Dvofotonski raspad b i d mezona u modelu prevladavajućih polova

We give a detailed study of the two-gamma decay of some heavy pseudoscalar mesons using the pole-dominance model. The transition matrix elements of PL to bare glueball (G0) are also computed, and it is found that the PL to glueball contribution is comparable with that of PL to π0. From our results, we have obtained the two-gamma decay width of DL and an upper limit of the two-gamma decay widths of BL and BsL mesons.Podrobno se proučavaju dvofotonski raspadi teških pseudoskalarnih mezona na osnovi modela prevladavajućih polova. Izračunavaju se matrični elementi prijelaza PL u golu gluonsku loptu (G0 ) i nalazi da je doprinos tog procesa usporediv s doprinosom prijelaza PL u π 0 . Izračunate su širina dvofotonskog raspada mezona DL i gornje granice širina dvofotonskih raspada BL i BsL mezona

Dvofotonski raspad b i d mezona u modelu prevladavajućih polova

We give a detailed study of the two-gamma decay of some heavy pseudoscalar mesons using the pole-dominance model. The transition matrix elements of PL to bare glueball (G0) are also computed, and it is found that the PL to glueball contribution is comparable with that of PL to π0. From our results, we have obtained the two-gamma decay width of DL and an upper limit of the two-gamma decay widths of BL and BsL mesons.Podrobno se proučavaju dvofotonski raspadi teških pseudoskalarnih mezona na osnovi modela prevladavajućih polova. Izračunavaju se matrični elementi prijelaza PL u golu gluonsku loptu (G0 ) i nalazi da je doprinos tog procesa usporediv s doprinosom prijelaza PL u π 0 . Izračunate su širina dvofotonskog raspada mezona DL i gornje granice širina dvofotonskih raspada BL i BsL mezona

Konstanta vezanja B-mezon – kvark i širina raspada B∗-mezona

The pion - quark coupling constant (gπq q) and the B-meson - quark coupling constant (gB-qq) have been found in the processes B*- → B-π0 and B*- → B-γ. Their decay widths have been calculated through the direct coupling of π0 and B- with quarks which are static inside B*- meson.Određuju se konstante vezanja pion – kvark (gπqq) i B-mezon – kvark (gB−qq) u procesima B∗−→B−π0 i B∗−→B−γ. Njihove se širine raspada računaju preko izravnog vezanja π0 i B− s kvarkovima koji miruju u B∗− mezonu

Konstanta vezanja B-mezon – kvark i širina raspada B∗-mezona

The pion - quark coupling constant (gπq q) and the B-meson - quark coupling constant (gB-qq) have been found in the processes B*- → B-π0 and B*- → B-γ. Their decay widths have been calculated through the direct coupling of π0 and B- with quarks which are static inside B*- meson.Određuju se konstante vezanja pion – kvark (gπqq) i B-mezon – kvark (gB−qq) u procesima B∗−→B−π0 i B∗−→B−γ. Njihove se širine raspada računaju preko izravnog vezanja π0 i B− s kvarkovima koji miruju u B∗− mezonu

Pilot Sensitivity to Simulator Flight Dynamics Model Formulation for Stall Training

A piloted simulation study was performed in the Cockpit Motion Facility at the National Aeronautics and Space Administration Langley Research Center. The research was motivated by the desire to reduce the commercial transport airplane fatal accident rate due to in-flight loss of control. The purpose of this study, which focused on a generic T-tail transport airplane, was to assess pilot sensitivity to flight dynamics model formulation used during a simulator stall recognition and recovery training/demonstration profile. To accomplish this, the flight dynamics model was designed with many configuration options. The model options were based on recently acquired static and dynamic stability and control data from sources that included wind tunnel, water tunnel, and computational fluid dynamics. The results, which are specific to a transport airplane stall recognition and recovery guided demonstration scenario, showed the two most important aerodynamic effects (other than stick pusher) to model were stall roll- off and the longitudinal static stability characteristic associated with the pitch break

A stochastic-Lagrangian particle system for the Navier-Stokes equations

This paper is based on a formulation of the Navier-Stokes equations developed by P. Constantin and the first author (\texttt{arxiv:math.PR/0511067}, to appear), where the velocity field of a viscous incompressible fluid is written as the expected value of a stochastic process. In this paper, we take $N$ copies of the above process (each based on independent Wiener processes), and replace the expected value with $\frac{1}{N}$ times the sum over these $N$ copies. (We remark that our formulation requires one to keep track of $N$ stochastic flows of diffeomorphisms, and not just the motion of $N$ particles.) We prove that in two dimensions, this system of interacting diffeomorphisms has (time) global solutions with initial data in the space \holderspace{1}{\alpha} which consists of differentiable functions whose first derivative is $\alpha$ H\"older continuous (see Section \ref{sGexist} for the precise definition). Further, we show that as $N \to \infty$ the system converges to the solution of Navier-Stokes equations on any finite interval $[0,T]$. However for fixed $N$, we prove that this system retains roughly $O(\frac{1}{N})$ times its original energy as $t \to \infty$. Hence the limit $N \to \infty$ and $T\to \infty$ do not commute. For general flows, we only provide a lower bound to this effect. In the special case of shear flows, we compute the behaviour as $t \to \infty$ explicitly.Comment: v3: Typo fixes, and a few stylistic changes. 17 pages, 2 figure

A stochastic perturbation of inviscid flows

We prove existence and regularity of the stochastic flows used in the stochastic Lagrangian formulation of the incompressible Navier-Stokes equations (with periodic boundary conditions), and consequently obtain a \holderspace{k}{\alpha} local existence result for the Navier-Stokes equations. Our estimates are independent of viscosity, allowing us to consider the inviscid limit. We show that as $\nu \to 0$, solutions of the stochastic Lagrangian formulation (with periodic boundary conditions) converge to solutions of the Euler equations at the rate of $O(\sqrt{\nu t})$.Comment: 13 pages, no figures

Coercivity and stability results for an extended Navier-Stokes system

In this article we study a system of equations that is known to {\em extend} Navier-Stokes dynamics in a well-posed manner to velocity fields that are not necessarily divergence-free. Our aim is to contribute to an understanding of the role of divergence and pressure in developing energy estimates capable of controlling the nonlinear terms. We address questions of global existence and stability in bounded domains with no-slip boundary conditions. Even in two space dimensions, global existence is open in general, and remains so, primarily due to the lack of a self-contained $L^2$ energy estimate. However, through use of new $H^1$ coercivity estimates for the linear equations, we establish a number of global existence and stability results, including results for small divergence and a time-discrete scheme. We also prove global existence in 2D for any initial data, provided sufficient divergence damping is included.Comment: 29 pages, no figure

Breathing mode frequencies of a rotating Fermi gas in the BCS-BEC crossover region

We study the breathing mode frequencies of a rotating Fermi gas trapped in a harmonic plus radial quartic potential. We find that as the radial anharmonicity increases, the lowest order radial mode frequency increases while the next lowest order radial mode frequency decreases. Then at a critical anharmonicity, these two modes merge and beyond this merge the cloud is unstable against the oscillations. The critical anharmonicity depends on both rotational frequency and the chemical potential. As a result of the large chemical potential in the BCS regime, even with a weak anharmonicity the lowest order mode frequency increases with decreasing the attractive interaction. For large enough anharmonicities in the weak coupling BCS limit, we find that the excitation of the breathing mode frequencies make the atomic cloud unstable.Comment: 6 pages, 8 fiqures. Formalism is modified to include the effect of negative quartic potentia