The intricate Galaxy disk: velocity asymmetries in Gaia-TGAS

We use the Gaia-TGAS data to compare the transverse velocities in Galactic longitude (coming from proper motions and parallaxes) in the Milky Way disk for negative and positive longitudes as a function of distance. The transverse velocities are strongly asymmetric and deviate significantly from the expectations for an axisymmetric Galaxy. The value and sign of the asymmetry changes at spatial scales of several tens of degrees in Galactic longitude and about 0.5 kpc in distance. The asymmetry is statistically significant at 95% confidence level for 57% of the region probed, which extends up to ~1.2 kpc. A percentage of 24% of the region studied shows absolute differences at this confidence level larger than 5 km/s and 7% larger than 10 km/s. The asymmetry pattern shows mild variations in the vertical direction and with stellar type. A first qualitative comparison with spiral arm models indicates that the arms are unlikely to be the main source of the asymmetry. We briefly discuss alternative origins. This is the first time that global all-sky asymmetries are detected in the Milky Way kinematics, beyond the local neighbourhood, and with a purely astrometric sample.Comment: Accepted for publication in A&A Letter

Quantum disentanglers

It is not possible to disentangle a qubit in an unknown state $|\psi>$ from a set of (N-1) ancilla qubits prepared in a specific reference state $|0>$. That is, it is not possible to {\em perfectly} perform the transformation $(|\psi,0...,0\r +|0,\psi,...,0\r +...+ |0,0,...\psi\r) \to |0,...,0>\otimes |\psi>$. The question is then how well we can do? We consider a number of different methods of extracting an unknown state from an entangled state formed from that qubit and a set of ancilla qubits in an known state. Measuring the whole system is, as expected, the least effective method. We present various quantum ``devices'' which disentangle the unknown qubit from the set of ancilla qubits. In particular, we present the optimal universal disentangler which disentangles the unknown qubit with the fidelity which does not depend on the state of the qubit, and a probabilistic disentangler which performs the perfect disentangling transformation, but with a probability less than one.Comment: 8 pages, 1 eps figur

Optimal Universal Disentangling Machine for Two Qubit Quantum States

We derive the optimal curve satisfied by the reduction factors, in the case of universal disentangling machine which uses only local operations. Impossibility of constructing a better disentangling machine, by using non-local operations, is discussed.Comment: 15 pages, 2 eps figures, 1 section added, 1 eps figure added, minor corrections, 2 reference numbers correcte

Training to Inhibit Negative Content Affects Memory and Rumination

Depressive rumination, the tendency to engage in repetitive self-focus in response to distress, seems to be affected by a variety of cognitive biases that in turn maintain negative emotional states. The current study examined whether the difficulty in inhibiting attention to negative information contributes to rumination and to rumination-related biases in memory. Seventy-nine ruminators underwent a 3-week computer-based training, designed to increase either inhibition of negative words or attention to them. On immediate post-training trials, as well as on 2-week follow-up tests, we found evidence for transfer of inhibition training. Training effects also occurred on session-by-session and post-training measures of state rumination, but not on a measure of trait rumination, assessed 2 weeks later. Finally, participants who were trained to inhibit negative material subsequently showed less negative bias on a memory test. These findings further establish the causal role of biased inhibition in rumination, and substantiate the view of rumination as a habit that encourages people to perceive, interpret, and remember events in a repetitive self-focused manner

Rumination: Cognitive Consequences of Training to Inhibit the Negative

Background and Objectives: To explore cognitive factors in ruminative thinking, we assessed the effect of a single-session of inhibition training on subsequent biases in attention and interpretation. Methods: We randomly assigned participants to either inhibit or attend to negative stimuli. Inhibition was assessed by using assessment trials embedded throughout the training, and interpretation bias was assessed following the training. Results: Trait rumination moderated training effects on both measures. Low ruminators in the inhibition-training condition maintained their level of inhibition of negative stimuli, but those in the attention-training condition showed a non-significant trend for decreased inhibition. Participants also showed a transfer-congruent tendency in interpretation bias, with reduced bias by those trained to inhibit negative stimuli, compared to those trained to attend to negative stimuli. In contrast, high ruminators in the inhibition training condition showed a training-incongruent decrease in inhibition of negative stimuli, but no change in inhibition when trained to attend to negative stimuli. No effects of the training on interpretation bias were observed among high ruminators. Finally, the training did not affect subsequent measures of mood or state rumination, even when trait rumination scores were taken into account. Limitations: This study used a single session of inhibition training rather than a multisession training, and this may explain the null effects among high ruminators. Conclusions: Findings highlight the critical role that trait rumination plays in moderating the effect of inhibition training. Our results suggest that inhibition training may provide an effective technique to change inhibition bias and later interpretation bias