2,295,139 research outputs found
Events, processes, and the time of a killing
The paper proposes a novel solution to the problem of the time of a killing (ToK), which persistently besets theories of act-individuation. The solution proposed claims to expose a crucial wrong-headed assumption in the debate, according to which ToK is essentially a problem of locating some event that corresponds to the killing. The alternative proposal put forward here turns on recognizing a separate category of dynamic occurents, viz. processes. The paper does not aim to mount a comprehensive defense of process ontology, relying instead on extant defenses. The primary aim is rather to put process ontology to work in diagnosing the current state of play over ToK, and indeed in solving it
Theory of decoherence due to scattering events and L\'evy processes
A general connection between the characteristic function of a L\'evy process
and loss of coherence of the statistical operator describing the center of mass
degrees of freedom of a quantum system interacting through momentum transfer
events with an environment is established. The relationship with microphysical
models and recent experiments is considered, focusing on the recently observed
transition between a dynamics described by a compound Poisson process and a
Gaussian process.Comment: 10 pages, revtex, no figures, to appear in Phys. Rev. Let
Hitting and returning into rare events for all alpha-mixing processes
We prove that for any -mixing stationnary process the hitting time of
any -string converges, when suitably normalized, to an exponential
law. We identify the normalization constant . A similar statement
holds also for the return time. To establish this result we prove two other
results of independent interest. First, we show a relation between the rescaled
hitting time and the rescaled return time, generalizing a theorem by Haydn,
Lacroix and Vaienti. Second, we show that for positive entropy systems, the
probability of observing any -string in consecutive observations, goes
to zero as goes to infinity
Strong memoryless times and rare events in Markov renewal point processes
Let W be the number of points in (0,t] of a stationary finite-state Markov
renewal point process. We derive a bound for the total variation distance
between the distribution of W and a compound Poisson distribution. For any
nonnegative random variable \zeta, we construct a ``strong memoryless time''
\hat \zeta such that \zeta-t is exponentially distributed conditional on {\hat
\zeta\leq t, \zeta>t}, for each t. This is used to embed the Markov renewal
point process into another such process whose state space contains a frequently
observed state which represents loss of memory in the original process. We then
write W as the accumulated reward of an embedded renewal reward process, and
use a compound Poisson approximation error bound for this quantity by
Erhardsson. For a renewal process, the bound depends in a simple way on the
first two moments of the interrenewal time distribution, and on two constants
obtained from the Radon-Nikodym derivative of the interrenewal time
distribution with respect to an exponential distribution.
For a Poisson process, the bound is 0.Comment: Published by the Institute of Mathematical Statistics
(http://www.imstat.org) in the Annals of Probability
(http://www.imstat.org/aop/) at http://dx.doi.org/10.1214/00911790400000005
Events with Isolated Charged Leptons and Large Missing Transverse Momentum at HERA
Striking events with isolated charged leptons, large missing transverse
momentum and large transverse momentum of the hadronic final state were
observed at the electron proton collider HERA in a data sample corresponding to
a luminosity of about 130 pb-1. The H1 collaboration observed 11 events with
isolated electrons or muons and with transverse momentum above 25 GeV. Only
3.4+-0.6 events were expected from Standard Model (SM) processes. Six of these
events have a transverse momentum of greater than 40 GeV, while 1.3+-0.3 events
were expected. The ZEUS collaboration observed good agreement with the SM.
However, ZEUS found two events with a similar event topology, but tau leptons
instead of electrons or muons in the final state. Only 0.2+-0.05 events were
expected from SM processes. For various hypotheses the compatibility of the
experimental results was investigated with respect to the SM and with respect
to possible explanations beyond the SM. Prospects for the high-luminosity
HERA-II data taking period are given
Event Generation and Statistical Sampling for Physics with Deep Generative Models and a Density Information Buffer
We present a study for the generation of events from a physical process with
deep generative models. The simulation of physical processes requires not only
the production of physical events, but also to ensure these events occur with
the correct frequencies. We investigate the feasibility of learning the event
generation and the frequency of occurrence with Generative Adversarial Networks
(GANs) and Variational Autoencoders (VAEs) to produce events like Monte Carlo
generators. We study three processes: a simple two-body decay, the processes
and including the decay of the top
quarks and a simulation of the detector response. We find that the tested GAN
architectures and the standard VAE are not able to learn the distributions
precisely. By buffering density information of encoded Monte Carlo events given
the encoder of a VAE we are able to construct a prior for the sampling of new
events from the decoder that yields distributions that are in very good
agreement with real Monte Carlo events and are generated several orders of
magnitude faster. Applications of this work include generic density estimation
and sampling, targeted event generation via a principal component analysis of
encoded ground truth data, anomaly detection and more efficient importance
sampling, e.g. for the phase space integration of matrix elements in quantum
field theories.Comment: 24 pages, 10 figure
Observation of Events with Isolated Charged Leptons and Large Missing Tra nsverse Momentum and of Events with Multi-Electrons at HERA
Striking events with isolated charged leptons, large missing transverse
momentum and large transverse momentum of the hadronic final state (PTX) have
been observed at the electron proton collider HERA. In the full HERA-I data
sample corresponding to an integrated luminosity of about 130 invpb, the H1
experiment observes 10 events with isolated electrons or muons and with PTX >25
GeV. Only 2.9 pm 0.4 events are expected from Standard Model (SM) processes.
Six of these events have PTX >40 GeV, while 1.1 pm 0.2 events are expected. The
ZEUS experiment observes good agreement with the SM. However, in a preliminary
search ZEUS has found two events with a similar event topology, but tau-leptons
instead of electrons or muons in the final state . Only 0.12 pm 0.02 events are
expected from SM processes.
Moreover, six events with two or more electrons forming an invariant mass
bigger than 100 GeV have been observed by the H1 experiment. Three events have
two electrons and three events have three electrons, while only 0.25 events are
expected in each case. The ZEUS measurement is in agreement with the SM
expectation.Comment: talk given at 38th Recontres de Moriond Electroweak Interactions and
Unified Theories, Les Arc (France) 200
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