108 research outputs found
Black holes with scalar hair in light of the Event Horizon Telescope
Searching for violations of the no-hair theorem (NHT) is a powerful way to
test gravity, and more generally fundamental physics, particularly with regards
to the existence of additional scalar fields. The first observation of a black
hole (BH) shadow by the Event Horizon Telescope (EHT) has opened a new direct
window onto tests of gravity in the strong-field regime, including probes of
violations of the NHT. We consider two scenarios described by the
Einstein-Maxwell equations of General Relativity and electromagnetism, to which
we add a scalar field. In the first case we consider a minimally-coupled scalar
field with a potential, whereas in the second case the field is
conformally-coupled to curvature. In both scenarios we construct charged BH
solutions, which are found to carry primary scalar hair. We then compute the
shadows cast by these two BHs as a function of their electric charge and scalar
hair parameter. Comparing these shadows to the shadow of M87* recently imaged
by the EHT collaboration, we set constraints on the amount of scalar hair
carried by these two BHs. The conformally-coupled case admits a regime for the
hair parameter, compatible with EHT constraints, describing a so-called mutated
Reissner-Nordstr\"{o}m BH: this solution was recently found to effectively
mimic a wormhole. Our work provides novel constraints on fundamental physics,
and in particular on violations of the no-hair theorem and the existence of
additional scalar fields, from the shadow of M87*.Comment: 33 pages, 6 figures, 1 table, references added, version accepted for
publication in JCA
No slip gravity in light of LISA standard sirens
Standard sirens (SS) are the gravitational wave analog of the astronomical
standard candles, and can provide powerful information about the dynamics of
the Universe up to very high values. In this work, we generate three mock
SS catalogs based on the merger of massive black hole binaries which are
expected to be observed in the LISA operating frequency band. Then, we perform
an analysis to test modifications of general relativity (GR) inspired by the No
Slip gravity framework. We find that in the best scenarios, we can constrain
the free parameters which quantify deviations from GR to 21\% accuracy, while
the Hubble parameter can be simultaneously fit to 6\% accuracy. In combination
with CMB information, we find a 15\% accuracy on the modified gravity free
parameters and 0.7\% accuracy on the Hubble parameter. The SS events at very
large cosmological distances to be observed in LISA band will provide a unique
way to test nature of gravity, but in the context of the analysis performed
here, it will not be possible to distinguish the No Slip gravity from GR.Comment: 8 pages, 6 figures, 3 tables, improved version. Accepted for
publication in MNRA
Magnetically charged black holes from non-linear electrodynamics and the Event Horizon Telescope
Non-linear electrodynamics (NLED) theories are well-motivated extensions of
QED in the strong field regime, and have long been studied in the search for
regular black hole (BH) solutions. We consider two well-studied and
well-motivated NLED models coupled to General Relativity: the Euler-Heisenberg
model and the Bronnikov model. After carefully accounting for the effective
geometry induced by the NLED corrections, we determine the shadows of BHs
within these two models. We then compare these to the shadow of the
supermassive BH M87* recently imaged by the Event Horizon Telescope
collaboration. In doing so, we are able to extract upper limits on the black
hole magnetic charge, thus providing novel constraints on fundamental physics
from this new extraordinary probe.Comment: 28 pages, 9 figures, 4 tables, accepted for publication in JCA
First record of Goniozus legneri (Hym.: Bethylidae), the larval ectoparasitoid of carob moth, in Iran
A larval parasitoid of carob moth, Ectomyelois ceratoniae (Zeller), was collected in pomegranate orchards in Fars province, Iran, during 2009-2010. This parasitoid, which is newly recorded from Iran, was identified as Goniozus legneri Gordh (Hym.: Bethylidae) by J. de Rond (Lelystad, The Netherlands)
A double-blind, randomized comparison study between Zytux� vs MabThera® in treatment of CLL with FCR regimen: Non-inferiority clinical trial
Background: Chronic lymphocytic leukemia (CLL) is characterized by accumulation of B cells in blood, lymphoid tissues and bone marrow. Addition of rituximab to CLL chemotherapy regimens has been associated with improved survival. The aim of this study was to establish efficacy and safety of Zytux� in comparison to MabThera® in treatment of CLL. Materials and Methods: Seventy CLL patients who met the criteria for entering the study were randomized into two groups (35 patients in each group). Both groups received Fludarabine and Cyclophosphamide plus Rituximab as part of the FCR regimen. Group A was treated with Zytux�, and group B was treated with MabThera®. A non-inferiority margin of 20 for the primary outcome was defined to examine the similarity between Zytux� and MabThera®. Results: Baseline demographic characteristics showed no statistically significant difference between the two groups. The two treatment groups were comparable in terms of laboratory and clinical findings, cellular index changes and CD (5, 19, 20 and 23) counts during therapy cycles and at the end of the treatment period. Regarding safety results, Zytux� demonstrated a similar profile of adverse reactions in comparison to MabThera®. Moreover, the overall response rate was 88 and 89 for Zytux� and MabThera®, respectively (CI -0.17, 0.18). Conclusion: Results showed non-inferiority of Zytux� in terms of efficacy and adverse events as a biosimilar version of MabThera®. © 2018, Tehran University of Medical Sciences (TUMS). All rights reserved
Simple method for the characterization of intense Laguerre-Gauss vector vortex beams
We report on a method for the characterization of intense, structured optical fields through the analysis of the size and surface structures formed inside the annular ablation crater created on the target surface. In particular, we apply the technique to laser ablation of crystalline silicon induced by femtosecond vector vortex beams. We show that a rapid direct estimate of the beam waist parameter is obtained through a measure of the crater radii. The variation of the internal and external radii of the annular crater as a function of the laser pulse energy, at fixed number of pulses, provides another way to evaluate the beam spot size through numerical fitting of the obtained experimental data points. A reliable estimate of the spot size is of paramount importance to investigate pulsed laser-induced effects on the target material. Our experimental findings offer a facile way to characterize focused, high intensity complex optical vector beams which are more and more applied in laser-matter interaction experiments
The relationship between neuropsychological function and responsiveness to vitamin D supplementation using artificial neural networks
Background: Vitamin D has recently attracted interest for its pleiotropic effects. Vitamin D supplements are a potentially important public health intervention, but the response to supplementation varies between individuals. Aim: We aimed to assess the association between several neuropsychological parameters and the magnitude of response to vitamin D supplementation using an artificial neural network method. Methods: Neuropsychological function was assessed in 619 participants using standard questionnaires. The study participants received vitamin D capsules containing 50,000 IU vitamin D per week over 9 weeks. To assess the relationship between responsiveness to vitamin D supplements and the impact on these neuropsychological parameters, the best-performing artificial neural network algorithms were selected from a combination of different transfer functions in hidden and output layers and variable numbers of hidden layers (between two and 50). The performance of the artificial neural network algorithm was assessed by receiver operating characteristic analysis and variables of importance were identified. Results: The artificial neural network algorithm with sigmoid transfer function in both hidden and output layers could predict responsiveness to vitamin D supplementation effectively. The sensitivity and specificity were between 0.60 and 0.70 and 0.66 and 0.70, respectively. Cognitive abilities (42.5), basal vitamin D (21.3), body mass index (9.5), and daytime sleepiness (8) are the most widely used variables to predict changes in serum vitamin D levels. Conclusions: Cognitive abilities status and baseline 25-hydroxyvitamin D are important novel modifiers of the enhancement in circulating 25-hydroxyvitamin D after vitamin D supplementation. © The Author(s) 2020
Learning Interpretable Rules for Multi-label Classification
Multi-label classification (MLC) is a supervised learning problem in which,
contrary to standard multiclass classification, an instance can be associated
with several class labels simultaneously. In this chapter, we advocate a
rule-based approach to multi-label classification. Rule learning algorithms are
often employed when one is not only interested in accurate predictions, but
also requires an interpretable theory that can be understood, analyzed, and
qualitatively evaluated by domain experts. Ideally, by revealing patterns and
regularities contained in the data, a rule-based theory yields new insights in
the application domain. Recently, several authors have started to investigate
how rule-based models can be used for modeling multi-label data. Discussing
this task in detail, we highlight some of the problems that make rule learning
considerably more challenging for MLC than for conventional classification.
While mainly focusing on our own previous work, we also provide a short
overview of related work in this area.Comment: Preprint version. To appear in: Explainable and Interpretable Models
in Computer Vision and Machine Learning. The Springer Series on Challenges in
Machine Learning. Springer (2018). See
http://www.ke.tu-darmstadt.de/bibtex/publications/show/3077 for further
informatio
- …