A linear programming based heuristic framework for min-max regret combinatorial optimization problems with interval costs

This work deals with a class of problems under interval data uncertainty, namely interval robust-hard problems, composed of interval data min-max regret generalizations of classical NP-hard combinatorial problems modeled as 0-1 integer linear programming problems. These problems are more challenging than other interval data min-max regret problems, as solely computing the cost of any feasible solution requires solving an instance of an NP-hard problem. The state-of-the-art exact algorithms in the literature are based on the generation of a possibly exponential number of cuts. As each cut separation involves the resolution of an NP-hard classical optimization problem, the size of the instances that can be solved efficiently is relatively small. To smooth this issue, we present a modeling technique for interval robust-hard problems in the context of a heuristic framework. The heuristic obtains feasible solutions by exploring dual information of a linearly relaxed model associated with the classical optimization problem counterpart. Computational experiments for interval data min-max regret versions of the restricted shortest path problem and the set covering problem show that our heuristic is able to find optimal or near-optimal solutions and also improves the primal bounds obtained by a state-of-the-art exact algorithm and a 2-approximation procedure for interval data min-max regret problems

Thunderstorm dynamics in a scale interaction

This paper presents a review of thunderstorm dynamics through the use of the vorticity equation with a focus on the development of rotation, an indicator of storm severity. The processes involved in the scale interaction are basically the tilting of vortex tubes while the divergence (or ballerina) term, being highly non-linear, provides intensification of incipient vorticity. A brief account of numerically simulated storms in Brazil with well defined wind shear in the storm environment is presented

Thermal Effects on Photon-Induced Quantum Transport

We theoretically investigate laser induced quantum transport in a two-level quantum dot attached to electric contacts. Our approach, based on nonequilibrium Green function technique, allows to include thermal effects on the photon-induced quantum transport and excitonic coherent dynamics. By solving a set of coupled integrodifferential equations, involving correlation and propagator functions, we obtain the photocurrent and the dot occupations as a function of time. The characteristic coherent Rabi oscillations are found in both occupations and photocurrent, with two distinct sources of decoherence: incoherent tunneling and thermal fluctuations. In particular, for increasing temperature the dot becomes more thermally occupied which shrinks the amplitude of the Rabi oscillations, due to Pauli blockade. Finally, due to the interplay between photon and thermal induced electron populations, the photocurrent can switch sign as time evolves and its stationary value can be maximized by tunning the laser intensity.Comment: 5 pages, 4 figure

Relativistic Bose-Einstein condensate in the rainbow gravity

In this paper, we study the effects of a modified theory of gravity - the rainbow gravity - on the relativistic Bose-Einstein condensate (BEC). We initially discuss some formal aspects of the model in order to compute the corrections to the relevant quantities of the condensate. Following, we evaluate the generating functional from which obtain some thermodynamic parameters. Then we calculate the corrected critical temperature $T_c$ that sets the relativistic Bose-Einstein condensate considering the three principal rainbow functions, finding, in addition, a phenomenological upper bound for the parameters involved in the model. Finally, we discuss how harder is for the particles at an arbitrary temperature $T<T_c$ to enter the condensed state compared to the usual scenario, {\it i.e.}, without rainbow gravity.Comment: 13 pages, 2 figure, matches version accepted in EP

Dressing approach to the nonvanishing boundary value problem for the AKNS hierarchy

We propose an approach to the nonvanishing boundary value problem for integrable hierarchies based on the dressing method. Then we apply the method to the AKNS hierarchy. The solutions are found by introducing appropriate vertex operators that takes into account the boundary conditions.Comment: Published version Proc. Quantum Theory and Symmetries 7 (QTS7)(Prague, Czech Republic, 2011