890 research outputs found
More on the Tensor Response of the QCD Vacuum to an External Magnetic Field
In this Letter we discuss a few issues concerning the magnetic susceptibility
of the quark condensate and the Son-Yamamoto (SY) anomaly matching equation. It
is shown that the SY relation in the IR implies a nontrivial interplay between
the kinetic and WZW terms in the chiral Lagrangian. It is also demonstrated
that in a holographic framework an external magnetic field triggers mixing
between scalar and tensor fields. Accounting for this, one may calculate the
magnetic susceptibility of the quark condensate to all orders in the magnetic
field.Comment: 20 pages, 2 figure
Axial anomaly: the modern status
The modern status of the problem of axial anomaly in QED and QCD is reviewed.
Two methods of the derivation of the axial anomaly are presented: 1) by
splitting of coordinates in the expression for the axial current and 2) by
calculation of triangle diagrams, where the anomaly arises from the surface
terms in momentum space. It is demonstrated, that the equivalent formulation of
the anomaly can be given, as a sum rule for the structure function in
dispersion representation of three point function of AVV interaction. It is
argued, that such integral representation of the anomaly has some advantages in
the case of description of the anomaly by contribution of hadronic states in
QCD. The validity of the t'Hooft consistency condition is discussed. Few
examples of the physical application of the axial anomaly are given.Comment: 17 pages, 3 figures, to be published in International Journal of
Modern Physics A, few minor correction were done, two references were adde
New Two-Dimensional Integrable Quantum Models from SUSY Intertwining
Supersymmetrical intertwining relations of second order in the derivatives
are investigated for the case of supercharges with deformed hyperbolic metric
. Several classes of particular solutions of these
relations are found. The corresponding Hamiltonians do not allow the
conventional separation of variables, but they commute with symmetry operators
of fourth order in momenta. For some of these models the specific SUSY
procedure of separation of variables is applied.Comment: 18 page
Exclusive photoproduction of hard dijets and magnetic susceptibility of QCD vacuum
We argue that coherent production of hard dijets by linearly polarized real
photons can provide direct evidence for chirality violation in hard processes,
the first measurement of the magnetic susceptibility of the quark condensate
and the photon distribution amplitude. It can also serve as a sensitive probe
of the generalized gluon parton distribution. Numerical calculations are
presented for HERA kinematics.Comment: 4 pages, 4 figure
Magnetic moment of the rho-meson in QCD sum rules
The rho-meson magnetic moment is calculated in the framework of QCD sum rules
in external fields. Bare loop calculations (parton model) give 2.0. The
contribution of the operators of dimension 6 reduces this value to 1.5.Comment: 8 pages, 1 figur
Numerical study of pi-junction using spin filtering barriers
We numerically investigate the Josephson transport through ferromagnetic
insulators (FIs) by taking into account its band structure. By use of the
recursive Green's function method, we found the formation of the pi junction in
the case of the fully spin-polarized FI (FPFI), e.g., LaBaCuO.
Moreover, the 0-pi transition is induced by increasing the thickness of FPFI.
On the other hand, Josephson current through the Eu chalcogenides shows the pi
junction behavior in the case of the strong d-f hybridization between the
conduction d and the localized f electrons of Eu. Such FI-based Josephson
junctions may become a element in the architecture of future quantum
information devices.Comment: 9 pages, 5 figure
Magnetic Moments of Decuplet Baryons in Light Cone QCD
We calculate the magnetic moments of decuplet baryons containing strange
quarks within the framework of light cone QCD sum rules taking into account the
SU(3) flavor symmetry breaking effects. It is obtained that magnetic moments of
the neutral \sso and \xis0 baryons are mainly determined by the SU(3)
breaking terms. A comparison of our results on the magnetic moments of the
decuplet baryons with the predictions of other approaches is presented.Comment: Latex, 20 pages, 6 figure
Thermoelectric transport in strained Si and Si/Ge heterostructures
The anisotropic thermoelectric transport properties of bulk silicon strained
in [111]-direction were studied by detailed first-principles calculations
focussing on a possible enhancement of the power factor. Electron as well as
hole doping were examined in a broad doping and temperature range. At low
temperature and low doping an enhancement of the power factor was obtained for
compressive and tensile strain in the electron-doped case and for compressive
strain in the hole-doped case. For the thermoelectrically more important high
temperature and high doping regime a slight enhancement of the power factor was
only found under small compressive strain with the power factor overall being
robust against applied strain. To extend our findings the anisotropic
thermoelectric transport of an [111]-oriented Si/Ge superlattice was
investigated. Here, the cross-plane power factor under hole-doping was
drastically suppressed due to quantum-well effects, while under electron-doping
an enhanced power factor was found. With that, we state a figure of merit of
ZT and ZT at T=\unit[300]{K} and T=\unit[900]{K} for the
electron-doped [111]-oriented Si/Ge superlattice. All results are discussed in
terms of band structure features
The "radiative Delta -> N gamma" decay in light cone QCD
The "g_{Delta N gamma}" coupling for the "Delta -> N gamma" decay is
calculated in framework of the light cone QCD sum rules and is found to be
g_{Delta N gamma} = (1.6 pm 0.2) GeV^(-1). Using this value of g_{Delta N
gamma} we estimate the branching ratio of the Delta^+ -> N gamma decay, which
is in a very good agreement with the experimental result.Comment: 9 pages, 1figures, LaTeX formatte
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