This paper discusses particle production in Schwarzchild-like spacetimes and in an uniform electric field. Both problems are approached using the method of complex path analysis. Particle production in Schwarzchild-like spacetimes with a horizon is obtained here by a new and simple semi-classical method based on the method of complex paths. Hawking radiation is obtained in the (t,r) co-ordinate system of the standard Schwarzchild metric {\it without} requiring the Kruskal extension. The co-ordinate singularity present at the horizon manifests itself as a singularity in the expression for the semi-classical propagator for a scalar field. We give a prescription whereby this singularity is regularised with Hawking's result being recovered. In the case of the electric field, standard quantum field theoretic methods can be used to obtain particle production in a purely time-dependent gauge. In a purely space-dependent gauge, however, the tunnelling interpretation has to be resorted to. We attempt, in this paper, to provide a tunnelling description for both the time and space dependent gauges. The usefulness of such a common description becomes evident when `mixed' gauges, which are functions of both space and time variables, are analysed. We report, in this paper, certain mixed gauges which have the interesting property that mode functions in these gauges are found to be a combination of {\it elementary} functions unlike the standard modes. Finally, we present an attempt to interpret particle production by the electric field as a tunnelling process between the two sectors of the Rindler spacetime.Comment: 26 pages, Latex file, one eps figur

Abstract. We apply the technique of complex paths to obtain Hawking radiation in different coordinate representations of the Schwarzschild space-time. The coordinate representations we consider do not possess a singularity at the horizon unlike the standard Schwarzschild coordinate. However, the event horizon manifests itself as a singularity in the expression for the semiclassical action. This singularity is regularized by using the method of complex paths and we find that Hawking radiation is recovered in these coordinates indicating the covariance of Hawking radiation as far as these coordinates are concerned.

We apply the technique of complex paths to obtain Hawking radiation in different coordinate representations of the Schwarzschild space-time. The coordinate representations we consider do not possess a singularity at the horizon unlike the standard Schwarzschild coordinate. However, the event horizon manifests itself as a singularity in the expression for the semiclassical action. This singularity is regularized by using the method of complex paths and we find that Hawking radiation is recovered in these coordinates indicating the covariance of Hawking radiation. This also shows that there is no correspondence between the particles detected by the model detector and the particle spectrum obtained by the quantum field theoretic analysis -a result known in other contexts as well. * 571 Mod. Phys. Lett. A 2001.16:571-578. Downloaded from www.worldscientific.com by GEORGE WASHINGTON UNIVERSITY on 02/05/15. For personal use only.

This research examines route choice, in the presence of real-time information, as a consequence of two underlying behavioral mechanisms: compliance and inertia. The compliance mechanism reflects the propensity of a user to comply with the information supplied by advanced traveler information systems (ATIS). The inertial mechanism represents the tendency of users to continue on their current paths. These two mechanisms in route choice are neither mutually exclusive nor collectively exhaustive. A framework is proposed to model these mechanisms explicitly. The proposed framework decomposes the route choice into two states by exploiting the user’s path choice structure (resulting from the current choice prior to the decision of interest) and the information supplied by ATIS. In each state, the mechanisms are incorporated by associating their utilities with those that reflect the specific attributes of the alternative paths. The resulting nested choice structure is implemented using the multinomial probit model. This framework is illustrated using route choice data obtained from dynamic interactive simulator experiments. The empirical results strongly support the simultaneous presence of both the compliance and inertia mechanisms in route choice behavior. The results also indicate that information quality, network loading and day-to-day evolution, level-of-service measures, and trip-makers’ prior experience are significant determinants of route choice through the inertial and compliance mechanisms. These findings have important implications in travel behavior forecasting, ATIS design and evaluation, demand management, and network state prediction.

In the path integral expression for a Feynman propagator of a spinless particle of mass m, the path integral amplitude for a path of proper length R(x, x ′ |gµν ) connecting events x and x ′ in a spacetime described by the metric tensor gµν is exp − [m R(x, x ′ |gµν )]. In a recent paper, assuming the path integral amplitude to be invariant under the duality transformation R → L 2 P /R , Padmanabhan has evaluated the modified Feynman propagator in an arbitrary curved spacetime. He finds that the essential feature of this 'principle of path integral duality' is that the Euclidean proper distance (∆x) 2 between two infinitesimally separated spacetime events is replaced by (∆x) 2 + 4L 2 P . In other words, under the duality principle the spacetime behaves as though it has a 'zero-point length' LP , a feature that is expected to arise in a quantum theory of gravity.In the Schwinger's proper time description of the Feynman propagator, the weightage factor for a path with a proper time s is exp −(m 2 s). Invoking Padmanabhan's 'principle of path integral duality' corresponds to modifying the weightage factor exp −(m 2 s) to exp − m 2 s + (L 2 P /s) . In this paper, we use this modified weightage factor in Schwinger's proper time formalism to evaluate the quantum gravitational corrections to some of the standard quantum field theoretic results in flat and curved spacetimes. In flat spacetime, we evaluate the corrections to: (1) the Casimir effect, (2) the effective potential for a self-interacting scalar field theory, (3) the effective Lagrangian for a constant electromagnetic background and (4) the thermal effects in the Rindler coordinates. In an arbitrary curved spacetime, we evaluate the corrections to: (1) the effective Lagrangian for the gravitational field and (2) the trace anomaly. In all these cases, we first present the conventional result and then go on to evaluate the corrections with the modified weightage factor. We find that the extra factor exp −(L 2 P /s) acts as a regulator at the Planck scale thereby 'removing' the divergences that otherwise appear in the theory. Finally, we discuss the wider implications of our analysis. I. THE PRINCIPLE OF PATH INTEGRAL DUALITYAll attempts to provide a quantum frame work for the gravitational field have so far proved to be unsuccessful. In the absence of a viable quantum theory of gravity, it is interesting to ask whether we can say anything at all about the effects of metric fluctuations on quantum field theory in flat and curved spacetimes.The Planck length L P ≡ (Gh/c 3 ) 1/2 is expected to play a vital role in the ultimate quantum theory of gravity. (We shall seth = c = 1.) Simple thought experiments clearly indicate that it is not possible to devise experimental procedures which will measure lengths with an accuracy greater than about O(L P ) [1]. Also, in some simple models of quantum gravity, when the spacetime interval is averaged over the metric fluctuations, it is found to be bounded from below at O(L 2 P ) [2]. These results suggest that one can think of...

A B S T R A C TCoronavirus papain-like proteases (PLPs or PLpro), such as the one encoded in the genome of the infectious Middle East Respiratory Syndrome (MERS) virus, have multiple enzymatic activities that promote viral infection. PLpro acts as a protease and processes the large coronavirus polyprotein for virus replication. PLpro also functions as both a deubiquitinating (DUB) and deISGylating (deISG) enzyme and removes ubiquitin (Ub) and interferon-stimulated gene 15 (ISG15) from cellular proteins. Both DUB and deISG activities are implicated in suppressing innate immune responses; however, the precise role of each activity in this process is still unclear due in part to the difficulties in separating each activity. In this study, we determine the first structure of MERS PLpro in complex with the full-length human ISG15 to a resolution of 2.3 Å. This structure and available structures of MERS PLpro-Ub complexes were used as molecular guides to design PLpro mutants that lack either or both DUB/deISG activities. We tested 13 different PLpro mutants for protease, DUB, and deISG activitites using fluorescence-based assays. Results show that we can selectively modulate DUB activity at amino acid positions 1649 and 1653 while mutation of Val1691 or His1652 of PLpro to a positive charged residue completely impairs both DUB/deISG activities. These mutant enzymes will provide new functional tools for delineating the importance of DUB versus deISG activity in virus-infected cells and may serve as potential candidates for attenuating the MERS virus in vivo for modified vaccine design efforts.

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