Magnetic collimation of protostellar winds into bipolar outflows

Researchers describe self-consistent 2-D magnetohydrodynamic (MHD) simulations of the collimation of an isotropic protostellar wind into bipolar outflows by magnetic stresses in the ambient medium. A variety of ambient field strengths, wind luminosities, and density profiles were studied. Collimation occurs when the energy of the magnetic field swept up by the expanding bubble approaches the bubble thermal energy. Measured axial and radial expansion rates are in good agreement with the analytical predictions of Konigl (1982)

A note on the time evolution of generalized coherent states

I consider the time evolution of generalized coherent states based on non-standard fiducial vectors, and show that only for a restricted class of fiducial vectors does the associated classical motion determine the quantum evolution of the states. I discuss some consequences of this for path integral representations.Comment: 9 pages. RevTe

Double point contact in Quantum Hall Line Junctions

We show that multiple point contacts on a barrier separating two laterally coupled quantum Hall fluids induce Aharonov-Bohm (AB) oscillations in the tunneling conductance. These quantum coherence effects provide new evidence for the Luttinger liquid behavior of the edge states of quantum Hall fluids. For a two point contact, we identify coherent and incoherent regimes determined by the relative magnitude of their separation and the temperature. We analyze both regimes in the strong and weak tunneling amplitude limits as well as their temperature dependence. We find that the tunneling conductance should exhibit AB oscillations in the coherent regime, both at strong and weak tunneling amplitude with the same period but with different functional form.Comment: 4 pages, 3 figures; new version, edited text, 2 new references; figure 2 has been edited; new paragraph in page 1 and minor typos have been correcte

Landauer Conductance of Luttinger Liquids with Leads

We show that the dc conductance of a quantum wire containing a Luttinger liquid and attached to non-interacting leads is given by $e^2/h$ per spin orientation, regardless of the interactions in the wire. This explains the recent observations of the absence of conductance renormalization in long high-mobility $GaAs$ wires by Tarucha, Honda and Saku (Solid State Communications {\bf 94}, 413 (1995)).Comment: 4 two-column pages, RevTeX + 1 uuencoded figure

Not Just a Private Club: Self Regulatory Organizations as State Actors When Enforcing Federal Law

In the Securities Exchange Act of 1934, Congress enacted a comprehensive scheme for regulating the national securities markets. Pursuant to that scheme, the Securities and Exchange Commission was given ultimate authority to enforce the newly enacted securities laws against market participants. The Exchange Act also created a prominent enforcement role for national securities exchanges, like the New York Stock Exchange. Congress required these self-regulatory organizations as a condition for their continued operation to enforce, among other things, compliance by their members with the provisions of the Exchange Act and the rules and regulations promulgated thereunder. The SROs were also given the power to sanction those members the SRO found to have violated federal law. The power and enforcement responsibilities conferred upon SROs under the Exchange Act raise the issue of whether constitutional protections such as due process and the right against self-incrimination apply in SRO enforcement proceedings when the SRO is enforcing federal law. The answer to that question, however, turns on whether SROs are state actors when enforcing federal law. State action is a fundamental prerequisite in cases alleging deprivation of constitutionally protected rights. At issue is whether SROs should be subject to the same constitutional limitations as the government when they are acting in the same capacity as the government in enforcing federal law, as required of them by the Exchange Act. Despite the Supreme Court\u27s extensive jurisprudence on the state action question, the Court has not addressed the issue of whether SROs are state actors. Lower courts have split on the question of whether SROs are state actors. The purpose of this Article is to explain why SROs should be considered state actors when enforcing federal law. The various Supreme Court precedents discussing the state action issue strongly suggest that when enforcing federal law, SROs are state actors. In that situation, SROs should be subject to the same constitutional limitations as the Commission or any other government agency. In Section II, the Article first examines the disciplinary responsibility of SROs imposed by the Exchange Act including the powers which the Commission has to coerce enforcement activity on the part of an SRO. Both the statutory and regulatory frameworks are analyzed. This Section then goes on to demonstrate the symbiotic relationship that exists between the Commission and the SROs in the context of SRO rule-making. This analysis examines the Commission\u27s role in approving rules and its authority to amend SRO rules and require SROs to adopt rules. This analysis is significant because the Commission\u27s authority in the rule-making area effectively allows the Commission to coerce SRO action, and because it demonstrates the heavily regulated nature of SRO activity. Section III then applies this analysis to the state action tests the Supreme Court currently employs. The Supreme Court has articulated several distinct tests for determining whether state action exists. This Section addresses two of the more relevant tests: (1) the coercion or encouragement test; and (2) the public function test. The Section explains the history and policy considerations that underlie each of these two tests, and demonstrates that under each of these tests SROs enforcing federal law should be considered state actors. In Section IV, the Article analyzes lower court decisions that have addressed the general topic of state action in the context of SROs. Finally, in Section V, the Article concludes that SROs are state actors when they enforce federal law. This conclusion not only follows from the Supreme Court\u27s extensive state action jurisprudence, but is also bolstered by the common sense argument that a dual system for enforcement of federal securities laws—one providing full constitutional protections and the other providing no such constitutional protections—is illogical. This dual enforcement system, which can lead to outcome determinative results based solely upon the prosecutorial forum, has a recognized historical foundation but is unsupported by current state action jurisprudence

Not Just a Private Club: Self Regulatory Organizations as State Actors When Enforcing Federal Law

In the Securities Exchange Act of 1934, Congress enacted a comprehensive scheme for regulating the national securities markets. Pursuant to that scheme, the Securities and Exchange Commission was given ultimate authority to enforce the newly enacted securities laws against market participants. The Exchange Act also created a prominent enforcement role for national securities exchanges, like the New York Stock Exchange. Congress required these self-regulatory organizations as a condition for their continued operation to enforce, among other things, compliance by their members with the provisions of the Exchange Act and the rules and regulations promulgated thereunder. The SROs were also given the power to sanction those members the SRO found to have violated federal law. The power and enforcement responsibilities conferred upon SROs under the Exchange Act raise the issue of whether constitutional protections such as due process and the right against self-incrimination apply in SRO enforcement proceedings when the SRO is enforcing federal law. The answer to that question, however, turns on whether SROs are state actors when enforcing federal law. State action is a fundamental prerequisite in cases alleging deprivation of constitutionally protected rights. At issue is whether SROs should be subject to the same constitutional limitations as the government when they are acting in the same capacity as the government in enforcing federal law, as required of them by the Exchange Act. Despite the Supreme Court\u27s extensive jurisprudence on the state action question, the Court has not addressed the issue of whether SROs are state actors. Lower courts have split on the question of whether SROs are state actors. The purpose of this Article is to explain why SROs should be considered state actors when enforcing federal law. The various Supreme Court precedents discussing the state action issue strongly suggest that when enforcing federal law, SROs are state actors. In that situation, SROs should be subject to the same constitutional limitations as the Commission or any other government agency. In Section II, the Article first examines the disciplinary responsibility of SROs imposed by the Exchange Act including the powers which the Commission has to coerce enforcement activity on the part of an SRO. Both the statutory and regulatory frameworks are analyzed. This Section then goes on to demonstrate the symbiotic relationship that exists between the Commission and the SROs in the context of SRO rule-making. This analysis examines the Commission\u27s role in approving rules and its authority to amend SRO rules and require SROs to adopt rules. This analysis is significant because the Commission\u27s authority in the rule-making area effectively allows the Commission to coerce SRO action, and because it demonstrates the heavily regulated nature of SRO activity. Section III then applies this analysis to the state action tests the Supreme Court currently employs. The Supreme Court has articulated several distinct tests for determining whether state action exists. This Section addresses two of the more relevant tests: (1) the coercion or encouragement test; and (2) the public function test. The Section explains the history and policy considerations that underlie each of these two tests, and demonstrates that under each of these tests SROs enforcing federal law should be considered state actors. In Section IV, the Article analyzes lower court decisions that have addressed the general topic of state action in the context of SROs. Finally, in Section V, the Article concludes that SROs are state actors when they enforce federal law. This conclusion not only follows from the Supreme Court\u27s extensive state action jurisprudence, but is also bolstered by the common sense argument that a dual system for enforcement of federal securities laws—one providing full constitutional protections and the other providing no such constitutional protections—is illogical. This dual enforcement system, which can lead to outcome determinative results based solely upon the prosecutorial forum, has a recognized historical foundation but is unsupported by current state action jurisprudence

Cosmological Radiation Hydrodynamics with ENZO

We describe an extension of the cosmological hydrodynamics code ENZO to include the self-consistent transport of ionizing radiation modeled in the flux-limited diffusion approximation. A novel feature of our algorithm is a coupled implicit solution of radiation transport, ionization kinetics, and gas photoheating, making the timestepping for this portion of the calculation resolution independent. The implicit system is coupled to the explicit cosmological hydrodynamics through operator splitting and solved with scalable multigrid methods. We summarize the numerical method, present a verification test on cosmological Stromgren spheres, and then apply it to the problem of cosmological hydrogen reionization.Comment: 14 pages, 3 figures, to appear in Recent Directions in Astrophysical Quantitative Spectroscopy and Radiation Hydrodynamics, Ed. I. Hubeny, American Institute of Physics (2009

Bohr-Sommerfeld quantization of spin Hamiltonians

The Bohr-Sommerfeld rule for a spin system is obtained, including the first quantum corrections. The rule applies to both integer and half-integer spin, and respects Kramers degeneracy for time-reversal invariant systems. It is tested for various models, in particular the Lipkin-Meshkov-Glick model, and found to agree very well with exact results.Comment: Revtex 4, no figures, 1 tabl

The Gradient Expansion for the Free-Energy of a Clean Superconductor

We describe a novel method for obtaining the gradient expansion for the free energy of a clean BCS superconductor. We present explicit results up to fourth order in the gradients of the order parameter.Comment: 33 pages, Late