Quantum Brownian motion of multipartite systems and their entanglement dynamics

We solve the model of N quantum Brownian oscillators linearly coupled to an environment of quantum oscillators at finite temperature, with no extra assumptions about the structure of the system-environment coupling. Using a compact phase-space formalism, we give a rather quick and direct derivation of the master equation and its solutions for general spectral functions and arbitrary temperatures. Since our framework is intrinsically nonperturbative, we are able to analyze the entanglement dynamics of two oscillators coupled to a common scalar field in previously unexplored regimes, such as off resonance and strong coupling.Comment: 10 pages, 6 figure

Initial state preparation with dynamically generated system-environment correlations

The dependence of the dynamics of open quantum systems upon initial correlations between the system and environment is an utterly important yet poorly understood subject. For technical convenience most prior studies assume factorizable initial states where the system and its environments are uncorrelated, but these conditions are not very realistic and give rise to peculiar behaviors. One distinct feature is the rapid build up or a sudden jolt of physical quantities immediately after the system is brought in contact with its environments. The ultimate cause of this is an initial imbalance between system-environment correlations and coupling. In this note we demonstrate explicitly how to avoid these unphysical behaviors by proper adjustments of correlations and/or the coupling, for setups of both theoretical and experimental interest. We provide simple analytical results in terms of quantities that appear in linear (as opposed to affine) master equations derived for factorized initial states.Comment: 6 pages, 2 figure

Why Limits on Contributions to Super PACs Should Survive \u3ci\u3eCitizens United\u3c/i\u3e

Soon after the Supreme Court decided Citizens United v. FEC, the D.C. Circuit held all limits on contributions to super PACs unconstitutional. Its decision in SpeechNow.org v. FEC created a regime in which contributions to candidates are limited but in which contributions to less responsible groups urging votes for these candidates are unbounded. No legislator voted for this system of campaign financing, and the judgment that the Constitution requires it is astonishing. Forty-two years ago, Buckley v. Valeo held that Congress could limit contributions to candidates because these contributions are corrupting or create an appearance of corruption. According to the D.C. Circuit, however, Congress may not prohibit multi-million-dollar contributions to satellite campaigns because these contributions do not create even an appearance of corruption. The D.C. Circuit said that a single sentence of the Citizens United opinion compelled its result. It wrote, “In light of the Court’s holding as a matter of law that independent expenditures do not corrupt or create the appearance of corruption, contributions to groups that make only independent expenditures also cannot corrupt or create the appearance of corruption.” This Article contends that, contrary to the D.C. Circuit’s reasoning, contributions to super PACs can corrupt even when expenditures by these groups do not. Moreover, the statement that the D.C. Circuit took as its premise was dictum, and the Supreme Court did not mean this statement to be taken in the way the D.C. Circuit took it. The Supreme Court’s long-standing distinction between contribution limits and expenditure limits does not rest on the untenable proposition thatcandidates cannot be corrupted by funds paid to and spent on their behalf by others. Rather, Buckley noted five differences between contributions and expenditures. A review of these differences makes clear that contributions to super PACs cannot be distinguished from the contributions to candidates whose limitation the Court upheld. The ultimate question posed by Buckley is whether super PAC contributions create a sufficient appearance of corruption to justify their limitation. This Article reviews the statements of candidates of both parties in the 2016 presidential election, the views of Washington insiders, and public opinion polls. It shows that SpeechNow has sharpened class divisions and helped to tear America apart. The Justice Department did not seek Supreme Court review of the SpeechNow decision. In a statement that belongs on a historic list of wrong predictions, Attorney General Holder explained that the decision would “affect only a small subset of federally regulated contributions.” Although eight years have passed since SpeechNow, the Supreme Court has not decided whether the Constitution guarantees the right to give unlimited funds to super PACs. A final section of this Article describes the efforts of members of Congress and candidates for Congress to bring that question before the Court. The Federal Election Commission is opposing their efforts, offering arguments that, if accepted, would be likely to keep the Court from ever deciding the issue

Topology of evolving networks: local events and universality

Networks grow and evolve by local events, such as the addition of new nodes and links, or rewiring of links from one node to another. We show that depending on the frequency of these processes two topologically different networks can emerge, the connectivity distribution following either a generalized power-law or an exponential. We propose a continuum theory that predicts these two regimes as well as the scaling function and the exponents, in good agreement with the numerical results. Finally, we use the obtained predictions to fit the connectivity distribution of the network describing the professional links between movie actors.Comment: 13 pages, 3 figure

Cloud atlas for the FIRE Cirrus Intensive Field Observation (IFO)

An Intensive Field Observation (IFO) of cirrus clouds was conducted over the mid-western U.S. during the period October 13 to November 2, 1986. This activity, part of the First ISCCP Regional Experiment (FIRE), included measurements made from specially deployed instruments on the ground, balloons, and aircraft as well as observations from existing operational and experimental satellites. One of the sets of satellite observations was the radiance measurements made with the 5-channel AVHRR radiometer on the NOAA 9 polar orbiting meteorological satellite. The ground resolution of the measurements at nadir is approx. 1 km. It is these measurements, made once each day at approximately 2:30 p.m. local time, that were used in determining the present cloud atlas. The area covered by the atlas is slightly larger than the area specified for the IFO, in order to be in alignment with the grid that will be used in a forthcoming atlas for the larger, ETO region. The atlas contains four pages of information for each satellite pass. The 1st page of each group shows the distribution of measured radiances in channel 1 (normalized to the incoming solar flux multiplied by the cosine of the solar zenith angle) and in channel 4 for the area as a whole and for each analysis box. The 2nd page shows the images in: channels 1 and 2, channel 3R; and channel 4. The 3rd page shows the retrieved parameters in graphical form for the region as a whole and for each analysis box, where cloud fraction appears as a contour plot with respect to optical thickness and cloudtop temperature. The 4th page provides a statistical summary of the retrieved parameters in numerical form for each analysis box

The low-mass population of the Rho Ophiuchi molecular cloud

Star formation theories are currently divergent regarding the fundamental physical processes that dominate the substellar regime. Observations of nearby young open clusters allow the brown dwarf (BD) population to be characterised down to the planetary mass regime, which ultimately must be accommodated by a successful theory. We hope to uncover the low-mass population of the Rho Ophiuchi molecular cloud and investigate the properties of the newly found brown dwarfs. We use near-IR deep images (reaching completeness limits of approximately 20.5 mag in J, and 18.9 mag in H and Ks) taken with the Wide Field IR Camera (WIRCam) at the Canada France Hawaii Telescope (CFHT) to identify candidate members of Rho Oph in the substellar regime. A spectroscopic follow-up of a small sample of the candidates allows us to assess their spectral type, and subsequently their temperature and membership. We select 110 candidate members of the Rho Ophiuchi molecular cloud, from which 80 have not previously been associated with the cloud. We observed a small sample of these and spectroscopically confirm six new brown dwarfs with spectral types ranging from M6.5 to M8.25