The degenerate gravitino scenario

In this work, we explore the "degenerate gravitino" scenario where the mass difference between the gravitino and the lightest MSSM particle is much smaller than the gravitino mass itself. In this case, the energy released in the decay of the next to lightest sypersymmetric particle (NLSP) is reduced. Consequently the cosmological and astrophysical constraints on the gravitino abundance, and hence on the reheating temperature, become softer than in the usual case. On the other hand, such small mass splittings generically imply a much longer lifetime for the NLSP. We find that, in the constrained MSSM (CMSSM), for neutralino LSP or NLSP, reheating temperatures compatible with thermal leptogenesis are reached for small splittings of order 10^{-2} GeV. While for stau NLSP, temperatures of 4x10^9 GeV can be obtained even for splittings of order of tens of GeVs. This "degenerate gravitino" scenario offers a possible way out to the gravitino problem for thermal leptogenesis in supersymmetric theories.Comment: 27 pages, 10 figures and 1 table. Minor typos and references fixed. Matches published version in JCAP

ЗАДОВОЛЕННЯ АКТУАЛЬНИХ ПОТРЕБ ЯК ФАКТОР ПСИХОЛОГІЧНОЇ АДАПТАЦІЇ ДО СТРЕСУ В СТУДЕНТІВ-ПСИХОЛОГІВ У ПЕРІОД СЕСІЇ

Background.  Intensi?cation of education provokes neurotic and psychosomatic disorders as well as destructive behaviour among young people. Currently there has been a growing interest in the factors of effective adaptation to the contemporary education system. Objective. This study is aimed to research the problem of students’ adaptation to stress during the examination period.Method.  The  needs  that  facilitate  stress  tension  during  the  examination  period were de?ned by ranking them by 70 students of Psychology (aged from 18 to 21 years old). The PSM-25 (L. Lemyre, R. Tessier, L. Fillion) was used for diagnostic somatic, behaviour and emotional effect of stress. The Beck Depression Inventory (A.T. Beck) was used for measuring the level of depression. Results. The correlations between the actual needs satisfaction and the stress level, as well as between the stress and depression level in students of Psychology during the examination period were found. Conclusions. The psychodiagnostic tools were used to study the level of satisfaction and types of actual needs. Most of research participants appeared to be adapted to mental stress during the examination period. Satisfaction of social and safety needs turned out to be the most signi?cant factor that in?uences the students’ adaptation to mental stress. Mental stress during the examination period correlates with level of depression.Изложены  результаты  исследования  уровня  стресса  у  студентов-психологов во время сессии. Исследована связь удовлетворения актуальных потребностей с уровнем нервно-психического напряжения у студентов-психологов во время сессии. Установлено, что удовлетворение социальных потребностей и потребности в безопасности способствует лучшей адаптации к экзаменационным стрессам.Розглянуто  проблему  адаптації  студентів  до  стресу  в  період  сесії. Представлено результати дослідження рівня стресу у студентів психологічних спеціальностей під час сесії. Установлено зв’язок між задоволенням актуальних потреб та рівнем нервово-психічного напруження у студентів-психологів у період сесії. Визначено, що задоволення потреби в безпеці та соціальних потреб – найпродуктивніші механізми зниження рівня стресу. Доведено вплив екзаменаційного стресу на виникнення депресії у студентів-психологів

Self-similarity and singularity formation in a coupled system of Yang-Mills-dilaton evolution equations

We study both analytically and numerically a coupled system of spherically symmetric SU(2) Yang-Mills-dilaton equation in 3+1 Minkowski space-time. It has been found that the system admits a hidden scale invariance which becomes transparent if a special ansatz for the dilaton field is used. This choice corresponds to transition to a frame rotated in the $\ln r-t$ plane at a definite angle. We find an infinite countable family of self-similar solutions which can be parametrized by the $N$ - the number of zeros of the relevant Yang-Mills function. According to the performed linear perturbation analysis, the lowest solution with N=0 only occurred to be stable. The Cauchy problem has been solved numerically for a wide range of smooth finite energy initial data. It has been found that if the initial data exceed some threshold, the resulting solutions in a compact region shrinking to the origin, attain the lowest N=0 stable self-similar profile, which can pretend to be a global stable attractor in the Cauchy problem. The solutions live a finite time in a self-similar regime and then the unbounded growth of the second derivative of the YM function at the origin indicates a singularity formation, which is in agreement with the general expectations for the supercritical systems.Comment: 10 pages, 5 figure

On the n=4 Supersymmetry for the FRW Model

In this work we have constructed the n=4 extended local conformal time supersymmetry for the Friedmann-Robertson-Walker (FRW) cosmological models. This is based on the superfield construction of the action, which is invariant under wordline local n=4 supersymmetry with $SU(2)_{local} \otimes SU(2)_{global}$ internal symmetry. It is shown that the supersymmetric action has the form of the localized (or superconformal) version of the action for n=4 supersymmetric quantum mechanics. This superfield procedure provides a well defined scheme for including supermatter.Comment: 8 pages. Accepted for publication in Phys. Rev

Sequences of Einstein-Yang-Mills-Dilaton Black Holes

Einstein-Yang-Mills-dilaton theory possesses sequences of neutral static spherically symmetric black hole solutions. The solutions depend on the dilaton coupling constant $\gamma$ and on the horizon. The SU(2) solutions are labelled by the number of nodes $n$ of the single gauge field function, whereas the SO(3) solutions are labelled by the nodes $(n_1,n_2)$ of both gauge field functions. The SO(3) solutions form sequences characterized by the node structure $(j,j+n)$, where $j$ is fixed. The sequences of magnetically neutral solutions tend to magnetically charged limiting solutions. For finite $j$ the SO(3) sequences tend to magnetically charged Einstein-Yang-Mills-dilaton solutions with $j$ nodes and charge $P=\sqrt{3}$. For $j=0$ and $j \rightarrow \infty$ the SO(3) sequences tend to Einstein-Maxwell-dilaton solutions with magnetic charges $P=\sqrt{3}$ and $P=2$, respectively. The latter also represent the scaled limiting solutions of the SU(2) sequence. The convergence of the global properties of the black hole solutions, such as mass, dilaton charge and Hawking temperature, is exponential. The degree of convergence of the matter and metric functions of the black hole solutions is related to the relative location of the horizon to the nodes of the corresponding regular solutions.Comment: 71 pages, Latex2e, 29 ps-figures include

Many-Body Superconformal Systems from Hamiltonian Reductions

We propose a new reduction mechanism which allows one to construct n-particle (super)conformal theories with pairwise interaction starting from a composite system involving n(n-1)/2+1 copies of the ordinary (super)conformal mechanics. Applications of the scheme include an N=4 superconformal extension for a complexification of the Calogero model and a D(2,1|\alpha)-invariant n-particle system.Comment: 12 pages, no figures. v2: Title changed. New material and acknowledgements adde