8,784 research outputs found
Derived -module endomorphism rings
Let be a Hopf algebra, be an -Galois extension. Let and
be the derived categories of right -modules and of right -modules
respectively. An object may be regarded as an object in
via the restriction functor. We discuss the relations of the derived
endomorphism rings
E_A(M^\cdot)=\op_{i\in\mathbb{Z}}\Hom_{D(A)}(M^\cdot,M^\cdot[i]) and
E_B(M^\cdot)=\op_{i\in\mathbb{Z}}\Hom_{D(B)}(M^\cdot,M^\cdot[i]). If is a
finite dimensional semisimple Hopf algebra, then is a graded
subalgebra of . In particular, if is a usual -module, a
necessary and sufficient condition for to be an -Galois graded
extension of is obtained. As an application of the results, we show
that the Koszul property is preserved under Hopf Galois graded extensions.Comment: to appear at Glasgow Mathematical Journa
Hopf algebra actions on differential graded algebras and applications
Let be a finite dimensional semisimple Hopf algebra, a differential
graded (dg for short) -module algebra. Then the smash product algebra
is a dg algebra. For any dg -module , there is a quasi-isomorphism of
dg algebras: \mathrm{RHom}_A(M,M)\#H\longrightarrow \mathrm{RHom}_{A\#H}(M\ot
H,M\ot H). This result is applied to -Koszul algebras, Calabi-Yau algebras
and AS-Gorenstein dg algebrasComment: to appear in Bull. Belg. Math So
Deformations of Koszul Artin-Schelter Gorenstein algebras
We compute the Nakayama automorphism of a PBW-deformation of a Koszul
Artin-Schelter Gorenstein algebra of finite global dimension, and give a
criterion for an augmented PBW-deformation of a Koszul Calabi-Yau algebra to be
Calabi-Yau. The relations between the Calabi-Yau property of augmented
PBW-deformations and that of non-augmented cases are discussed. The Nakayama
automorphisms of PBW-deformations of Koszul Artin-Schelter Gorenstein algebras
of global dimensions 2 and 3 are given explicitly. We show that if a
PBW-deformation of a graded Calabi-Yau algebra is still Calabi-Yau, then it is
defined by a potential under some mild conditions. Some classical results are
also recovered. Our main method used in this paper is elementary and based on
linear algebra. The results obtained in this paper will be applied in a
subsequent paper.Comment: to appear at Manuscripta Mat
Unification of Flavor SU(3) Analyses of Heavy Hadron Weak Decays
Analyses of heavy mesons and baryons hadronic charmless decays using the
flavor SU(3) symemtry can be formulated in two different forms. One is to
construct the SU(3) irreducible representation amplitude (IRA) by decomposing
effective Hamiltonian, and the other is to draw the topological diagrams (TDA).
In the flavor SU(3) limit, we study various ,
decays, and two-body nonleptonic decays of beauty/charm baryons, and
demonstrate that when all terms are included these two ways of analyzing the
decay amplitudes are completely equivalent. Furthermore we clarify some
confusions in drawing topological diagrams using different ways of describing
beauty/charm baryons.Comment: 36 pages, 6 figures, 16 table
Three photon absorption in ZnO and ZnS crystals
We report a systematic investigation of both three-photon absorption
(3PA)spectra and wavelength dispersions of Kerr-type nonlinear refraction in
wide-gap semiconductors. The Z-scan measurements are recorded for both ZnO and
ZnS with femtosecond laser pulses. While the wavelength dispersions of the Kerr
nonlinearity are in agreement with a two-band model, the wavelength dependences
of the 3PA are found to be given by (3Ephoton/Eg-1)5/2(3Ephoton/Eg)-9. We also
evaluate higher-order nonlinear optical effects including the fifth-order
instantaneous nonlinear refraction associated with virtual three-photon
transitions, and effectively seventh-order nonlinear processes induced by
three-photon-excited free charge carriers. These higher-order nonlinear effects
are insignificant with laser excitation irradiances up to 40 GW/cm2. Both
pump-probe measurements and three-photon figures of merits demonstrate that ZnO
and ZnS should be a promising candidate for optical switching applications at
telecommunication wavelengths.Comment: 13 pages, 7 figure
Gapped spin liquid with -topological order for kagome Heisenberg model
We apply symmetric tensor network state (TNS) to study the nearest neighbor
spin-1/2 antiferromagnetic Heisenberg model on Kagome lattice. Our method keeps
track of the global and gauge symmetries in TNS update procedure and in tensor
renormalization group (TRG) calculation. We also introduce a very sensitive
probe for the gap of the ground state -- the modular matrices, which can also
determine the topological order if the ground state is gapped. We find that the
ground state of Heisenberg model on Kagome lattice is a gapped spin liquid with
the -topological order (or toric code type), which has a long
correlation length unit cell length. We justify that the TRG
method can handle very large systems with over thousands of spins. Such a long
explains the gapless behaviors observed in simulations on smaller systems
with less than 300 spins or shorter than 10 unit cell length. We also discuss
experimental implications of the topological excitations encoded in our
symmetric tensors.Comment: 10 pages, 7 figure
Theoretical investigation of the thermal performance of a novel solar loop-heat-pipe façade-based heat pump water heating system
The aim of the paper was to present a dedicated theoretical investigation into the thermal performance of a novel solar loop-heat-pipe façade based heat pump water heating system. This involved thermo-fluid analyses, computer numerical model development, the model running up, modelling result analyses and conclusion. An energy balance network was established on each part and the whole range of the system to address the associated energy conversion and transfer processes. On basis of this, a computer numerical model was developed and run up to predict the thermal performance of such a system at different system configurations, layouts and operational conditions. It was suggested that the loop heat pipes could be filled with either water, R134a, R22 or R600a; of which R600a is the favourite working fluid owing to its relatively larger heat transfer capacity and positive pressure in operation. Variations in the system configuration, i.e., glazing covers, heat exchangers, would lead to identifiable differences in the thermal performance of the system, represented by the thermal efficiency and COP. Furthermore, impact of the external operational parameters, i.e., solar radiation and ambient air temperature, to the system's thermal performance was also investigated. The research was based on an innovative loop-heat-pipe façade and came up with useful results reflecting the thermal performance of the combined system between the façade and heat pump. This would help promote development and market penetration of such an innovative solar heating technology, and thus contribute to achieving the global targets in energy saving and carbon emission reduction
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