Miracle-dz/UniFAR-FTUs huggingface dataset:
MD Simulation for Head-on Collision of Liquid Nanodroplets Obeying Modified L-J Potential

This project models and studies the `head-on' collision of liquid helium nanodroplets within a vacuum, using molecular dynamics simulation techniques. Programs written in MATLAB and C are utilized in tandem to facilitate computer experimentation that achieves this goal. The most expensive computation, that of collision simulation, is handled by a HPC cluster `ALICE' at the University of Leicester. Colliding droplets are modelled as roughly spherical collections of points, cut from a simple cubic lattice, obeying a modified Lennard-Jones potential, with average velocities initialized to ensure a `head-on' collision. These point-sets are then allowed to collide within a cuboid region, designed to take advantage of the observed angular distribution of post-collision fragmentation (favoring a plane orthogonal to `collision axis'). To implement the developed theoretical model, an existing C script by D. C. Rapaport, for modelling a homogeneous liquid state, is edited by the author to fit the given, highly heterogeneous scenario. To do analysis on the resulting positions and velocities of points in time, a precise definition of `droplet' was required. An object is defined, from the perspective of metric space, to satisfy this need. An existing cluster analysis algorithm, DBSCAN, is used to apply this definition to the points in simulation. The results presented here focus on three distinct properties of post-collision droplets, these being size, speed and temperature; for collision speed varying across ten equidistant averages chosen based on visual examination of collisions. Quantitative evidence of post-collision droplet speed being inversely proportional to droplet radius is presented, droplet temperature distribution post-collision is noted, and qualitative change in collision behavior across a certain threshold of collision speed is observed.
The thermal instability of the warm absorber in NGC 3783

We model the observed X-ray spectral continuum shape, ionic column densities, and absorption measure distribution (AMD) of the warm absorber in the Seyfert galaxy NGC 3783. We assume a photo-ionized medium with a uniform total (gas+radiation) pressure. The irradiation causes the wind to be radiation pressure compressed (RPC). We compare the observational characteristics derived from the 900 ksec Chandra observation to radiative transfer computations in pressure equilibrium using the radiative transfer code TITAN. We explore different values of the ionization parameter xi of the incident flux and adjust the hydrogen-equivalent column density, N_H0 of the warm absorber to match the observed soft X-ray continuum. We derive theoretical column densities for a broad range of ionic species of iron and neon and an AMD that we compare to the observations. We find an extension of the degeneracy between xi and N_H0 for the constant pressure models previously discussed for NGC 3783. Including the ionic column densities of iron and neon in the comparison between observations and data we conclude that a range of ionization parameters between 4000 and 8000 ergs cm/s is preferred. For the first time, we present theoretical AMD for a constant pressure wind in NGC 3783 that correctly reproduces the observed level and is in approximate agreement with the observational appearance of an instability region. Using a variety of observational indicators, we confirm that the X-ray outflow of NGC 3783 can be described as an RPC medium in pressure equilibrium. The observed AMD agrees with a uniformly hot or a uniformly cold thermal state. The measured ionic column densities suggest that the wind tends to the uniformly cold thermal state. The occurrence of thermal instability in the warm absorber model may depend on the computational method and the spatial scale on which the radiative transfer is solved.
Scaling and Pattern Formation in Condensed Matter Systems

In this dissertation, I present analytical and numerical work regarding the scaling behavior of three physical systems, with increasing levels of complexity. I begin by analyzing the scaling behavior of Griffiths ferromagnets near the Griffithsparamagnetic transition point. By deriving the asymptotic behavior of the magnetization of the system using an ansatz for the Yang-Lee zero density, which is a generic form of the density with the presence of disorder, I find that the scaling behavior of Griffiths ferromagnet is completely different from that of conventional (pure) ferromagnets—the scaling is dominated by an essential singularity in the external magnetic field, due to the ferromagnetic response of arbitrarily large pure (disorder free) ferromagnetic islands in the system. Excellent agreement is found by comparing this prediction to the experimental data on La0.7Ca0. 3MnO3, from which I also extract the critical exponents. Next I report on studies of landscape formation due to carbonate precipitation near geothermal hot springs. This system forms complex patterns due to coupling between the fluid flow, precipitation kinematics and landscape dynamics. I formulate a mathematical framework to describe this complex geological process. I derive analytically the shape and stability of the spherically symmetric domes. The solution agrees with field observations and simulation results, up to a point at which surface tension becomes important and the fluid breaks into rivulets. Although our theory does not take into account surface tension, it does describe its own failure and predicts a scaling behavior about the angle at which rivulets begin. This scaling behavior is
Molecular observations of comets C/2012 S1 (ISON) and C/2013 R1 (Lovejoy): HNC/HCN ratios and upper limits to PH3

We present molecular observations carried out with the IRAM 30m telescope at wavelengths around 1.15 mm towards the Oort cloud comets C/2012 S1 (ISON) and C/2013 R1 (Lovejoy) when they were at 0.6 and 1 au, respectively, from the Sun. We detect HCN, HNC, and CH3OH in both comets, together with the ion HCO+ in comet ISON and a few weak unidentified lines in comet Lovejoy, one of which might be assigned to methylamine (CH3NH2). The monitoring of the HCN J = 3-2 line showed a tenfold enhancement in comet ISON on November 14.4 UT due to an outburst of activity whose exact origin is unknown, although it might be related to some break-up of the nucleus. The set of CH3OH lines observed was used to derive the kinetic temperature in the coma, 90 K in comet ISON and 60 K in comet Lovejoy. The HNC/HCN ratios derived, 0.18 in ISON and 0.05 in Lovejoy, are similar to those found in most previous comets and are consistent with an enhancement of HNC as the comet approaches the Sun. Phosphine (PH3) was also searched for unsuccessfully in both comets through its fundamental 1-0 transition, and 3 sigma upper limits corresponding to PH3/H2O ratios 4-10 times above the solar P/O elemental ratio were derived.
Dyonic AdS black holes in maximal gauged supergravity

We present two new classes of dyonic anti-de Sitter black hole solutions of four-dimensional maximal N=8, SO(8) gauged supergravity. They are (1) static black holes of N=2, U(1)4 gauged supergravity with four electric and four magnetic charges, with spherical, planar or hyperbolic horizons; and (2) rotating black holes of N=2, U(1)2 gauged supergravity with two electric and two magnetic charges. We study their thermodynamics, and point out that the formulation of a consistent thermodynamics for dyonic anti-de Sitter black holes is dependent on the existence of boundary conditions for the gauge fields. We identify several distinct classes of boundary conditions for gauge fields in U(1)4 supergravity. We study a general family of metrics containing the rotating solutions, and find Killing-Yano tensors with torsion in two conformal frames, which underlie separability. © 2014 American Physical Society.
The post-common envelope central stars of the planetary nebulae Henize 2-155 and Henize 2-161

We present a study of Hen 2-155 and Hen 2-161, two planetary nebulae which bear striking morphological similarities to other planetary nebulae known to host close-binary central stars. Both central stars are revealed to be photometric variables while spectroscopic observations confirm that Hen 2-155 is host to a double-eclipsing, post-common-envelope system with an orbital period of 3 h 33 m making it one of the shortest period binary central stars known. The observations of Hen 2-161 are found to be consistent with a post-common-envelope binary of period ∼1 day. A detailed model of the central star of Hen 2-155 is produced, showing the nebular progenitor to be a hot, post-AGB remnant of approximately 0.62 M� , consistent with the age of the nebula, and the secondary star to be an M dwarf whose radius is almost twice the expected zero age main sequence radius for its mass. In spite of the small numbers, all main-sequence companions, of planetary nebulae central stars, to have had their masses and radii constrained by both photometric and spectroscopic observations have also been found to display this “inflation”. The cause of the “inflation” is uncertain but is probably related to rapid accretion, immediately before the recent common-envelope phase, to which the star has not yet thermally adjusted. The chemical composition of both nebulae is also analysed, showing both to display elevated abundance discrepancy factors. This strengthens the link between elevated abundance discrepancy factors and close binarity in the nebular progenitor.
Expectation maximization hard thresholding methods for sparse signal reconstruction

Reconstructing a high dimensional sparse signal from low dimensional linear measurements has been an important problem in various research disciplines including statistics, machining learning, data mining and signal processing. In this dissertation, we develop a probabilistic framework for sparse signal reconstruction and propose several novel algorithms for computing the maximum likelihood (ML) estimates under this framework. We first consider an underdetermined linear model where the regression-coefficient vector is the sum of an unknown deterministic sparse signal component and a zero-mean white Gaussian component with an unknown variance. Our reconstruction schemes are based on an expectation-conditional maximization either (ECME) iteration that aims at maximizing the likelihood function with respect to the unknown parameters for a given signal sparsity level. We propose a double overrelaxation (DORE) thresholding scheme for accelerating the ECME iteration and prove that, under certain conditions, the ECME and DORE iterations converge to local maxima of the likelihood function and achieve near-optimal or perfect recovery of approximately sparse or sparse signals, respectively. If the signal sparsity level is unknown, we introduce an unconstrained sparsity selection (USS) criterion and a tuning-free automatic double overrelaxation (ADORE) thresholding method that employs USS to estimate the sparsity level. In applications such as tomographic imaging, the signal of interest is nonnegative. We modify our probabilistic model and the ECME algorithm to incorporate the additional signal nonnegativity constraint. The maximization step of the modified ECME iteration is approximated by a difference map iteration. We compare the proposed and existing sparse reconstruction methods using simulated and real-data tomographic imaging experiments. Finally, we develop a generalized expectation-maximization (GEM) algorithm for sparse
Information transmission over an amplitude damping channel with an arbitrary degree of memory

We study the performance of a partially correlated amplitude damping channel acting on two qubits. We derive lower bounds for the single-shot classical capacity by studying two kinds of quantum ensembles, one which allows to maximize the Holevo quantity for the memoryless channel and the other allowing the same task but for the full-memory channel. In these two cases, we also show the amount of entanglement which is involved in achieving the maximum of the Holevo quantity. For the single-shot quantum capacity we discuss both a lower and an upper bound, achieving a good estimate for high values of the channel transmissivity. We finally compute the entanglement-assisted classical channel capacity.
Titan-Hyperion Resonance and the Tidal Q of Saturn

Lainey et al. (2012), by re-analyzing long-baseline astrometry of Saturn's moons, have found that the moons' tidal evolution is much faster than previously thought, implying an order of magnitude stronger tidal dissipation within Saturn. This result is controversial and implies recent formation of at least some of the mid-sized icy moons of Saturn. Here we show that this more intensive tidal dissipation is in full agreement with the evolved state of the Titan-Hyperion resonance. This resonance was previously thought to be non-tidal in origin, as the amount of tidal evolution required for its assembly is beyond what is possible in models that assume that all the major moons are primordial. We find that the survival of the Titan-Hyperion resonance is in agreement with a past Titan-Iapetus 5:1 resonance, but not with unbroken tidal evolution of Rhea from the rings to its current distance.
An ordering of dependence

An ordering of dependence is defined on the space of probability measures on a finite product space, with fixed marginals. The definition of this ordering involves the Lorenz curve of the likelihood ratio of a probability measure w.r. t. the product measure of the marginals. A minimal element w.r. t. this dependence ordering always exists and equals the product measure. Conditions for the existence of a maximal element are examined. The ordering is generalized to the case of infinite spaces. Comparison with some other orders of dependence is considered.
Super-resolution single-beam imaging via compressive sampling

Based on compressive sampling techniques and short exposure imaging, super-resolution imaging with thermal light is experimentally demonstrated exploiting the sparse prior property of images for standard conventional imaging system. Differences between super-resolution imaging demonstrated in this letter and super-resolution ghost imaging via compressive sampling (arXiv. Quant-ph/0911.4750v1 (2009)), and methods to further improve the imaging quality are also discussed.
Assessment of the breadth of binding promiscuity of heme towards human proteins

Abstract Heme regulates important biological processes by transient interactions with many human proteins. The goal of the present study was to assess extends of protein binding promiscuity of heme. To this end we evaluated interaction of heme with >9000 human proteins. Heme manifested high binding promiscuity by binding to most of the proteins in the array. Nevertheless, some proteins have outstanding heme binding capacity. Bioinformatics analyses revealed that apart from typical haemoproteins, these proteins are frequently involved in metal binding or have the potential to recognize DNA. This study can contribute for understanding the regulatory functions of labile heme.
The T(3)-Gauge Model, the Einstein-Like Gauge Equation, and Volterra Dislocations with Modified Asymptotics

Abstract Three-dimensional Lagrangian field theory is investigated as the T (3)-gauge model of static defects in continuous solids. The gauge Lagrangian is proposed in the Hilbert–Einstein form, and the non-conventional incompatibility law is given by an Einstein-like gauge equation with the elastic stress tensor as “matter” source. The stress function method is used, and two solutions to the linearized gauge equation (i.e., two modified stress functions) are obtained which are short-ranged in comparison with the Airy and Prandtl stress functions of classical Volterra dislocations. The modified stress functions obtained enable two ways of influencing the asymptotical behaviour of the edge and screw dislocations. Namely, the classically known rule 1/ ρ is changed either at spatial extension (in favour of more fast decay of the modified stress components), or within the defect's cores (linear stresses of background Volterra defects become smoothed out due to formation of a core region).
A new viable region of the inert doublet model

The inert doublet model, a minimal extension of the Standard Model by a second Higgs doublet, is one of the simplest and most attractive scenarios that can explain the dark matter. In this paper, we demonstrate the existence of a new viable region of the inert doublet model featuring dark matter masses between MW and about 160 GeV. Along this previously overlooked region of the parameter space, the correct relic density is obtained thanks to cancellations between different diagrams contributing to dark matter annihilation into gauge bosons (W+W− and Z0Z0). First, we explain how these cancellations come about and show several examples illustrating the effect of the parameters of the model on the cancellations themselves and on the predicted relic density. Then, we perform a full scan of the new viable region and analyze it in detail by projecting it onto several two-dimensional planes. Finally, the prospects for the direct and the indirect detection of inert Higgs dark matter within this new viable region are studied. We find that present direct detection bounds already rule out a fraction of the new parameter space and that future direct detection experiments, such as Xenon100, will easily probe the remaining part in its entirety.
CMB-Galaxy correlation in Unified Dark Matter Scalar Field Cosmologies

We present an analysis of the cross-correlation between the CMB and the large-scale structure (LSS) of the Universe in Unified Dark Matter (UDM) scalar field cosmologies. We work out the predicted cross-correlation function in UDM models, which depends on the speed of sound of the unified component, and compare it with observations from six galaxy catalogues (NVSS, HEAO, 2MASS, and SDSS main galaxies, luminous red galaxies, and quasars). We sample the value of the speed of sound and perform a likelihood analysis, finding that the UDM model is as likely as the ΛCDM, and is compatible with observations for a range of values of c∞ (the value of the sound speed at late times) on which structure formation depends. In particular, we obtain an upper bound of c∞2 ≤ 0.009 at 95% confidence level, meaning that the ΛCDM model, for which c∞2 = 0, is a good fit to the data, while the posterior probability distribution peaks at the value c∞2 = 10−4 . Finally, we study the time dependence of the deviation from ΛCDM via a tomographic analysis using a mock redshift distribution and we find that the largest deviation is for low-redshift sources, suggesting that future low-z surveys will be best suited to constrain UDM models.
Theory of Simple Glasses

This manuscript has been prepared as a thesis to obtain the French "Habilitation a diriger des recherches (HDR)" which allows one to supervise PhD students. I review here my work on the glass and jamming transition. I tried to explain this subject in a concise and self-contained way, highlighting what I consider the main motivations for its study and trying to put my work in a broader perspective. Basically I tried to tell this story in the same way as I would tell it to a student who contacted me to start a PhD thesis on these topics.
Generalizing the Lomb-Scargle periodogram

This paper is an elaboration of an issue that arose in the paper “Nonuniform Sampling: Bandwidth and Aliasing” [1]. In that paper the single frequency estimation problem was explored using Bayesian probability theory for quadrature data that were sampled nonuniformly and nonsimultaneously. In the process of discussing single frequency estimation, it was shown that the Lomb-Scargle periodogram is the sufficient statistic for single frequency estimation for a stationary sinusoid given real nonuniformly sampled data. Here we demonstrate that the Lomb-Scargle periodogram may be generalized in a straightforward manner to nonuniformly nonsimultaneously sampled quadrature data when the sinusoid has arbitrary decay. This generalized Lomb-Scargle periodogram is the sufficient statistic for single frequency estimation in a wide class of problems ranging from stationary frequency estimation in real uniformly sampled data, to frequency estimation for a single sinusoid having exponential, Gaussian, or arbitrary decay .
Extreme Values, Quantile Estimation, and Value at Risk

Extreme price movements in the financial markets are rare, but important. The stock market crash on Wall Street in October 1987 and other big financial crises such as the Long Term Capital Management have attracted a great deal of attention among practitioners and researchers, and some people even called for government regulations on the derivative markets. In recent years, the seemingly large daily price movements in high-tech stocks have further generated discussions on market risk and margin setting for financial institutions. As a result, value at risk (VaR) has become a widely used measure of market risk in risk management. In this chapter, we discuss various methods for calculating VaR and the statistical theories behind these methods. In particular, we consider the extreme value theory developed in the statistical literature for studying rare (or extraordinary) events and its application to VaR. Both unconditional and conditional concepts of extreme values are discussed. The unconditional approach to VaR calculation for a financial position uses the historical returns of the instruments involved to compute VaR. However, a conditional approach uses the historical data and explanatory variables to calculate VaR. Other approaches to VaR calculation discussed in the chapter are RiskMetrics, econometric modeling using volatility models, and empirical quantile. We use daily log returns of IBM stock to illustrate the actual calculation of all the methods discussed. The results obtained can therefore be used to compare the performance of different methods. Figure 7.1 shows the time plot of daily log returns of IBM stock from July 3, 1962 to December 31, 1998 for 9190 observations.
NEAR-INFRARED IMAGING POLARIMETRY OF INNER REGION OF GG TAU A DISK

By performing non-masked polarization imaging with Subaru/HiCIAO, polarized scattered light from the inner region of the disk around the GG Tau A system was successfully detected in the H band, with a spatial resolution of approximately 0. ″07, revealing the complicated inner disk structures around this young binary. This paper reports the observation of an arc-like structure to the north of GG Tau Ab, and part of a circumstellar structure that is noticeable around GG Tau Aa, extending to a distance of approximately 28 au from the primary star. The speckle noise around GG Tau Ab constrains its disk radius to au. Based on the size of the circumbinary ring and the circumstellar disk around GG Tau Aa, the semimajor axis of the binary’s orbit is likely to be 62 au. A comparison of the present observations with previous Atacama Large Millimeter Array and near-infrared H2 emission observations suggests that the north arc could be part of a large streamer flowing from the circumbinary ring to sustain the circumstellar disks. According to the previous studies, the circumstellar disk around GG Tau Aa has enough mass and can sustain itself for a duration sufficient for planet formation; thus, our study indicates that planets can form within close (separation ≲ 100 au) young binary systems.