6 research outputs found
Scalar Field Probes of Power-Law Space-Time Singularities
We analyse the effective potential of the scalar wave equation near generic
space-time singularities of power-law type (Szekeres-Iyer metrics) and show
that the effective potential exhibits a universal and scale invariant leading
x^{-2} inverse square behaviour in the ``tortoise coordinate'' x provided that
the metrics satisfy the strict Dominant Energy Condition (DEC). This result
parallels that obtained in hep-th/0403252 for probes consisting of families of
massless particles (null geodesic deviation, a.k.a. the Penrose Limit). The
detailed properties of the scalar wave operator depend sensitively on the
numerical coefficient of the x^{-2}-term, and as one application we show that
timelike singularities satisfying the DEC are quantum mechanically singular in
the sense of the Horowitz-Marolf (essential self-adjointness) criterion. We
also comment on some related issues like the near-singularity behaviour of the
scalar fields permitted by the Friedrichs extension.Comment: v2: 21 pages, JHEP3.cls, one reference adde
Grid Awareness Under Normal Conditions and Cyber-Threats
The situational grid awareness is becoming increasingly important for power system operations due to smaller operational margins, wide range of uncertainties entailed by renewables and highly critical infrastructure failures due to potential cyber-attacks. In this chapter, we look at some of the state-of-the-art technologies to monitor events in a power system under normal operating condition, followed by detection algorithms for regular business risk events, such as faults and equipment failures, and finally, we look into methods for quantifying vulnerability of under the rare and men-orchestrated cyber-attacks. First, we outline an architecture of a central piece of today’s grid awareness system, Wide Area Monitoring, Protection and Control technology. Next, we review an event detection method used to identify and record faults and failures in the grid. Finally, we present a method for vulnerability assessment of grids under cyber-attacks