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991.
This paper deals with the Pontryagin maximum principle for optimal control problems governed by 3D Navier–Stokes equations with pointwise control constraint. The obtained result is proved by using some results on regularity of solutions of the Navier–Stokes equations and techniques of optimal control theory. 相似文献
992.
V. V. Valkov D. M. Dzebisashvili A. F. Barabanov 《Theoretical and Mathematical Physics》2017,191(2):752-763
The spin–fermion model, which is an effective low-energy realization of the three-band Emery model after passing to the Wannier representation for the px and py orbitals of the subsystem of oxygen ions, reduces to the generalized Kondo lattice model. A specific feature of this model is the existence of spin-correlated hoppings of the current carriers between distant cells. Numerical calculations of the spectrum of spin-electron excitations highlight the important role of the long-range spin-correlated hoppings. 相似文献
993.
In the Brans–Dicke cosmology framework, we study holographic dark energy models with interaction and with power-law and logarithmic entropy corrections for different cutoffs. We consider conditions on the Brans–Dicke parameter compared with the conditions for the acceleration and phantom phases to show which entropy-corrected models can have acceleration and a phantom phase in the early Universe and at the present. Moreover, we determine which of the considered models are classically stable and which are unstable in early times and at the present. 相似文献
994.
E. V. Trifonov 《Theoretical and Mathematical Physics》2017,192(1):974-981
We propose a procedure for multiplying solutions of linear and nonlinear one-dimensional wave equations, where the speed of sound can be an arbitrary function of one variable. We obtain exact solutions. We show that the functional series comprising these solutions can be used to solve initial boundary value problems. For this, we introduce a special scalar product. 相似文献
995.
V. A. Andreev D. M. Davidović L. D. Davidović Milena D. Davidović Miloš D. Davidović 《Theoretical and Mathematical Physics》2017,192(1):1080-1096
We consider scale transformations (q, p) → (λq, λp) in phase space. They induce transformations of the Husimi functions H(q, p) defined in this space. We consider the Husimi functions for states that are arbitrary superpositions of n-particle states of a harmonic oscillator. We develop a method that allows finding so-called stretched states to which these superpositions transform under such a scale transformation. We study the properties of the stretched states and calculate their density matrices in explicit form. We establish that the density matrix structure can be described using negative binomial distributions. We find expressions for the energy and entropy of stretched states and calculate the means of the number-ofstates operator. We give the form of the Heisenberg and Robertson–Schrödinger uncertainty relations for stretched states. 相似文献
996.
Adapting some methods for real-valued Gibbs measures on Cayley trees to the p-adic case, we construct several p-adic distributions on the set ?p of p-adic integers. In addition, we give conditions under which these p-adic distributions become p-adic measures (i.e., bounded distributions). 相似文献
997.
We present Noether symmetries of a geodetic Lagrangian for a time-conformal cylindrically symmetric space–time. We introduce a time-conformal factor in the general cylindrically symmetric space–time to make it nonstatic and then find approximate Noether symmetries of the action of the corresponding Lagrangian. Taking the perturbation up to the first order, we find all Lagrangians for cylindrically symmetric space–times for which approximate Noether symmetries exist. 相似文献
998.
We present a sequence of anisotropic Bianchi type-II dark-energy models in the framework of the Brans–Dicke theory of gravity with a variable equation of state (EoS) parameter and a constant deceleration parameter. We use power-law relations between the scalar field φ and the scale factor A and between the average Hubble parameter H and the average scale factor A to obtain most of the analytic solutions. The dark-energy EoS parameter ω and its range admitted by the models agrees well with the most recent observational data. It has been observed that the cosmological constant Λ is decreasing with time, which is consistent with recent cosmological observations. We study the dynamical stability and physical features of the models. 相似文献
999.
1000.