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Koszul property of diagonal subalgebras  [PDF]
Neeraj Kumar
Mathematics , 2013,
Abstract: Let S=K[x_1,...,x_n] be a polynomial ring over a field K and I a homogeneous ideal in S generated by a regular sequence f_1,f_2,...,f_k of homogeneous forms of degree d. We study a generalization of a result of Conca, Herzog, Trung, and Valla [9] concerning Koszul property of the diagonal subalgebras associated to I. Each such subalgebra has the form K[(I^e)_{ed+c}], where c and e are positive integers. For k=3, we extend [9, Corollary 6.10] by proving that K-algebra K[(I^e)_{ed+c}] is Koszul as soon as c >= d/2. We also extend [9, Corollary 6.10] in another direction by replacing the polynomial ring with a Koszul ring.
The Restricted Isometry Property for Random Block Diagonal Matrices  [PDF]
Armin Eftekhari,Han Lun Yap,Christopher J. Rozell,Michael B. Wakin
Mathematics , 2012,
Abstract: In Compressive Sensing, the Restricted Isometry Property (RIP) ensures that robust recovery of sparse vectors is possible from noisy, undersampled measurements via computationally tractable algorithms. It is by now well-known that Gaussian (or, more generally, sub-Gaussian) random matrices satisfy the RIP under certain conditions on the number of measurements. Their use can be limited in practice, however, due to storage limitations, computational considerations, or the mismatch of such matrices with certain measurement architectures. These issues have recently motivated considerable effort towards studying the RIP for structured random matrices. In this paper, we study the RIP for block diagonal measurement matrices where each block on the main diagonal is itself a sub-Gaussian random matrix. Our main result states that such matrices can indeed satisfy the RIP but that the requisite number of measurements depends on certain properties of the basis in which the signals are sparse. In the best case, these matrices perform nearly as well as dense Gaussian random matrices, despite having many fewer nonzero entries.
Parametrization of spectral surfaces of a class of periodic 5-diagonal matrices  [PDF]
Ionela Moale,Peter Yuditskii
Mathematics , 2011,
Abstract: The main result of this work is a parametric description of the spectral surfaces of a class of periodic 5-diagonal matrices, related to the strong moment problem. This class is a self-adjoint twin of the class of CMV matrices. Jointly they form the simplest possible classes of 5-diagonal matrices.
Realization of Robust Diagonal Dominance by Dynamic Compensator
用动态补偿器实现鲁棒对角优势

Zhao Chang''an,Jin Changxi,
赵长安
,金昌喜

自动化学报 , 1994,
Abstract: In this paper, the realization of robust diagonal dominance by dynamic compensator is investigated. The condition for the realization of robust diagonal dominance by using a dynamic compensator and the algorithm for such dynamic compensator are presented. An example for illustration is given.
Off-diagonal generalized vector dominance in DIS and QCD  [PDF]
G. Cvetic,D. Schildknecht,A. Shoshi
Physics , 1999,
Abstract: We review the generalized vector dominance (GVD) approach to DIS at small values of the scaling variable, x. In particular, we concentrate on a recent formulation of GVD that explicitly incorporates the configuration of the gamma^* -> q qbar transition and a QCD-inspired ansatz for the (qqbar)p scattering amplitude. The destructive interference, originally introduced in off-diagonal GVD is traced back to the generic strcuture of two-gluon exchange. Asymptotically, the transverse photoabsorption cross section behaves as (ln Q^2)/Q^2, implying a logarithmic violation of scaling for F_2, while the longitudinal-to-transverse ratio decreases as 1/\ln Q^2. We also briefly comment on vector-meson production.
Effective Mass Generation of Off-diagonal Gluons and Abelian Dominance in the Maximally Abelian Gauge in QCD  [PDF]
K. Amemiya,H. Suganuma
Physics , 1999, DOI: 10.1016/S0920-5632(00)91692-X
Abstract: We study the properties of gluons in QCD in the maximally abelian (MA) gauge. In the MA gauge, the off-diagonal gluon behaves as the massive vector boson with the mass $\Meff \simeq 1.2 {\rm GeV}$, and therefore the off-diagonal gluon cannot carry the long-range interaction for $r \gg \Meff^{-1} \simeq 0.2$ fm. The essence of the infrared abelian dominance in the MA gauge is physically explained with the generation of the off-diagonal gluon mass $\Meff \simeq 1.2 {\rm GeV}$ induced by the MA gauge fixing, and the off-diagonal gluon mass generation would predict general infrared abelian dominance in QCD in the MA gauge. We report also the off-diagonal gluon propagator at finite temperature.
The lifting property for classes of mappings
Janusz J. Charatonik
International Journal of Mathematics and Mathematical Sciences , 2000, DOI: 10.1155/s0161171200002763
Abstract: The lifting property of continua for classes of mappings isdefined. It is shown that the property is preserved under theinverse limit operation. The results, when applied to the class ofconfluent mappings, exhibit conditions under which the inducedmapping between hyperspaces is confluent. This generalizesprevious results in this topic.
Off-Diagonal Generalized Vector-Dominance and Colour-Dipoles in Low-x DIS  [PDF]
D. Schildknecht
Physics , 2000,
Abstract: We briefly summarize the equivalence of off-diagonal generalized vector dominance and the colour-dipole approach to deep-inelastic scattering (DIS) in the diffraction region of values of $x \simeq Q^2/W^2 << 1$.
Universality Classes of Diagonal Quantum Spin Ladders  [PDF]
M. A. Martin-Delgado,J. Rodriguez-Laguna,G. Sierra
Physics , 2004, DOI: 10.1103/PhysRevB.72.104435
Abstract: We find the classification of diagonal spin ladders depending on a characteristic integer $N_p$ in terms of ferrimagnetic, gapped and critical phases. We use the finite algorithm DMRG, non-linear sigma model and bosonization techniques to prove our results. We find stoichiometric contents in cuprate $CuO_2$ planes that allow for the existence of weakly interacting diagonal ladders.
Off-diagonal Gluon Mass Generation and Infrared Abelian Dominance in the Maximally Abelian Gauge in Lattice QCD  [PDF]
K. Amemiya,H. Suganuma
Physics , 1998, DOI: 10.1103/PhysRevD.60.114509
Abstract: We study effective mass generation of off-diagonal gluons and infrared abelian dominance in the maximally abelian (MA) gauge. Using the SU(2) lattice QCD, we investigate the propagator and the effective mass of the gluon field in the MA gauge with the U(1)$_3$ Landau gauge fixing. The Monte Carlo simulation is performed on the $12^3 \times 24$ lattice with $2.2 \le \beta \le 2.4$, and also on the $16^4$ and $20^4$ lattices with $2.3 \le \beta \le 2.4$. In the MA gauge, the diagonal gluon component $A_\mu^3$ shows long-range propagation, and infrared abelian dominance is found for the gluon propagator. In the MA gauge, the off-diagonal gluon component $A_\mu^\pm$ behaves as a massive vector boson with the effective mass $M_{\rm off} \simeq 1.2$ GeV in the region of $r \gsim 0.2$ fm, and its propagation is limited within short range. We conjecture that infrared abelian dominance can be interpreted as infrared inactivity of the off-diagonal gluon due to its large mass generation induced by the MA gauge fixing.
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