共查询到20条相似文献,搜索用时 31 毫秒
1.
This paper examines the effect of substitution of water by heavy water in a polymer solution of polystyrene (molecular weight=13000)
and acetone. A critical double point (CDP), at which the upper and the lower partially-miscible regions merge, occurs at nearly
the same coordinates as for the system [polystyrene+acetone+water]. The shape of the critical line for [polystyrene+acetone+heavy
water] is highly asymmetric. An explanation for the occurrence of the water-induced CDP in [polystyrene+acetone] is advanced
in terms of the interplay between contact energy dissimilarity and free-volume disparity of the polymer and the solvent. The
question of the possible existence of a one-phasehole in an hourglass phase diagram is addressed in [polystyrene+acetone+water]. Our data exclude such a possibility. 相似文献
2.
《中国物理 B》2019,(8)
The adiabatic control is a powerful technique for many practical applications in quantum state engineering, light-driven chemical reactions and geometrical quantum computations. This paper reveals a speed limit of nonadiabatic transition in a general time-dependent parametric quantum system that leads to an upper bound function which lays down an optimal criteria for the adiabatic controls. The upper bound function of transition rate between instantaneous eigenstates of a time-dependent system is determined by the power fluctuations of the system relative to the minimum gap between the instantaneous levels. In a parametric Hilbert space, the driving power corresponds to the quantum work done by the parametric force multiplying the parametric velocity along the parametric driving path. The general two-state time-dependent models are investigated as examples to calculate the bound functions in some general driving schemes with one and two driving parameters. The calculations show that the upper bound function provides a tighter real-time estimation of nonadiabatic transition and is closely dependent on the driving frequencies and the energy gap of the system. The deviations of the real phase from Berry phase on different closed paths are induced by the nonadiabatic transitions and can be efficiently controlled by the upper bound functions. When the upper bound is adiabatically controlled, the Berry phases of the electronic spin exhibit nonlinear step-like behaviors and it is closely related to topological structures of the complicated parametric paths on Bloch sphere. 相似文献
3.
陈小余 《Frontiers of Physics》2012,7(4):444-448
We exactly evaluate the entanglement of a six vertex and a nine vertex graph states which correspond to non ??two-colorable?? graphs. to non ??two-colorable?? graphs. The upper bound of entanglement for five vertex ring graph state is improved to 2. is improved to 2.9275, less than the upper bound determined by local operations and classical communication. communication. An upper bound of entanglement is proposed based on the definition of graph state. state. 相似文献
4.
《Applied Acoustics》1987,21(3):241-246
This study deals with the determination of upper and lower bounds for the fundamental frequency of the structural system described in the title. The upper bound is determined by approximating the fundamental mode shape by means of a polynomial coordinate function in the angular coordinate, which includes an exponential optimization parameter. The fundamental frequency equation is generated by means of the Rayleigh-Ritz method, and the resulting upper bound is minimized with respect to the previously mentioned exponential parameter. The lower bound for the frequency coefficient is obtained by means of an extension of Dunkerley's method. 相似文献
5.
Upper bound for the time derivative of entropy for a dynamical system driven by coloured cross-correlated white noises
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It is shown how the cross-correlation time and strength of coloured cross-correlated white noises can set an upper bound for the time derivative of entropy in a nonequilibrium system. The value of upper bound can be calculated directly based on the Schwartz inequality principle and the Fokker--Planck equation of the dynamical system driven by coloured cross-correlated white noises. The present calculations can be used to interpret the interplay of the dissipative constant and cross-correlation
time and strength of coloured cross-correlated white noises on the upper bound. 相似文献
6.
It is shown that rigorous upper and lower bounds to the wave-vector dependent susceptibility of the Ising Model are obtained either when an upper bound to the spin pair correlation function and a lower bound to the susceptibility at zero wave-vector are given, or when a lower bound to the former and an upper bound to the latter are given. An example of the numerical computation of the bounds is presented for the Ising model on the sc lattice. 相似文献
7.
K.-H. Ma C. S. Yu H. S. Song 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2010,59(2):317-320
By a variational definition of the entanglement measure – negativity, we derive an upper bound of negativity of superpositions
in terms of the negativities of the quantum states being superposed. It is shown that the upper bound has a simple formulation.
In particular, in many cases the upper bound is tighter than the previous bounds. 相似文献
8.
Prabir Daripa 《Physica A》2011,390(18-19):3069-3076
We consider the linear stability of three-layer Hele-Shaw flows with each layer having constant viscosity and viscosity increasing in the direction of a basic uniform flow. While the upper bound results on the growth rate of long waves are well known from our earlier works, lower bound results on the growth rate of short stable waves are not known to date. In this paper, we obtain such a lower bound. In particular, we show the following results: (i) the lower bound for stable short waves is also a lower bound for all stable waves, and the exact dispersion curve for the most stable eigenvalue intersects the dispersion curve based on the lower bound at a wavenumber where the most stable eigenvalue is zero; (ii) the upper bound for unstable long waves is also an upper bound for all unstable waves, and the exact dispersion curve for the most unstable eigenvalue intersects the dispersion curve based on the upper bound at a wavenumber where the most unstable eigenvalue is zero. Numerical results are provided which support these findings. 相似文献
9.
Igal Sason 《Entropy (Basel, Switzerland)》2021,23(3)
This paper studies the problem of upper bounding the number of independent sets in a graph, expressed in terms of its degree distribution. For bipartite regular graphs, Kahn (2001) established a tight upper bound using an information-theoretic approach, and he also conjectured an upper bound for general graphs. His conjectured bound was recently proved by Sah et al. (2019), using different techniques not involving information theory. The main contribution of this work is the extension of Kahn’s information-theoretic proof technique to handle irregular bipartite graphs. In particular, when the bipartite graph is regular on one side, but may be irregular on the other, the extended entropy-based proof technique yields the same bound as was conjectured by Kahn (2001) and proved by Sah et al. (2019). 相似文献
10.
We compute the pressure of the random energy model (REM) and generalized random energy model (GREM) by establishing variational
upper and lower bounds. For the upper bound, we generalize Guerra’s “broken replica symmetry bounds,” and identify the random
probability cascade as the appropriate random overlap structure for the model. For the REM the lower bound is obtained, in
the high temperature regime using Talagrand’s concentration of measure inequality, and in the low temperature regime using
convexity and the high temperature formula. The lower bound for the GREM follows from the lower bound for the REM by induction.
While the argument for the lower bound is fairly standard, our proof of the upper bound is new. 相似文献
11.
D. Bruss 《Applied physics. B, Lasers and optics》1999,69(5-6):401-405
Both perfect cloning and perfect state estimation of an unknown pure quantum state are impossible, due to principles of quantum
mechanics. Nevertheless, they can be performed imperfectly. A link between these two scenarios allows us to derive an upper
bound for the fidelity in one of them, given an upper bound is known in the other. Furthermore, it is shown that also a lower
bound on cloning is related to an upper bound on state estimation.
Received: 15 June 1999 / Revised version: 23 September 1999 / Published online: 10 November 1999 相似文献
12.
In globally hyperbolic space-times there is a finite upper bound on the proper time lengths of nonspacelike curves between two chronologically related events. We show that if global hyperbolicity is replaced by a weaker causality condition, then there can exist chronologically related events in the space-time such that the proper time lengths of nonspacelike curves joining them grow without bound. We also show that the existence of a finite upper bound on the lengths of nonspacelike curves between two chronologically related events implies only chronology of the space-time but not causality. 相似文献
13.
A.B. Ku 《Journal of sound and vibration》1977,54(3):311-316
A better upper bound than the Rayleigh quotient is the Timoshenko quotient, the evaluation of which depends on a pair of compatible admissible moment and displacement functions. Based on both Rayleigh and Timoshenko quotients, a lower bound is readily computed. By means of an iteration procedure, both the upper and lower bound converge to the fundamental natural frequency. 相似文献
14.
We study the fully entangled fraction of a quantum state. An upper bound is obtained for arbitrary bipartite system. This upper bound only depends on the Frobenius norm of the state. 相似文献
15.
There is an upper bound for the L(1) norm of the difference of two nonnegative object functions when they both produce the same data in a digital imaging system. This bound is achieved for a certain class of systems and an arbitrary nonnegative object. For the L(2) norm of the difference, with the same conditions on the object functions, there is no upper bound. 相似文献
16.
Lu KangAlison R. Keimowitz Michaeleen R. MunrowStewart E. Novick 《Journal of Molecular Spectroscopy》2002,213(2):122-129
The rotational spectra of the argon acetone weakly bound complex was studied by pulsed jet Fabry-Perot Fourier transform microwave spectroscopy. Over 500 transitions of the complex were measured between 5.5 and 26 GHz from J=2-1 to J=12-11. The two methyl groups undergo hindered internal rotation resulting in four or five internal rotation states. The microwave transitions are within these states, resulting in a splitting of each rotational transition into four and sometimes five distinct transitions. The three-fold barrier to internal rotation is determined to be 260 cm−1, 2% less than the 266 cm−1 barrier in acetone itself. The structure of the complex has the argon atom above the heavy atom plane of the acetone, 3.52 Å from the CO bond and approximately in the Cs plane, which is perpendicular to the CCC plane of acetone. 相似文献
17.
We give an analytic quantitative relation between Hardy’s non-locality and Bell operator. We find that Hardy’s non-locality is a sufficient condition for the violation of Bell inequality, the upper bound of Hardy’s non-locality allowed by information causality just corresponds to Tsirelson bound of Bell inequality and the upper bound of Hardy’s non-locality allowed by the principle of no-signaling just corresponds to the algebraic maximum of Bell operator. Then we study the Cabello’s argument of Hardy’s non-locality (a generalization of Hardy’s argument) and find a similar relation between it and violation of Bell inequality. Finally, we give a simple derivation of the bound of Hardy’s non-locality under the constraint of information causality with the aid of the above derived relation between Hardy’s non-locality and Bell operator. 相似文献
18.
We find tight upper bound on the coherence of a superposition of two states in terms of the coherence of the two states constituting the superposition with $l_{1}$-norm of coherence. Our upper bound is tighter than the one presented by Liu, et al. [Quantum Inf. Process. 15 (2016) 4209.] We also generalize the results to the case that the superposition is constituted with more than two states in high dimension, and we give the corresponding upper bounds. 相似文献
19.
O. B. Zaslavskii 《General Relativity and Gravitation》1992,24(9):973-983
The entropy upper bound for a charged black hole in equilibrium with thermal radiation is derived by means of a general model-independent approach. This bound in some ways improves that proposed by Bekenstein by taking into account the energy of the electrical field. The corresponding lower bound for the Euclidean action is also obtained. The particular role of black-hole physics in the context under consideration is discussed. 相似文献
20.
We derive a model-independent upper bound on the scale of Majorana-neutrino mass generation. The upper bound is 4pi (nu2)/square root3 m(nu), where nu approximately 246 GeV is the weak scale and m(nu) is the Majorana-neutrino mass. For neutrino masses implied by neutrino oscillation experiments, all but one of these bounds are less than the Planck scale, and they are all within a few orders of magnitude of the grand-unification scale. 相似文献