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991.
We address the question of the classification of gapped ground states in one dimension that cannot be distinguished by a local order parameter. We introduce a family of quantum spin systems on the one-dimensional chain that have a unique gapped ground state in the thermodynamic limit that is a simple product state, but which on the left and right half-infinite chains have additional zero energy edge states. The models, which we call Product Vacua with Boundary States, form phases that depend only on two integers corresponding to the number of edge states at each boundary. They can serve as representatives of equivalence classes of such gapped ground states phases and we show how the AKLT model and its SO(2J + 1)-invariant generalizations fit into this classification. 相似文献
992.
Sven Dobner Martin Höhl Niklas M. Lüpken Carsten Fallnich 《Applied physics. B, Lasers and optics》2014,116(4):793-798
We show in proof-of-principle experiments an axial resolution improvement in two-photon-excited fluorescence and polymerization enabled by the short coherence length of two counter-propagating ultrashort laser pulses. The interference of these pulses generate a spatial interference fringe pattern, whose width scales inversely to the spectral bandwidth and is therefore considerably shorter than the effective focal length of a laser beam conventionally focused from only one side. 相似文献
993.
We present the derivation of the macroscopic equations for systems with an axial dynamic preferred direction. In addition
to the usual hydrodynamic variables, we introduce the time derivative of the local preferred direction as a new variable and
discuss its macroscopic consequences including new cross-coupling terms. Such an approach is expected to be useful for a number
of systems for which orientational degrees of freedom are important including, for example, the formation of dynamic macroscopic
patterns shown by certain bacteria such a Proteus mirabilis. We point out similarities in symmetry between the additional macroscopic variable discussed here, and the magnetization
density in magnetic systems as well as the so-called [^(l)]\hat l vector in superfluid 3He-A. Furthermore we investigate the coupling to a gel-like system for which one has the strain tensor and relative rotations
between the new variable and the network as additional macroscopic variables. 相似文献
994.
Sven Zschocke Thomas Hilger Burkhard Kämpfer 《The European Physical Journal A - Hadrons and Nuclei》2011,47(12):151
The operator product expansion (OPE) for heavy-light-quark pseudoscalar mesons (D -mesons and B -mesons) in medium is determined, both for a moving meson with respect to the surrounding medium as well as for a meson at
rest. First of all, the OPE is given in terms of normal-ordered operators up to mass dimension 5, and the mass of the heavy
quark and the mass of the light quark are kept finite. The Wilson coefficients of such an expansion are infrared (IR) divergent
in the limit of a vanishing light-quark mass. A consistent separation of scales necessitates an OPE in terms of non-normal-ordered
operators, which implies operator mixing, where the IR-divergences are absorbed into the operators. It is shown that the Wilson
coefficients of such an expansion are IR-stable, and the limit of a vanishing light-quark mass is perfomed. Details of the
major steps for the calculation of the Wilson coefficients are presented. By a comparison with previous results obtained by
other theoretical groups we have found serious disagreements. 相似文献
995.
4OR - A linearization technique for binary quadratic programs (BQPs) that comprise linear constraints is presented. The technique, called “inductive linearization”, extends concepts for... 相似文献
996.
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Transmetalation of Sn[N(SiMe3)2]2 with calcium granules in tetrahydropyran (thp) yields colorless [(thp)2Ca{N(SiMe3)2}2] ( 1 ) which is soluble in common organic solvents. The calcium center is in a distorted tetrahedral environment with Ca–N and Ca–O bond lengths of 231.08(11) and 240.23(9) pm, respectively. The molecular structure is dominated by steric factors leading to a NCaN bond angle of 119.43(6)°. 相似文献
1000.