ShantanuT01/DACTYL-Pretraining huggingface dataset:
A quantum analogue of the famous Blackwell Theorem in classical statistics has recently been proposed. Given two quantum channels A and B, a set of payoff functions have been proven to have values for B at least as high as they are for A if and only if there exists a quantum garbling channel E such that A=EB. When such a channel E exists, we can globally compare A and B in terms of their `noisiness'. We show that this method of channel noise comparison is equivalent to one obtained by considering the degradation of the distinguishability of states. Here, the channel A is said to be at least as noisy as the channel B if any ensemble of states, fed into each channel and possibly entangled with ancillae, emerges no more distinguishable from A than it does from channel B, where distinguishability is quantified by the minimum error discrimination probability. We also provide a novel application to eavesdropper detection in quantum cryptography.
Polarized emission from polycyclic aromatic hydrocarbons (PAHs) potentially provides a new way to test basic physics of the alignment of ultrasmall grains. In this paper, we present a new model of polarized PAH emission that takes into account the effect of PAH alignment with the magnetic field. We first generate a large sample of the grain angular momentum $\bf J$ by simulating the alignment of PAHs due to resonance paramagnetic relaxation that accounts for various interaction processes. We then calculate the polarization level of PAH emission features, for the different phases of the ISM, including the cold neutral medium (CNM), reflection nebulae (RN), and photodissociation regions (PDRs). We find that a moderate degree of PAH alignment can significantly enhance the polarization degree of PAH emission compared to the previous results obtained with randomly oriented $\bf J$. In particular, we find that smallest, negatively charged PAHs in RN can be excited to slightly suprathermal rotation due to enhanced ion collisional excitation, resulting in an increase of the polarization with the ionization fraction. Our results suggest that RN is the most favorable environment to observe polarized PAH emission and to test alignment physics of nanoparticles. Finally, we present an explicit relationship between the polarization level of PAH emission and the degree of external alignment for the CNM and RN. The obtained relationship will be particularly useful for testing alignment physics of PAHs by future observations.
Manganese dioxide nanorods were synthesized using novel solution route. The phase and microstructure of synthesized materials were identified using X ray diffraction, scanning electron and transmission electron microscopic measurements. The material crystallizes into beta crystallographic phase and consists of nanorods of diameter in the range of about 10-14 nm and length about 50 nm. The Fourier Transform Infrared (FTIR) spectroscopic and thermogravimetric analysis (TGA) measurements were carried out to understand the materials microscopic and thermal properties. The material exhibits characteristic Mn O vibrational frequencies, confirming the phase purity of material. The electrochemical performance of beta MnO2 nanorods was evaluated using cyclic voltammetry and galvanostatic charge and discharge measurements using inhouse developed supercapacitor device assembly. We observed about 125 F per g specific capacitance for beta MnO2 nanorods electrode materials.
We show in this paper that, when properly rescaled in time and in space, the characteristic polynomial of a random unitary matrix converges almost surely to a random analytic function whose zeros, which are on the real line, form a determinantal point process with sine kernel. We prove this result in the framework of virtual isometries to circumvent the fact that the rescaled characteristic polynomial does not even have a moment of order one, hence making the classical techniques of random matrix theory difficult to apply.
A new method is applied to solve the Baxter equation for the one dimensional system of noncompact spins. Dynamics of such an ensemble is equivalent to that of a set of reggeized gluons exchanged in the high energy limit of QCD amplitudes. The technique offers more insight into the old calculation of the intercept of hard Pomeron, and provides new results in the odderon channel.
Let $(X_t,t\geq0)$ be a continuous time simple random walk on $\mathbb{Z}^d$ ($d\geq3$), and let $l_T(x)$ be the time spent by $(X_t,t\geq0)$ on the site $x$ up to time $T$. We prove a large deviations principle for the $q$-fold self-intersection local time $I_T=\sum_{x\in\mathbb{Z}^d}l_T(x)^q$ in the critical case $q=\frac{d}{d-2}$. When $q$ is integer, we obtain similar results for the intersection local times of $q$ independent simple random walks.
The ground-state phases of mixed diamond chains with ($S, \tau^{(1)}, \tau^{(2)})=(1/2,1/2,1)$, where $S$ is the magnitude of vertex spins, and $\tau^{(1)}$ and $\tau^{(2)}$ are those of apical spins, are investigated. The apical spins $\tau^{(1)}$ and $\tau^{(2)}$ are connected with each other by an exchange coupling $\lambda$. Other exchange couplings are set equal to unity. This model has an infinite number of local conservation laws. For large $\lambda$, the ground state is equivalent to that of the uniform spin $1/2$ chain. Hence, the ground state is a gapless spin liquid. For $\lambda \leq 0$, the ground state is a Lieb-Mattis ferrimagnetic phase with spontaneous magnetization $m_{\rm sp}=1$ per unit cell. For intermediate $\lambda$, we find a series of ferrimagnetic phases with $m_{\rm sp}=1/p$ where $p$ takes positive integer values. The phases with $p \geq 2$ are accompanied by the spontaneous breakdown of the $p$-fold translational symmetry. It is suggested that the phase with arbitrarily large $p$, namely infinitesimal spontaneous magnetization, is allowed as $\lambda$ approaches the transition point to the gapless spin liquid phase.
We use Enzo, a hybrid Eulerian AMR/N-body code including non-gravitational heating and cooling, to explore the morphology of the X-ray gas in clusters of galaxies and its evolution in current generation cosmological simulations. We employ and compare two observationally motivated structure measures: power ratios and centroid shift. Overall, the structure of our simulated clusters compares remarkably well to low-redshift observations, although some differences remain that may point to incomplete gas physics. We find no dependence on cluster structure in the mass-observable scaling relations, T_X-M and Y_X-M, when using the true cluster masses. However, estimates of the total mass based on the assumption of hydrostatic equilibrium, as assumed in observational studies, are systematically low. We show that the hydrostatic mass bias strongly correlates with cluster structure and, more weakly, with cluster mass. When the hydrostatic masses are used, the mass-observable scaling relations and gas mass fractions depend significantly on cluster morphology, and the true relations are not recovered even if the most relaxed clusters are used. We show that cluster structure, via the power ratios, can be used to effectively correct the hydrostatic mass estimates and mass-scaling relations, suggesting that we can calibrate for this systematic effect in cosmological studies. Similar to observational studies, we find that cluster structure, particularly centroid shift, evolves with redshift. This evolution is mild but will lead to additional errors at high redshift. Projection along the line of sight leads to significant uncertainty in the structure of individual clusters: less than 50% of clusters which appear relaxed in projection based on our structure measures are truly relaxed.
We compare the response of five different models of two interacting electrons in a quantum dot to an external short lived radial excitation that is strong enough to excite the system well beyond the linear response regime. The models considered describe the Coulomb interaction between the electrons in different ways ranging from mean-field approaches to configuration interaction (CI) models, where the two-electron Hamiltonian is diagonalized in a large truncated Fock space. The radially symmetric excitation is selected in order to severely put to test the different approaches to describe the interaction and correlations of an electron system in a nonequilibrium state. As can be expected for the case of only two electrons none of the mean-field models can in full details reproduce the results obtained by the CI model. Nonetheless, some linear and nonlinear characteristics are reproduced reasonably well. All the models show activation of an increasing number of collective modes as the strength of the excitation is increased. By varying slightly the confinement potential of the dot we observe how sensitive the properties of the excitation spectrum are to the Coulomb interaction and its correlation effects. In order to approach closer the question of nonlinearity we solve one of the mean-field models directly in a nonlinear fashion without resorting to iterations.
Contrastive visual pretraining based on the instance discrimination pretext task has made significant progress. Notably, recent work on unsupervised pretraining has shown to surpass the supervised counterpart for finetuning downstream applications such as object detection and segmentation. It comes as a surprise that image annotations would be better left unused for transfer learning. In this work, we investigate the following problems: What makes instance discrimination pretraining good for transfer learning? What knowledge is actually learned and transferred from these models? From this understanding of instance discrimination, how can we better exploit human annotation labels for pretraining? Our findings are threefold. First, what truly matters for the transfer is low-level and mid-level representations, not high-level representations. Second, the intra-category invariance enforced by the traditional supervised model weakens transferability by increasing task misalignment. Finally, supervised pretraining can be strengthened by following an exemplar-based approach without explicit constraints among the instances within the same category.
Some coherent sheaves on projective varieties have a non reduced versal deformation space. For example, this is the case for most unstable rank 2 vector bundles on ${\mathbb P}_2$. In particular, it may happen that some moduli spaces of stable sheaves are non reduced.   We consider the case of some sheaves on ribbons (double structures on smooth projective curves): the quasi locally free sheaves of rigid type. Le $E$ be such a sheaf.   -- Let ${\mathcal E}$ be a flat family of sheaves containing $E$. We find that it is a reduced deformation of $E$ when some canonical family associated to ${\mathcal E}$ is also flat.   -- We consider a deformation of the ribbon to reduced projective curves with two components, and find that $E$ can be deformed in two distinct ways to sheaves on the reduced curves. In particular some components $\bf M$ of the moduli spaces of stable sheaves deform to two components of the moduli spaces of sheaves on the reduced curves, and $\bf M$ appears as the "limit" of varieties with two components, whence the non reduced structure of $\bf M$.
We study polylithiated molecules as building blocks for hydrogen storage materials, using first-principles calculations. $\clifour$ and $\olitwo$ bind 12 and 10 hydrogen molecules, respectively, with an average binding energy of 0.10 and 0.13 eV, leading to gravimetric densities of 37.8 and 40.3 weight % H. Bonding between Li and C or O is strongly polar and $\hyd$ molecules attach to the partially charged Li atoms without dissociating, which is favorable for (de)hydrogenation kinetics. CLi$_n$ and OLi$_m$ molecules can be chemically bonded to graphene sheets to hinder the aggregation of such molecules. In particular B or Be doped graphene strongly bind the molecules without seriously affecting the hydrogen binding energy. It still leads to a hydrogen storage capacity in the range 5-8.5 wt % H.
We measure and analyse the clustering of the Baryon Oscillation Spectroscopic Survey (BOSS) relative to the line-of-sight (LOS), for LOWZ and CMASS galaxy samples drawn from the final Data Release 12 (DR12). The LOWZ sample contains 361\,762 galaxies with an effective redshift of $z_{\rm lowz}=0.32$, and the CMASS sample 777\,202 galaxies with an effective redshift of $z_{\rm cmass}=0.57$. From the power spectrum monopole and quadrupole moments around the LOS, we measure the growth of structure parameter $f$ times the amplitude of dark matter density fluctuations $\sigma_8$ by modeling the Redshift-Space Distortion signal. When the geometrical Alcock-Paczynski effect is also constrained from the same data, we find joint constraints on $f\sigma_8$, the product of the Hubble constant and the comoving sound horizon at the baryon drag epoch $H(z)r_s(z_d)$, and the angular distance parameter divided by the sound horizon $D_A(z)/r_s(z_d)$. We find $f(z_{\rm lowz})\sigma_8(z_{\rm lowz})=0.394\pm0.062$, $D_A(z_{\rm lowz})/r_s(z_d)=6.35\pm0.19$, $H(z_{\rm lowz})r_s(z_d)=(11.41\pm 0.56)\,{10^3\rm km}s^{-1}$ for the LOWZ sample, and $f(z_{\rm cmass})\sigma_8(z_{\rm cmass})=0.444\pm0.038$, $D_A(z_{\rm cmass})/r_s(z_d)=9.42\pm0.15$, $H(z_{\rm cmass})r_s(z_d)=(13.92 \pm 0.44)\, {10^3\rm km}s^{-1}$ for the CMASS sample. We find general agreement with previous BOSS DR11 measurements. Assuming the Hubble parameter and angular distance parameter are fixed at fiducial $\Lambda$CDM values, we find $f(z_{\rm lowz})\sigma_8(z_{\rm lowz})=0.485\pm0.044$ and $f(z_{\rm cmass})\sigma_8(z_{\rm cmass})=0.436\pm0.022$ for the LOWZ and CMASS samples, respectively.
We consider a self-interacting, massive scalar field (non)minimally coupled to new massive gravity in three dimensions. For this model, we first derive a family of black hole solutions depending on a unique integration constant and parameterized in terms of the nonminimal coupling parameter. Imposing the absence of naked singularities restricts the parameters in such a way that the field vanishes at infinity and fixes the metric to be asymptotically AdS. Within this family of solutions it is possible to find a black hole supported by a minimally coupled scalar field and therefore the existence of these solutions is not inherent to the presence of the nonminimal coupling. The Wald formula for the entropy, being proportional to the lapse function evaluated at the horizon, yields a zero entropy in spite of the fact that the solution has a non zero temperature. As a consequence, the unique integration constant may be interpreted as a sort of gravitational hair. As in the source free case, we show that the same field equations admit as well asymptotically Lifshitz black hole solutions in a different region of the space of parameters. These Lifshitz solutions are divided in three families for which all the parameters entering in the action may be expressed in term of the dynamical exponent.
We show that the recently constructed higher-derivative 6D SYM theory involves an internal chiral anomaly breaking gauge invariance. The anomaly is cancelled when adding to the theory an adjoint matter hypermultiplet.
The possibility of dual equivalence between the self-dual and the Maxwell-Chern-Simons (MCS) models when the latter is coupled to dynamical, U(1) fermionic charged matter is examined. The proper coupling in the self-dual model is then disclosed using the iterative gauge embedding approach. We found that the self-dual potential needs to couple directly to the Chern-Kernel of the source in order to establish this equivalence besides the need for a self-interaction term to render the matter sector unchanged.
The Gaia Sausage (GS) and the Sequoia represent the major accretion events that formed the stellar halo of the Milky Way. A detailed chemical study of these main building blocks provides a pristine view of the early steps of the Galaxy's assembly. We present the results of the analysis of the UVES high-resolution spectroscopic observations at the 8.2m VLT of 9 Sausage/Sequoia members selected kinematically using Gaia DR2. We season this set of measurements with archival data from Nissen & Schuster (2011) and GALAH DR3 (2020). Here, we focus on the neutron-capture process by analysing Sr, Y, Ba and Eu behavior. We detect clear enhancement in Eu abundance ([Eu/Fe]~0.6-0.7) indicative of large prevalence of r-process in the stellar n-capture makeup. We are also able to trace the evolution of the heavy element production across a wide range of metallicity. The barium to europium changes from a tight, flat sequence with [Ba/Eu]=-0.7 reflecting dominant contribution from exploding massive stars, to a clear upturn at higher iron abundances, betraying the onset of contamination from asymptotic giant branch (AGB) ejecta. Additionally, we discover two clear sequences in [Fe/H]-[Ba/Fe] plane likely caused by distinct levels of s-process pollution and mixing within the GS progenitor.
We present an automatic annotation pipeline to recover 9D cuboids and 3D shapes from pre-trained off-the-shelf 2D detectors and sparse LIDAR data. Our autolabeling method solves an ill-posed inverse problem by considering learned shape priors and optimizing geometric and physical parameters. To address this challenging problem, we apply a novel differentiable shape renderer to signed distance fields (SDF), leveraged together with normalized object coordinate spaces (NOCS). Initially trained on synthetic data to predict shape and coordinates, our method uses these predictions for projective and geometric alignment over real samples. Moreover, we also propose a curriculum learning strategy, iteratively retraining on samples of increasing difficulty in subsequent self-improving annotation rounds. Our experiments on the KITTI3D dataset show that we can recover a substantial amount of accurate cuboids, and that these autolabels can be used to train 3D vehicle detectors with state-of-the-art results.
In dense, static, polydisperse granular media under isotropic pressure, the probability density and the correlations of particle-wall contact forces are studied. Furthermore, the probability density functions of the populations of pressures measured with different sized circular pressure cells is examined. The questions answered are: (i) What is the number of contacts that has to be considered so that the measured pressure lies within a certain error margin from its expectation value? (ii) What is the statistics of the pressure probability density as function of the size of the pressure cell? Astonishing non-random correlations between contact forces are evidenced, which range at least 10 to 15 particle diameter. Finally, an experiment is proposed to tackle and better understand this issue.
Mixed order phase transitions (MOT), which display discontinuous order parameter and diverging correlation length, appear in several seemingly unrelated settings ranging from equilibrium models with long-range interactions to models far from thermal equilibrium. In a recent paper [1] an exactly soluble spin model with long-range interactions that exhibits MOT was introduced and analyzed both by a grand canonical calculation and a renormalization group analysis. The model was shown to lay a bridge between two classes of one dimensional models exhibiting MOT, namely between spin models with inverse distance square interactions and surface depinning models. In this paper we elaborate on the calculations done in [1]. We also analyze the model in the canonical ensemble, which yields a better insight into the mechanism of MOT. In addition, we generalize the model to include Potts and general Ising spins, and also consider a broader class of interactions which decay with distance with a power law different from 2.
Recent deep networks that directly handle points in a point set, e.g., PointNet, have been state-of-the-art for supervised learning tasks on point clouds such as classification and segmentation. In this work, a novel end-to-end deep auto-encoder is proposed to address unsupervised learning challenges on point clouds. On the encoder side, a graph-based enhancement is enforced to promote local structures on top of PointNet. Then, a novel folding-based decoder deforms a canonical 2D grid onto the underlying 3D object surface of a point cloud, achieving low reconstruction errors even for objects with delicate structures. The proposed decoder only uses about 7% parameters of a decoder with fully-connected neural networks, yet leads to a more discriminative representation that achieves higher linear SVM classification accuracy than the benchmark. In addition, the proposed decoder structure is shown, in theory, to be a generic architecture that is able to reconstruct an arbitrary point cloud from a 2D grid. Our code is available at http://www.merl.com/research/license#FoldingNet
A calculation of the hadronic matrix elements for K\to\pi\pi including \pi-\pi rescattering effects in a dispersion integral is presented. I study the dependence of the results on the matching scale \mu and use them to calculate the CP-parameter (\epsilon\prime/\epsilon). I find improved stability on the matching scale and good agreement with the experimental results.
This paper examines systems of poly-harmonic equations of the Hardy--Sobolev type and the closely related weighted systems of integral equations involving Riesz potentials. Namely, it is shown that the two systems are equivalent under some appropriate conditions. Then a sharp criterion for the existence and non-existence of positive solutions is determined for both differential and integral versions of a Hardy--Sobolev type system with variable coefficients. In the constant coefficient case, Liouville type theorems for positive radial solutions are also established using radial decay estimates and Pohozaev type identities in integral form.
The maximum size $A_2(8,6;4)$ of a binary subspace code of packet length $v=8$, minimum subspace distance $d=6$, and constant dimension $k=4$ is $257$, where the $2$ isomorphism types are extended lifted maximum rank distance codes. In finite geometry terms the maximum number of solids in $\operatorname{PG}(7,2)$, mutually intersecting in at most a point, is $257$. The result was obtained by combining the classification of substructures with integer linear programming techniques. This implies that the maximum size $A_2(8,6)$ of a binary mixed-dimension code of packet length $8$ and minimum subspace distance $6$ is $257$ as well.