ShantanuT01/DACTYL-Pretraining huggingface dataset:
We report electron transport measurements of a silicon double dot formed in multi-gated metal-oxide-semiconductor structures with a 15-nm-thick silicon-on-insulator layer. Tunable tunnel coupling enables us to observe an excitation spectrum in weakly coupled dots and an energy level anticrossing in strongly coupled ones. Such a quantum dot molecule with both charge and energy quantization provides the essential prerequisite for future implementation of silicon-based quantum computations.
The properties of quintessence are examined through the study of the variation of the electromagnetic coupling. We consider two simple quintessence models with a modified exponential potential and study the parameter space constraints derived from the existing observational bounds on the variation of the fine structure constant and the most recent Wilkinson Microwave Anisotropy Probe observations.
The extension of the Nambu-Jona-Lasino Model with six and eight quark interactions to include the Polyakov loop is analysed. Several interesting features are determined to be an effect of the choice of the regularization procedure. The use of a Pauli-Villars covariant regularization enables a coherent and correct description of several quantities.
We investigate the monopole excitations of the soliton in the Nambu--Jona--Lasinio model. By studying the solutions to the corresponding Bethe--Salpeter equation in the background of the soliton we exclude the existence of real large amplitude fluctuations. This allows us to treat the collective coordinate for the monopole excitations, which parametrizes the extension of the soliton, in the harmonic approximation. The canonical quantization of this coordinate yields a spectrum which agrees reasonably well with the empirical data for the Roper resonance, N(1440), and the corresponding one for the Delta, $\Delta$(1600). We also comment on going beyond the harmonic approximation.
We present an analysis of the 2-150 keV spectrum of the transient X-ray pulsar V0332+53 taken with the Rossi X-Ray Timing Explorer (RXTE) in 2004 December. We report on the detection of three cyclotron resonance features at 27, 51, and 74 keV in the phase-averaged data, corresponding to a polar magnetic field of 2.7 x 10^12 G. After 4U0115+63, this makes V0332+53 the second accreting neutron star in which more than two cyclotron lines have been detected; this has now also been confirmed by INTEGRAL. Pulse-phase spectroscopy reveals remarkably little variability of the cyclotron line through the 4.4 s X-ray pulse.
Profile decompositions for "critical" Sobolev-type embeddings are established, allowing one to regain some compactness despite the non-compact nature of the embeddings. Such decompositions have wide applications to the regularity theory of nonlinear partial differential equations, and have typically been established for spaces with Hilbert structure. Following the method of S. Jaffard, we treat settings of spaces with only Banach structure by use of wavelet bases. This has particular applications to the regularity theory of the Navier-Stokes equations, where many natural settings are non-Hilbertian.
PSR J1744-3922 is a binary pulsar exhibiting highly variable pulsed radio emission. We report on a statistical multi-frequency study of the pulsed radio flux variability which suggests that this phenomenon is extrinsic to the pulsar and possibly tied to the companion, although not strongly correlated with orbital phase. The pulsar has an unusual combination of characteristics compared to typical recycled pulsars: a long spin period (172 ms); a relatively high magnetic field strength (1.7x10^10 G); a very circular, compact orbit of 4.6 hours; and a low-mass companion (0.08 Msun). These spin and orbital properties are likely inconsistent with standard evolutionary models. We find similarities between the properties of the PSR J1744-3922 system and those of several other known binary pulsar systems, motivating the identification of a new class of binary pulsars. We suggest that this new class could result from either: a standard accretion scenario of a magnetar or a high-magnetic field pulsar; common envelope evolution with a low-mass star and a neutron star, similar to what is expected for ultra-compact X-ray binaries; or, accretion induced collapse of a white dwarf. We also report the detection of a possible K'=19.30(15) infrared counterpart at the position of the pulsar, which is relatively bright if the companion is a helium white dwarf at the nominal distance, and discuss its implications for the pulsar's companion and evolutionary history.
R. Sulzgruber's rim hook insertion and the Hillman-Grassl correspondence are two distinct bijections between the reverse plane partitions of a fixed partition shape and multisets of rim-hooks of the same partition shape. It is known that Hillman-Grassl may be equivalently defined using the Robinson-Schensted-Knuth correspondence, and we show the analogous result for Sulzgruber's insertion. We refer to our description of Sulzgruber's insertion as diagonal RSK. As a consequence of this equivalence, we show that Sulzgruber's map from multisets of rim hooks to reverse plane partitions can be expressed in terms of Greene-Kleitman invariants.
We study theoretically the detection and possible utilization of electric current-induced mechanical torques in ferromagnetic-normal metal heterostructures that are generated by spin-flip scattering or the absorption of transverse spin currents by a ferromagnet. To this end, we analyze the DC voltage signals over a spin valve that is driven by an AC current. In agreement with recent studies, this "rectification", measured as a function of AC frequency and applied magnetic field, contains important information on the magnetostatics and --dynamics. Subsequently, we show that the vibrations excited by spin-transfer to the lattice can be detected as a splitting of the DC voltage resonance. Finally, we propose a concept for a spin-transfer-driven electric nanomotor based on integrating metallic nanowires with carbon nanotubes, in which the current-induced torques generate a rotary motion.
Results are presented from a long-term astrometry program on PSR B0919+06 using the NRAO Very Long Baseline Array. With ten observations (seven epochs) between 1994--2000, we measure a proper motion of 18.35 +/- 0.06 mas/yr in RA, 86.56 +/- 0.12 mas/yr in Dec, and a parallax of 0.83 +/- 0.13 mas (68% confidence intervals). This yields a pulsar distance of 1.21 +/- 0.19 kpc, making PSR B0919+06 the farthest pulsar for which a trigonometric parallax has been obtained, and the implied pulsar transverse speed is 505 +/- 80 km/s. Combining the distance estimate with interstellar scintillation data spanning 20 years, we infer the existence of a patchy or clumpy scattering screen along the line of sight in addition to the distributed electron density predicted by models for the Galaxy, and constrain the location of this scattering region to within about 250 parsecs of the Sun. Comparison with the lines of sight towards other pulsars in the same quadrant of the Galaxy permits refinement of our knowledge of the local interstellar matter in this direction.
We study the small deviation probabilities of a family of very smooth self-similar Gaussian processes. The canonical process from the family has the same scaling property as standard Brownian motion and plays an important role in the study of zeros of random polynomials.   Our estimates are based on the entropy method, discovered in Kuelbs and Li (1992) and developed further in Li and Linde (1999), Gao (2004), and Aurzada et al. (2009). While there are several ways to obtain the result w.r.t. the $L_2$ norm, the main contribution of this paper concerns the result w.r.t. the supremum norm. In this connection, we develop a tool that allows to translate upper estimates for the entropy of an operator mapping into $L_2[0,1]$ by those of the operator mapping into $C[0,1]$, if the image of the operator is in fact a H\"older space.   The results are further applied to the entropy of function classes, generalizing results of Gao et al. (2010).
Let $X$ be a smooth irreducible projective curve. Recently, Pauly and Pe\'on-Nieto shows that a vector bundle over $X$ is very stable if and only if the Hitchin map on the vector space of Higgs field on that vector bundle is proper. In this notes, we generalize this result to principal $G-$bundles for any semisimple linear algebraic group $G$. We also study the relation between very stability and other stability conditions in the case of $\text{SL}_2-$bundles.
Using the recent result of Bourgain, Demeter and Guth on Vinogradov's mean value, a number of new results about small fractional parts of polynomials and fractional parts of additive forms are obtained. These improve work of Baker, Cook, Danicic, Vaughan and Wooley.
We generalize recent study of the stability of isotropic (spherical) rotating membranes to the anisotropic ellipsoidal membrane. We find that while the stability persists for deformations of spin $l=1$, the quadrupole and higher spin deformations ($l\geq 2$) lead to instabilities. We find the relevant instability modes and the corresponding eigenvalues. These indicate that the ellipsoidal rotating membranes generically decay into finger-like configurations.
Published articles concerning the intermediate (third) subgroup of GRBs are surveyed. From a statistical perspective this subgroup may exist, however its significance depends on which data set is used. Its astrophysical meaning is unclear because the occurrence of this subgroup can also be an artificial selection effect. Hence, GRBs from this subgroup need not be given by a physically different phenomenon. The aim of this contribution is to search for the answer to the question in the title.
In a graph G, the cardinality of the smallest ordered set of vertices that distinguishes every element of V(G)U E(G) is called the mixed metric dimension of G, and it is denoted by mdim(G). In [12] it was conjectured that for a graph G with cyclomatic number c(G) it holds that mdim(G) <= L1(G) + 2c(G) where L1(G) is the number of leaves in G. It is already proven that the equality holds for all trees and more generally for graphs with edge-disjoint cycles in which every cycle has precisely one vertex of degree >= 3. In this paper we determine that for every Theta graph G, the mixed metric dimension mdim(G) equals 3 or 4, with 4 being attained if and only if G is a balanced Theta graph. Thus, for balanced Theta graphs the above inequality is also tight. We conclude the paper by further conjecturing that there are no other graphs, besides the ones mentioned here, for which the equality mdim(G) = L1(G) + 2c(G) holds.
The temperature driven flow lines of the Hall and dissipative magnetoconductance data (\sigma_{xy},\sigma_{xx}) are studied in the fractional quantum Hall regime for a 2D electron system in GaAs/Al_{x}Ga_{1-x}As heterostructures. The flow lines are rather well described by a recent unified scaling theory developed for both the integer and the fractional quantum Hall effect in a totally spin-polarized 2D electron system which predicts that one (\sigma_{xy},\sigma_{xx}) point determines a complete flow line.
Random sequential adsorption of linear and square particles with excluded volume interaction is studied numerically on planar lattices considering Gaussian distributions of lateral sizes of the incident particles, with several values of the average and of the width-to-average ratio $w$. When the coverage is plotted as function of the logarithm of time $t$, the maximum slope is attained at a time $t_M$ of the same order of the time $\tau$ of incidence of one monolayer, which is related to the molecular flux and/or sticking coefficients. For various values of the average $\mu$ and $w$, we obtain $1.5\tau < t_M < 5\tau$ for linear particles and $.3\tau< t_M < \tau$ for square particles. At $t_M$, the coverages with linear and square particles are near .3 and .2, respectively. Extrapolations show that coverages may vary with $\mu$ up to 20% and 2% for linear and square particles, respectively, for $\mu\ge 64$, fixed time, and constant $w$. All coverage $\theta$ versus $\log t$ plots have approximately the same shape, but other quantities measured at times of order $t_M$ help to distinguish narrow and broad incident distributions. The adsorbed particle size distributions are close to the incident ones up to long times for small $w$, but appreciably change in time for larger $w$, acquiring a monotonically decreasing shape for $w = 1/2$ at times of order $100\tau$ . At $t_M$, incident and adsorbed distributions are approximately the same for $w \le 1/8$ and show significant differences for $w \ge 1/2$; this result may be used as a consistency test in applications of the model. The pair correlation function $g (r; t)$ for $w = 1/8$ has a well defined oscillatory structure at $10t_M$, with a minimum at $r\approx\mu$ and maximum at $r \approx 1.5\mu$, but this structure is not observed for $w \ge 1/4$.
We consider the problem of fault-tolerant quantum computation in the presence of slow error diagnostics, either caused by measurement latencies or slow decoding algorithms. Our scheme offers a few improvements over previously existing solutions, for instance it does not require active error correction and results in a reduced error-correction overhead when error diagnostics is much slower than the gate time. In addition, we adapt our protocol to cases where the underlying error correction strategy chooses the optimal correction amongst all Clifford gates instead of the usual Pauli gates. The resulting Clifford frame protocol is of independent interest as it can increase error thresholds and could find applications in other areas of quantum computation.
We study topological properties of density wave states with broken translational symmetry in two-dimensional multi-orbital systems with a particular focus on t$_{2g}$ orbitals in square lattice. Due to distinct symmetry properties of d-orbitals, a nodal charge or spin density wave state with Dirac points protected by lattice symmetries can be achieved. When an additional order parameter with opposite reflection symmetry is introduced to a nodal density wave state, the system can be fully gapped leading to a band insulator. Among those, topological density wave (TDW) insulators can be realized, when an effective staggered on-site potential generates a gap to a pair of Dirac points connected by the inversion symmetry which have the same topological winding numbers. We also present a mean-field phase diagram for various density wave states, and discuss experimental implications of our results.
Dynamo action in fully convective stars is a debated issue that also questions our understanding of magnetic field generation in partly convective Sun-like stars. During the past few years, spectropolari- metric observations have demonstrated that fully convective objects are able to trigger strong large-scale and long-lived magnetic fields. We present here the first spectropolarimetric study of a sample of active late M dwarfs (M5-M8) carried out with ESPaDOnS@CFHT. It reveals the co-existence of two distinct types of magnetism among stars having similar masses and rotation rates. A possible explanation for this unexpected discovery is the existence of two dynamo branches in this parameter regime, we discuss here the possible identification with the weak vs strong field bistability predicted for the geodynamo.
Doppler tomography can provide a powerful means of determining black hole spin when our view to the central regions are revealed and obscured by optically thick orbiting material, and can provide an independent estimate that does not suffer as many degeneracies as traditional methods. For low mass AGN, time-dependent obscuration is expected to leave a signature in the changing spectrum of the disc emission which extends into the soft X-ray bandpass. We create a spectral model incorporating Doppler tomography and apply it to the case of the low mass (8 $\times$ 10$^{5}$ M$_{\odot}$) AGN, RX J1301.9+2747 which shows unusual timing properties in the form of short-lived flares that we argue are best explained by the orbit of a window through an optically thick wind. Modelling the phase-resolved spectrum over the course of the highest data quality flare indicates a very low spin even when we relax our constraints. This is the lowest mass AGN for which a spin has been measured and the first via this technique. We note that, as the mass and spin are very low, this appears to favour supermassive black hole (SMBH) growth by chaotic rather than constant accretion.
In an anisotropic universe, observers not positioned at a point of special symmetry should observe cosmic parallax - the relative angular motion of test galaxies over cosmic time. It was recently argued that the non-observance of this effect in upcoming precision astrometry missions such as Gaia may be used to place strong bounds on the position of off-center observers in a void-model universe described by the Lemaitre-Tolman-Bondi metric. We consider the analogous effect in anisotropic cosmological models described by an axisymmetric homogeneous Bianchi type I metric and discuss whether any observation of cosmic parallax would distinguish between different anisotropic evolutions.
We present dynamical models of NGC 4494, which we built using our iterative method presented in a previous paper. These models are live N-body models consisting of equal mass particles, and they are steady state as confirmed by a fully self-consistent evolution. Our goals were twofold. The first one -- namely to test whether our iterative method could indeed be used to construct galactic models following given observational constraints, both photometric and kinematic -- was fully achieved. Our method allowed us to go beyond a simple spherical model and to make full sets of rotating, axisymmetric models without any limitations to the velocity distribution. Our second goal was to understand better the structure of NGC 4494, and more specifically to set constraints on its halo mass. For this we tried three families of models: without halo, with a light halo and with a heavy halo, respectively. Our models reproduce well the photometry and the kinematics, the latter except specific regions where some non-equilibrium or non-axisymmetric structure could be present in the galaxy (e.g. the kinematically decoupled core). However, the lower order moments of the velocity distribution (up to and including the second order) do not allow us to discriminate between the three halos. On the other hand, when we extend the comparison to the higher order moments of the velocity distribution obtained from the long-slit data, we find that our light halo model fits the data better than the no halo, or the heavy halo models. They also reproduce the shape of the angular dependence of the PNe velocity dispersion in the outermost parts of the galaxy, but not the amplitude of its azimuthal variation. This may imply that a yet more general class of models, such as triaxial, may be necessary for a yet better fit.
We use inelastic neutron scattering to study magnetic excitations of Sc$_{1-x}$U$_{x}$Pd$_3$ for U concentrations ($x=0.25$, 0.35) near the spin glass quantum critical point (QCP). The excitations are spatially incoherent, broad in energy ($E=\hbar\omega$), and follow $\omega/T$ scaling at all wave vectors investigated. Since similar $\omega/T$ scaling has been observed for UCu$_{5-x}$Pd$_x$ and CeCu$_{6-x}$Au$_{x}$ near the antiferromagnetic (AF) QCP, we argue that the observed non Fermi liquid (NFL) behavior in these $f$-electron materials arises from the critical phenomena near a T=0 K phase transition, irrespective of the nature of the transition.
We prove two conjectures of Paule and Radu from their recent paper on broken k-diamond partitions.
Detection of the electromagnetic emission from coalescing binary neutron stars (BNS) is important for understanding the merger and afterglow. We present a search for a radio counterpart to the gravitational-wave source GW190425, a BNS merger, using Apertif on the Westerbork Synthesis Radio Telescope (WSRT). We observe a field of high probability in the associated localisation region for 3 epochs at 68, 90 and 109 days post merger. We identify all sources that exhibit flux variations consistent with the expected afterglow emission of GW190425. We also look for possible transients. These are sources which are only present in one epoch. In addition, we quantify our ability to search for radio afterglows in fourth and future observing runs of the gravitational-wave detector network using Monte Carlo simulations. We found 25 afterglow candidates based on their variability. None of these could be associated with a possible host galaxy at the luminosity distance of GW190425. We also found 55 transient afterglow candidates that were only detected in one epoch. All turned out to be image artefacts. In the fourth observing run, we predict that up to three afterglows will be detectable by Apertif. While we did not find a source related to the afterglow emission of GW190425, the search validates our methods for future searches of radio afterglows.
At the beginning of binary black hole simulations, there is a pulse of spurious radiation (or junk radiation) resulting from the initial data not matching astrophysical quasi-equilibrium inspiral exactly. One traditionally waits for the junk radiation to exit the computational domain before taking physical readings, at the expense of throwing away a segment of the evolution, and with the hope that junk radiation exits cleanly. We argue that this hope does not necessarily pan out as junk radiation could excite long-lived constraint violation. Another complication with the initial data is that it contains orbital eccentricity that needs to be removed, usually by evolving the early part of the inspiral multiple times with gradually improved input parameters. We show that this procedure is also adversely impacted by junk radiation. In this paper, we do not attempt to eliminate junk radiation directly, but instead tackle the much simpler problem of ameliorating its long-lasting effects. We report on the success of a method that achieves this goal by combining the removal of junk radiation and eccentricity into a single "joint-elimination" procedure. This approach has the following benefits: (1) We do not have to contend with the influence of junk radiation on eccentricity measurements for later iterations of the eccentricity reduction procedure. (2) We re-enforce constraints periodically by invoking the initial data solver, removing the constraint violation excited by junk radiation previously. (3) The wasted simulation segment associated with the junk radiation's evolution is absorbed into the eccentricity reduction iterations. Furthermore, (1) and (2) together allow us to carry out our joint-elimination procedure at low resolution, even when the subsequent "production run" is intended as a high resolution simulation.