A nonparametric test of exogeneity

This paper is concerned with inference about a function g that is identified by a conditional moment restriction involving instrumental variables. The function is nonparametric. It satisfies mild regularity conditions but is otherwise unknown. The paper presents test of the hypothesis that g is the mean of a random variable Y conditional on a covariate X. The need to test this hypothesis arises frequently in economics. The test does not require nonparametric instrumental-variables (IV) estimation of g and is not subject to the ill-posed inverse problem that nonparametric IV estimation entails. The test is consistent whenever g differs from the conditional mean function of Y on a set of non-zero probability. Moreover, the power of the test is arbitrarily close to 1 uniformly over a set of functions g whose distance from the conditional mean function is O(n^{-1/2}) where n is the sample size

Strong-coupling Jet Energy Loss from AdS/CFT

We propose a novel definition of a holographic light hadron jet and consider the phenomenological consequences, including the very first fully self-consistent, completely strong-coupling calculation of the jet nuclear modification factor $R_{AA}$, which we find compares surprisingly well with recent preliminary data from LHC. We show that the thermalization distance for light parton jets is an extremely sensitive function of the \emph{a priori} unspecified string initial conditions and that worldsheets corresponding to non-asymptotic energy jets are not well approximated by a collection of null geodesics. Our new string jet prescription, which is defined by a separation of scales from plasma to jet, leads to the re-emergence of the late-time Bragg peak in the instantaneous jet energy loss rate; unlike heavy quarks, the energy loss rate is unusually sensitive to the very definition of the string theory object itself. A straightforward application of the new jet definition leads to significant jet quenching, even in the absence of plasma. By renormalizing the in-medium suppression by that in the vacuum we find qualitative agreement with preliminary CMS $R_{AA}^{jet}(p_T)$ data in our simple plasma brick model. We close with comments on our results and an outlook on future work.Comment: 28 pages, 9 figure

Self-Gravitating Strings and String/Black Hole Correspondence

In a recent essay, we discussed the possibility of using polymer sizing to model the collapse of a single, long excited string to a black hole. In this letter, we apply this idea to bring further support to string/black hole correspondence. In particular, we reproduce Horowitz and Polchinki's results for self-gravitating fundamental strings and speculate on the nature of the quantum degrees of freedom of black holes in string theory.Comment: 8 pages, harvma

Supplement to the 1975 report on active and planned spacecraft and experiments

A listing and brief description of spacecraft and experiments designed to update the January 1975 report on active and planned spacecraft and experiments to March 31, 1975 was presented. The information is given in two sections. In the first, spacecraft and experiments that have become known to NSSDC since the original report or that have changed significantly are described. In the second, an alphabetical listing is given for all spacecraft and experiments described in the first section and in the original report. It also updates status of operation and launch dates to March 31, 1975

Supplement no. 1 to the January 1974 report on active and planned spacecraft and experiments

Updated information and descriptions on spacecraft and experiments are listed according to spacecraft name and principle experimental investigator. A cumulative index of active and planned spacecraft and experiments is provided; bar graph indexes for electromagnetic radiation experiments are included in table form

Atmospheric densities from Explorer 17 density gauges and a comparison with satellite drag data

Atmospheric density data from Explorer XVII GAUGES and satellite drag dat

Fundamental Bounds on First Passage Time Fluctuations for Currents

Current is a characteristic feature of nonequilibrium systems. In stochastic systems, these currents exhibit fluctuations constrained by the rate of dissipation in accordance with the recently discovered thermodynamic uncertainty relation. Here, we derive a conjugate uncertainty relationship for the first passage time to accumulate a fixed net current. More generally, we use the tools of large-deviation theory to simply connect current fluctuations and first passage time fluctuations in the limit of long times and large currents. With this connection, previously discovered symmetries and bounds on the large-deviation function for currents are readily transferred to first passage times.Comment: 7 pages including S

Proof of the Finite-Time Thermodynamic Uncertainty Relation for Steady-State Currents

The thermodynamic uncertainty relation offers a universal energetic constraint on the relative magnitude of current fluctuations in nonequilibrium steady states. However, it has only been derived for long observation times. Here, we prove a recently conjectured finite-time thermodynamic uncertainty relation for steady-state current fluctuations. Our proof is based on a quadratic bound to the large deviation rate function for currents in the limit of a large ensemble of many copies.Comment: 3 page