806 research outputs found
Selfish Dark Matter
We present a mechanism where a particle asymmetry in one sector is used to
generate an asymmetry in another sector. The two sectors are not coupled
through particle number violating interactions and are not required to be in
thermal contact with each other. When this mechanism is applied to baryogenesis
in asymmetric dark matter models, we find that the dark matter particles can be
extremely light, e.g. much lighter than an eV, and that in some cases there is
no need to annihilate away the symmetric component of dark matter. We discuss a
concrete realization of the mechanism with signals in direct detection, at the
LHC, at -factories or future beam dump experiments.Comment: 18+5 pages, 2 figures; Journal version: Added references, small
changes to the free-streaming length estimate
Геомеханика разрушения и регламент тампонажного упрочнения пород вокруг наклонных стволов вязкопластическими растворами
Наведено підсумки шахтних досліджень руйнування порід навколо стволів вугільних шахт та обґрунтовано параметри їх зміцнення вязкопластичними розчинами.Research results are mine destruction of rocks around the shafts of coal mines and reasonable options to strengthen viscoplastic solutions
Binary Models for Marginal Independence
Log-linear models are a classical tool for the analysis of contingency
tables. In particular, the subclass of graphical log-linear models provides a
general framework for modelling conditional independences. However, with the
exception of special structures, marginal independence hypotheses cannot be
accommodated by these traditional models. Focusing on binary variables, we
present a model class that provides a framework for modelling marginal
independences in contingency tables. The approach taken is graphical and draws
on analogies to multivariate Gaussian models for marginal independence. For the
graphical model representation we use bi-directed graphs, which are in the
tradition of path diagrams. We show how the models can be parameterized in a
simple fashion, and how maximum likelihood estimation can be performed using a
version of the Iterated Conditional Fitting algorithm. Finally we consider
combining these models with symmetry restrictions
Exploring physiological signals on people with Duchenne muscular dystrophy for an active trunk support: a case study
Measurement of the CMS Magnetic Field
The measurement of the magnetic field in the tracking volume inside the
superconducting coil of the Compact Muon Solenoid (CMS) detector under
construction at CERN is done with a fieldmapper designed and produced at
Fermilab. The fieldmapper uses 10 3-D B-sensors (Hall probes) developed at
NIKHEF and calibrated at CERN to precision 0.05% for a nominal 4 T field. The
precise fieldmapper measurements are done in 33840 points inside a cylinder of
1.724 m radius and 7 m long at central fields of 2, 3, 3.5, 3.8, and 4 T. Three
components of the magnetic flux density at the CMS coil maximum excitation and
the remanent fields on the steel-air interface after discharge of the coil are
measured in check-points with 95 3-D B-sensors located near the magnetic flux
return yoke elements. Voltages induced in 22 flux-loops made of 405-turn
installed on selected segments of the yoke are sampled online during the entire
fast discharge (190 s time-constant) of the CMS coil and integrated offline to
provide a measurement of the initial magnetic flux density in steel at the
maximum field to an accuracy of a few percent. The results of the measurements
made at 4 T are reported and compared with a three-dimensional model of the CMS
magnet system calculated with TOSCA.Comment: 4 pages, 5 figures, 15 reference
Demographic Inference and Representative Population Estimates from Multilingual Social Media Data
Social media provide access to behavioural data at an unprecedented scale and
granularity. However, using these data to understand phenomena in a broader
population is difficult due to their non-representativeness and the bias of
statistical inference tools towards dominant languages and groups. While
demographic attribute inference could be used to mitigate such bias, current
techniques are almost entirely monolingual and fail to work in a global
environment. We address these challenges by combining multilingual demographic
inference with post-stratification to create a more representative population
sample. To learn demographic attributes, we create a new multimodal deep neural
architecture for joint classification of age, gender, and organization-status
of social media users that operates in 32 languages. This method substantially
outperforms current state of the art while also reducing algorithmic bias. To
correct for sampling biases, we propose fully interpretable multilevel
regression methods that estimate inclusion probabilities from inferred joint
population counts and ground-truth population counts. In a large experiment
over multilingual heterogeneous European regions, we show that our demographic
inference and bias correction together allow for more accurate estimates of
populations and make a significant step towards representative social sensing
in downstream applications with multilingual social media.Comment: 12 pages, 10 figures, Proceedings of the 2019 World Wide Web
Conference (WWW '19
Constraints on a Massive Dirac Neutrino Model
We examine constraints on a simple neutrino model in which there are three
massless and three massive Dirac neutrinos and in which the left handed
neutrinos are linear combinations of doublet and singlet neutrinos. We examine
constraints from direct decays into heavy neutrinos, indirect effects on
electroweak parameters, and flavor changing processes. We combine these
constraints to examine the allowed mass range for the heavy neutrinos of each
of the three generations.Comment: latex, 29 pages, 7 figures (not included), MIT-CTP-221
Functional connectivity of the Precuneus reflects effectiveness of visual restitution training in chronic hemianopia
Contains fulltext :
222045.pdf (publisher's version ) (Open Access
Elaborating Transition Interface Sampling Methods
We review two recently developed efficient methods for calculating rate
constants of processes dominated by rare events in high-dimensional complex
systems. The first is transition interface sampling (TIS), based on the
measurement of effective fluxes through hypersurfaces in phase space. TIS
improves efficiency with respect to standard transition path sampling (TPS)
rate constant techniques, because it allows a variable path length and is less
sensitive to recrossings. The second method is the partial path version of TIS.
Developed for diffusive processes, it exploits the loss of long time
correlation. We discuss the relation between the new techniques and the
standard reactive flux methods in detail. Path sampling algorithms can suffer
from ergodicity problems, and we introduce several new techniques to alleviate
these problems, notably path swapping, stochastic configurational bias Monte
Carlo shooting moves and order-parameter free path sampling. In addition, we
give algorithms to calculate other interesting properties from path ensembles
besides rate constants, such as activation energies and reaction mechanisms.Comment: 36 pages, 5 figure
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