General Formula for the Momentum Imparted to Test Particles in Arbitrary Spacetimes

Ehlers and Kundt have provided an approximate procedure to demonstrate that gravitational waves impart momentum to test particles. This was extended to cylindrical gravitational waves by Weber and Wheeler. Here a general, exact, formula for the momentum imparted to test particles in arbitrary spacetimes is presented.Comment: 6 page

Characterization of whole-body vibration for monorail passenger ride comfort

Train travel has always been a major mode of public transport in developed countries. In the inner cities monorails are often used, which are operated at elevated rail or beam, the main advantage being traffic interactions can be minimized while maintaining its original landscape. Ride comfort is the basic requirement for every passenger in all kind of public transports. In monorail, vibration is considered as major factor of discomfort, it transmitted to human body, which contribute many health issues. The aim of this study was to evaluate the whole-body vibration transmission and the effects to the monorail passengers. There were total of twenty-four experiments conducted in a two-car train monorail on its complete line from Kuala Lumpur Sentral to Titiwangsa stations. Human vibration meter (HVM-100) with tri-axial accelerometer pad was used to measure the WBV of passengers and International Standards Organization (ISO) 2631-1: 1997 was used for analysis. The experimental results show that the daily vibration exposure 0.81 m/s2 was higher than the action value 0.5 m/s2 of the standard during peak operation and 0.82 m/s2 during off-peak operation. The health effect was measured 9.90 m/s1.75 during peak operation and 9.94 m/s1.75 during off-peak operation; both values are observed in moderate health effect zone as per standard (8.5 m/s1.75 to 17 m/s1.75). Moreover, the passenger ride comfort was measured, it was found to be fairly-uncomfortable at rear bogie and not-uncomfortable at center of car. The statistical analysis has proven the significance of orientation, location and operating hours by significant value p = 0.000 (i.e. p < α) with 29.5% of the variance has been accounted between groups. This provides justification to standardization of proper priority seating zone. The findings of this study can assist in the standard specification for seating design of monorail. The statistical analysis shows that all results are statistically significant for orientations, locations as well as operations

Applying Formal Methods to Networking: Theory, Techniques and Applications

Despite its great importance, modern network infrastructure is remarkable for the lack of rigor in its engineering. The Internet which began as a research experiment was never designed to handle the users and applications it hosts today. The lack of formalization of the Internet architecture meant limited abstractions and modularity, especially for the control and management planes, thus requiring for every new need a new protocol built from scratch. This led to an unwieldy ossified Internet architecture resistant to any attempts at formal verification, and an Internet culture where expediency and pragmatism are favored over formal correctness. Fortunately, recent work in the space of clean slate Internet design---especially, the software defined networking (SDN) paradigm---offers the Internet community another chance to develop the right kind of architecture and abstractions. This has also led to a great resurgence in interest of applying formal methods to specification, verification, and synthesis of networking protocols and applications. In this paper, we present a self-contained tutorial of the formidable amount of work that has been done in formal methods, and present a survey of its applications to networking.Comment: 30 pages, submitted to IEEE Communications Surveys and Tutorial

Comments on matter collineations of plane symmetric, cylindrically symmetric and spherically symmetric spacetimes

Comments are made on some recently published papers on matter collineations of plane symmetric, cylindrically symmetric and spherically symmetric spacetimes

Primordial Black Holes in Phantom Cosmology

We investigate the effects of accretion of phantom energy onto primordial black holes. Since Hawking radiation and phantom energy accretion contribute to a {\it decrease} of the mass of the black hole, the primordial black hole that would be expected to decay now due to the Hawking process would decay {\it earlier} due to the inclusion of the phantom energy. Equivalently, to have the primordial black hole decay now it would have to be more massive initially. We find that the effect of the phantom energy is substantial and the black holes decaying now would be {\it much} more massive -- over 10 orders of magnitude! This effect will be relevant for determining the time of production and hence the number of evaporating black holes expected in a universe accelerating due to phantom energy.Comment: 17 pages, 10 figures, accepted for publication in Gen. Relativ. Gravi

Higgs dark energy in inert doublet model

Scalar fields are among the possible candidates for dark energy. This paper is devoted to the scalar fields from the inert doublet model, where instead of one as in the standard model, two SU(2) Higgs doublets are used. The component fields of one SU(2) doublet ($\phi_1$) act in an identical way to the standard model Higgs while the component fields of the second SU(2) doublet ($\phi_2$) are taken to be the dark energy candidate (which is done by assuming that the phase transition in the field has not yet occurred). It is found that one can arrange for late time acceleration (dark energy) by using an SU(2) Higgs doublet in the inert Higgs doublet model, whose vacuum expectation value is zero, in the quintessential regime.Comment: 6 pages, 4 figure