A model of quantum collapse induced by gravity

We discuss a model where a spontaneous quantum collapse is induced by the gravitational interaction, treated classically. Its dynamics couples the standard wave function of a system with the Bohmian positions of its particles, which are considered as the only source of the gravitational attraction. The collapse is obtained by adding a small imaginary component to the gravitational coupling. It predicts extremely small perturbations of microscopic systems, but very fast collapse of QSMDS (quantum superpositions of macroscopically distinct quantum states) of a solid object, varying as the fifth power of its size. The model does not require adding any dimensional constant to those of standard physics.Comment: Version pubished in EPJ

Modified Sch\"odinger dynamics with attractive densities

The linear Schr\"{o}dinger equation does not predict that macroscopic bodies should be located at one place only. Quantum mechanics textbooks generally solve the problem by introducing the projection postulate, which forces definite values to emerge during position measurements; many other interpretations have also been proposed.\ Here, in the same spirit as the GRW and CSL theories, we modify the Schr\"{o}dinger equation in a way that efficiently cancels macroscopic density fluctuations in space.\ Instead of introducing the stochastic dynamics of GRW or CSL, we assume a deterministic dynamics that includes an attraction term towards the density in space of the de Broglie-Bohm position of particles. This automatically ensures macroscopic uniqueness, so that the state vector can be considered as a direct representation of physical reality.Comment: 14 pages, no figure. This is the version accepted by the European Physical Journal, with a few additions in the text and a few more references. A typo has been corrected in Eq (4

Detection of dependence patterns with delay

The Unitary Events (UE) method is a popular and efficient method used this last decade to detect dependence patterns of joint spike activity among simultaneously recorded neurons. The first introduced method is based on binned coincidence count \citep{Grun1996} and can be applied on two or more simultaneously recorded neurons. Among the improvements of the methods, a transposition to the continuous framework has recently been proposed in \citep{muino2014frequent} and fully investigated in \citep{MTGAUE} for two neurons. The goal of the present paper is to extend this study to more than two neurons. The main result is the determination of the limit distribution of the coincidence count. This leads to the construction of an independence test between $L\geq 2$ neurons. Finally we propose a multiple test procedure via a Benjamini and Hochberg approach \citep{Benjamini1995}. All the theoretical results are illustrated by a simulation study, and compared to the UE method proposed in \citep{Grun2002}. Furthermore our method is applied on real data

Self-immolation a common suicidal behaviour in eastern Sri Lanka.

A high number of self-burning injuries are noted in Batticaloa. The epidemiology, outcome and psychosocial aspects of 87 patients admitted with such burns over a 2-year-period was studied. The patients were compared with accidental burns and patients using other methods of suicide. Seventy nine percent of the victims were females and 72% were in the 15-34 years age-group. Most had marital problems. The majority were Tamils, but Muslims were fairly well represented. The median extent of burn was 48% of total body surface area (TBSA), with the top of the body mainly affected. The use of fire proved to have a high mortality in a group of patients who did not really want to die; 61 (70%) died. Mortality was higher than for accidental burns after matching for age and burn extent. The survivors had long hospital stays and suffered severe disfigurement. The cases where the patient denied self-harm, but in which the injuries were suggestive of this motive, were strikingly similar in age, sex and burn extent to the suicide group. In contrast, poison suicide records showed a male predominance and a gross under-representation of Muslims. Fire is a very significant method of suicide in our area. Social make-up and poor problem-solving ability may be contributing factors

Quantum properties of a single beam splitter

When a single beam-splitter receives two beams of bosons described by Fock states (Bose-Einstein condensates at very low temperatures), interesting generalizations of the two-photon Hong-Ou-Mandel effect take place for larger number of particles. The distributions of particles at two detectors behind the beam splitter can be understood as resulting from the combination of two effects, the spontaneous phase appearing during quantum measurement, and the quantum angle. The latter introduces quantum "population oscillations", which can be seen as a generalized Hong-Ou-Mandel effect, although they do not always correspond to even-odd oscillations.Comment: 14 pages, 11 figure

Angular momentum conservation in measurements on spin Bose-Einstein condensates

We discuss a thought experiment where two operators, Alice and Bob, perform transverse spin measurements on a quantum system; this system is initially in a double Fock spin state, which extends over a large distance in space so that the two operators are far away from each other. Standard quantum mechanics predicts that, when Alice makes a few measurements, a large transverse component of the spin angular momentum may appear in Bob's laboratory. A paradox then arises since local angular momentum conservation seems to be violated. It has been suggested that this angular momentum may be provided by the interaction with the measurement apparatuses. We show that this solution of the paradox is not appropriate, so that another explanation must be sought. The general question is the retroaction of a quantum system onto a measurement apparatus. For instance, when the measured system is entangled with another quantum system, can its reaction on a measurement apparatus be completely changed? Is angular momentum conserved only on average over several measurements, but not during one realization of the experiment?Comment: 11 pages, 3 figure