Have Pentaquark States Been seen?

The status of the search for pentaquark baryons is reviewed in light of new results from the first two dedicated experiments from CLAS at Jefferson Lab and of new analyses from several laboratories on the $Theta^+(1540)$. Evidence for and against two heavier pentaquark states is also discussed.Comment: Added some references, corrected typo

Spin and orbital angular momentum of the proton

Since the announcement of the proton spin crisis by the European Muon Collaboration there has been considerable progress in unravelling the distribution of spin and orbital angular momentum within the proton. We review the current status of the problem, showing that not only have strong upper limits have been placed on the amount of polarized glue in the proton but that the experimental determination of the spin content has become much more precise. It is now clear that the origin of the discrepancy between experiment and the naive expectation of the fraction of spin carried by the quarks and anti-quarks in the proton lies in the non-perturbative structure of the proton. We explain how the features expected in a modern, relativistic and chirally symmetric description of nucleon structure naturally explain the current data. The consequences of this explanation for the presence of orbital angular momentum on quarks and gluons is reviewed and comparison made with recent results from lattice QCD and experimental data.Comment: Lectures at Aligarh University (4th DAE-BRNS Workshop on Hadron Physics, Feb 18-21, 200

Entanglement entropy in de Sitter: no pure states for conformal matter

In this paper, we consider the entanglement entropy of conformal matter for finite and semi-infinite entangling regions, as well as the formation of entanglement islands in four-dimensional de Sitter spacetime partially reduced to two dimensions. We analyze complementarity and pure state condition of the entanglement entropy of pure states and show that they never hold in the given setup. We consider two different types of Cauchy surfaces in the extended static patch and flat coordinates, correspondingly. For former, we found that entanglement entropy of a pure state is always bounded from below by a constant and never becomes zero, as required by quantum mechanics. In turn, the difference between the entropies for some region and its complement, which should be zero for a pure state, in direct calculations essentially depends on how the boundaries of these regions evolve with time. Regarding the flat coordinates, it is impossible to regularize spacelike infinity in a way that would be compatible with complementarity and pure state condition, as opposed, for instance, to two-sided Schwarzschild black hole. Finally, we discuss the information paradox in de Sitter and show that the island formula does not resolve it. Namely, we give examples of a region with a time-limited growth of entanglement entropy, for which there is no island solution, and the region, for which entanglement entropy does not grow, but the island solution exists.Comment: v1: 25 pages, 10 figures; v2: 25 pages, 10 figures, references added, notation clarifie

Entanglement Islands and Infrared Anomalies in Schwarzschild Black Hole

In this paper, island formation for entangling regions of finite size in the asymptotically flat eternal Schwarzschild black hole is considered. We check the complementarity property of entanglement entropy which was implicitly assumed in previous studies for semi-infinite regions. This check reveals the emergence of infrared anomalies after regularization of a Cauchy surface. A naive infrared regularization based on ``mirror symmetry'' is considered and its failure is shown. We introduce an improved regularization that gives a correct limit agreed with the semi-infinite results from previous studies. As the time evolution goes, the endpoints of a finite region compatible with the improved regularization become separated by a timelike interval. We call this phenomenon the ``Cauchy surface breaking''. Shortly before the Cauchy surface breaking, finite size configurations generate asymmetric entanglement islands in contrast to the semi-infinite case. Depending on the size of the finite regions, qualitatively new behaviour arises, such as discontinuous evolution of the entanglement entropy and the absence of island formation. Finally, we show that the island prescription does not help us to solve the information paradox for certain finite size regions.Comment: v1: 55 pages, 19 figures; v2: 57 pages, 19 figures, references added, Sec. 5 presentation improve

Stable marriage and roommates problems with restricted edges: complexity and approximability

In the Stable Marriage and Roommates problems, a set of agents is given, each of them having a strictly ordered preference list over some or all of the other agents. A matching is a set of disjoint pairs of mutually acceptable agents. If any two agents mutually prefer each other to their partner, then they block the matching, otherwise, the matching is said to be stable. We investigate the complexity of finding a solution satisfying additional constraints on restricted pairs of agents. Restricted pairs can be either forced or forbidden. A stable solution must contain all of the forced pairs, while it must contain none of the forbidden pairs. Dias et al. (2003) gave a polynomial-time algorithm to decide whether such a solution exists in the presence of restricted edges. If the answer is no, one might look for a solution close to optimal. Since optimality in this context means that the matching is stable and satisfies all constraints on restricted pairs, there are two ways of relaxing the constraints by permitting a solution to: (1) be blocked by as few as possible pairs, or (2) violate as few as possible constraints n restricted pairs. Our main theorems prove that for the (bipartite) Stable Marriage problem, case (1) leads to View the MathML source-hardness and inapproximability results, whilst case (2) can be solved in polynomial time. For non-bipartite Stable Roommates instances, case (2) yields an View the MathML source-hard but (under some cardinality assumptions) 2-approximable problem. In the case of View the MathML source-hard problems, we also discuss polynomially solvable special cases, arising from restrictions on the lengths of the preference lists, or upper bounds on the numbers of restricted pairs

A new approach to calculate the gluon polarization

We derive the Leading-Order master equation to extract the polarized gluon distribution G(x;Q^2) = x \deltag(x;Q^2) from polarized proton structure function, g1p(x;Q^2). By using a Laplace-transform technique, we solve the master equation and derive the polarized gluon distribution inside the proton. The test of accuracy which are based on our calculations with two different methods confirms that we achieve to the correct solution for the polarized gluon distribution. We show that accurate experimental knowledge of g1p(x;Q^2) in a region of Bjorken x and Q^2, is all that is needed to determine the polarized gluon distribution in that region. Therefore, to determine the gluon polarization \deltag /g,we only need to have accurate experimental data on un-polarized and polarized structure functions (F2p (x;Q^2) and g1p(x;Q^2)).Comment: 12 pages, 5 figure

3D Chiral MetaCrystals

Fine control of the chiral light-matter interaction at the nanoscale, by exploiting designed metamaterial architecture, represents a cutting-edge craft in the field of biosensing, quantum, and classic nanophotonics. Recently, artificially engineered 3D nanohelices demonstrate programmable wide chiroptical properties by tuning materials and architecture, but fundamental diffractive aspects that are at the origin of chiral resonances still remain elusive. Here, a novel concept of a 3D chiral metacrystal, where the chiroptical properties are finely tuned by in-plane and out-of-plane diffractive coupling, is proposed. Different chiral dipolar modes can be excited along the helix arms, generating far field optical resonances and radiation pattern with in-plane side lobes, and suggesting that a combination of efficient dipole excitation and diffractive coupling matching controls the collective oscillations among the neighbor helices. The proposed concept of compact chiral metacrystal can be suitable for integration with quantum emitters and open perspectives in novel schemes of enantiomeric detection

Effect of thickness on the piezoelectric properties of LiNbO3 films

The results were obtained using the equipment of Research and Education Center and the Center of collective use “Nanotechnology” of Southern Federal University

ОПТИМИЗАЦИЯ ФОРМЫ ФЮЗЕЛЯЖА, НАПРАВЛЕННАЯ НА УМЕНЬШЕНИЕ АЭРОДИНАМИЧЕСКОГО СОПРОТИВЛЕНИЯ КОМПОНОВКИ «КРЫЛО - ФЮЗЕЛЯЖ» ПРИ СВЕРХЗВУКОВЫХ СКОРОСТЯХ

The problem of fuselage shape optimization of the wing-body configuration is considered in the following three formulations. In the first one, the angle of attack is fixed and equal to zero, the wing has a symmetric airfoil, and the fuselage is based on circular cross sections. In the second one, the fuselage cross sections are elliptical. In the third one, the angle of attack is varied, the lifting force coefficient is fixed, the wing is preliminary optimized, the fuselage is designed by the cross sections that consist of upper and lower half-ellipses with a possibility of a shift along vertical axis. The configuration volume, fuselage length, shape and position of the wing are fixed. The drag coefficient is the objective function. The optimization is carried out by the Indirect Optimization based on Self-Organization (IOSO) technology. Aerodynamic coef- ficients are obtained from the solution of the RANS equations with SST turbulence model by the ANSYS CFX software on the structured multiblock meshes. The results obtained by the optimization are compared with the configuration that is designed by traditional means. The fuselage of this configuration has a cylindrical part in the area of the wing-fuselage connection and nose part of the von Karman’s ogive shape. The solution of the optimization problem in the first formulation reduces drag coefficient at zero angle of attack by approximately 3 %. The use of the fuselage with elliptical cross sections makes it possible to reduce drag coefficient at zero angle of attack by 9 %. The solution of the optimization problem in first two formulations reduces drag coefficient at the wide range of angles of attack. When the lifting coefficient is selected for the third problem formulation as constraint the drag reduction is about 7 %. Additional drag reduction of about 2,5 % is obtained by the use of the fuselage asymmetric relative to the horizontal plane. The optimal fuselage design has a specific grotto in the lower part of the fuselage - the constriction from the sides with continuing height growth. The nose part of the optimal fuselage is widened, has a triangular shape in the top view and is deflected down.В работе рассмотрена оптимизация формы фюзеляжа в конфигурации «крыло - фюзеляж». Рассмотрено три постановки задачи. В первой угол атаки зафиксирован и равен нулю, крыло имеет симметричный профиль, а фюзеляж задается круговыми сечениями. Во второй фюзеляж задается эллиптическими сечениями. В третьей угол атаки варьируется, коэффициент подъемной силы зафиксирован, крыло предварительно оптимизировано, а фюзеляж задается сечениями, состоящими из верхнего и нижнего полуэллипсов с возможностью смещения сечения вдоль вертикальной оси. Во всех постановках задачи объем компоновки, длина фюзеляжа, форма и положение крыла, форма первого и последнего сечений фюзеляжа зафиксированы. В роли целевой функции выступает коэффициент сопротивления. Оптимизация проведена с помощью непрямого метода оптимизации, основанного на самоорганизации. Аэродинамические коэффициенты получались в результате решения уравнений Рейнольдса с замыканием по модели турбулентности SST в коммерческом программном пакете Ansys CFX на структурированных многоблочных расчетных сетках. Результаты оптимизации сравниваются с конфигурацией, спроектированной традиционным образом. Фюзеляж этой конфигурации имеет цилиндрический участок в области стыка с крылом и носовую часть в виде оживала Кармана. Решение задачи оптимизации в первой постановке снижает коэффициент сопротивления компоновки «крыло - фюзеляж» при нулевом угле атаки примерно на 3 %. Использование фюзеляжей эллиптического сечения позволяет снизить коэффициент сопротивления на нулевом угле атаки на 9 %. Решение задач оптимизации в первых двух постановках позволяет снизить сопротивление в широком диапазоне углов атаки. При коэффициенте подъемной силы, выбранном для третьей постановки задачи в качестве ограничения, величина уменьшения сопротивления составляет порядка 7 %. Дальнейшее снижение сопротивления за счет использования вариации формы фюзеляжа, несимметричной относительно горизонтальной плоскости, составляет порядка 2,5 %. При этом фюзеляж оптимальной конфигурации имеет характерный подфюзеляжный «грот» - поджатие с боков при продолжающемся нарастании высоты. Носовая часть оптимального фюзеляжа расширена, имеет треугольную форму в плане и отклонена вниз