Miracle-dz/UniFAR-FTUs huggingface dataset:
Homoclinic chaos in the dynamics of a general Bianchi type-IX model

The dynamics of a general Bianchi IX model with three scale factors is examined. The matter content of the model is assumed to be comoving dust plus a positive cosmological constant. The model presents a critical point of saddle-center-center type in the finite region of phase space. This critical point engenders in the phase space dynamics the topology of stable and unstable four dimensional tubes $R \times S^3$, where $R$ is a saddle direction and $S^3$ is the manifold of unstable periodic orbits in the center-center sector. A general characteristic of the dynamical flow is an oscillatory mode about orbits of an invariant plane of the dynamics which contains the critical point and a Friedmann-Robertson-Walker (FRW) singularity. We show that a pair of tubes (one stable, one unstable) emerging from the neighborhood of the critical point towards the FRW singularity have homoclinic transversal crossings. The homoclinic intersection manifold has topology $R \times S^2$ and is constituted of homoclinic orbits which are bi-asymptotic to the $S^3$ center-center manifold. This is an invariant signature of chaos in the model, and produces chaotic sets in phase space. The model also presents an asymptotic DeSitter attractor at infinity and initial conditions sets are shown to have fractal basin boundaries connected to the escape into the DeSitter configuration (escape into inflation), characterizing the critical point as a chaotic scatterer.
Very long optical paths in air

Two different multiple traversal optical systems are described; one gives the longest paths, the other the best compensation for vibration and misalignment problems. In the first, seven mirrors in a near confocal arrangement permit a large aperture beam of light to pass through a restricted volume for a discrete and very large number of times. A rectangular array of images corresponding to different numbers of passes appears on four mirrors at one end of the system. At the other end, three mirrors form the array and illuminate each image in it from one or more different directions. The possible numbers of passes are (4mn − 2)k + 2, where m and n are any integers representing, respectively, the number of columns and half the number of rows in the array. k is the number of different directions from which the array is illuminated. Geometrically, the beam may be isolated after thousands of passes; practically, the number is limited by reflection losses. In the second system the addition of four diagonal mirrors to a White cell converts the two lines of images on the single mirror to a rectangular array of images, almost squaring the maximum possible number of passes. With multiples of four rows of images in the array, the position of the output image is invariant to small errors in alignment of the mirrors.
Higher order statistics of the galaxy distribution using generating functions

In this paper we lay the groundwork and develop a formalism for subsequent analyses of the higher order statistics of the galaxy distribution in various catalogs, applying the method of generating functions. The generating function of the distribution is connected to the continuum limit characteristic function. The continuum moments are replaced by the factorial moments of the discrete distribution during the transition to the discrete. The generating function of the distribution is related to the generating function of other relevant quantities like the Q N 's, describing the hierarchy of correlation functions, the moments, and factorial moments, and the combinants, a new and natural statistic to characterize the distribution
On the point transformations for the second order differential equations. I

Point transformations for the ordinary differential equations of the form $y''=P(x,y)+3 Q(x,y) y'+3 R(x,y) (y')^2+S(x,y) (y')^3$ are considered. Some classical results are resumed. Solution for the equivalence problem for the equations of general position is described.
High-mass star formation in Orion B triggered by cloud–cloud collision: Merging molecular clouds in NGC 2024

We performed new comprehensive 13CO(J = 2–1) observations toward NGC 2024, the most active star-forming region in Orion B, with an angular resolution of ∼100″ obtained with Nanten2. We found that the associated cloud consists of two independent velocity components. The components are physically connected to the H ii region as evidenced by their close correlation with the dark lanes and the emission nebulosity. The two components show complementary distribution with a displacement of ∼0.6 pc. Such complementary distribution is typical to colliding clouds discovered in regions of high-mass star formation. We hypothesize that a cloud–cloud collision between the two components triggered the formation of the late O-type stars and early B stars localized within 0.3 pc of the cloud peak. The duration time of the collision is estimated to be 0.3 million years from a ratio of the displacement and the relative velocity ∼3 km s−1 corrected for probable projection. The high column density of the colliding cloud ∼1023 cm−2 is similar to those in the other high-mass star clusters in RCW 38, Westerlund 2, NGC 3603, and M 42, which are likely formed under trigger by cloud–cloud collision. The present results provide an additional piece of evidence favorable to high-mass star formation by a major cloud–cloud collision in Orion.
The supernova-regulated ISM. III. Generation of vorticity, helicity and mean flows

The forcing of interstellar turbulence, driven mainly by supernova explosions, is irrotational in nature, but the development of significant amounts of vorticity and helicity, accompanied by large-scale dynamo action, has been reported. Several earlier investigations examined vorticity production in simpler systems; here all the relevant processes can be considered simultaneously. We also investigate the mechanisms for the generation of net helicity and large-scale flow in the system. We use a three-dimensional, stratified, rotating and shearing local simulation domain of the size 1x1x2 kpc$^3$, forced with SN explosions occurring at the rate typical of the solar neighbourhood in the Milky Way. In addition to the nominal simulation run with realistic Milky Way parameters, we vary the rotation and shear rates, but keep the absolute value of their ratio fixed. Reversing the sign of shear vs. rotation allows us to separate the rotation- and shear-generated contributions. As in earlier studies, we find the generation of significant amounts of vorticity, with on average 65% of the kinetic energy being in the rotational modes. The vorticity production can be related to the baroclinicity of the flow, especially in the regions of hot, dilute clustered supernova bubbles. In these regions, the vortex stretching acts as a sink of vorticity. The net helicities produced by rotation and shear are of opposite signs for physically motivated rotation laws, with the solar neighbourhood parameters resulting in the near cancellation of the total net helicity. We also find the excitation of oscillatory mean flows, the strength and oscillation period of which depend on the Coriolis and shear parameters; we interpret these as signatures of the anisotropic kinetic (AKA) effect. We use the method of moments to fit for the turbulent transport coeffcients, and find $\alpha_{\rm AKA}$ values of the order 3-5 km/s.
Dynamical obstruction in a constrained system and its realization in lattices of superconducting devices

Hard constraints imposed in statistical mechanics models can lead to interesting thermodynamical behaviors, but may at the same time raise obstructions in the thoroughfare to thermal equilibration. Here we study a variantof Baxter's three-color model in which local interactions and defects are included, and discuss its connection to triangular arrays of Josephson junctions of superconductors with broken time-reversal symmetry and kagome networks of superconducting wires. The model is equivalent to an Ising model in a hexagonal lattice with the additional constraint that the magnetization of each hexagon is ′6 or 0. Defects in the superconducting models correspond to violations of this constraint, and include fractional and integer vortices, as well as open strings within two-color loops. In the absence of defects, and for ferromagnetic interactions, we find that the system is critical for a range of temperatures (critical line) that terminates when it undergoes an exotic first-order phase transition with a jump from a zero magnetization state into the fully magnetized state at finite temperature. Dynamically. however, we find that the system becomes frozen into domains. The domain walls are made of perfectly straight segments, and domain growth appears frozen within the time scales studied with Monte Carlo simulations, with the system trapped into a "polycrystalline" phase. This dynamical obstruction has its origin in the topology of the allowed reconfigurations in phase space, which consist of updates of closed loops of spins. Only an extreme rare-event dominated proliferation of confined defects may overcome this obstruction, at much longer time scales. Also as a consequence of the dynamical obstruction, there exists a dynamical temperature, lower than the (avoided) static critical temperature, at which the system is seen to jump from a "supercooled liquid" to the polycrystalline phase within our Monte Carlo time scale. In contrast. for antiferromagnetic interactions, we argue that the system orders for infinitesimal coupling because of the constraint, and we observe no interesting dynamical effects.
Mutual conversions between generalised arithmetic expansions and free binary decision diagrams

Calculation of generalised arithmetic expansions from free binary decision diagrams of incompletely specified Boolean functions is shown. The way of decomposing generalised arithmetic expansion coefficients in terms of cofactors of Boolean functions is presented. Based on the decomposition a second new algorithm to synthesise quasi-optimal free binary decision diagrams directly from generalised arithmetic expansion of Boolean functions is developed.
Extension of LMS stability condition over a wide set of signals

A sufficient condition for least mean squares (LMS) algorithm stability with a small set of assumptions is derived in this paper. The derivation is not, contrary to the majority of currently known conditions, based on the independence assumption or other statistic properties of the input signals. Moreover, it does not make use of the small‐step‐size assumption, neither does it assume the input signals are stationary. Instead, it uses a theory of discrete systems and properties of a discrete state‐space matrix. Therefore, the result can be applied to a wide set of signals, including deterministic and nonstationary signals. The location of all eigenvalues of the matrix responsible for the LMS algorithm stability has been calculated. Simulation experiments, where the step size reaches a couple of hundreds without loss of stability, are shown to support the theory. On the other hand, simulation where the calculations based on the small‐step‐size theory provide a too large estimation of the upper bound for the step size, while the new condition gives a proper solution, is also presented. Therefore, the new condition may be used in cases where fast adaptation is necessary and when the independence theory or the small‐step‐size assumptions do not hold. Copyright © 2014 John Wiley & Sons, Ltd.
A Simple and Practical Algorithm for Accurate Gravitational Magnification Maps

Abstract In this brief communication, a new method is outlined for modelling magnification patterns on an observer’s plane using a first-order approximation to the null geodesic path equations for a point mass lens. For each ray emitted from a source, an explicit calculation is made for the change in position on the observer’s plane due to each lens mass. By counting the number of points in each small area of the observer’s plane, the magnification at that point can be determined. This allows for a very simple and transparent algorithm. A short Matlab code sample for creating simple magnification maps due to multiple point lenses is included in an appendix.
Uncovering novel phase transitions in dense dry polar active fluids using a lattice Boltzmann method

The dynamics of dry active matter have implications for a diverse collection of biological phenomena spanning a range of length and time scales, such as animal flocking, cell tissue dynamics, and swarming of inserts and bacteria. Uniting these systems are a common set of symmetries and conservation laws, defining dry active fluids as a class of physical system. Many interesting behaviours have been observed at high densities, which remain difficult to simulate due to the computational demand. Here, we show how two-dimensional dry active fluids in a dense regime can be studied using a simple modification of the lattice Boltzmann method. We apply our method on a model that exhibits motility-induced phase separation, and an active model with contact inhibition of locomotion, which has relevance to collective cell migration. For the latter, we uncover multiple novel phase transitions: two first-order and one potentially critical. We further support our simulation results with an analytical treatment of the hydrodynamic equations obtained via a Chapman–Enskog coarse-graining procedure.
Phase diagram of three-flavor quark matter under compact star constraints

The phase diagram of three-flavor quark matter under compact star constraints is investigated within a Nambu--Jona-Lasinio model. Global color and electric charge neutrality is imposed for $\ensuremath{\beta}$-equilibrated superconducting quark matter. The constituent quark masses and the diquark condensates are determined self-consistently in the plane of temperature and quark chemical potential. Both strong and intermediate diquark coupling strengths are considered. We show that in both cases, gapless superconducting phases do not occur at temperatures relevant for compact star evolution, i.e., below $T\ensuremath{\sim}50\text{ }\text{ }\mathrm{MeV}$. The stability and structure of isothermal quark star configurations are evaluated. For intermediate coupling, quark stars are composed of a mixed phase of normal (NQ) and two-flavor superconducting (2SC) quark matter up to a maximum mass of $1.21\text{ }\text{ }{M}_{\ensuremath{\bigodot}}$. At higher central densities, a phase transition to the three-flavor color flavor locked (CFL) phase occurs and the configurations become unstable. For the strong diquark coupling we find stable stars in the 2SC phase, with masses up to $1.33\text{ }\text{ }{M}_{\ensuremath{\bigodot}}$. A second family of more compact configurations (twins) with a CFL quark matter core and a 2SC shell is also found to be stable. The twins have masses in the range $1.30\dots{}1.33\text{ }\text{ }{M}_{\ensuremath{\bigodot}}$. We consider also hot isothermal configurations at temperature $T=40\text{ }\text{ }\mathrm{MeV}$. When the hot maximum mass configuration cools down, due to emission of photons and neutrinos, a mass defect of $0.1\text{ }\text{ }{M}_{\ensuremath{\bigodot}}$ occurs and two final state configurations are possible.
The Evolution of the Galaxy Sizes in the New Technology Telescope Deep Field: A Comparison with Cold Dark Matter Models

The sizes of the field galaxies with I ≤ 25 have been measured in the New Technology Telescope (NTT) Deep Field. Intrinsic sizes have been obtained after deconvolution of the point-spread function with a multi-Gaussian method. The reliability of the method has been tested using both simulated data and Hubble Space Telescope (HST) observations of the same field. The distribution of the half-light radii is peaked at rhl ≃ 0. ″3, in good agreement with that derived from HST images at the same magnitude. An approximate morphological classification has been obtained using the asymmetry and concentration parameters. The intrinsic sizes of the galaxies are shown as a function of their redshifts and absolute magnitudes using photometric redshifts derived from the multicolor catalog. While the brighter galaxies with morphological parameters typical of the normal spirals show a flat distribution in the range rd = 1 - 6 kpc, the fainter population at 0.4 < z < 0.8 dominates at small sizes. To explore the significance of this behavior, an analytical rendition of the standard cold dark matter model for the disk size evolution has been computed. The model showing the best fit to the local luminosity function and the Tully-Fisher relation is able to reproduce at intermediate redshifts a size distribution in general agreement with the observations, although it tends to underestimate the number of galaxies fainter than MB ~ -19 with disk sizes rd ~ 1-2 kpc.
Coherent amplification of classical pion fields during the cooling of droplets of quark plasma

In the framework of the linear {sigma} model, we study the time evolution of a system of classical {sigma} and pion fields coupled to quarks. For this purpose we solve numerically the classical transport equation for relativistic quarks coupled to the nonlinear Klein-Gordon equations for the meson fields. We examine evolution starting from variety of initial conditions corresponding to spherical droplets of hot quark matter, which might mimic the behavior of a quark plasma produced in high-energy nucleus-nucleus collisions. For large droplets we find a strong amplification of the pion field that oscillates in time. This leads to a coherent production of pions with a particular isospin and so would have similar observable effects to a disoriented chiral condensate which various authors have suggested might be a signal of the chiral phase transition. The mechanism for amplification of the pion field found here does not rely on this phase transition and is better thought of as a {open_quotes}pion laser{close_quotes} which is driven by large oscillations of the {sigma} field. {copyright} {ital 1997} {ital The American Physical Society}
EPCM – an efficient power controlled MAC protocol for mobile ad hoc network

To reduce interference and to save a significant amount of energy, a control of transmission power is employed in Mobile Ad hoc Network. Many researchers have reported numerous transmission power control schemes to achieve the objective. Some of those techniques use higher transmission power for control packets (Request To Send/Clear To Send) and lesser power for Data and ACK packets. These schemes, though save some amount of energy, achieve least aggregate throughput due to poor spatial reuse and hidden terminal interference. In this paper, an efficient Power Controlled Medium Access Control (EPCM) scheme is evinced, which uses uniform interference aware and minimum transmission power for both Control and Data packet. The performance of EPCM is evaluated and compared with three reported Medium Access Control protocols which are based on transmission power control schemes and is observed that the proposed protocol achieves better throughput and minimal energy consumption while avoiding the hidden terminal problem.
Progenitors of Core-Collapse Supernovae

Abstract Massive stars have a strong impact on their surroundings, in particular when they produce a core-collapse supernova at the end of their evolution. In these proceedings, we review the general evolution of massive stars and their properties at collapse as well as the transition between massive and intermediate-mass stars. We also summarise the effects of metallicity and rotation. We then discuss some of the major uncertainties in the modelling of massive stars, with a particular emphasis on the treatment of convection in 1D stellar evolution codes. Finally, we present new 3D hydrodynamic simulations of convection in carbon burning and list key points to take from 3D hydrodynamic studies for the development of new prescriptions for convective boundary mixing in 1D stellar evolution codes.
Seasonal modulation of seismicity: the competing/collaborative effect of the snow and ice load on the lithosphere

Seasonal patterns associated with stress modulation, as evidenced by earthquake occurrence, have been detected in regions characterized by present day mountain building and glacial retreat in the Northern Hemisphere. In the Himalaya and the Alps, seismicity is peaking in spring and summer; opposite behaviour is observed in the Apennines. This diametrical behaviour, confirmed by recent strong earthquakes, well correlates with the dominant tectonic regime: peak in spring and summer in shortening areas, peak in fall and winter in extensional areas. The analysis of the seasonal effect is extended to several shortening (e.g. Zagros and Caucasus) and extensional regions, and counter-examples from regions where no seasonal modulation is expected (e.g. Tropical Atlantic Ridge). This study generalizes to different seismotectonic settings the early observations made about short-term (seasonal) and long-term (secular) modulation of seismicity and confirms, with some statistical significance, that snow and ice thaw may cause crustal deformations that modulate the occurrence of major earthquakes.
Tight-binding g-factor calculations of CdSe nanostructures

The Lande g factors for CdSe quantum dots and rods are investigated within the framework of the semiempirical tight-binding method. We describe methods for treating both the n-doped and neutral nanostructures, and then apply these to a selection of nanocrystals of variable size and shape, focusing on approximately spherical dots and rods of differing aspect ratio. For the negatively charged n-doped systems, we observe that the g factors for near-spherical CdSe dots are approximately independent of size, but show strong shape dependence as one axis of the quantum dot is extended to form rodlike structures. In particular, there is a discontinuity in the magnitude of the g factor and a transition from anisotropic to isotropic g factor tensor at aspect ratio ∼1.3. For the neutral systems, we analyze the electron g factor of both the conduction- and valence-band electrons. We find that the behavior of the electron g factor in the neutral nanocrystals is generally similar to that in the n-doped case, showing the same strong shape dependence and discontinuity in magnitude and anisotropy. In smaller systems the g factor value is dependent on the details of the surface model. Comparison with recent measurements of g factors for CdSe nanocrystals suggests that the shape-dependent transition may be responsible for the observations of anomalous numbers of g factors at certain nanocrystal sizes.
Type Ia Supernova Distances at Redshift >1.5 from the Hubble Space Telescope Multi-cycle Treasury Programs: The Early Expansion Rate

We present an analysis of 15 Type Ia supernovae (SNe Ia) at redshift (9 at ) recently discovered in the CANDELS and CLASH Multi-Cycle Treasury programs using WFC3 on the Hubble Space Telescope. We combine these SNe Ia with a new compilation of ∼1050 SNe Ia, jointly calibrated and corrected for simulated survey biases to produce accurate distance measurements. We present unbiased constraints on the expansion rate at six redshifts in the range based only on this combined SN Ia sample. The added leverage of our new sample at leads to a factor of ∼3 improvement in the determination of the expansion rate at z = 1.5, reducing its uncertainty to ∼20%, a measurement of . We then demonstrate that these six derived expansion rate measurements alone provide a nearly identical characterization of dark energy as the full SN sample, making them an efficient compression of the SN Ia data. The new sample of SNe Ia at usefully distinguishes between alternative cosmological models and unmodeled evolution of the SN Ia distance indicators, placing empirical limits on the latter. Finally, employing a realistic simulation of a potential Wide-Field Infrared Survey Telescope SN survey observing strategy, we forecast optimistic future constraints on the expansion rate from SNe Ia.