Extracts from the Internet

D^*_sJ(2860)^- particle

The states of D^*_sJ(2860)^- particle with spins 1 and 3 were identified by LHCb collaboration on Large Hadron Collider. These states were revealed with 10 σconfidence as intermediate resonances in the B⁰_s → анти-D⁰K^-π⁺ reaction. Although the presence of D^*_sJ(2860)^- resonance for energy of ≈ 2.85 GeV had been noticed before, its structure was first established in the LHCb experiment. The D^*_sJ(2860)^- particle consists of anti-c and s quarks which depending on the spin and the orbital angular momentum can represent a family of different resonant states, and such a spin 3 state was observed for the first time. The birth of a spin 3 particle in B-meson decays was also observed for the first time. Source: LHCb experiment

Quantum paradoxes

“Quantum Cheshire cat”. T. Denkmayr (The Vienna University of Technology, Austria) et al. were the first to demonstrate in experiment the quantum-mechanical effect referred to as “quantum Cheshire cat”, where the object and its quantum property are spatially separated. The experiment with a neutron interferometer was implemented at the Institute Laue-Langevin (Grenoble, France). On passing through a silicon crystal, a neutron beam split into two beams in which neutron spins underwent some flips, and at the interferometer outlet neutrons with certain spin states were selected. Thus, the spin states were preselected and post-selected and a “quantum Cheshire cat” was created, which was shown with the help of weak quantum measurements. The neutron absorber had an effect on the neutron flux only if it was located in the first interferometer arm and a weak magnetic field displaced the interference pattern only upon an impact on the second arm. This proved the fact that neutrons passed along one interferometer arm, while their spin states (magnetic moments) passed along the other arm. This effects can be applied in high-precision measurements. Source: Nature Communications 5 4492 (2014)

“The pigeonhole paradox”. The quantum-mechanical “pigeonhole paradox” takes its name from the classical assertion that if three pigeons reside in two holes, then at least two pigeons will necessarily find themselvesin one of the holes. Y. Aharonov (Tel Aviv University, Israel; Chapman University, USA) et al. showed in their theoretical work that such an assertion may appear to be incorrect in quantum mechanics. Namely, three particles can be placed in two quantum boxes in such a manner that none of the boxes will contain two particles at a time. As an example, the authors pointed out concrete linear combinations of wave functions corresponding to the initial and final state in which at no intermediate instant of a quantum system evolution a state occurs in which two or three particles could reside in one box because the corresponding probability amplitude is equal to zero. The authors suggested the idea of an experiment with three electrons in two interferometer arms. When flying along one path electrons repulse by their charges, and therefore their measured position will differ from the case where two electrons never pass simultaneously along one path. Source: arXiv:1407.3194 [quant-ph]

Soliton vortices in an ultracold gas

The existence of long-lived soliton vortices, i.e., phase defects of the order parameter, in a degenerate ultracold gas was confirmed for the first time in two experiments. A small elongated cloud of superfluid Fermi gas of ⁶Li atoms in an optical dipole trap was studied by 3D-tomography in the experiment performed in the Massachusetts Institute of Technology. Soliton vortices were created by the phase shift of the order parameter by way of laser radiation, and their precession near the phase transition point was observed. In the experiment carried out by researchers from the University of Trento (Italy) and P.L. Kapitsa Institute of Physical Problems (Russia) a small elongated cloud of Bose – Einstein condensate of sodium atoms was observed by the absorption methods at the stage of its free expansion. The entangled regions of lowered density around the vortex filaments testified to the presence of soliton vortices. In the previous experiments of the same research teams, soliton vortices had also been born, but the structures then observed were interpreted differently, namely, as other type solitons. Having established in the new experiments that the correct explanation is the soliton vortices, the researchers arrived at agreement of the experimental data and the theoretical calculations for the lifetime and other characteristics of the solitons. Sources: Phys. Rev. Lett. 113 065301 (2014), Phys. Rev. Lett. 113 065302 (2014)

Time asymmetry in a turbulent flow

The turbulence process is time asymmetric (time irreversible) because the energy is pumped over from larger- to smaller-scale turbulent pulsations. At the Max Planck Institute for Dynamics and Self-Organization (Germany) an experiment was performed which traced the kinematics of this asymmetry for individual elements of the liquid. A turbulent motion in a vessel was generated by rotating blades, and the polystyrene microspheres positions in water,that served as markers of motion, was traced using high-speed video cameras. The theoretical prediction was confirmed that within small time intervals the time difference of mean squares of distances between particles of a forward and backward turbulent flowis positive (i.e., this difference increases faster under time reversal) and increases as ⟨ R²(-t)⟩-⟨ R²(t)⟩ ∼ t³. The data on the asymmetry are still more clear for an ensemble of four particles which at the initial instant of time form a regular tetrahedron. The difference of intermediate eigenvalues of the tetrahedron strain tensor increases linearly in time ⟨g₂(t)-g₂(-t)⟩ ∼ t. The third and first degree of t in the indicated dependences reflect the fact of turbulent flow asymmetry under time reversal t → -t. Source: Phys. Rev. Lett. 113 054501 (2014)

An intermediate-mass black hole in galaxy M82

Analyzing the X-ray Rossi telescope data, D.R. Pasham, T.E. Strohmayer, and R.F. Mushotzky (University of Maryland and the Goddard Space Flight Center, USA) showed that the ultrabright X-ray source X-1 in galaxy M82 is most likely to be a black hole (BH) of mass 400M_☉. Two modes of quasi-periodic pulsations with frequencies of 5.1 Hz and 3.3 Hz were revealed with 4.7 σ confidence. The modes remained stable over the entire observational period. Similar double modes with the 3:2 frequency ratio are already known for (3-50M_☉) stellar-mass BH. Although the nature of double pulsations has not been exactly clarified, their frequencies correlate with BH masses. If this correlation holds true also for X-1, the BH mass appears to be equal to (428 ± 105)M_☉. X-1 has already been supposed to contain a BH of mass (10²-10⁴)M_☉, but a possibility of a stellar-mass BH with super-Eddington luminosity has also been hypothesized. The double pulsations having been discovered, the latter hypothesis turned out to be hardly probable. The result obtained is one of the strongest evidences of the existence of intermediate-mass BH: between stellar-mass BH and supermassive BH in galactic nuclei. Source: Nature 513 74 (2014)