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The impact of news on measures of undiversifiable risk: evidence from the UK stock market
Using UK equity index data, this paper considers the impact of news
on time varying measures of beta, the usual measure of undiversifiable risk.
The empirical model implies that beta depends on news about the market and
news about the sector. The asymmetric response of beta to news about the
market is consistent across all sectors considered. Recent research is divided as
to whether abnormalities in equity returns arise from changes in expected
returns in an efficient market or over-reactions to new information. The
evidence suggests that such abnormalities may be due to changes in expected
returns caused by time-variation and asymmetry in beta
Scaling in the Bombay Stock Exchange Index
In this paper we study BSE Index financial time series for fractal and
multifractal behaviour. We show that Bombay stock Exchange (BSE)Index time
series is mono-fractal and can be represented by a fractional Brownian motion.Comment: 11 pages,3 figure
Topological Graph Polynomials in Colored Group Field Theory
In this paper we analyze the open Feynman graphs of the Colored Group Field
Theory introduced in [arXiv:0907.2582]. We define the boundary graph
\cG_{\partial} of an open graph \cG and prove it is a cellular complex.
Using this structure we generalize the topological (Bollobas-Riordan) Tutte
polynomials associated to (ribbon) graphs to topological polynomials adapted to
Colored Group Field Theory graphs in arbitrary dimension
One vertex spin-foams with the Dipole Cosmology boundary
We find all the spin-foams contributing in the first order of the vertex
expansion to the transition amplitude of the Bianchi-Rovelli-Vidotto Dipole
Cosmology model. Our algorithm is general and provides spin-foams of
arbitrarily given, fixed: boundary and, respectively, a number of internal
vertices. We use the recently introduced Operator Spin-Network Diagrams
framework.Comment: 23 pages, 30 figure
A Far Ultraviolet Study of the Old Nova V841 Oph
We have carried out a synthetic spectral analysis of archival IUE spectra of
the old nova V841 Oph (Nova Oph 1848) taken 15 years apart. The spectra reveal
a rising continuum shortward of 1560\AA, a C {\sc iv} P-Cygni profile
indicative of wind outflow associated with disk accretion in one spectrum, a
deep Ly profile, and strong N {\sc v} (1238\AA, 1242\AA) and O {\sc v}
(1371\AA) wind/coronal absorption lines. Numerous sharp interstellar resonance
lines are also present. A grid of high gravity atmospheres and accretion disk
models, spanning a wide range of inclinations, accretion rates and white dwarf
masses was compared to the de-reddened spectra. We find that, for a steady
state accretion disk model to account for the FUV spectra, the accretion rate
is only 3 10 M_{\sun}/yr, 147 years after its outburst
in 1848, with an implied distance within 300 pc. The accretion rate at
147 years post-outburst is smaller than expected for an old nova.Comment: 6 b/w figures, 2 tables, preprint accepted in the November 2005 issue
of PAS
Cognitive conflicts in major depression : Between desired change and personal coherence
This is an open access article under the terms of the Creative Commons Attribution-NonCommercial License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited and is not used for commercial purposesThe notion of intrapsychic conflict has been present in psychopathology for more than a century within different theoretical orientations. However, internal conflicts have not received enough empirical attention, nor has their importance in depression been fully elaborated. This study is based on the notion of cognitive conflict, understood as implicative dilemma (ID), and on a new way of identifying these conflicts by means of the Repertory Grid Technique. Our aim was to explore the relevance of cognitive conflicts among depressive patientsPeer reviewedFinal Published versio
Impact of Investor's Varying Risk Aversion on the Dynamics of Asset Price Fluctuations
While the investors' responses to price changes and their price forecasts are
well accepted major factors contributing to large price fluctuations in
financial markets, our study shows that investors' heterogeneous and dynamic
risk aversion (DRA) preferences may play a more critical role in the dynamics
of asset price fluctuations. We propose and study a model of an artificial
stock market consisting of heterogeneous agents with DRA, and we find that DRA
is the main driving force for excess price fluctuations and the associated
volatility clustering. We employ a popular power utility function,
with agent specific and
time-dependent risk aversion index, , and we derive an approximate
formula for the demand function and aggregate price setting equation. The
dynamics of each agent's risk aversion index, (i=1,2,...,N), is
modeled by a bounded random walk with a constant variance . We show
numerically that our model reproduces most of the ``stylized'' facts observed
in the real data, suggesting that dynamic risk aversion is a key mechanism for
the emergence of these stylized facts.Comment: 17 pages, 7 figure
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