Pricing in Social Networks with Negative Externalities

We study the problems of pricing an indivisible product to consumers who are embedded in a given social network. The goal is to maximize the revenue of the seller. We assume impatient consumers who buy the product as soon as the seller posts a price not greater than their values of the product. The product's value for a consumer is determined by two factors: a fixed consumer-specified intrinsic value and a variable externality that is exerted from the consumer's neighbors in a linear way. We study the scenario of negative externalities, which captures many interesting situations, but is much less understood in comparison with its positive externality counterpart. We assume complete information about the network, consumers' intrinsic values, and the negative externalities. The maximum revenue is in general achieved by iterative pricing, which offers impatient consumers a sequence of prices over time. We prove that it is NP-hard to find an optimal iterative pricing, even for unweighted tree networks with uniform intrinsic values. Complementary to the hardness result, we design a 2-approximation algorithm for finding iterative pricing in general weighted networks with (possibly) nonuniform intrinsic values. We show that, as an approximation to optimal iterative pricing, single pricing can work rather well for many interesting cases, but theoretically it can behave arbitrarily bad

Tourette’s disorder and other tic disorders in DSM-5: a comment

Classification of tic disorders will be revised in the forthcoming edition of the Diagnostic and Statistical Manual of Mental Disorders (5th ed.; DSM-5). We do not support the suggestion to move tic disorders to “Anxiety and Obsessive–Compulsive Disorders”, if the section “Disorders Usually First Diagnosed in Infancy, Childhood, or Adolescence” is not retained. Other than that, most proposed changes of the criteria for tic disorders contain a number of welcome improvements, e.g., the more unified definition of tics including the removal of the term “stereotyped” and the better capture of the temporal pattern of tics (e.g., removal of the maximum 3 months criterion for a tic-free period in chronic tic disorders). But, unfortunately there are some inconsistencies in detail, e.g., the unification of diagnostic criteria for tic disorders had not been consistently pursued in transient tic disorder. In sum, the proposed DSM-5 criteria could be seen as an important step forward particularly in clinical routine. However, continued research is needed to justify the existing and proposed classification of tic disorders as well as to better clarify what other changes should be made in the DSM-5 and beyond

Quantum Simulation of Spin Chains Coupled to Bosonic Modes with Superconducting Circuits

We propose the implementation of a digital quantum simulation of spin chains coupled to bosonic field modes in superconducting circuits. Gates with high fidelities allows one to simulate a variety of Ising magnetic pairing interactions with transverse field, Tavis-Cummings interaction between spins and a bosonic mode, and a spin model with three-body terms. We analyze the feasibility of the implementation in realistic circuit quantum electrodynamics setups, where the interactions are either realized via capacitive couplings or mediated by microwave resonators.Comment: Chapter in R. S. Anderssen et al. (eds.), Mathematics for Industry 11 (Springer Japan, 2015

From Rotating Atomic Rings to Quantum Hall States

Considerable efforts are currently devoted to the preparation of ultracold neutral atoms in the emblematic strongly correlated quantum Hall regime. The routes followed so far essentially rely on thermodynamics, i.e. imposing the proper Hamiltonian and cooling the system towards its ground state. In rapidly rotating 2D harmonic traps the role of the transverse magnetic field is played by the angular velocity. For particle numbers significantly larger than unity, the required angular momentum is very large and it can be obtained only for spinning frequencies extremely near to the deconfinement limit; consequently, the required control on experimental parameters turns out to be far too stringent. Here we propose to follow instead a dynamic path starting from the gas confined in a rotating ring. The large moment of inertia of the fluid facilitates the access to states with a large angular momentum, corresponding to a giant vortex. The initial ring-shaped trapping potential is then adiabatically transformed into a harmonic confinement, which brings the interacting atomic gas in the desired quantum Hall regime. We provide clear numerical evidence that for a relatively broad range of initial angular frequencies, the giant vortex state is adiabatically connected to the bosonic $\nu=1/2$ Laughlin state, and we discuss the scaling to many particles.Comment: 9 pages, 5 figure

Conservation of energy and momenta in nonholonomic systems with affine constraints

We characterize the conditions for the conservation of the energy and of the components of the momentum maps of lifted actions, and of their `gauge-like' generalizations, in time-independent nonholonomic mechanical systems with affine constraints. These conditions involve geometrical and mechanical properties of the system, and are codified in the so-called reaction-annihilator distribution

Quantum-fluid dynamics of microcavity polaritons

Semiconductor microcavities offer a unique system to investigate the physics of weakly interacting bosons. Their elementary excitations, polaritons--a mixture of excitons and photons--behave, in the low density limit, as bosons that can undergo a phase transition to a regime characterised by long range coherence. Condensates of polaritons have been advocated as candidates for superfluidity; and the formation of vortices as well as elementary excitations with a linear dispersion are actively sought after. In this work, we have created and set in motion a macroscopically degenerate state of polaritons and let it collide with a variety of defects present in the sample. Our experiments show striking manifestations of a coherent light-matter packet that displays features of a superfluid, although one of a highly unusual character as it involves an out-of-equilibrium dissipative system where it travels at ultra-fast velocity of the order of 1% the speed of light. Our main results are the observation of i) a linear polariton dispersion accompanied with diffusion-less motion, ii) flow without resistance when crossing an obstacle, iii) suppression of Rayleigh scattering and iv) splitting into two fluids when the size of the obstacle is comparable with the size of the wavepacket. This work opens the way to the investigation of new phenomenology of out-of-equilibrium condensates.Comment: 22 pages, 5 figure

New Jersey Center for Tourette Syndrome Sharing Repository: methods and sample description

<p>Abstract</p> <p>Background</p> <p>Tourette Syndrome is a neuropsychiatric disorder characterized by chronic motor and phonic tics. Affected individuals and their family members are at an increased risk for other neuropsychiatric conditions including obsessive-compulsive disorder and attention deficit hyperactivity disorder. While there is consistent evidence that genetic factors play a significant etiologic role, no replicable susceptibility alleles have thus far been identified.</p> <p>Description</p> <p>Here we discuss a sharing resource of clinical and genetic data, the New Jersey Center for Tourette Syndrome Sharing Repository, whose goal is to provide clinical data, DNA, and lymphoblastoid cell lines to qualified researchers.</p> <p>Conclusion</p> <p>Opening access to the data and patient material to the widest possible research community will hasten the identification of causal genetic factors and facilitate better understanding and treatment of this often impairing disorder.</p

Signatures of Many-Body Localization in a Controlled Open Quantum System

In the presence of disorder, an interacting closed quantum system can undergo many-body localization (MBL) and fail to thermalize. However, over long times, even weak couplings to any thermal environment will necessarily thermalize the system and erase all signatures of MBL. This presents a challenge for experimental investigations of MBL since no realistic system can ever be fully closed. In this work, we experimentally explore the thermalization dynamics of a localized system in the presence of controlled dissipation. Specifically, we find that photon scattering results in a stretched exponential decay of an initial density pattern with a rate that depends linearly on the scattering rate. We find that the resulting susceptibility increases significantly close to the phase transition point. In this regime, which is inaccessible to current numerical studies, we also find a strong dependence on interactions. Our work provides a basis for systematic studies of MBL in open systems and opens a route towards extrapolation of closed-system properties from experiments.We acknowledge financial support by the European Commission (UQUAM, AQuS) and the Nanosystems Initiative Munich (NIM). Work at Strathclyde is supported by the EOARD via AFOSR Grant No. FA2386-14-1-5003. This research was supported in part by the National Science Foundation under Grant No. NSF PHY11-25915. M. H. F. acknowledges additional support from the Swiss Society of Friends of the Weizmann Institute of Science and S. S. H. acknowledges additional support from the Australian Research Council through Discovery Early Career Research Award No. DE150100315

Delayed Appearance of High Altitude Retinal Hemorrhages

When closely examined, a very large amount of climbers exhibit retinal hemorrhages during exposure to high altitudes. The incidence of retinal hemorrhages may be greater than previously appreciated as a definite time lag was observed between highest altitude reached and development of retinal bleeding. Retinal hemorrhages should not be considered warning signs of impending severe altitude illness due to their delayed appearance