87,646 research outputs found
Data and uncertainty in extreme risks - a nonlinear expectations approach
Estimation of tail quantities, such as expected shortfall or Value at Risk,
is a difficult problem. We show how the theory of nonlinear expectations, in
particular the Data-robust expectation introduced in [5], can assist in the
quantification of statistical uncertainty for these problems. However, when we
are in a heavy-tailed context (in particular when our data are described by a
Pareto distribution, as is common in much of extreme value theory), the theory
of [5] is insufficient, and requires an additional regularization step which we
introduce. By asking whether this regularization is possible, we obtain a
qualitative requirement for reliable estimation of tail quantities and risk
measures, in a Pareto setting
Sound the Alarm: Limitations of Liability in Alarm Service Contracts
Home and business owners increasingly rely on alarm systems to protect against theft and property damage. When a burglary or fire occurs and an alarm service customer discovers that the alarm company negligently failed to call the police or fire department, the customer understandably would expect redress for the company’s failure to provide its service. Many customers would be surprised, though, to discover that an alarm company’s liability is often contractually limited to a relatively token amount unrelated to the cost of the service, even when the alarm company is negligent. Some states view these limitations of liability as exculpatory clauses and determine their enforceability based on whether they are unconscionable or violate public policy. Other states view them as liquidated damages and apply a penalty test to determine their enforceability. This Note addresses the differences between these two approaches in the context of the unique remedy difficulties inherent in alarm service contracts. This Note then argues that the prevailing policy rationales for enforcing alarm service provisions that limit a party’s liability for its own negligence are misguided and advocates that these provisions should not be enforced as a matter of public policy
Representing filtration consistent nonlinear expectations as -expectations in general probability spaces
We consider filtration consistent nonlinear expectations in probability
spaces satisfying only the usual conditions and separability. Under a
domination assumption, we demonstrate that these nonlinear expectations can be
expressed as the solutions to Backward Stochastic Differential Equations with
Lipschitz continuous drivers, where both the martingale and the driver terms
are permitted to jump, and the martingale representation is infinite
dimensional. To establish this result, we show that this domination condition
is sufficient to guarantee that the comparison theorem for BSDEs will hold, and
we generalise the nonlinear Doob-Meyer decomposition of Peng to a general
context
Chandra detection of extended X-ray emission from the recurrent nova RS Ophiuchi
Radio, infrared, and optical observations of the 2006 eruption of the
symbiotic recurrent nova RS Ophiuchi (RS Oph) showed that the explosion
produced non-spherical ejecta. Some of this ejected material was in the form of
bipolar jets to the east and west of the central source. Here we describe Xray
observations taken with the Chandra X-ray Observatory one and a half years
after the beginning of the outburst that reveal narrow, extended structure with
a position angle of approximately 300 degrees (east of north). Although the
orientation of the extended feature in the X-ray image is consistent with the
readout direction of the CCD detector, extensive testing suggests that the
feature is not an artifact. Assuming it is not an instrumental effect, the
extended X-ray structure shows hot plasma stretching more than 1,900 AU from
the central binary (taking a distance of 1.6 kpc). The X-ray emission is
elongated in the northwest direction - in line with the extended infrared
emission and some minor features in the published radio image. It is less
consistent with the orientation of the radio jets and the main bipolar optical
structure. Most of the photons in the extended X-ray structure have energies of
less than 0.8 keV. If the extended X-ray feature was produced when the nova
explosion occurred, then its 1".2 length as of 2007 August implies that it
expanded at an average rate of more than 2 mas/d, which corresponds to a flow
speed of greater than 6,000 km/s (d/1.6 kpc) in the plane of the sky. This
expansion rate is similar to the earliest measured expansion rates for the
radio jets.Comment: accepted in Ap
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