30 research outputs found
Kicked Bose-Einstein condensates: in search of exponential instability
No full textBose-Einstein condensates subject to short pulses (`kicks') from standing waves of light represent a nonlinear analogue of the well-known chaos paradigm, the quantum kicked rotor. We review briefly our current understanding of dynamicalor exponential instability in weakly kicked BECs. Previous studies of the onset of dynamical instability associated it with some form of classical chaos. We show it is due to parametric instability : resonant driving of certain collective modes. We map the zones of instability and calculate the Liapunov exponents
Nonlinear Phenomena in Complex Systems: From Nano to Macro Scale
No full textTopics of complex system physics and their interdisciplinary applications to different problems in seismology, biology, economy, sociology, energy and nanotechnology are covered in this new work from renowned experts in their fields. In particular, contributed papers contain original results on network science, earthquake dynamics, econophysics, sociophysics, nanoscience and biological physics. Most of the papers use interdisciplinary approaches based on statistical physics, quantum physics and other topics of complex system physics. Papers on econophysics and sociophysics are focussed on societal aspects of physics such as, opinion dynamics, public debates and financial and economic stability. This work will be of interest to statistical physicists, economists, biologists, seismologists and all scientists working in interdisciplinary topics of complexity
Non-Linear Dynamics and Fundamental Interactions
No full textThe book is directed to researchers and graduate students pursuing an advanced degree. It provides details of techniques directed towards solving problems in non-linear dynamics and chos that are, in general, not amenable to a perturbative treatment. The consideration of fundamental interactions is a prime example where non-perturbative techniques are needed. Extension of these techniques to finite temperature problems is considered. At present these ideas are primarily used in a perturbative context. However, non-perturbative techniques have been considered in some specific cases. Experts in the field on non-linear dynamics and chaos and fundamental interactions elaborate the techniques and provide a critical look at the present status and explore future directions that may be fruitful. The text of the main talks will be very useful to young graduate students who are starting their studies in these areas
Quantum dynamics of a hydrogen-like atom in a time-dependent box: non-adiabatic regime
No full textWe consider a hydrogen atom confined in time-dependent trap created by a spherical impenetrable box with time-dependent radius. For such model we study the behavior of atomic electron under the (non-adiabatic) dynamical confinement caused by the rapidly moving wall of the box. The expectation values of the total and kinetic energy, average force, pressure and coordinate are analyzed as a function of time for linearly expanding, contracting and harmonically breathing boxes. It is shown that linearly extending box leads to de-excitation of the atom, while the rapidly contracting box causes the creation of very high pressure on the atom and transition of the atomic electron into the unbound state. In harmonically breathing box diffusive excitation of atomic electron may occur in analogy with that for atom in a microwave field
Coulomb impurities in graphene driven by fast ions
No full textWe provide a theoretical model for electronic transitions in a two-dimensional (2D) artificial atom in a graphene monolayer. The artificial atom is due to the presence of a charged adatom (Coulomb impurity) in the layer and interacts with a fast ultrarelativistic ion moving parallel to the layer. We compute the probability and cross-sections for the corresponding electronic transitions by means of an exact solution of the time-dependent 2D Dirac equation describing the interaction of the planar atom with the electromagnetic field of the ultrarelativistic projectile
Particle transport in graphene nanoribbon driven by ultrashort pulses
No full textWe study charge transport in a graphene zigzag nanoribbon driven by an external
time-periodic kicking potential. Using the exact solution of the time-dependent Dirac
equation with a delta-kick potential acting in each period, we study the time evolution of
the population transfer probability and the time-dependent optical conductivity. By
variation of the kicking parameters, the conductivity becomes widely tunable
NATO Advanced Research Wokshop “Recent Trends in Energy Security: With Special Emphasis on Low-Dimensional Functional Materials”
No full textMaintaining and improving energy security is one of the biggest challenges worldwide. The NATO ARW conference in Tashkent, October 2012, was devoted to discussing visions and concepts that are currently discussed in different research fields. Leading scientists have written concise contributions to introduce the reader to this exciting topic. The present volume summarizes the discussions at the conference
Coulomb impurities in graphene driven by ultrashort electromagnetic pulses: Excitation, ionization, and pair creation
No full textWe provide a theory for electronic transitions induced by ultrashort electromagnetic pulses in two-dimensional artificial relativistic atoms which are created by a charged impurity in a gapped graphene monolayer. Using a non-perturbative sudden-perturbation approximation, we derive and discuss analytical expressions for the probabilities for excitation, ionization and electron-hole pair creation in this system
