual effect on the atmospheric evolution that uncertainties in initial soil temperature and moisture fields could bring about during the summer months. The purpose of this study is to examine the role of the soil states in medium-range weather predictability. A limited area weather prediction model is used with the atmosphere/ land-surface system in coupled or uncoupled mode. It covers Europe and part of the north Atlantic, and is driven by prescribed sea-surface temperatures over the sea, and by atmospheric reanalyses at its lateral boundaries. A series of 3 member ensembles of summer simulations are used to assess the predictability of a reference simulation assumed to be perfect. In a first step, two ensembles are simulated: the first with the atmosphere coupled to the land-surface model, the second in the uncoupled mode with perfect soil conditions prescribed every 6 hours. Subsequent experiments are combinations thereof, in which the uncoupled and coupled modes alternate in the course of a simulation. The results show that there are "stable" and "unstable" periods in the weather evolution under consideration. During the stable periods, the predictability (measured in terms of ensemble spread at 500 hPa) of the coupled and uncoupled dynamical systems is almost identical; prescribing the perfect soil conditions has a negligible impact upon the atmospheric predictability. In contrast, the predictability during an unstable phase is found to be remarkably improved in the uncoupled ensembles. This effect results from guiding the atmospheric phase-space trajectory along its perfect evolution. It persists even when switching back from the uncoupled to the coupled mode prior to the onset of the unstable phase, a result that underlines the importance of soil moisture and temperature in data assimilation systems
Characteristics of home-cooked dishes eaten all over Japan up to the 1960s
departmental bulletin pape
Anomaly-Free Supersymmetric SO(2N+2)/U(N+1) sigma-Model Based on the SO(2N+1) Lie Algebra of the Fermion Operators
The extended supersymmetric (SUSY) sigma-model has been proposed on the bases
of SO(2N+1) Lie algebra spanned by fermion annihilation-creation operators and
pair operators. The canonical transformation, extension of an SO(2N) Bogoliubov
transformation to an SO(2N+1) group, is introduced. Embedding the SO(2N+1)
group into an SO(2N+2) group and using SO(2N+2)/U(N+1) coset variables, we have
investigated the SUSY sigma-model on the Kaehler manifold, the coset space
SO(2N+2)/U(N+1). We have constructed the Killing potential, extension of the
potential in the SO(2N)/U(N) coset space to that in the SO(2N+2)/U(N+1) coset
space. It is equivalent to the generalized density matrix whose diagonal-block
part is related to a reduced scalar potential with a Fayet-Ilipoulos term. The
f-deformed reduced scalar potential is optimized with respect to vacuum
expectation value of the sigma-model fields and a solution for one of the
SO(2N+1) group parameters has been obtained. The solution, however, is only a
small part of all solutions obtained from anomaly-free SUSY coset models. To
construct the coset models consistently, we must embed a coset coordinate in an
anomaly-free spinor representation (rep) of SO(2N+2) group and give
corresponding Kaehler and Killing potentials for an anomaly-free
SO(2N+2)/U(N+1) model based on each positive chiral spinor rep. Using such
mathematical manipulation we construct successfully the anomaly-free
SO(2N+2)/U(N+1) SUSY sigma-model and investigate new aspects which have never
been seen in the SUSY sigma-model on the Kaehler coset space SO(2N)/U(N). We
reach a f-deformed reduced scalar potential. It is minimized with respect to
the vacuum expectation value of anomaly-free SUSY sigma-model fields. Thus we
find an interesting f-deformed solution very different from the previous
solution for an anomaly-free SO(2.5+2)/(SU(5+1)*U(1)) SUSY sigma-model.Comment: 24 pages, no fiure
Nonlinear Bogolyubov-Valatin transformations and quaternions
In introducing second quantization for fermions, Jordan and Wigner
(1927/1928) observed that the algebra of a single pair of fermion creation and
annihilation operators in quantum mechanics is closely related to the algebra
of quaternions H. For the first time, here we exploit this fact to study
nonlinear Bogolyubov-Valatin transformations (canonical transformations for
fermions) for a single fermionic mode. By means of these transformations, a
class of fermionic Hamiltonians in an external field is related to the standard
Fermi oscillator.Comment: 6 pages REVTEX (v3: two paragraphs appended, minor stylistic changes,
eq. (39) corrected, references [10]-[14], [36], [37], [41], [67]-[69] added;
v4: few extensions, references [62], [63] added, final version to be
published in J. Phys. A: Math. Gen.
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