The Unique Signature of Shell Curvature in Gamma-Ray Bursts

As a result of spherical kinematics, temporal evolution of received gamma-ray emission should demonstrate signatures of curvature from the emitting shell. Specifically, the shape of the pulse decay must bear a strict dependence on the degree of curvature of the gamma-ray emitting surface. We compare the spectral evolution of the decay of individual GRB pulses to the evolution as expected from curvature. In particular, we examine the relationship between photon flux intensity (I) and the peak of the \nu F\nu distribution (E_{peak}) as predicted by colliding shells. Kinematics necessitate that E_{peak} demonstrate a power-law relationship with I described roughly as: I=E_{peak}^{(1-\zeta)} where \zeta represents a weighted average of the low and high energy spectral indices. Data analyses of 24 BATSE gamma-ray burst pulses provide evidence that there exists a robust relationship between E_{peak} and I in the decay phase. Simulation results, however, show that a sizable fraction of observed pulses evolve faster than kinematics allow. Regardless of kinematic parameters, we found that the existence of curvature demands that the I - E_{peak} function decay be defined by \sim (1-\zeta). Efforts were employed to break this curvature dependency within simulations through a number of scenarios such as anisotropic emission (jets) with angular dependencies, thickness values for the colliding shells, and various cooling mechanisms. Of these, the only method successful in dominating curvature effects was a slow cooling model. As a result, GRB models must confront the fact that observed pulses do not evolve in the manner which curvature demands.Comment: 3 pages, To appear in Proc. from the 2nd Workshop on Gamma-Ray Bursts in the Afterglow Er

A Nonlinear Model of the Business Cycle

The usual index of leading indicators has constant weights on its components and is therefore implicitly premised on the assumption that the dynamical properties of the economy remain the same over time and across phases of the business cycle. We explore the possibility that the business cycle has phases, for example, recessions, recoveries and normal growth, each with its unique dynamics. Based on this possibility we develop a nonlinear model of the business cycle that combines a number of previous approaches. We model the state of the economy as a latent variable with a threshold autoregression structure. In addition to dependence on its own lags the latent variable is also determined by observed economic and financial variables. In turn these variables are modeled as following a nonlinear vector autoregression with regimes defined by the latent business cycle variable. A Markov Chain Monte Carlo algorithm is developed to estimate the model. Special attention is paid to specification of prior distributions given the large dimension of the model. We also investigate using the business cycle chronology of the NBER to aid in the classification of the latent variable. The two main empirical objectives of the model are to provide more accurate predictions of economic variables particularly at turning points and to describe how the dynamics differ across business cycle phasesnonlinear, business cycle, Bayesian

Preserving the validity of the Two-Higgs Doublet Model up to the Planck scale

We examine the constraints on the two Higgs doublet model (2HDM) due to the stability of the scalar potential and absence of Landau poles at energy scales below the Planck scale. We employ the most general 2HDM that incorporates an approximately Standard Model (SM) Higgs boson with a flavor aligned Yukawa sector to eliminate potential tree-level Higgs-mediated flavor changing neutral currents. Using basis independent techniques, we exhibit robust regimes of the 2HDM parameter space with a 125 GeV SM-like Higgs boson that is stable and perturbative up to the Planck scale. Implications for the heavy scalar spectrum are exhibited.Comment: 36 pages, 4 figures, 4 tables (Version 3: typographical error in eq. (A.28) corrected

Toward the AdS/CFT gravity dual for High Energy Collisions: I.Falling into the AdS

In the context of the AdS/CFT correspondence we discuss the gravity dual of a high energy collision in a strongly coupled ${\cal N}=4$ SYM gauge theory. We suggest a setting in which two colliding objects are made of non-dynamical heavy quarks and antiquarks, which allows to treat the process in classical string approximation. Collision ``debris'' consist of closed as well as open strings. If the latter have ends on two outgoing charges, and thus are being ``stretched'' along the collision axes. We discuss motion in AdS of some simple objects first -- massless and massive particles -- and then focus on open strings. We study the latter in a considerable detail, concluding that they rapidly become ``rectangular'' in proper time -spatial rapidity $\tau-y$ coordinates with well separated fragmentation part and a near-free-falling rapidity-independent central part. Assuming that in the collisions of ``walls'' of charges multiple stretching strings are created, we also consider the motion of a 3d stretching membrane. We then argue that a complete solution can be approximated by two different vacuum solutions of Einstein eqns, with matter membrane separating them. We identify one of this solution with Janik-Peschanski stretching black hole solution, and show that all objects approach its (retreating) horizon in an universal manner.Comment: v2 was redone, with new material and different introduction. It now includes introduction to the second paper of the series as well, in which we calculate "holograms" of falling objects, namely their stress tensor on the boundar

Behavior at a Nesting Site and Prey of \u3ci\u3eCrabro Cribrellifer\u3c/i\u3e (Hymenoptera: Sphecidae)

In Michigan, Crabro cribrellifer tends to show nest clumping within a nest aggregation. Its nesting behavior is similar to that of other Crabro, and it preys on Neoitamus flavofemoratus (Diptera: Asilidae) on warm days in July. Miltogrammine flies Metopia campestris are active at the nesting site

Constraints on the Gamma-ray Burst Luminosity Function from PVO and BATSE

We examine the width of the gamma-ray burst luminosity function through the distribution of GRB peak fluxes as detected by the Pioneer Venus Orbiter (PVO) and the Burst and Transient Source Experiment (BATSE). The strength of the analysis is greatly enhanced by using a merged catalog of peak fluxes from both instruments with good cross-calibration of their sensitivities. The range of peak fluxes is increased by approximately a factor of 20 relative to the BATSE catalog. Thus, more sensitive investigations of the $\log N-\log P$ distribution are possible. We place constraints on the width of the luminosity function of gamma-ray bursts brighter than the BATSE completeness limit by comparing the intensity distribution in the merged catalog with those produced by a variety of spatial density and luminosity functions. For the models examined, $90\%$ of the {\em detectable\/} bursts have peak luminosities within a range of 10, indicating that the peak luminosities of gamma-ray bursts span a markedly less wide range of values than many other of their measurable properties. We also discuss for which slopes of a power-law luminosity function the observed width is at the upper end of the constrained range. This is important in determining the power-law slopes for which luminosity-duration correlations could be important.Comment: 10 pages latex + 2 uuencoded figures; APJL accepte

Oil Supply and Tax Incentive

macroeconomics, oil, tax incentive