ShantanuT01/DACTYL-Pretraining huggingface dataset:
Unusually large low field magetoresistance (LFMR), ~ 10 %, at 300 K has been observed with the sample of mono-dispersed Fe3O4 magnetite nanospheres, ~ 200 nm, compactly cold-pressed and sintered at 800 C. A detailed analysis on the transport and magnetic measurements indicates that the electron conduction is dominated by the spin-dependent scattering or tunneling at the grain boundaries. At low temperature, 140 K and 100 K near the Verwey transition, ~ 115 K, the LFMR (below 2 kOe) does not show any sign of dependence on the transition, and does not follow the variation of magnetization to reach the saturation region either. On the other hand, at 300 K, the MR saturates fast with the magnetization below 2 kOe. This temperature dependent property in LFMR is very likely attributed to the scattering or tunneling of the conduction electron passing through the grain boundary layer with spin disordered state.
We have completed an optical spectroscopic survey of an unbiased, extinction-limited sample of candidate young stars covering 1.3 square degrees of the Rho Ophiuchi star forming region. While infrared, X-ray, and optical surveys of the cloud have identified many young stellar objects (YSOs), these surveys are biased towards particular stages of stellar evolution and are not optimal for studies of the disk frequency and initial mass function.We have obtained over 300 optical spectra to help identify 135 association members based on the presence of H-alpha in emission, lithium absorption, X-ray emission, a mid-infrared excess, a common proper motion, reflection nebulosity, and/or extinction considerations. Spectral types along with R and I band photometry were used to derive effective temperatures and bolometric luminosities for association members to compare with theoretical tracks and isochrones for pre-main-sequence stars. An average age of 3.1 Myr is derived for this population which is intermediate between that of objects embedded in the cloud core of Rho Ophiuchi and low mass stars in the Upper Scorpius subgroup. Consistent with this age we find a circumstellar disk frequency of 27% plus or minus 5%. We also constructed an initial mass function for an extinction-limited sample of 123 YSOs (A_v less than or equal to 8 mag), which is consistent with the field star initial mass function for YSOs with masses > 0.2 M_sun. There may be a deficit of brown dwarfs but this result relies on completeness corrections and requires confirmation.
Optomechanical systems show tremendous promise for high sensitivity sensing of forces and modification of mechanical properties via light. For example, similar to neutral atoms and trapped ions, laser cooling of mechanical motion by radiation pressure can take single mechanical modes to their ground state. Conventional optomechanical cooling is able to introduce additional damping channel to mechanical motion, while keeping its thermal noise at the same level, and as a consequence, the effective temperature of the mechanical mode is lowered. However, the ratio of temperature to quality factor remains roughly constant, preventing dramatic advances in quantum sensing using this approach. Here we propose an approach for simultaneously reducing the thermal load on a mechanical resonator while improving its quality factor. In essence, we use the optical interaction to dynamically modify the dominant damping mechanism, providing an optomechanically-induced effect analogous to a phononic band gap. The mechanical mode of interest is assumed to be weakly coupled to its heat bath but strongly coupled to a second mechanical mode, which is cooled by radiation pressure coupling to a red detuned cavity field. We also identify a realistic optomechanical design that has the potential to realize this novel cooling scheme.
The chiral SU(3) quark model is extended to include coupling between vector chiral field and quarks. By using this model, the phase shifts of NN scattering for different partial waves are studied. The results are very similar to those of the chiral SU(3) quark model calculation, in which one gluon exchange (OGE) plays dominate role in the short range part of the quark-quark interactions. Only in the $^1S_0$ case, the one channel phase shifts of the extended chiral SU(3) quark model are obviously improved.
We study certain N=1 preserving deformations of four-dimensional N=2 superconformal field theories (SCFTs) with non-abelian flavor symmetry. The deformation is described by adding an N=1 chiral multiplet transforming in the adjoint representation of the flavor symmetry with a superpotential coupling, and giving a nilpotent vacuum expectation value to the chiral multiplet which breaks the flavor symmetry. This triggers a renormalization group flow to an infrared SCFT. Remarkably, we find classes of theories flow to enhanced N=2 supersymmetric fixed points in the infrared under the deformation. They include generalized Argyres-Douglas theories and rank-one SCFTs with non-abelian flavor symmetries. Most notably, we find renormalization group flows from the deformed conformal SQCDs to the $(A_1, A_n)$ Argyres-Douglas theories. From these "Lagrangian descriptions," we compute the full superconformal indices of the $(A_1, A_n)$ theories and find agreements with the previous results. Furthermore, we study the cases, including the $T_N$ and $R_{0,N}$ theories of class $\mathcal{S}$ and some of rank-one SCFTs, where the deformation gives genuine N=1 fixed points.
There has been recent interest in the question of whether QCD collinear singularities can be viewed as the OPE of a two-dimensional CFT. We analyze a version of this question for the self-dual limit of pure gauge theory (incorporating states of both helicities). We show that the known one-loop collinear singulaties do not form an associative chiral algebra. The failure of associativity can be traced to a novel gauge anomaly on twistor space. We find that associativity can be restored for certain gauge groups if we introduce an unusual axion, which cancels the twistor space anomaly by a Green-Schwarz mechanism. Alternatively, associativity can be restored for some gauge groups with carefully chosen matter.
We present mid infrared (Mid-IR) spectra of the Compton-thick Seyfert 2 galaxy NGC\,3281, obtained with the Thermal-Region Camera Spectrograph (T-ReCS) at the Gemini South telescope. The spectra present a very deep silicate absorption at 9.7\,$\mu$m, and [S{\sc\,iv]}\,10.5\,$\mu$m and [Ne{\sc\,ii]}\,12.7\,$\mu$m ionic lines, but no evidence of PAH emission. We find that the nuclear optical extinction is in the range 24 $\leq$ A$_{V}$ $\leq$ 83\,mag. A temperature T = 300\,K was found for the black-body dust continuum component of the unresolved 65\,pc nucleus and at 130\,pc SE, while the region at 130\,pc reveals a colder temperature (200\,K). We describe the nuclear spectrum of NGC\,3281 using a clumpy torus model that suggests that the nucleus of this galaxy hosts a dusty toroidal structure. According to this model, the ratio between the inner and outer radius of the torus in NGC\,3281 is $R_0/R_d$ = 20, with {\bf 14} clouds in the equatorial radius with optical depth of $\tau_{V}$ = 40\,mag. We would be looking in the direction of the torus equatorial radius ($i$ = {\bf 60$^{\circ}$}), which has outer radius of R$_{0}\,\sim$ 11\,pc. The column density is N$_{H}\approx$\,{\bf 1.2}\,$\times\,10^{24}\,cm^{-2}$ and iron K$\alpha$ equivalent width ($\approx$ 0.5 - 1.2\,keV) are used to check the torus geometry. Our findings indicate that the X-ray absorbing column density, which classifies NGC\,3281 as a Compton-thick source, may also be responsible for the absorption at 9.7\,$\mu$m providing strong evidence that the silicate dust responsible for this absorption can be located in the AGN torus.
We derive general evolution equations describing the ensemble-average quantum dynamics generated by disordered Hamiltonians. The disorder average affects the coherence of the evolution and can be accounted for by suitably tailored effective coupling agents and associated rates which encode the specific statistical properties of the Hamiltonian's eigenvectors and eigenvalues, respectively. Spectral disorder and isotropically disordered eigenvector distributions are considered as paradigmatic test cases.
Spiral patterns are important agents of galaxy evolution. In this review, I describe how the redistribution of angular momentum by recurrent transient spiral patterns causes the random speeds of stars to rise over time, metallicity gradients to be reduced, and drives large-scale turbulence in the disk, which could be important for galactic dynamos. I also outline a possible mechanism for the recurrence of spiral instabilities and supporting evidence from solar neighborhood kinematics. Finally, I confirm that cloud scattering alone would predict the local velocity ellipsoid to be flattened, contrary to long-held expectations.
A series of infrared-active optical phonons have been detected in type-I clathrate Ba$_8$Ga$_{16}$Ge$_{30}$ by terahertz time-domain spectroscopy. The conductivity spectra with the lowest-lying peaks at 1.15 and 1.80 THz are identified with so-called rattling phonons, i.e., optical modes of the guest ion Ba$^{2+}(2)$ with $T_{1u}$ symmetry in the oversized tetrakaidecahedral cage. The temperature dependence of the spectra from these modes are totally consistent with calculations based on a one-dimensional anharmonic potential model that, with decreasing temperature, the shape becomes asymmetrically sharp associated with a softening for the weight to shift to lower frequency. These temperature dependences are determined, without any interaction effects, by the Bose-factor for optical excitations of anharmonic phonons with the nonequally spaced energy levels.
Using a sample of 24264 optically selected AGNs from the SDSS DR7 database, we characterise how the profile of the [OIII] emission line relates to bolometric luminosity (L_Bol), Eddington ratio, radio loudness, radio luminosity (L_Rad) and optical class (Sy 1/2) to determine what drives the kinematics of this kpc-scale line emitting gas. Spectral stacking is used to characterise how the average [OIII] profile changes as a function of these variables. After accounting for the correlation between L_Bol and L_Rad, we report that L_Rad has the strongest influence on the [OIII] profile, with moderate radio luminosity AGNs (log(L_Rad)=23-25 W/Hz) having the broadest [OIII] profiles. When binned according to Eddington ratio, only AGNs in our highest bin (i.e., R_Edd>0.3) show any signs of having broadened [OIII] profiles, although the small numbers of such extreme AGNs mean we cannot rule out that other processes (e.g., radio jets) are responsible for this broadening. We find no significant difference between the [OIII] profiles of broad and narrow-line Seyfert 1s. The [OIII] profiles of Sy 1 and 2 AGNs show the same trends in terms of line width, but Sy 1 AGNs display a much stronger blue wing, which we interpret as evidence of outflowing ionised gas. Using multi-component line fitting we calculate the proportions of AGNs with broad [OIII] profiles, finding that moderate radio luminosity AGNs are roughly 5 times more likely to have extremely broad [OIII] lines (FWHM>1000km/s) compared to lower L_Rad AGNs. Our results are consistent with the most disturbed gas kinematics being induced by compact radio cores (rather than powerful radio jets), although broadened [OIII] lines are also present, but much rarer, in low L_Rad systems (<10^23 W/Hz). Our catalogue of multi-component fits is freely available as an online resource.
We calculate quarkonium spectral functions in a quark-gluon plasma using a potential model based on full QCD lattice calculations of the free energy of static quark-antiquark pair. We estimate the binding energy and the thermal width of different quarkonium states. The estimated upper limit for the dissociation temperatures is considerably lower than the ones suggested in the recent literature.
If $N={q^k}{n^2}$ is an odd perfect number given in Eulerian form, then the Descartes-Frenicle-Sorli conjecture predicts that $k=1$. Brown has recently announced a proof for the inequality $q < n$, and a partial proof that $q^k < n$ holds under many cases. In this article, we give a strategy for strengthening Brown's result to $q^2 < n$.
Trumpler 20 is an old open cluster (OC) located toward the Galactic centre, at about 3 kpc from the Sun and $\sim$7 kpc from the Galactic centre. Its position makes this cluster particularly interesting in the framework of the chemical properties of the Galactic disc because very few old OCs reside in the inner part of the disc. For this reason it has been selected as a cluster target of the Gaia-ESO Survey, and spectra of many stars in the main sequence and red clump phases are now available. Moreover, although it has been studied by several authors in the past, no consensus on the evolutionary status of Tr 20 has been reached. The heavy contamination of field stars (the line of sight of Tr 20 crosses the Carina spiral arm) complicates a correct interpretation. Another interesting aspect of the cluster is that it shows a broadened main-sequence turn-off and a prominent and extended red-clump, characteristics that are not easily explained by classical evolutionary models. Exploiting both spectroscopic information from the Gaia-ESO Survey (and the ESO archive) and literature photometry, we obtain a detailed and accurate analysis of the properties of the cluster. We make use of the first accurate metallicity measurement ever obtained from several spectra of red clump stars, and of cluster membership determination using radial velocities. According to the evolutionary models adopted, we find that Tr 20 has an age in the range 1.35-1.66 Gyr, an average reddening $E(B-V)$ in the range 0.31-0.35 mag, and a distance modulus $(m-M)_0$ between 12.64 and 12.72 mag. The spectroscopic metallicity is [Fe/H]=+0.17 dex. We discuss the structural properties of the object and constrain possible hypotheses for its broadened upper main sequence by estimating the effect of differential reddening and its extended red clump.
3D reconstruction aims to reconstruct 3D objects from 2D views. Previous works for 3D reconstruction mainly focus on feature matching between views or using CNNs as backbones. Recently, Transformers have been shown effective in multiple applications of computer vision. However, whether or not Transformers can be used for 3D reconstruction is still unclear. In this paper, we fill this gap by proposing 3D-RETR, which is able to perform end-to-end 3D REconstruction with TRansformers. 3D-RETR first uses a pretrained Transformer to extract visual features from 2D input images. 3D-RETR then uses another Transformer Decoder to obtain the voxel features. A CNN Decoder then takes as input the voxel features to obtain the reconstructed objects. 3D-RETR is capable of 3D reconstruction from a single view or multiple views. Experimental results on two datasets show that 3DRETR reaches state-of-the-art performance on 3D reconstruction. Additional ablation study also demonstrates that 3D-DETR benefits from using Transformers.
We report the results of spectropolarimetric study of the classical Cepheid $\eta$ Aql. We found that the longitudinal magnetic field of $\eta$ Aql sinusoidally varies with the radial pulsation period, while the amplitude $B$, mean field $B_0$, and phases of maximum and minimum field change from year to year. We hypothesize that possible reasons of those variations are stellar axial rotation or dynamo mechanisms.
Einstein's general relativity predicts that orbital motion of accreted gas approaching a neutron star (NS) in a NS low-mass X-ray binary (LMXB) system occurs on a time scale proportional to the NS mass. Radiation of the gas accounts for most of the observed LMXBs variability. In more than a dozen of sources twin-peak quasi-periodic oscillations (QPOs) have been observed. Inspired by the expected proportionality between periods of orbital motion and NS mass we present a straightforward comparison among these sources. We investigate relations between QPO periods and their ratios and identify characteristic time scales of QPOs associated to individual sources. These timescales are likely determined by the relative mass of each NS. We show that the characteristic time scale of the millisecond pulsar XTE J1807.4-294 is longer than for most other NS LMXBs. Consequently, models of QPOs that consider geodesic orbital frequencies imply that the X-ray pulsars' mass has to be about 50 % higher than the average mass of other sources. Consideration of other X-ray pulsars indicates that the exceptionality of XTE J1807.4-294 cannot be related to NS magnetic field in any simple manner. We suggest that QPOs observed in this source can help to discriminate between the proposed versions of the NS equation of state.
The problem of existence of a self-adjoint time operator conjugate to a Hamiltonian with SU(1,1) dynamical symmetry is investigated. In the space spanned by the eigenstates of the generator $K_3$ of the SU(1,1) group, the time operator for the quantum singular harmonic potential of the form $\omega ^2x2 + g/x2$ is constructed explicitly, and shown that it is related to the time-of-arrival operator of Aharonov and Bohm. Our construction is fully algebraic, involving only the generators of the SU(1,1) group.
We propose a novel architecture for depth estimation from a single image. The architecture itself is based on the popular encoder-decoder architecture that is frequently used as a starting point for all dense regression tasks. We build on AdaBins which estimates a global distribution of depth values for the input image and evolve the architecture in two ways. First, instead of predicting global depth distributions, we predict depth distributions of local neighborhoods at every pixel. Second, instead of predicting depth distributions only towards the end of the decoder, we involve all layers of the decoder. We call this new architecture LocalBins. Our results demonstrate a clear improvement over the state-of-the-art in all metrics on the NYU-Depth V2 dataset. Code and pretrained models will be made publicly available.
We have successfully observed linear dichroism in angle-resolved Yb3+ 3d5/2 core-level photoemission spectra for YbB12 in cubic symmetry. Its anisotropic 4f charge distribution due to the crystal-field splitting is responsible for the linear dichroism, which has been verified by spectral simulations using ionic calculations with the full multiplet theory for a single-site Yb3+ ion in cubic symmetry. The observed linear dichroism as well as the polarization-dependent spectra in two different photoelectron directions for YbB12 are quantitatively reproduced by theoretical analysis for the Gamma_8 ground state, indicating the Gamma_8 ground-state symmetry for the Yb3+ ions mixed with the Yb2+ state.
We investigate how the neutron drip line is related to the density dependence of the symmetry energy, by using a macroscopic nuclear model that allows us to calculate nuclear masses in a way dependent on the equation of state of asymmetric nuclear matter. The neutron drip line obtained from these masses is shown to appreciably shift to a neutron-rich side in a nuclear chart as the density derivative of the symmetry energy increases. Such shift is clearly seen for light nuclei, a feature coming mainly from the surface property of neutron-rich nuclei.
In this paper, we study a class of boundary value problems (BVPs) with Robin conditions in some $L^p$ spaces for polyharmonic equation on Lipschitz domains. Utilizing polyharmonic fundamental solutions, these Robin BVPs are solved by the method of layer potentials. The crucial ingedients of our approach are the classical single layer potential and its higher order analog (which are called multi-layer $S$-potentials), and the main results generalize ones of second order (Laplacian) case to higher order (polyharmonic) case.
This work proposes a new end-to-end DCNN based approach for motion segmentation, especially for video sequences captured with such non-static cameras, called MOSNET. While other approaches focus on spatial or temporal context only, the proposed approach uses 3D convolutions as a key technology to factor in, spatio-temporal features in cohesive video frames. This is done by capturing temporal information in features with a low and also with a high level of abstraction. The lean network architecture with about 21k trainable parameters is mainly based on a pre-trained VGG-16 network. The MOSNET uses a new feature map fusion technique, which enables the network to focus on the appropriate level of abstraction, resolution, and the appropriate size of the receptive field regarding the input. Furthermore, the end-to-end deep learning based approach can be extended by feature based image alignment as a pre-processing step, which brings a gain in performance for some scenes. Evaluating the end-to-end deep learning based MOSNET network in a scene independent manner leads to an overall F-measure of 0.803 on the CDNet2014 dataset. A small temporal window of five input frames, without the need of any initialization is used to obtain this result. Therefore the network is able to perform well on scenes captured with non-static cameras where the image content changes significantly during the scene. In order to get robust results in scenes captured with a moving camera, feature based image alignment can implemented as pre-processing step. The MOSNET combined with pre-processing leads to an F-measure of 0.685 when cross-evaluating with a relabeled LASIESTA dataset, which underpins the capability generalise of the MOSNET.
This work investigates a method for generating medium fidelity reactor model cross sections. The methodology used here couples a neutron transport code with a depletion calculator. Together the two can be used to generate time dependent group cross sections for medium fidelity reactor models in fuel cycle simulation. This work analyzes XSgen, a software that performs the functions mentioned above. Addtionally, it is shown that XSgen is capable of creating datasets for a medium fidelity reactor model known as Bright-lite. The results of this work show that XSgen produces datasets that match NEA benchmarks for both uranium based LWR, and MOX reactors.
The results of a deep submillimetre observation using SCUBA of the powerful radio galaxy 3C324, at redshift z=1.206, are presented. At 850 microns, emission from the location of the host radio galaxy is marginally detected at the 4.2 sigma level, 3.01 +/- 0.72 mJy, but there is no detection of emission at 450 microns to a 3 sigma limit of 21 mJy. A new 32 GHz radio observation using the Effelsberg 100m telescope confirms that the sub-millimetre signal is not associated with synchrotron emission. These observations indicate that both the mass of warm dust within 3C324, and the star formation rate, lie up to an order of magnitude below the values recently determined for radio galaxies at z = 3 to 4. The results are compared with dust masses and star formation rates derived in other ways for 3C324.
We present classical solutions for a D5 and NS5-branes in a pp-wave background. The worldvolume coordinates for these branes lie along a six dimensional pp-wave configuration obtained from $AdS_3 \times S_3$ in a Penrose limit. One in addition has nontrivial R-R 3-form field strength as well as a dilaton background. Classical solutions for Dp-branes (p> 5), as well as their bound states, are then generated in both IIA and IIB string theories by using T-duality symmetries. We also briefly discuss the construction of Dp-branes in pp-wave backgrounds, obtained from string theories on $AdS_m\times S^m$. Finally, the construction of the above D5-brane solution is presented from the point of view of the Green-Schwarz worldsheet string theory and its low lying spectrum is discussed.