27,242 research outputs found
Statistical fluctuations in pedestrian evacuation times and the effect of social contagion
Mathematical models of pedestrian evacuation and the associated simulation
software have become essential tools for the assessment of the safety of public
facilities and buildings. While a variety of models are now available, their
calibration and test against empirical data are generally restricted to global,
averaged quantities, the statistics compiled from the time series of individual
escapes (" microscopic " statistics) measured in recent experiments are thus
overlooked. In the same spirit, much research has primarily focused on the
average global evacuation time, whereas the whole distribution of evacuation
times over some set of realizations should matter. In the present paper we
propose and discuss the validity of a simple relation between this distribution
and the " microscopic " statistics, which is theoretically valid in the absence
of correlations. To this purpose, we develop a minimal cellular automaton, with
novel features that afford a semi-quantitative reproduction of the experimental
" microscopic " statistics. We then introduce a process of social contagion of
impatient behavior in the model and show that the simple relation under test
may dramatically fail at high contagion strengths, the latter being responsible
for the emergence of strong correlations in the system. We conclude with
comments on the potential practical relevance for safety science of
calculations based on " microscopic " statistics
Competition and dual users in complex contagion processes
We study the competition of two spreading entities, for example innovations,
in complex contagion processes in complex networks. We develop an analytical
framework and examine the role of dual users, i.e. agents using both
technologies. Searching for the spreading transition of the new innovation and
the extinction transition of a preexisting one, we identify different phases
depending on network mean degree, prevalence of preexisting technology, and
thresholds of the contagion process. Competition with the preexisting
technology effectively suppresses the spread of the new innovation, but it also
allows for phases of coexistence. The existence of dual users largely modifies
the transient dynamics creating new phases that promote the spread of a new
innovation and extinction of a preexisting one. It enables the global spread of
the new innovation even if the old one has the first-mover advantage.Comment: 9 pages, 4 figure
Cross-Border Information Transfers: Evidence from Profit Warnings Issued by European Firms
This paper reports evidence on cross-border accounting information transfers associated with profit warning announcements. Using a sample of firms from 29 European countries, we find that negative earnings surprises disclosed by firms in one country affect investorsâ perceptions of comparable nonannouncing firms in other countries. The form and magnitude of cross-border effects is consistent with domestic transfers. Tests explaining variation in cross-border information transfers provide some (albeit rather limited) evidence that effects vary according to a range of firm-, industry- and country-level characteristics.Information transfers; Profit warnings
Whither Capitalism? Financial externalities and crisis
As with global warming, so with financial crises â externalities have a lot to answer for. We
look at three of them. First the financial accelerator due to âfire salesâ of collateral assets -- a
form of pecuniary externality that leads to liquidity being undervalued. Second the ârisk-
shiftingâ behaviour of highly-levered financial institutions who keep the upside of risky
investment while passing the downside to others thanks to limited liability. Finally, the
network externality where the structure of the financial industry helps propagate shocks
around the system unless this is checked by some form of circuit breaker, or âring-fenceâ.
The contrast between crisis-induced Great Recession and its aftermath of slow growth in the
West and the rapid - and (so far) sustained - growth in the East suggests that successful
economic progress may depend on how well these externalities are managed
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