We demonstrate experimentally that matter waves can be coherently and adiabatically loaded and controlled in one-, two-, and three-dimensional strongly driven optical lattices. This coherent control is then used in order to reversibly induce the superfluid-Mott insulator phase transition by changing the strength of the driving. Our findings pave the way for studies of driven quantum systems and new methods for controlling matter waves.

/pdf/coherent-control-of-dressed-matter-waves-2iofuha5il.pdf

Coherent control of dressed matter waves.

We present the results of an extensive timing analysis of the 1999 outburst of the soft X-ray transient and black hole candidate XTE J1859+226 as observed with the Rossi X-Ray Timing Explorer . Three main different types of low frequency (1-9 Hz) quasi-periodic oscillations (QPOs) were observed and classified, strengthening the general picture that is emerging for the variability properties of black hole X-ray binaires. Rapid transitions between different power spectral shapes were observed and their link with the count rate was studied. Furthermore, we show that a frequency of ~6 Hz seems to hold a particular place: one of the three QPO types we found was very stable when at this frequency, as it happens in Z sources as well. The coherence of its subharmonic peak was higher when the fundamental was close to 6 Hz, thus suggesting the presence of some resonance at this frequency.

/pdf/a-study-of-the-low-frequency-quasi-periodic-oscillations-in-11pwwzarkv.pdf

A study of the low-frequency quasi-periodic oscillations in the X-ray light curves of the black hole candidate XTE J1859+226

We have observed Feshbach resonances in collisions between ultracold $^{52}\mathrm{Cr}$ atoms. This is the first observation of collisional Feshbach resonances in an atomic species with more than one valence electron. The zero nuclear spin of $^{52}\mathrm{Cr}$ and thus the absence of a Fermi-contact interaction leads to regularly spaced resonance sequences. By comparing resonance positions with multichannel scattering calculations we determine the $s$-wave scattering length of the lowest $^{2S+1}\ensuremath{\Sigma}_{g}^{+}$ potentials to be $112(14)\text{ }\text{ }{a}_{0}$, $58(6)\text{ }\text{ }{a}_{0}$, and $\ensuremath{-}7(20)\text{ }\text{ }{a}_{0}$ for $S=6$, 4, and 2, respectively, where ${a}_{0}=0.0529\text{ }\text{ }\mathrm{nm}$.

https://arxiv.org/pdf/cond-mat/0412049.pdf

Observation of Feshbach resonances in an ultracold gas of 52Cr.

In optical fibres, weak modulations can grow at the expense of a strong pump to form a triangular comb of sideband pairs, until the process is reversed. Repeated cycles of such conversion and back-conversion constitute a manifestation of the universal nonlinear phenomenon known as Fermi–Pasta–Ulam recurrence. However, it remains a major challenge to observe the coexistence of different types of recurrences owing to the spontaneous symmetry-breaking nature of such a phenomenon. Here, we implement a novel non-destructive technique that allows the evolution in amplitude and phase of frequency modes to be reconstructed via post-processing of the fibre backscattered light. We clearly observe how control of the input modulation seed results in different recursive behaviours emerging from the phase-space structure dictated by the spontaneously broken symmetry. The proposed technique is an important tool to characterize other mixing processes and new regimes of rogue-wave formation and wave turbulence in fibre optics.

https://hal.archives-ouvertes.fr/hal-02385106/document

Fibre multi-wave mixing combs reveal the broken symmetry of Fermi-Pasta-Ulam recurrence

A simple qualitative physical explanation is suggested for the phenomenon of dynamic stabilization of the inverted rigid planar pendulum whose pivot is constrained to oscillate with a high frequency in the vertical direction. A quantitative theory based on the suggested approach is developed. A computer program simulating the physical system supports the analytical investigation. The simulation reveals subtle details of the motion and aids the analytical study of the subject in a manner that is mutually reinforcing.

http://butikov.faculty.ifmo.ru/Applets/Inverted.pdf

On the dynamic stabilization of an inverted pendulum

The phenomenon of parametric resonance is explained and investigated both analytically and with the help of a computer simulation. Parametric excitation is studied for the example of the rotary oscillations of a simple linear system— mechanical torsion spring pendulum excited by periodic variations of its moment of inertia. Conditions and characteristics of parametric resonance and regeneration are found and discussed in detail. Ranges of frequencies within which parametric excitation is possible are determined. Stationary oscillations at the boundaries of these ranges are investigated. The simulation experiments aid greatly an understanding of basic principles and peculiarities of parametric excitation and complement the analytical study of the subject in a manner that is mutually reinforcing.

/pdf/parametric-excitation-of-a-linear-oscillator-11qziyo8op.pdf

Parametric excitation of a linear oscillator

A simple treatment of the important old problem of the torque-induced rotation of a spinning symmetrical top is suggested. Our discussion is appropriate for teaching introductory mechanics and general physics to undergraduate students and is free from the difficulties of a traditional approach to the problem. The origin of nutation that accompanies forced precession is explained in detail, with an accent on its relationship to the torque-free precession of a symmetrical body. A small simulation program is developed that visualizes the investigated motion and illustrates its principal features. The program facilitates understanding about the counterintuitive behaviour of a gyroscope on a qualitative level.

/pdf/precession-and-nutation-of-a-gyroscope-4y4iba8srr.pdf

Precession and nutation of a gyroscope

A simple qualitative physical explanation is suggested for the phenomenon of subharmonic resonances of a rigid planar pendulum whose axis is forced to oscillate with a high frequency in the vertical direction. An approximate quantitative theory based on the suggested approach is developed. The spectral composition of the subharmonic resonances is investigated quantitatively, and the boundaries of these modes in the parameter space are determined. New related modes of regular behaviour are described and explained. The conditions of the inverted pendulum stability are determined with greater precision than previous results. A computer program simulating the physical system supports the analytical investigation.

/pdf/subharmonic-resonances-of-the-parametrically-driven-pendulum-2ci5me0nzk.pdf

Subharmonic resonances of the parametrically driven pendulum

Computer simulation experiments are especially good tools for helping students understand basic principles of physics. In this a, I have developed a package of simulation programs called Physics of Oscillations. One of its programs is suited for examining the phenomenon of paramagnetic resonance in a linear system. The program simulates the parametric excitation of the rotary oscillations of a mechanical torsion-spring pendulum whose moment of inertia is subject to periodic variations. I discuss the conditions and characteristics of parametric resonance, including paramagnetic regeneration. Instructors and their students can also use the Physics of Oscillations package to explore other problems, such as ranges of frequencies within which parametric excitation is possible and stationary oscillations on the boundaries of these ranges. The simulation experiments complement the analytical study of the subject in a manner that is mutually reinforcing.

https://ieeexplore.ieee.org/iel5/5992/16549/00764219.pdf

Eugene I. Butikov

Papers

On the dynamic stabilization of an inverted pendulum

Parametric excitation of a linear oscillator

Precession and nutation of a gyroscope

Subharmonic resonances of the parametrically driven pendulum

Parametric resonance