1,801 research outputs found
Tannakian categories, linear differential algebraic groups, and parameterized linear differential equations
We provide conditions for a category with a fiber functor to be equivalent to
the category of representations of a linear differential algebraic group. This
generalizes the notion of a neutral Tannakian category used to characterize the
category of representations of a linear algebraic group.Comment: 26 pages; corrected misprints; simplified Definition 2; more
references adde
Topological superconducting phases in disordered quantum wires with strong spin-orbit coupling
Zeeman fields can drive semiconductor quantum wires with strong spin-orbit
coupling and in proximity to s-wave superconductors into a topological phase
which supports end Majorana fermions and offers an attractive platform for
realizing topological quantum information processing. Here, we investigate how
potential disorder affects the topological phase by a combination of analytical
and numerical approaches. Most prominently, we find that the robustness of the
topological phase against disorder depends sensitively and non-monotonously on
the Zeeman field applied to the wire.Comment: 6 pages, 3 figures; published versio
The Decay Properties of the 1^{-+} Hybrid State
Within the framework of the QCD sum rules, we consider the three-point
correlation function, work at the limit q^2 -> 0 and m_\pi -> 0, and pick out
the singular term ~ {1\over q^2} to extract the pionic coupling constants of
the 1^{-+} hybrid meson. Then we calculate the decay widths of different modes.
The decay width of the S-wave modes b_1 \pi, f_1\pi increases quickly as the
hybrid meson mass and decay momentum increase. But for the low mass hybrid
meson around 1.6 GeV, the P-wave decay mode \rho \pi is very important and its
width is around 180 MeV, while the widths of \eta \pi and \eta^\prime \pi are
strongly suppressed. We suggest the experimental search of \pi_1(1600) through
the decay chains at BESIII: e^+e^- -> J/\psi(\psi') -> \pi_1 +\gamma or e^+e^-
-> J/\psi(\psi') -> \pi_1 +\rho where the \pi_1 state can be reconstructed
through the decay modes \pi_1 -> \rho\pi -> \pi^+\pi^-\pi^0 or \pi_1 ->
f_1(1285)\pi^0. It is also interesting to look for \pi_1 using the available
BELLE/BABAR data through the process e^+e^- -> \gamma^\ast -> \rho\pi_1,
b_1\pi_1, \gamma \pi_1 etc.Comment: one reference correcte
Massive liquid Ar and Xe detectors for direct Dark Matter searches
A novel experiment for direct searches of the Dark Matter with liquid argon
double-phase chamber with a mass of liquid Ar up to several hundred tons is
proposed. To suppress the b-, g- and n0- backgrounds, the comparison of
scintillation and ionization signals for every event is suggested. The addition
in liquid Ar of photosensitive Ge(CH3)4 or C2H4 and suppression of triplet
component of scintillation signals ensures the detection of scintillation
signals with high efficiency and provides a complete suppression of the
electron background. For the detection of photoelectrons and ionization
electrons, highly stable and reliable GEM detectors must be used.Comment: 8 pages, 2 figures, 1 tabl
Functional renormalization-group approach to the Pokrovsky-Talapov model via modified massive Thirring fermion model
A possibility of the topological Kosterlitz-Thouless~(KT) transition in the
Pokrovsky-Talapov~(PT) model is investigated by using the functional
renormalization-group (RG) approach by Wetterich. Our main finding is that the
nonzero misfit parameter of the model, which can be related with the linear
gradient term (Dzyaloshinsky-Moriya interaction), makes such a transition
impossible, what contradicts the previous consideration of this problem by
non-perturbative RG methods. To support the conclusion the initial PT model is
reformulated in terms of the 2D theory of relativistic fermions using an
analogy between the 2D sine-Gordon and the massive Thirring models. In the new
formalism the misfit parameter corresponds to an effective gauge field that
enables to include it in the RG procedure on an equal footing with the other
parameters of the theory. The Wetterich equation is applied to obtain flow
equations for the parameters of the new fermionic action. We demonstrate that
these equations reproduce the KT type of behavior if the misfit parameter is
zero. However, any small nonzero value of the quantity rules out a possibility
of the KT transition. To confirm the finding we develop a description of the
problem in terms of the 2D Coulomb gas model. Within the approach the breakdown
of the KT scenario gains a transparent meaning, the misfit gives rise to an
effective in-plane electric field that prevents a formation of bound
vortex-antivortex pairs.Comment: 12 pages, 3 figure
Nuclear magnetic susceptibility of metals with magnetic impurities
We consider the contribution of magnetic impurities to the nuclear magnetic
susceptibility and to the specific heat of a metal. The impurity
contribution to the magnetic susceptibility has a behaviour, and the
impurity contribution to the specific heat has a behaviour, both in an
extended region of temperatures . In the case of a dirty metal the RKKY
interaction of nuclear spins and impurity spins is suppressed for low
temperatures and the main contribution to and is given by their
dipole-dipole interaction.Comment: 9 pages, 4 figures, REVTE
Pion quark structure in QCD
We describe the present status of the pion distribution amplitude as it
originated from two sources: (i) a nonperturbative approach, based on QCD sum
rules with nonlocal condensates and (ii) a NLO QCD analysis of the CLEO data on
F^{\gamma\gamma^*\pi}(Q^2), supplemented by the recent high-precision lattice
calculations of the second moment of the pion distribution amplitude.Comment: 4 pages, 2 figures, talk at the 9th International Workshop on Meson
Production, Properties and Interaction, Krakow, Poland, 9--13 June 200
Semileptonic decays of pseudoscalar mesons to scalar "f_0" meson
The transition form factors of (D_s -> f_0 l nu), (D -> f_0 l nu) and (B_u ->
f_0 l nu) decays are calculated in 3-point QCD sum rule method, assuming that
"f_0" is a quark-antiquark state with a mixture of strange and light quarks.
The branching ratios of these decays are calculated in terms of the mixing
angle.Comment: 12 pages, 4 figures, LaTeX formatte
Twist-3 distribution amplitudes of scalar mesons from QCD sum rules
We study the twist-3 distribution amplitudes for scalar mesons made up of two
valence quarks based on QCD sum rules.
By choosing the proper correlation functions, we derive the moments of the
scalar mesons up to the first two order. Making use of these moments, we then
calculate the first two Gegenbauer coefficients for twist-3 distribution
amplitudes of scalar mesons. It is found that the second Gegenbauer
coefficients of scalar density twist-3 distribution amplitudes for
and mesons are quite close to that for , which indicates that the
SU(3) symmetry breaking effect is tiny here. However, this effect could not be
neglected for the forth Gegenbauer coefficients of scalar twist-3 distribution
amplitudes between and . Besides, we also observe that the first two
Gegenbauer coefficients corresponding to the tensor current twist-3
distribution amplitudes for all the , and are very small.
The renormalization group evolution of condensates, quark masses, decay
constants and moments are considered in our calculations. As a byproduct, it is
found that the masses for isospin I=1, scalar mesons are around
GeV and GeV respectively, while the mass for
isospin state composed of is GeV.Comment: replaced with revised version, to be published in Phys. Rev.
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