2,257 research outputs found
Neutron depolarization studies of Pd-Ni-Fe-P alloy
Bulk metallic glasses based on the quaternary alloy Pd-Ni-Fe-P exhibit interesting phase behavior depending on temperature and applied magnetic field. Previous work has suggested that a range of magnetic phases including paramagnetic, superparamagnetic, ferromagnetic and spin glass can be observed in this system. We have applied one dimensional neutron depolarization to explore the correlation of magnetic moments in Pd40Ni22.5Fe17.5P20 alloy as a function of temperature and applied magnetic field. The results provided evidence for correlation lengths of ~ 200 Å. The nature of the correlations and the formation mechanism of the induced ferromagnetic phase are discusse
Two-band fast Hartley transform
This article has been made available through the Brunel Open Access Publishing Fund.Efficient algorithms have been developed over the past 30 years for computing the forward and inverse discrete Hartley transforms (DHTs). These are similar to the fast Fourier transform (FFT) algorithms for computing the discrete Fourier transform (DFT). Most of these methods seek to minimise the complexity of computations and or the number of operations. A new approach for the computation of the radix-2 fast Hartley transform (FHT) is presented. The proposed algorithm, based on a two-band decomposition of the input data, possesses a very regular structure, avoids the input or out data shuffling, requires slightly less multiplications than the existing approaches, but increases the number of additions
Higher derivative corrections in holographic Zamolodchikov-Polchinski theorem
We study higher derivative corrections in holographic dual of
Zamolodchikov-Polchinski theorem that states the equivalence between scale
invariance and conformal invariance in unitary d-dimensional Poincare invariant
field theories. From the dual holographic perspective, we find that a
sufficient condition to show the holographic theorem is the generalized strict
null energy condition of the matter sector in effective (d+1)-dimensional
gravitational theory. The same condition has appeared in the holographic dual
of the "c-theorem" and our theorem suggests a deep connection between the two,
which was manifested in two-dimensional field theoretic proof of the both.Comment: 13 pages, v2: reference added, v3 some clarification adde
Synchronization of fractional order chaotic systems
The chaotic dynamics of fractional order systems begin to attract much
attentions in recent years. In this brief report, we study the master-slave
synchronization of fractional order chaotic systems. It is shown that
fractional order chaotic systems can also be synchronized.Comment: 3 pages, 5 figure
Quasiparticle contribution to heat carriers relaxation time in DyBaCuO from heat diffusivity measurements
It is shown that the controversy on phonons or electrons being the most
influenced heat carriers below the critical temperature of high-T
superconductors can be resolved. Electrical and thermal properties of the same
DyBaCuO monodomain have been measured for two highly different
oxygenation levels. While the oxygenated sample DyBaCuO has very
good superconducting properties ( K), the DyBaCuO
sample exhibits an insulator behavior. A careful comparison between
measurements of the {\bf thermal diffusivity} of both samples allows us to
extract the electronic contribution. This contribution to the relaxation time
of heat carriers is shown to be large below and more sensitive to the
superconducting state than the phonon contribution.Comment: 13 pages, 6 figure
Thermal Conductivity Tensor in YBaCuO: Effects of a Planar Magnetic Field
We have measured the thermal conductivity tensor of a twinned
YBaCuO single crystal as a function of angle between
the magnetic field applied parallel to the CuO planes and the heat current
direction, at different magnetic fields and at T=13.8 K. Clear fourfold and
twofold variations in the field-angle dependence of and
were respectively recorded in accordance with the d-wave pairing
symmetry of the order parameter. The oscillation amplitude of the transverse
thermal conductivity was found to be larger than the
longitudinal one in the range of magnetic field studied here
(). From our data we obtain quantities that are free
from non-electronic contributions and they allow us a comparison of the
experimental results with current models for the quasiparticle transport in the
mixed state.Comment: 9 Figures, Phys. Rev. B(in press
Yu, Salamon, and Lu reply
The thermal conductivity anomaly in YBa2Cu307-„has been attributed [I] entirely to the phonon contribution tcL, due to reduced electron-phonon scattering below T,. As demonstrated in the Comment of Cohn et al. [2], with five or more parameters available the data can be fit equally well with or without a charge-carrier contribution x,. The goal of our analysis [3] was to bring the thermal conductivity data into agreement with the emerging picture of quasiparticle transport below T,. We made the simplifying assumption that quasiparticle and phonon systems are largely decoupled, and chose a particularly simple form for the underlying tcL. No assumption was made concerning the Wiedemann-Franz ratio beyond asserting that tc, should be temperature independent above T,
Einstein energy associated with the Friedmann -Robertson -Walker metric
Following Einstein's definition of Lagrangian density and gravitational field
energy density (Einstein, A., Ann. Phys. Lpz., 49, 806 (1916); Einstein, A.,
Phys. Z., 19, 115 (1918); Pauli, W., {\it Theory of Relativity}, B.I.
Publications, Mumbai, 1963, Trans. by G. Field), Tolman derived a general
formula for the total matter plus gravitational field energy () of an
arbitrary system (Tolman, R.C., Phys. Rev., 35(8), 875 (1930); Tolman, R.C.,
{\it Relativity, Thermodynamics & Cosmology}, Clarendon Press, Oxford, 1962));
Xulu, S.S., arXiv:hep-th/0308070 (2003)). For a static isolated system, in
quasi-Cartesian coordinates, this formula leads to the well known result , where is the
determinant of the metric tensor and is the energy momentum tensor of
the {\em matter}. Though in the literature, this is known as "Tolman Mass", it
must be realized that this is essentially "Einstein Mass" because the
underlying pseudo-tensor here is due to Einstein. In fact, Landau -Lifshitz
obtained the same expression for the "inertial mass" of a static isolated
system without using any pseudo-tensor at all and which points to physical
significance and correctness of Einstein Mass (Landau, L.D., and Lifshitz,
E.M., {\it The Classical Theory of Fields}, Pergamon Press, Oxford, 2th ed.,
1962)! For the first time we apply this general formula to find an expression
for for the Friedmann- Robertson -Walker (FRW) metric by using the same
quasi-Cartesian basis. As we analyze this new result, physically, a spatially
flat model having no cosmological constant is suggested. Eventually, it is seen
that conservation of is honoured only in the a static limit.Comment: By mistake a marginally different earlier version was loaded, now the
journal version is uploade
Generalized Penner models to all genera
We give a complete description of the genus expansion of the one-cut solution
to the generalized Penner model. The solution is presented in a form which
allows us in a very straightforward manner to localize critical points and to
investigate the scaling behaviour of the model in the vicinity of these points.
We carry out an analysis of the critical behaviour to all genera addressing all
types of multi-critical points. In certain regions of the coupling constant
space the model must be defined via analytical continuation. We show in detail
how this works for the Penner model. Using analytical continuation it is
possible to reach the fermionic 1-matrix model. We show that the critical
points of the fermionic 1-matrix model can be indexed by an integer, , as it
was the case for the ordinary hermitian 1-matrix model. Furthermore the 'th
multi-critical fermionic model has to all genera the same value of
as the 'th multi-critical hermitian model. However, the
coefficients of the topological expansion need not be the same in the two
cases. We show explicitly how it is possible with a fermionic matrix model to
reach a multi-critical point for which the topological expansion has
alternating signs, but otherwise coincides with the usual Painlev\'{e}
expansion.Comment: 27 pages, PostScrip
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