ShantanuT01/DACTYL-Pretraining huggingface dataset:
We study band alignment in wurtzite-zincblende polytype InAs heterostructured nanowires using temperature dependent resonance Raman measurements. Nanowires having two different wurtzite fractions are investigated. Using visible excitation wavelengths in resonance Raman measurements, we probe the electronic band alignment of these semiconductor nanowires near a high symmetry point of the Brillouin zone (E$_{1}$ gap). The strain in the crystal structure, as revealed from the shift of the phonon mode, explains the observed band alignment at the wurtzite-zincblende interface. Our experimental results are further supported by electronic structure calculations for such periodic heterostructured interface.
We simulate the evolution of dense-cool clumps embedded in the intra-cluster medium (ICM) of cooling flow clusters of galaxies in response to multiple jet-activity cycles, and find that the main heating process of the clumps is mixing with the hot shocked jets' gas, the bubbles, while shocks have a limited role. We use the PLUTO hydrodynamical code in two dimensions with imposed axisymmetry, to follow the thermal evolution of the clumps. We find that the inflation process of hot bubbles, that appear as X-ray deficient cavities in observations, is accompanied by complicated induced vortices inside and around the bubbles. The vorticity induces efficient mixing of the hot bubbles' gas with the ICM and cool clumps, resulting in a substantial increase of the temperature and entropy of the clumps. For the parameters used by us heating by shocks barely competes with radiative cooling, even after 25 consecutive shocks excited during 0.5 Gyr of simulation. Some clumps are shaped to filamentary structure that can turn to observed optical filaments. We find that not all clumps are heated. Those that cool to very low temperatures will fall in and feed the central supermassive black hole (SMBH), hence closing the feedback cycle in what is termed the cold feedback mechanism.
We present a way of measuring with high precision the anharmonicity of a quantum oscillator coupled to an optical field via radiation pressure. Our protocol uses a sequence of pulsed interactions to perform a loop in the phase space of the mechanical oscillator, which is prepared in a thermal state. We show how the optical field acquires a phase depending on the anharmonicity. Remarkably, one only needs small initial cooling of the mechanical motion to probe even small anharmonicities. Finally, by applying tools from quantum estimation theory, we calculate the ultimate bound on the estimation precision posed by quantum mechanics and compare it with the precision obtainable with feasible measurements such as homodyne and heterodyne detection on the cavity field. In particular we demonstrate that homodyne detection is nearly optimal in the limit of a large number of photons of the field and we discuss the estimation precision of small anharmonicities in terms of its signal-to-noise ratio.
Let $f$ be a normalized cuspidal eigen-newform of level coprime to $p$ with $a_p(f)=0$. We formulate both integral signed Iwasawa main conjectures and analytic Iwasawa man conjectures attached to the symmetric square motive of $f$ twisted by an auxiliary Dirichlet character. We show that the Beilinson--Flach elements attached to the symmetric square motive factorize into integral signed Beilinson--Flach elements, giving evidence towards the existence a rank-two Euler system predicted by Perrin-Riou. We use these integral elements to prove one inclusion in the integral and analytic Iwasawa main conjectures.
We derive the hard functions for all 2->2 processes in massless QCD up to next-to-next-to-leading order (NNLO) in the strong coupling constant. By employing the known one- and two-loop helicity amplitudes for these processes, we obtain analytic expressions for the ultraviolet and infrared finite, minimally subtracted hard functions, which are matrices in color space. These hard functions will be useful in carrying out higher-order resummations in processes such as dijet and highly energetic top-quark pair production by means of soft-collinear effective theory methods.
Using some theory of (rational) elliptic surfaces plus elementary properties of a Mordell-Weil group regarded as module over the endomorphism ring of a (CM) elliptic curve, we present examples of such surfaces with j-invariant zero. In particular, a K3 example is given with the maximal possible rank 18, plus that many explicit independent sections on it. Several other high rank cases are discussed; for instance Shioda's example with rank 68.
The persistent spin helix (PSH) that has been widely and exclusively studied in zinc-blende structures is revealed for the first time on the surface of a wurtzite structure. Through first-principles calculations of the ZnO(10-10) surface, a quasi-one dimensional orientation of the spin textures is identified. Further, the wavelength of this particular PSH is smaller than that observed with various zinc-blende quantum well structures, thus indicating that wurtzite-structured surfaces are suitable for spintronics applications.
We consider a family of distance graphs in $\mathbb{R}^n$ and find its independent numbers in some cases.   Define graph $J_{\pm}(n,k,t)$ in the following way: the vertex set consists of all vectors from $\{-1,0,1\}^n$ with $k$ nonzero coordinates; edges connect the pairs of vertices with scalar product $t$. We find the independence number of $J_{\pm}(n,k,t)$ for $n > n_0 (k,t)$ in the cases $t = 0$ and $t = -1$; these cases for $k = 3$ are solved completely. Also the independence number is found for negative odd $t$ and $n > n_0 (k,t)$.
This work presents a study of perturbations of symmetric Boolean functions. In particular, it establishes a connection between exponential sums of these perturbations and Diophantine equations of the form $$ \sum_{l=0}^n \binom{n}{l} x_l=0,$$ where $x_j$ belongs to some fixed bounded subset $\Gamma$ of $\mathbb{Z}$. The concepts of trivially balanced symmetric Boolean function and sporadic balanced Boolean function are extended to this type of perturbations. An observation made by Canteaut and Videau for symmetric Boolean functions of fixed degree is extended. To be specific, it is proved that, excluding the trivial cases, balanced perturbations of fixed degree do not exist when the number of variables grows. Some sporadic balanced perturbations are presented. Finally, a beautiful but unexpected identity between perturbations of two very different symmetric Boolean functions is also included in this work.
An accurate theoretical description of structure formation at least in the mildly non-linear regime is essential for comparison with data from next generation galaxy surveys. In a recent approach one follows the time evolution of correlators directly and finds a hierarchy of evolution equations with increasing order (Pietroni 2008). So far, in this so called time renormalisation group method the trispectrum was neglected in order to obtain a closed set of equations. In this work we study the influence of the trispectrum on the evolution of the power spectrum. In order to keep the numerical cost at a manageable level we use the tree-level trispectrum from Eulerian perturbation theory. In comparison to numerical simulations we find improvement in the mildly non-linear regime up to k = 0.25 h/Mpc. Beyond k = 0.25 h/Mpc the perturbative description of the trispectrum fails and the method performs worse than without the trispectrum included. Our results reinforce the conceptual advantage of the time renormalisation group method with respect to perturbation theory.
We focus in future proposals to measure coherent neutrino-nuclei scattering and we show that such kind of experiments are very sensitive to nonstandard neutrino interactions with quarks. First in a model independent parametrization and then we focused in particular models such as leptoquarks and models with extra neutral gauge bosons and with R-parity breaking interactions. We show that in all these three different types of new physics it is possible to obtain competitive bounds to those of future collider experiments. For the particular case of leptoquarks we found that the expected sensitivity to the coupling and mass for most of the future experimental setups is quite better than the current constraints.
Nearby Compact Groups of Galaxies (CGs) are very complex systems, tracing their history is a challenge (e.g. Stephan's Quintet). The presence of a diffuse X-rays emission that often peaks in the center of CGs shows that CGs are bound structures, they show numerous signs of interaction but their lifetime in much longer than their crossing times. Hickson CGs clearly show different stages of evolution, from weakly interacting galaxies to merging systems. CGs infalling into clusters may provide a mechanism to form clusters at high redshifts (e.g. in A1367). Massive versions of today's CGs may have been the best candidate precursors of fossil groups. Do CGs mimic the high redshift universe? This is still an open question. Indeed, their high density and low velocity dispersion should induce a high interaction rate and fast merging, CGs are nevertheless long-lived structures. On the other hand, there is probably no (or a few) isolated CGs in the high z universe. CGs may fuel high z clusters, they may produce fossil groups and fossil ellipticals. CGs at high z are difficult to detect and are still to be discovered. Interpretation of distant kinematics of galaxies may need nearby sample of galaxies to disentangle beam-smearing from evolutionary effects (e.g. HCG 31). Beam smearing effects may bias the Tully-Fisher relation (shifted towards lower M/L).
We propose an engineered reservoir inducing the relaxation of a cavity field towards non-classical states. It is made up of two-level atoms crossing the cavity one at a time. Each atom-cavity interaction is first dispersive, then resonant, then dispersive again. The reservoir pointer states are those produced by an effective Kerr Hamiltonian acting on a coherent field. We thereby stabilize squeezed states and quantum superpositions of multiple coherent components in a cavity having a finite damping time. This robust method could be implemented in state-of-the-art experiments and lead to interesting insights into mesoscopic quantum state superpositions and into their protection against decoherence.
A chiral U(3)*U(3) Lagrangian containing, besides the usual meson fields, their first radial excitations is constructed. The Lagrangian is derived by bosonization of the Nambu-Jona-Lasinio quark model with separable non-local interactions, with form factors corresponding to 3-dimensional ground and excited state wave functions. The spontaneous breaking of chiral symmetry is governed by the NJL gap equation. The first radial excitations of the pions, kaons and vector meson nonet are described with the help of five different form factors. Each form factor contains only one arbitrary parameter. The masses of these meson states and the weak decay constants $F_{\pi'}, F_K and F_{K'}$ are calculated.
We consider a system of one-dimensional non-interacting fermions in external harmonic confinement. Using an efficient Green's function method we evaluate the exact profiles and the pair correlation function, showing a direct signature of the Fermi statistics and of the single quantum-level occupancy. We also study the dynamical properties of the gas, obtaining the spectrum both in the collisionless and in the collisional regime. Our results apply as well to describe a one-dimensional Bose gas with point-like hard-core interactions.
The observed power spectrum of redshifted 21cm fluctuations is known to be sensitive to the astrophysical properties of the galaxies that drove reionization. Thus, detailed measurements of the 21cm power spectrum and its evolution could lead to measurements of the properties of early galaxies that are otherwise inaccessible. In this paper, we study the effect of mass and redshift dependent escape fractions of ionizing radiation on the ability of forthcoming experiments to constrain galaxy formation via the redshifted 21cm power spectrum. We use a model for reionization which combines the hierarchical galaxy formation model GALFORM implemented within the Millennium-II dark matter simulation, with a semi-numerical scheme to describe the resulting ionization structure. Using this model we show that the structure and distribution of ionised regions at fixed neutral fraction, and hence the slope and amplitude of the 21 cm power spectrum, is dependent on the variation of ionising photon escape fraction with galaxy mass and redshift. However, we find that the influence of the unknown escape fraction and its evolution is smaller than the dominant astrophysical effect provided by SNe feedback strength in high redshift galaxies. The unknown escape fraction of ionizing radiation from galaxies is therefore unlikely to prevent measurement of the properties of high redshift star formation using observations of the 21cm power spectrum.
In this paper, we propose a new unified dark fluid (UDF) model with equation of state (EoS) $w(a)=-\alpha/(\beta a^{-n}+1)$, which includes the generalized Chaplygin gas model (gGg) as its special case, where $\alpha$, $\beta$ and $n$ are three positive numbers. It is clear that this model reduces to the gCg model with EoS $w(a)=-B_s/(B_s+(1-B_s)a^{-3(1+\alpha)})$, when $\alpha=1$, $\beta=(1-B_s)/B_s$ and $n=3(1+\alpha)$. By combination the cold dark matter and the cosmological constant, one can coin a EoS of unified dark fluid in the form of $w(a)=-1/(1+(1-\Omega_{\Lambda})a^{-3}/\Omega_{\Lambda})$. With this observations, our proposed EoS provides a possible deviation from $\Lambda$CDM model when the model parameters $\alpha$ and $n$ deviate from 1 and 3 respectively. By using the currently available cosmic observations from type Ia supernovae (SN Ia) Union2.1, baryon acoustic oscillation (BAO) and cosmic microwave background radiation (CMB), we test the viability of this model and detect the possible devotion from the $\Lambda$CDM model. The results show that the new UDF model fits the cosmic observation as well as that of the $\Lambda$CDM model and no deviation is found from the $\Lambda$CDM model in $3\sigma$ confidence level. However, our new UDF model can give a non-zero sound speed, as a contrast, which is zero for the $\Lambda$CDM model. We expect the large structure formation information can distinct the new UDF model from the $\Lambda$CDM model.
Applications of satellite data in areas such as weather tracking and modeling, ecosystem monitoring, wildfire detection, and land-cover change are heavily dependent on the trade-offs to spatial, spectral and temporal resolutions of observations. In weather tracking, high-frequency temporal observations are critical and used to improve forecasts, study severe events, and extract atmospheric motion, among others. However, while the current generation of geostationary satellites have hemispheric coverage at 10-15 minute intervals, higher temporal frequency observations are ideal for studying mesoscale severe weather events. In this work, we apply a task specific optical flow approach to temporal up-sampling using deep convolutional neural networks. We apply this technique to 16-bands of GOES-R/Advanced Baseline Imager mesoscale dataset to temporally enhance full disk hemispheric snapshots of different spatial resolutions from 15 minutes to 1 minute. Experiments show the effectiveness of task specific optical flow and multi-scale blocks for interpolating high-frequency severe weather events relative to bilinear and global optical flow baselines. Lastly, we demonstrate strong performance in capturing variability during a convective precipitation events.
We have analysed a sample of 23 hot DAs to better understand the source of the circumstellar features reported in previous work. Unambiguous detections of circumstellar material are again made at eight stars. The velocities of the circumstellar material at three of the white dwarfs are coincident with the radial velocities of ISM along the sight line to the stars, suggesting that the objects may be ionising the ISM in their locality. In three further cases, the circumstellar velocities are close to the ISM velocities, indicating that these objects are either ionising the ISM, or evaporated planetesimals/material in a circumstellar disc. The circumstellar velocity at WD 1614-084 lies far from the ISM velocities, indicating either the ionisation of an undetected ISM component or circumstellar material. The material seen at WD 0232+035 can be attributed to the photoionisation of material lost from its M dwarf companion. The measured column densities of the circumstellar material lie within the ionised ISM column density ranges predicted to exist in hot DA Stromgren spheres.
We analyze a Chandra-HETGS observation of the single G-type giant HR 9024. The high flux allows us to examine spectral line and continuum diagnostics at high temporal resolution, to derive plasma parameters (thermal distribution, abundances, temperature, ...). A time-dependent 1D hydrodynamic loop model with semi-length 10$^{12}$cm ($\sim R_{\star}$), and impulsive footpoint heating triggering the flare, satisfactorily reproduces the observed evolution of temperature and emission measure, derived from the analysis of the strong continuum emission. The observed characteristics of the flare appear to be common features in very large flares in active stars (also pre-main sequence stars), possibly indicating some fundamental physics for these very dynamic and extreme phenomena in stellar coronae.
Radio relics have been discovered in many galaxy clusters. They are believed to trace shock fronts induced by cluster mergers. Cosmological simulations allow us to study merger shocks in detail since the intra-cluster medium is heated by shock dissipation. Using high resolution cosmological simulations, identifying shock fronts and applying a parametric model for the radio emission allows us to simulate the formation of radio relics. We analyze a simulated shock front in detail. We find a rather broad Mach number distribution. The Mach number affects strongly the number density of relativistic electrons in the downstream area, hence, the radio luminosity varies significantly across the shock surface. The abundance of radio relics can be modeled with the help of the radio power probability distribution which aims at predicting radio relic number counts. Since the actual electron acceleration efficiency is not known, predictions for the number counts need to be normalized by the observed number of radio relics. For the characteristics of upcoming low frequency surveys we find that about thousand relics are awaiting discovery.
The Zeta function of a curve $C$ over a finite field may be expressed in terms of the characteristic polynomial of a unitary matrix $\Theta_C$. Following the work of Rudnick, we compute the expected value of $\mbox{tr}(\Theta_C^n)$ over the moduli space of hyperelliptic curves of genus $g$, over a fixed finite field $\mathbb{F}_q$, in the limit of large genus. As an application, we compute the expected value of the number of points on $C$ in $\mathbb{F}_{q^n}$ as the genus tends to infinity. We also look at biases in both expected values for small values of $n$.
We discuss bulk viscosity due to non-leptonic processes involving hyperons and Bose-Einstein condensate of negatively charged kaons in neutron stars. It is noted that the hyperon bulk viscosity coefficient is a few order of magnitude larger than that of the case with the condensate. Further it is found that the hyperon bulk viscosity is suppressed in a superconducting phase. The hyperon bulk viscosity efficiently damps the r-mode instability in neutron stars irrespective of whether a superconducting phase is present or not in neutron star interior.
Neutral Hydrogen (HI) provides a very important fuel for star formation, but is difficult to detect at high redshift due to weak emission, limited sensitivity of modern instruments, and terrestrial radio frequency interference (RFI) at low frequencies. We the first attempt to use gravitational lensing to detect HI line emission from three gravitationally lensed galaxies behind the cluster Abell 773, two at redshift of 0.398 and one at z=0.487, using the Green Bank Telescope. We find a 3 sigma upper limit for a galaxy with a rotation velocity of 200 km/s is M_HI=6.58x10^9 and 1.5x10^10 M_solar at z=0.398 and z=0.487. The estimated HI masses of the sources at z=0.398 and z=0.487 are a factor of 3.7 and ~30 times lower than our detection limits at the respective redshifts. To facilitate these observations we have used sigma clipping to remove both narrow- and wide-band RFI but retain the signal from the source. We are able to reduce the noise of the spectrum by ~25% using our routine instead of discarding observations with too much RFI. The routine is most effective when ~10 of the integrations or fewer contains RFI. These techniques can be used to study HI in highly magnified distant galaxies that are otherwise too faint to detect.
Let $X$ be a hyperk\"ahler variety, and let $Z\subset X$ be a Lagrangian subvariety. Conjecturally, $Z$ should have trivial intersection with certain parts of the Chow ring of $X$. We prove this conjecture for certain Hilbert schemes $X$ having a Lagrangian fibration, and $Z\subset X$ a general fibre of the Lagrangian fibration.
Rectified linear units (ReLU) are well-known to be helpful in obtaining faster convergence and thus higher performance for many deep-learning-based applications. However, networks with ReLU tend to perform poorly when the number of filter parameters is constrained to a small number. To overcome it, in this paper, we propose a novel network utilizing maxout units (MU), and show its effectiveness on super-resolution (SR) applications. In general, the MU has been known to make the filter sizes doubled in generating the feature maps of the same sizes in classification problems. In this paper, we first reveal that the MU can even make the filter sizes halved in restoration problems thus leading to compaction of the network sizes. To show this, our SR network is designed without increasing the filter sizes with MU, which outperforms the state of the art SR methods with a smaller number of filter parameters. To the best of our knowledge, we are the first to incorporate MU into SR applications and show promising performance results. In MU, feature maps from a previous convolutional layer are divided into two parts along channels, which are then compared element-wise and only their max values are passed to a next layer. Along with some interesting properties of MU to be analyzed, we further investigate other variants of MU and their effects. In addition, while ReLU have a trouble for learning in networks with a very small number of convolutional filter parameters, MU do not. For SR applications, our MU-based network reconstructs high-resolution images with comparable quality compared to previous deep-learning-based SR methods, with lower filter parameters.
We present two different models with electroweak scale right-handed neutrinos. One of the models is created under the constraint that any addition to the Standard Model must not introduce new higher scales. The model contains right-handed neutrinos with electroweak scale masses and a lepton number violating singlet scalar field. The scalar phenomenology is also presented. The second model is a triplet Higgs model where again the right-handed neutrinos have electroweak scale masses. In this case the model has a rich scalar phenomenology and in particular we present the analysis involving the doubly charged Higgs.