ISO Detection of CO⁺ toward the protostar IRAS 16293-2422

In this letter we report the detection of eight high-N rotational transitions of CO+ towards a low mass protostar, IRAS 16293-2422. The source was observed with the Long Wavelength Spectrometer on board the Infrared Space Observatory. This is the first time that CO+ has been detected in a low luminosity source and the first time that high-N lines have been detected in any source. The detection of these lines was not predicted by models and consequently, their interpretation is a challenge. We discuss the possibility that the observed CO+ emission originates in the dense inner regions illuminated by the UV field created in the accretion shock (formed by infalling material), and conclude that this is an improbable explanation. We have also considered the possibility that a strong, dissociative J-shock at ~ 500 AU from the star is the origin of the CO+ emission. This model predicts CO+ column densities in rough agreement with the observations if the magnetic field is ~ 1 mG and the shock velocity is 100 km s-1

Gauge Orbit Types for Theories with Classical Compact Gauge Group

We determine the orbit types of the action of the group of local gauge transformations on the space of connections in a principal bundle with structure group O(n), SO(n) or $Sp(n)$ over a closed, simply connected manifold of dimension 4. Complemented with earlier results on U(n) and SU(n) this completes the classification of the orbit types for all classical compact gauge groups over such space-time manifolds. On the way we derive the classification of principal bundles with structure group SO(n) over these manifolds and the Howe subgroups of SO(n).Comment: 57 page

Detection of CO⁺ with ISO towards the protostar IRAS16293-242

We observed the low luminosity (and low mass) protostar IRAS16293-2422 with the Long Wavelength Spectrometer on board the Infrared Space Observatory. The observed line spectrum is very reach and shows transitions of several molecules and atoms. Here we report the detection of eight high-N rotational transitions of CO+. This is the first time that CO+ has been detected in a low luminosity source and the first time that high-N lines have been detected in any source. The detection of these lines was not predicted by models and consequently, their interpretation is a challenge. We discuss the possibility that the observed CO+ emission originates in the dense inner regions illuminated by the UV field created in the accretion shock (formed by infalling material), and conclude that this is an improbable explanation. We have also considered the possibility that a strong, dissociative J-shock at ~500 AU from the star is the origin of the CO+ emission. This model predicts CO+ column densities in rough agreement with the observations if the magnetic field is ~1 mG and the shock velocity is 100 km s-1

Transporting treatment effects from difference-in-differences studies

Difference-in-differences (DID) is a popular approach to identify the causal effects of treatments and policies in the presence of unmeasured confounding. DID identifies the sample average treatment effect in the treated (SATT). However, a goal of such research is often to inform decision-making in target populations outside the treated sample. Transportability methods have been developed to extend inferences from study samples to external target populations; these methods have primarily been developed and applied in settings where identification is based on conditional independence between the treatment and potential outcomes, such as in a randomized trial. This paper develops identification and estimators for effects in a target population, based on DID conducted in a study sample that differs from the target population. We present a range of assumptions under which one may identify causal effects in the target population and employ causal diagrams to illustrate these assumptions. In most realistic settings, results depend critically on the assumption that any unmeasured confounders are not effect measure modifiers on the scale of the effect of interest. We develop several estimators of transported effects, including a doubly robust estimator based on the efficient influence function. Simulation results support theoretical properties of the proposed estimators. We discuss the potential application of our approach to a study of the effects of a US federal smoke-free housing policy, where the original study was conducted in New York City alone and the goal is extend inferences to other US cities

Fluctuations of Spatial Patterns as a Measure of Classical Chaos

In problems where the temporal evolution of a nonlinear system cannot be followed, a method for studying the fluctuations of spatial patterns has been developed. That method is applied to well-known problems in deterministic chaos (the logistic map and the Lorenz model) to check its effectiveness in characterizing the dynamical behaviors. It is found that the indices $\mu _q$ are as useful as the Lyapunov exponents in providing a quantitative measure of chaos.Comment: 10 pages + 7 figures (in ps file), LaTex, Submitted to Phys. Rev.

Void Analysis of Hadronic Density Fluctuations at Phase Transition

The event-to-event fluctuations of hadron multiplicities are studied for a quark system undergoing second-order phase transition to hadrons. Emphasis is placed on the search for an observable signature that is realistic for heavy-ion collisions. It is suggested that in the 2-dimensional y-phi space the produced particles selected in a very narrow p_T window may exhibit clustering patterns even when integrated over the entire emission time. Using the Ising model to simulate the critical phenomenon and taking into account a p_T distribution that depends on the emission time, we study in the framework of the void analysis proposed earlier and find scaling behavior. The scaling exponents turn out to be larger than the ones found before for pure configurations without mixing. The signature is robust in that it is insensitive to the precise scheme of simulating time evolution. Thus it should reveal whether or not the dense matter created in heavy-ion collisions is a quark-gluon plasma before hadronization.Comment: 11 pages in LaTeX + 6 figures in p

Further results on the cross norm criterion for separability

In the present paper the cross norm criterion for separability of density matrices is studied. In the first part of the paper we determine the value of the greatest cross norm for Werner states, for isotropic states and for Bell diagonal states. In the second part we show that the greatest cross norm criterion induces a novel computable separability criterion for bipartite systems. This new criterion is a necessary but in general not a sufficient criterion for separability. It is shown, however, that for all pure states, for Bell diagonal states, for Werner states in dimension d=2 and for isotropic states in arbitrary dimensions the new criterion is necessary and sufficient. Moreover, it is shown that for Werner states in higher dimensions (d greater than 2), the new criterion is only necessary.Comment: REVTeX, 19 page

Dynamics of a Quantum Reference Frame

We analyze a quantum mechanical gyroscope which is modeled as a large spin and used as a reference against which to measure the angular momenta of spin-1/2 particles. These measurements induce a back-action on the reference which is the central focus of our study. We begin by deriving explicit expressions for the quantum channel representing the back-action. Then, we analyze the dynamics incurred by the reference when it is used to sequentially measure particles drawn from a fixed ensemble. We prove that the reference thermalizes with the measured particles and find that generically, the thermal state is reached in time which scales linearly with the size of the reference. This contrasts a recent conclusion of Bartlett et al. that this takes a quadratic amount of time when the particles are completely unpolarized. We now understand their result in terms of a simple physical principle based on symmetries and conservation laws. Finally, we initiate the study of the non-equilibrium dynamics of the reference. Here we find that a reference in a coherent state will essentially remain in one when measuring polarized particles, while rotating itself to ultimately align with the polarization of the particles

Decorrelation Stretches (DCS) of Visible Images as a Tool for Sedimentary Provenance Investigations on Earth and Mars

The surface of Mars exhibits vast expanses of mafic sediments and ancient sedimentary rocks that record signals of climate and environment. To decipher the paleoenvironments, the sediment sources and transport histories must be con-strained, but it is not well known how physical fractionation and aqueous alteration affect mafic sediments during glacial, eolian, and fluvial processes. Semi-Autonomous Navigation for Detrital Environments (SAND-E), a NASA Planetary Science and Technology through Analog Research (PSTAR) project, bridges this gap through studies of sediment-grain properties and mineralogy in the glacio-XRD)-derived mineralogies