ShantanuT01/DACTYL-Pretraining huggingface dataset:
We examine how fast radio burst (FRB)-like signals predicted to be generated during the merger of a binary neutron star (BNS) may be detected in low-frequency radio observations triggered by the aLIGO/Virgo gravitational wave detectors. The rapidity, directional accuracy, and sensitivity of follow-up observations with the Murchison Widefield Array (MWA) are considered. We show that with current methodology, the rapidity criteria fails for triggered MWA observations above 136 MHz for BNS mergers within the aLIGO/Virgo horizon, for which little dispersive delay is expected. A calculation of the expected reduction in response time by triggering on `negative latency' alerts from aLIGO/Virgo observations of gravitational waves generated by the BNS inspiral is presented. This allows for observations up to 300 MHz where the radio signal is expected to be stronger. To compensate for the poor positional accuracy expected from these alerts, we propose a new MWA observational mode that is capable of viewing one quarter of the sky. We show the sensitivity of this mode is sufficient to detect an FRB-like burst from an event similar to GW170817 if it occurred during the ongoing aLIGO/Virgo third science run (O3).
Single-photon sources play a key role in photonic quantum technologies. Semiconductor quantum dots can emit indistinguishable single photons under resonant excitation. However, the resonance fluorescence technique typically requires cross-polarization filtering which causes a loss of the unpolarized quantum dot emission by 50%. To solve this problem, we demonstrate a method to generate indistinguishable single photons with optically controlled polarization by two laser pulses off-resonant with neutral exciton states. This scheme is realized by exciting the quantum dot to the biexciton state and subsequently driving the quantum dot to an exciton eigenstate. Combining with magnetic field, we demonstrated the generation of photons with optically controlled polarization (polarization degree of 101(2)%), laser-neutral exciton detuning up to 0.81 meV, high single-photon purity (99.6(1)%) and indistinguishability (85(4)%). Laser pulses can be blocked using polarization and spectral filtering. Our work makes an important step towards indistinguishable single-photon sources with near-unity collection efficiency.
We derive self-consistent expressions of current and noise for single-electron transistors driven by time-dependent perturbations. We take into account effects of the electrical environment, higher-order co-tunneling, and time-dependent perturbations under the two-charged state approximation using the Schwinger-Kedysh approach combined with the generating functional technique. For a given generating functional, we derive exact expressions for tunneling currents and noises and present the forms in terms of transport coefficients. It is also shown that in the adiabatic limit our results encompass previous formulas. In order to reveal effects missing in static cases, we apply the derived results to simulate realized radio-frequency single-electron transistor. It is found that photon-assisted tunneling affects largely the performance of the single-electron transistor by enhancing both responses to gate charges and current noises. On various tunneling resistances and frequencies of microwaves, the dependence of the charge sensitivity is also discussed.
We study the renormalization of the properties of low lying charm and hidden charm scalar mesons in a nuclear medium, concretely of the D_{s0}(2317) and the theoretical hidden charm state X(3700). We find that for the D_{s0}(2317), with negligible width at zero density, the width becomes about 100 MeV at normal nuclear matter density, while in the case of the X(3700) the width becomes as large as 200 MeV. We discuss the origin of this new width and trace it to reactions occurring in the nucleus, while offering a guideline for future experiments testing these changes. We also show how those medium modifications will bring valuable information on the nature of the scalar resonances and the mechanisms of the interaction of D mesons with nucleons and nuclei.
Current-driven skyrmion motion in random granular films is investigated with interesting findings. For a given current, there exists a critical disorder strength below which its transverse motion could either be boosted below a critical damping or be hindered above the critical damping, resulting in current and disorder dependences of skyrmion Hall angle. The boosting comes mainly from the random force that is opposite to the driving force (current). The critical damping depends on the current density and disorder strength. However, the longitudinal motion of a skyrmion is always hindered by the disorder. Above the critical disorder strength, skyrmions are pinned. The disorder-induced random force on a skyrmion can be classified as static and kinetic ones, similar to the friction force in the Newtonian mechanics. In the pinning phase, the static (pinning) random force is transverse to the current density. The kinetic random force is opposite to the skyrmion velocity when skyrmions are in motion. Furthermore, we provide strong evidences that the Thiele equation can perfectly describe skyrmion dynamics in granular films. These findings provide insight to skyrmion motion and should be important for skyrmiontronics.
Spectroscopic observations with a resolution of 4.5 Angst were performed for a sample of eight galactic nuclei extracted from the Second Byurakan Survey, and one companion galaxy of SBS 1204+505B. The EW and FWHM of the emission lines were measured, and useful line ratios and diagnostic diagrams were used for object classification and reddening estimates.   Intrinsic reddening quantities were calculated for all non QSO,i.e. seven objects. Particularly the amount of reddening, BV color excess, extinction coefficient and optical depths in the V band, at Halpha and Hbeta wavelengths, and at 5100 Angst. The broad line region size was also estimated for seven objects, as well as the central black hole masses. Three mass estimates were usually performed for each object and compared. A peculiar line, probably He I lambda 5048, is detected in the QSO SBS 1626+554. Evidence for a stratified narrow line region is found for the two narrow line Seyfert 1 galaxies included in the sample. A revised classification is proposed for two objects, and the companion galaxy of SBS 1204+505B is reported as a nuclear starburst galaxy.
The level of solar magnetic activity, as exemplified by the number of sunspots and by energetic events in the corona, varies on a wide range of time scales. Most prominent is the 11-year solar cycle, which is significantly modulated on longer time scales. Drawing from dynamo theory together with empirical results of past solar activity and of similar phenomena on solar-like stars, we show that the variability of the solar cycle can be essentially understood in terms of a weakly nonlinear limit cycle affected by random noise. In contrast to ad-hoc `toy models' for the solar cycle, this leads to a generic normal-form model, whose parameters are all constrained by observations. The model reproduces the characteristics of the variable solar activity on time scales between decades and millennia, including the occurrence and statistics of extended periods of very low activity (grand minima). Comparison with results obtained with a Babcock-Leighton-type dynamo model confirms the validity of the normal-mode approach.
We propose a scalable and data-driven approach to learn shape distributions from large databases of healthy organs. To do so, volumetric segmentation masks are embedded into a common probabilistic shape space that is learned with a variational auto-encoding network. The resulting latent shape representations are leveraged to derive zeroshot and few-shot methods for abnormal shape detection. The proposed distribution learning approach is illustrated on a large database of 1200 healthy pancreas shapes. Downstream qualitative and quantitative experiments are conducted on a separate test set of 224 pancreas from patients with mixed conditions. The abnormal pancreas detection AUC reached up to 65.41% in the zero-shot configuration, and 78.97% in the few-shot configuration with as few as 15 abnormal examples, outperforming a baseline approach based on the sole volume.
We present forecasts for constraints on deviations from Gaussian distribution of primordial density perturbations from future X-ray surveys of galaxy clusters. Our analysis is based on computing the Fisher-Matrix for number counts and large-scale power spectrum of clusters. We consider a survey with high-sensitivity and wide-area to detect about 2.5 x 10^5 extended sources. Based on the self-calibration approach, and including Planck priors in our analysis, we constrain 9 cosmological parameters and 4 nuisance parameters, which define the relation between cluster mass and X-ray flux. Because of the scale dependence of large-scale bias induced by local-shape non-Gaussianity, we find that the power spectrum provides strong constraints on the non-Gaussianity f_nl parameter, which complement the stringent constraints on the power spectrum normalization, \sigma_8, from the number counts. To quantify the joint constraints on theese two parameters, that specify the timing of structure formation for a fixed background expansion, we define the figure-of-merit FoM_SFT = (det[Cov(sigma_8,f_nl)])^{-1/2}. We find that our surveys constrain deviations from Gaussianity with a precision of \Delta f_nl~10 at 1 \sigma confidence level, with FoM_SFT~39. We point out that constraints on f_nl are weakly sensitive to the uncertainties in the knowledge of nuisance parameters. As an application of non-Gaussian constraints from available data, we analyse the impact of positive skewness on the occurrence of XMMU-J2235, a massive distant cluster discovered at z~1.4. We confirm that in a WMAP-7 Gaussian Lambda CDM cosmology, within the survey volume, ~5x10^{-3} objects like this are expected to be found: to increase this probability by a factor of at least 10, one needs to evade either the available constraints on f_nl or sigma_8.
In recent years, a new approach to the theory of nuclear reactions leading to a break-down of the interacting subsytems into various channels has been developed. This approach was named the Antisymmetrized Molecular Dynamic (AMD), and its main idea lies in the description of the nucleons by wave packets in which the antisymmetrization effects (but not other quantum effects) are accounted for. In the present review, the basic principles of AMD are illustrated on the examples of simplest nuclear systems, and the results are compared with those provided by an exact quantum-mechanical description in the Fock-Bargmann space. The applicability region of AMD is discussed, in particular, in the cases of systems with discrete spectrum, and a relation between the classical AMD trajectories and the quantum distributions is established. At the same time, a new interpretation of Brink orbitals and Slater determinants built on them as eigenfunctions of the coordinate operator defined in the Fock-Bargmann space is proposed. It is shown that these functions form the cluster geometry of nuclear systems.
Photometric redshifts are a key tool to extract as much information as possible from planned cosmic shear experiments. In this work we aim to test the performances that can be achieved with observations in the near-infrared from space and in the optical from the ground. This is done by performing realistic simulations of multi-band observations of a patch of the sky, and submitting these mock images to software usually applied to real images to extract the photometry and then a redshift estimate for each galaxy. In this way we mimic the most relevant sources of uncertainty present in real data analysis, including blending and light pollution between galaxies. As an example we adopt the infrared setup of the ESA-proposed Euclid mission, while we simulate different observations in the optical, modifying filters, exposure times and seeing values. Finally, we consider directly some future ground-based experiments, such as LSST, Pan-Starrs and DES. The results highlight the importance of u-band observations, especially to discriminate between low (z < 0.5) and high (z ~ 3) redshifts, and the need for good observing sites, with seeing FWHM < 1. arcsec. The former of these indications clearly favours the LSST experiment as a counterpart for space observations, while for the other experiments we need to exclude at least 15 % of the galaxies to reach a precision in the photo-zs equal to $<\frac{\sigma_z}{1+z}>$ < 0.05.
We study graphene nanoribbons (GNRs) with armchair edges in the presence of Rashba spin-orbit interaction (RSOI). We impose the boundary conditions on the tight binding Hamiltonians for bulk graphene with RSOI by means of a sine transform and study in detail the influence of RSOI on the spectra and the spin polarization. We show that the spin polarization perpendicular to the GNR changes sign when reversing the momentum along the GNR if the bands are coupled by strong RSOI. Furthermore, we derive a linearized approximation to the RSOI Hamiltonian and find that only the neighboring modes of an energy band have to be taken into account in order to achieve a good approximation for the same band. Due to their experimental availability and various proposals for engineering appropriate RSOI, GNRs with armchair edges are a promising candidate for possible spintronics applications.
This paper has been withdrawn because Proposition 2.2 (c) is false. This invalids the main results of section 2 and 3. We thank A. Canonaco for pointing us the error.
We study the statistics of growing networks in which each link carries a weight (k_i k_j)^theta, where k_i and k_j are the node degrees at the endpoints of link ij. Network growth is governed by preferential attachment in which a newly-added node attaches to a node of degree k with rate A_k=k+lambda. For general values of theta and lambda, we compute the total weight of a network as a function of the number of nodes N and the distribution of link weights. Generically, the total weight grows as N for lambda>theta-1, and super-linearly otherwise. The link weight distribution is predicted to have a power law form that is modified by a logarithmic correction for the case lambda=0. We also determine the node strength, defined as the sum of the weights of the links that attach to the node, as function of k. Using known results for degree correlations, we deduce the scaling of the node strength on k and N.
We generalize the recoil polarization method for the determination of the proton form factor to the case of the disintegration of vector polarized deuterons by longitudinally polarized electrons, $\vec d(\vec e, e'n)p$. We suggest to measure for this reaction, in the kinematics of quasi-elastic $en$-scattering, the ratio $R_{xz}=A_x/A_z$ of the asymmetries induced by the $x$- and $z$-components of the deuteron vector polarization. In the framework of the relativistic impulse approximation the ratio $R_{xz}$ is sensitive to $G_{En}$ in a wide interval of momentum transfer squared, whereas it depends weakly on the details of the $np$-interaction and on the choice of the deuteron wave function. Moreover, in the range $0.5\le Q^2\le$1.5 GeV$^2$, the ratio $R_{xz}$ shows a smooth dependence on $Q^2$, making the analysis simpler.
Let C_1 and C_2 be two degenerations of genus g curves. We prove that if two degenerations defines the same conjugacy classes in the mapping class group, they are equivalent under analytic deformations.
The reaction rates of the key stellar reaction of $^{14}$O($\alpha$,p)$^{17}$F have been reexamined. The previous conclusion, the 6.15-MeV state ($J^{\pi}$=1$^-$) dominating this reaction rate, has been overthrown by a careful reanalysis of the previous experimental data [J. G\'{o}mez del Campo {\it et al.}, Phys. Rev. Lett. {\bf 86}, 43 (2001)]. According to the present $R$-matrix analysis, the previous 1$^-$ assignment for the 6.15-MeV state is definitely wrong. Most probably, the 6.286-MeV state is the 1$^-$ state and the 6.15-MeV state is a 3$^-$ one, and hence the resonance at $E_x$=6.286 MeV ($J^{\pi}$=1$^-$) dominates the reaction rates in the temperature region of astrophysical interests. The newly calculated reaction rates for the $^{14}$O($\alpha$,p)$^{17}$F reaction are quite different from the previous ones, for instance, it's only about 1/6 of the previous value around 0.4 GK, while it's about 2.4 times larger than the previous value around 2 GK. The astrophysical implications have been discussed based on the present conclusions.
The growth of a supermassive black hole (BH) is determined by how much gas the host galaxy is able to feed it, which in turn is controlled by the cosmic environment, through galaxy mergers and accretion of cosmic flows that time how galaxies obtain their gas, but also by internal processes in the galaxy, such as star formation and feedback from stars and the BH itself. In this paper, we study the growth of a 10^12 Msun halo at z=2, which is the progenitor of al group of galaxies at z=0, and of its central BH by means of a high-resolution zoomed cosmological simulation, the Seth simulation. We study the evolution of the BH driven by the accretion of cold gas in the galaxy, and explore the efficiency of the feedback from supernovae (SNe). For a relatively inefficient energy input from SNe, the BH grows at the Eddington rate from early times, and reaches self-regulation once it is massive enough. We find that at early cosmic times z>3.5, efficient feedback from SNe forbids the formation of a settled disc as well as the accumulation of dense cold gas in the vicinity of the BH and starves the central compact object. As the galaxy and its halo accumulate mass, they become able to confine the nuclear inflows provided by major mergers and the BH grows at a sustained near-to-Eddington accretion rate. We argue that this mechanism should be ubiquitous amongst low-mass galaxies, corresponding to galaxies with a stellar mass below <10^9 Msun in our simulations.
Under this method second order \textbf{partial differential equations (PDE's)} can be reduce to first order PDE's, simplifying the Initial value problem \textbf{IVP} or Border value Problem \textbf{BVP} for most cases of second-order differential equation, letting easiest proofs for existence and uniqueness of the PVI and BVP problems.
For an algebraic number field K with 3-class group \(Cl_3(K)\) of type (3,3), the structure of the 3-class groups \(Cl_3(N_i)\) of the four unramified cyclic cubic extension fields \(N_i\), \(1\le i\le 4\), of K is calculated with the aid of presentations for the metabelian Galois group \(G_3^2(K)=Gal(F_3^2(K) | K)\) of the second Hilbert 3-class field \(F_3^2(K)\) of K. In the case of a quadratic base field \(K=\mathbb{Q}(\sqrt{D})\) it is shown that the structure of the 3-class groups of the four \(S_3\)-fields \(N_1,\ldots,N_4\) frequently determines the type of principalization of the 3-class group of K in \(N_1,\ldots,N_4\). This provides an alternative to the classical principalization algorithm by Scholz and Taussky. The new algorithm, which is easily automatizable and executes very quickly, is implemented in PARI/GP and is applied to all 4596 quadratic fields K with 3-class group of type (3,3) and discriminant \(-10^6<D<10^7\) to obtain extensive statistics of their principalization types and the distribution of their second 3-class groups \(G_3^2(K)\) on various coclass trees of the coclass graphs G(3,r), \(1\le r\le 6\), in the sense of Eick, Leedham-Green, and Newman.
We analyze the free ambitwistor string field theory action for the bosonic string, heterotic string and both GSO sectors of the Type II string. The spectrum contains non-unitary states and provides an interesting consistency test for one-loop ambitwistor string computations.
Cathodoluminescence spectra employing a shadow mask technique of InGaN layers grown by metal organic chemical vapor deposition on Si(111) substrates are reported. Sharp lines originating from InGaN quantum dots are observed. Temperature dependent measurements reveal thermally induced carrier redistribution between the quantum dots. Spectral diffusion is observed and was used as a tool to correlate up to three lines that originate from the same quantum dot. Variation of excitation density leads to identification of exciton and biexciton. Binding and anti-binding complexes are discovered.
A tidal disruption event (TDE) involves the shredding of a star in the proximity of a supermassive black hole (SMBH). The nearby ($\approx$230 Mpc) relatively radio-quiet, thermal emission dominated source AT2019dsg is the first TDE with a potential neutrino association. The origin of non-thermal emission remains inconclusive; possibilities include a relativistic jet or a sub-relativistic outflow. Distinguishing between them can address neutrino production mechanisms. High-resolution very long baseline interferometry 5-GHz observations provide a proper motion of 0.94 $\pm$ 0.65 mas yr$^{-1}$ ($3.2 \pm 2.2~c$; $1-\sigma$). Modelling the radio emission favors an origin from the interaction between a decelerating outflow (velocity $\approx$ 0.1 $c$) and a dense circum-nuclear medium. The transition of the synchrotron self-absorption frequency through the observation band marks a peak flux density of 1.19 $\pm$ 0.18 mJy at 152.8 $\pm$ 16.2 days. An equipartition analysis indicates an emission region distance of $\geqslant$ 4.7 $\times$ 10$^{16}$ cm, magnetic field strength $\geqslant$ 0.17 G, and number density $\geqslant$ 5.7 $\times$ 10$^{3}$ cm$^{-3}$. The disruption involves a $\approx$ 2 $M_\odot$ star with a penetration factor $\approx 1$ and a total energy output of $\leqslant$ 1.5 $\times$ 10$^{52}$ erg. The outflow is radiatively driven by accretion of stellar debris onto the SMBH. Neutrino production is likely related to the acceleration of protons to PeV energies and the availability of a suitable cross-section at the outflow base. The present study thus helps exclude jet-related origins for non-thermal emission and neutrino production, and constrains non-jetted scenarios.
We investigate the possibility of measuring magnetic field strength in G-band bright points through the analysis of Zeeman polarization in molecular CH lines. To this end we solve the equations of polarized radiative transfer in the G band through a standard plane-parallel model of the solar atmosphere with an imposed magnetic field, and through a more realistic snapshot from a simulation of solar magneto-convection. This region of the spectrum is crowded with many atomic and molecular lines. Nevertheless, we find several instances of isolated groups of CH lines that are predicted to produce a measurable Stokes V signal in the presence of magnetic fields. In part this is possible because the effective Land\'{e} factors of lines in the stronger main branch of the CH A$^{2}\Delta$--X$^{2}\Pi$ transition tend to zero rather quickly for increasing total angular momentum $J$, resulting in a Stokes $V$ spectrum of the G band that is less crowded than the corresponding Stokes $I$ spectrum. We indicate that, by contrast, the effective Land\'{e} factors of the $R$ and $P$ satellite sub-branches of this transition tend to $\pm 1$ for increasing $J$. However, these lines are in general considerably weaker, and do not contribute significantly to the polarization signal. In one wavelength location near 430.4 nm the overlap of several magnetically sensitive and non-sensitive CH lines is predicted to result in a single-lobed Stokes $V$ profile, raising the possibility of high spatial-resolution narrow-band polarimetric imaging. In the magneto-convection snapshot we find circular polarization signals of the order of 1% prompting us to conclude that measuring magnetic field strength in small-scale elements through the Zeeman effect in CH lines is a realistic prospect.