ShantanuT01/DACTYL-Pretraining huggingface dataset:
This paper derives an upper limit on the density $\rho_{\scriptstyle\Lambda}$ of dark energy based on the requirement that cosmological structure forms before being frozen out by the eventual acceleration of the universe. By allowing for variations in both the cosmological parameters and the strength of gravity, the resulting constraint is a generalization of previous limits. The specific parameters under consideration include the amplitude $Q$ of the primordial density fluctuations, the Planck mass $M_{\rm pl}$, the baryon-to-photon ratio $\eta$, and the density ratio $\Omega_M/\Omega_b$. In addition to structure formation, we use considerations from stellar structure and Big Bang Nucleosynthesis (BBN) to constrain these quantities. The resulting upper limit on the dimensionless density of dark energy becomes $\rho_{\scriptstyle\Lambda}/M_{\rm pl}^4<10^{-90}$, which is $\sim30$ orders of magnitude larger than the value in our universe $\rho_{\scriptstyle\Lambda}/M_{\rm pl}^4\sim10^{-120}$. This new limit is much less restrictive than previous constraints because additional parameters are allowed to vary. With these generalizations, a much wider range of universes can develop cosmic structure and support observers. To constrain the constituent parameters, new BBN calculations are carried out in the regime where $\eta$ and $G=M_{\rm pl}^{-2}$ are much larger than in our universe. If the BBN epoch were to process all of the protons into heavier elements, no hydrogen would be left behind to make water, and the universe would not be viable. However, our results show that some hydrogen is always left over, even under conditions of extremely large $\eta$ and $G$, so that a wide range of alternate universes are potentially habitable.
We consider various possible scenarios to explain the recent observation of a claimed broad H$\alpha$ absorption in our Galactic halo with peak optical depth $\tau \simeq 0.01$ and equivalent width $W \simeq 0.17 \, \rm \AA$. We show that the absorbed feature cannot arise from the circumgalactic and ISM H$\alpha$ absorption. As the observed absorption feature is quite broad $\Delta\lambda \simeq 30 \, \rm \AA$, we also consider CNO lines that lie close to H$\alpha$ as possible alternatives to explain the feature. We show such lines could also not account for the observed feature. Instead, we suggest that it can arise from diffuse interstellar bands (DIBs) carriers or polyaromatic hydrocarbons (PAHs) absorption. While we identify several such lines close to the H$\alpha$ transition, we are unable to determine the molecule responsible for the observed feature, partly because of selection effects that prevents us from identifying DIBs/PAHs features close to H$\alpha$ using local observations. Deep integration on a few extragalactic sources with high spectral resolution might allow us to distinguish between different possible explanations.
We study the selective excitation at infrared and THz frequencies of optical and acoustic plasmonic modes supported by thin topological insulators. These modes are characterized by effective net charge or net spin density, respectively, and we study their excitation by combining many-body and electromagnetic calculations. We first show that non-locality can significantly modify the plasmonic response: it changes the energy of propagating plasmons up to tens of percent. We then discuss how, by changing the distance between a dipolar source and a semi-infinite 10 nm thin film, it is possible to control the excitation of acoustic and optical propagating plasmons, which can propagate over a distance of several plasmonic wavelengths. Furthermore, we consider 10 nm thin TI nanodisks and study the excitation of acoustic and optical localized plasmon modes by a point dipole source and plane wave illumination, respectively. The resonant plasmonic modes appear at frequencies that strongly depends on the size of the disk, and that can be potentially tuned by applying electrostatic gating to modify the Fermi Energy of the conductive 2-dimensional layer that forms at the interfaces of the TI. We observe a spectral shift from ~29 $\mu$m to ~34 $\mu$m by changing the Fermi Energy from 250meV to 350meV. Last, the electromagnetic energy of these plasmonics modes can be confined to very small regions, of effective volume ~(120 nm)^3 for the smaller disk considered, much less than the free-space wavelength cubed $\lambda$^3 ~(35000 nm)^3. The strong confinement is desirable for achieving very efficient coupling with nearby systems. Our detailed study thus shows that thin topological insulators are a promising system to control both the spin and charge oscillations associated with the plasmonic resonances, with possible applications to fast, compact and electrically-controlled spintronics devices.
3D reconstruction is a fundamental issue in many applications and the feature point matching problem is a key step while reconstructing target objects. Conventional algorithms can only find a small number of feature points from two images which is quite insufficient for reconstruction. To overcome this problem, we propose SeFM a sequential feature point matching algorithm. We first utilize the epipolar geometry to find the epipole of each image. Rotating along the epipole, we generate a set of the epipolar lines and reserve those intersecting with the input image. Next, a rough matching phase, followed by a dense matching phase, is applied to find the matching dot-pairs using dynamic programming. Furthermore, we also remove wrong matching dot-pairs by calculating the validity. Experimental results illustrate that SeFM can achieve around 1,000 to 10,000 times matching dot-pairs, depending on individual image, compared to conventional algorithms and the object reconstruction with only two images is semantically visible. Moreover, it outperforms conventional algorithms, such as SIFT and SURF, regarding precision and recall.
Context. Millimetric observations have measured high degrees of molecular deuteration in several species seen around low-mass protostars. The Herschel Space Telescope, launched in 2009, is now providing new measures of the deuterium fractionation of water, the main constituent of interstellar ices. Aims. We aim at theoretically studying the formation and the deuteration of water, which is believed to be formed on interstellar grain surfaces in molecular clouds. Methods. We used our gas-grain astrochemical model GRAINOBLE, which considers the multilayer formation of interstellar ices. We varied several input parameters to study their impact on water deuteration. We included the treatment of ortho- and para-states of key species, including H2, which affects the deuterium fractionation of all molecules. The model also includes relevant laboratory and theoretical works on the water formation and deuteration on grain surfaces. In particular, we computed the transmission probabilities of surface reactions using the Eckart model, and we considered ice photodissociation following molecular dynamics simulations. Results. The use of a multilayer approach allowed us to study the influence of various parameters on the abundance and the deuteration of water. Deuteration of water is found to be very sensitive to the ortho-to-para ratio of H2 and to the total density, but it also depends on the gas/grain temperatures and the visual extinction of the cloud. Since the deuteration is very sensitive to the physical conditions, the comparison with sub-millimetric observation towards the low-mass protostar IRAS 16293 allows us to suggest that water ice is formed together with CO2 in molecular clouds with limited density, whilst formaldehyde and methanol are mainly formed in a later phase, where the condensation becomes denser and colder.
We review recent progress in understanding the evolution of hot interstellar gas in the halos of elliptical galaxies. Non-homologous variations in the physical size of the hot gas account for the large variations of x-ray luminosity among ellipticals of similar L_B. By combining ROSAT and Einstein data we derive the distribution of total mass in NGC 4472. From 0.1r_e to 1r_e the total mass is identical to the expected stellar mass. Therefore stellar mass to light ratios can be determined from x-ray observations! Also the widely used ``mass dropout'' assumption must be incorrect in this important part of the cooling flow. Recent ROSAT observations indicate gas temperatures in excess of the virial stellar temperature, totally unlike standard cooling flow models. However, these new results can be understood if an additional massive component of ``circumgalactic'' gas is assumed to fill the outer galactic halos beyond most of the stars. This old hot gas, first heated during the epoch of galaxy formation, continues to flow into the stellar parts of ellipticals today, combining with gas expelled from evolving stars. This dual origin of hot interstellar gas further complicates recent discussions of abundances in the hot interstellar gas.
In this paper we present a new data-driven method for robust skin detection from a single human portrait image. Unlike previous methods, we incorporate human body as a weak semantic guidance into this task, considering acquiring large-scale of human labeled skin data is commonly expensive and time-consuming. To be specific, we propose a dual-task neural network for joint detection of skin and body via a semi-supervised learning strategy. The dual-task network contains a shared encoder but two decoders for skin and body separately. For each decoder, its output also serves as a guidance for its counterpart, making both decoders mutually guided. Extensive experiments were conducted to demonstrate the effectiveness of our network with mutual guidance, and experimental results show our network outperforms the state-of-the-art in skin detection.
We introduce a new effective strategy to assign group and cluster membership probabilities $P_{mem}$ to galaxies using photometric redshift information. Large dynamical ranges both in halo mass and cosmic time are considered. The method takes the magnitude distribution of both cluster and field galaxies as well as the radial distribution of galaxies in clusters into account using a non-parametric formalism and relies on Bayesian inference to take photometric redshift uncertainties into account. We successfully test the method against 1,208 galaxy clusters within redshifts $z=0.05-2.58$ and masses $10^{13.29-14.80}~M_\odot$ drawn from wide field simulated galaxy mock catalogs developed for the Euclid mission. Median purity $(55^{+17}_{-15})\%$ and completeness $(95^{+5}_{-10})\%$ are reached for galaxies brighter than 0.25$L_\ast$ within $r_{200}$ of each simulated halo and for a statistical photometric redshift accuracy $\sigma((z_s-z_p)/(1+z_s))=0.03$. The mean values $p=56\%$ and $c=93\%$ have sub-percent uncertainties. Accurate photometric redshifts ($\sigma((z_s-z_p)/(1+z_s))\lesssim0.05$) and robust estimates for the cluster redshift and the center coordinates are required. The method is applied to derive accurate richness estimates. A statistical comparison between the true ($N_{\rm true}$) vs estimated richness ($\lambda=\sum P_{mem}$) yields on average to unbiased results, $Log(\lambda/N_{\rm true})=-0.0051\pm0.15$. The scatter around the mean of the logarithmic difference between $\lambda$ and the halo mass is 0.10~dex, for massive halos $\gtrsim10^{14.5}~M_\odot$. Our estimates could be useful to calibrate independent cluster mass estimates from weak lensing, SZ, and X-ray studies. Our method can be applied to any list of galaxy clusters or groups in both present and forthcoming surveys such as SDSS, CFHTLS, DES, LSST, and Euclid.
We present a study of the variation of spatial structure of stellar populations within dwarf galaxies as a function of the population age. We use deep Hubble Space Telescope/Advanced Camera for Surveys imaging of nearby dwarf galaxies in order to resolve individual stars and create composite colour-magnitude diagrams (CMDs) for each galaxy. Using the obtained CMDs, we select Blue Helium Burning stars (BHeBs), which can be unambiguously age-dated by comparing the absolute magnitude of individual stars with stellar isochrones. Additionally, we select a very young (<10 Myr) population of OB stars for a subset of the galaxies based on the tip of the young main-sequence. By selecting stars in different age ranges we can then study how the spatial distribution of these stars evolves with time. We find, in agreement with previous studies, that stars are born within galaxies with a high degree of substructure which is made up of a continuous distribution of clusters, groups and associations from parsec to hundreds of parsec scales. These structures disperse on timescales of tens to hundreds of Myr, which we quantify using the two-point correlation function and the Q-parameter developed by Cartwright & Whitworth (2004). On galactic scales, we can place lower limits on the time it takes to remove the original structure (i.e., structure survives for at least this long), tevo, which varies between ~100~Myr (NGC~2366) and ~350 Myr (DDO~165). This is similar to what we have found previously for the SMC (~80~Myr) and the LMC (~175 Myr). We do not find any strong correlations between tevo and the luminosity of the host galaxy.
The role of external forces in systems exhibiting anomalous diffusion is discussed on the basis of the describing Langevin equations. Since there exist different possibilities to include the effect of an external field the concept of {\it biasing} and {\it decoupled} external fields is introduced. Complementary to the recently established Langevin equations for anomalous diffusion in a time-dependent external force-field [{\it Magdziarz et al., Phys. Rev. Lett. {\bf 101}, 210601 (2008)}] the Langevin formulation of anomalous diffusion in a decoupled time-dependent force-field is derived.
Let $ A$ be a subset of group $G_0$   with $|{A^{-1}A}|\le 2|A|-2.$ We show that there are an element $a\in A$ and a non-null proper subgroup $H$ of $G$ such that one of the following holds: \begin{itemize}   \item $x^{-1}Hy \subset A^{-1}A,$ for all $(x,y)\in A^2\setminus (Ha)^2,$   \item $xHy^{-1} \subset AA^{-1},$ for all $(x,y)\in A^2\setminus (aH)^2.$ \end{itemize} where $G$ is the subgroup generated by ${A^{-1}A}.$   Assuming that $A^{-1}A\neq G$ and that $ |A^{-1}A|< \frac{5|A|}3,$ we show that there are a normal subgroup $K$ of $G$ and a subgroup $H$ with $K\subset H\subset A^{-1}A $ and $2|K|\ge |H|$ such that $$A^{-1}AK=KA^{-1}A=A^{-1}A\ \text{and}\ 6|K|\ge |A^{-1}A|=3|H|.$$
If A is an Abelian variety, endowed with a polarization L, we study the function N_A(t) which counts the number of Abelian subvarieties S in A such that for the induced polarization L|_S the Euler characteristic \chi(L|_S) is bounded above by t. We give an estimate for the asymptotic order of growth of this function.
The aim of this study is to demonstrate how the logarithmic millimeter continuum gradient observed using the Atacama Large Millimeter/submillimeter Array (ALMA) may be used to estimate optical thickness in the solar atmosphere. We discuss how using multi-wavelength millimeter measurements can refine plasma analysis through knowledge of the absorption mechanisms. Here we use sub-band observations from the publicly available science verification (SV) data, whilst our methodology will also be applicable to regular ALMA data. The spectral resolving capacity of ALMA SV data is tested using the enhancement coincident with an X-ray Bright Point (XBP) and from a plasmoid ejection event near active region NOAA12470 observed in Band 3 (84-116 GHz) on 17/12/2015. We compute the interferometric brightness temperature light-curve for both features at each of the four constituent sub-bands to find the logarithmic millimetre spectrum. We compared the observed logarithmic spectral gradient with the derived relationship with optical thickness for an isothermal plasma to estimate the structure's optical thicknesses. We conclude, within 90% confidence, that the stationary enhancement has an optical thickness between $0.02 \leq \tau \leq 2.78$, and that the moving enhancement has $0.11 \leq \tau \leq 2.78$, thus both lie near to the transition between optically thin and thick plasma at 100 GHz. From these estimates, isothermal plasmas with typical Band 3 background brightness temperatures would be expected to have electron temperatures of $\sim 7370 - 15300$ K for the stationary enhancement and between $\sim 7440 - 9560$ K for the moving enhancement, thus demonstrating the benefit of sub-band ALMA spectral analysis.
Precision agriculture has become a key factor for increasing crop yields by providing essential information to decision makers. In this work, we present a deep learning method for simultaneous segmentation and counting of cranberries to aid in yield estimation and sun exposure predictions. Notably, supervision is done using low cost center point annotations. The approach, named Triple-S Network, incorporates a three-part loss with shape priors to promote better fitting to objects of known shape typical in agricultural scenes. Our results improve overall segmentation performance by more than 6.74% and counting results by 22.91% when compared to state-of-the-art. To train and evaluate the network, we have collected the CRanberry Aerial Imagery Dataset (CRAID), the largest dataset of aerial drone imagery from cranberry fields. This dataset will be made publicly available.
We have calculated numerically electron exchange, correlation energies and dynamical polarization function for newly discovered silicene, germanene and black phosphorus (BP), consisting of puckered layers of elemental phosphorus atoms, broadening the range of two-dimensional (2D) materials at various temperatures. As a matter of fact, monolayer BP, produced by mechanical and liquid exfoliation techniques, has been predicted to be an insulator with a large energy splitting 1.6 eV for the quasiparticle band structure. We compare the dependence of these energies on the chemical potential, field-induced gap and the temperature and concluded that in many cases they behave qualitatively similarly, i.e., increasing with the doping, decreasing significantly at elevated temperatures, and displaying different dependence on the asymmetry gap at various temperatures. Furthermore, we used the dynamical polarizability to investigate the new "split" plasmon branches in the puckered lattices and predict a unique splitting, different from that in gapped graphene, for various energy gaps. Our results are crucial for stimulating electronic, transport and collective studies of these novel materials, as well as for enhancing silicene-based fabrication and technologies for photovoltaics and transistor devices.
By using 14 different versions and parametrizations of a proximity potential and two new versions of the potential proposed in this paper, we perform a comparative study of fusion barriers by studying 26 symmetric reactions. The mass asymmetry $\eta_{A}$ = $(\frac{A_{2}-A_{1}}{A_{2}+A_{1}}),$ however, is very large. Our detailed investigation reveals that most of the proximity potentials reproduce experimental data within $\pm$8% on the average. A comparison of fusion cross sections indicates that Bass 80, AW 95, and Denisov DP potentials have a better edge than other potentials. We also propose new versions of the proximity potential as well as Denisov parametrized potential. These new versions improve the agreement with the data.
We consider the decay of the thermodynamic Casimir force in phases with a finite correlation length. For the case of the strip, we use properties of low energy two-dimensional field theory to show that the decay depends on the symmetry properties of the boundary conditions, in distinctive ways that we determine exactly. Features characteristic of the bulk universality class may induce modifications that we also discuss. Symmetry breaking and symmetry preserving boundary conditions exchange their role with respect to the decay of the force when exchanging spontaneously broken with disordered phases. Several of our arguments extend to higher dimensions.
Polycrystalline samples of the Y-diluted antiferromagnet CeNiGe3 (T_N = 5.5 K) and Th-diluted ferromagnet UNiSi2 (T_C = 95 K) were studied by means of x-ray powder diffraction, magnetization and specific heat measurements performed in a wide temperature range. The lattice parameters of the Ce1-xYxNiGe3 alloys decrease linearly with increasing the Y content, while the unit cell volume of U1-xThxNiSi2 increases linearly with rising the Th content. The ordering temperatures of the systems decrease monotonically with increasing x down to about 1.2 K in Ce0.4Y0.6NiGe3 and 26 K in U0.3Th0.7NiSi2, forming a dome of a long-range magnetic order on their magnetic phase diagrams. The suppression of the magnetic order is associated with distinct broadening of the anomalies at T_N,C due to crystallographic disorder being a consequence of the alloying. Below the magnetic percolation threshold xc of about 0.68 and 0.75 in the Ce- and U-based alloys, respectively, the long-range magnetic order smoothly evolves into a short-range one, forming a tail on the magnetic phase diagrams. The observed behaviour Ce1-xYxNiGe3 and U1-xThxNiSi2 is characteristic of diluted magnetic alloys. (c) 2012 IOP Publishing Ltd.
We show that for a normal isolated singularity the module of square-integrable regular differential forms of top degree is not integral over the module of K\"ahler differential forms. This is related to the fibre dimension of the Nash transform.
Experiments determining the lifetime of excited electrons in crystalline copper reveal states which cannot be interpreted as Bloch states [S. Ogawa {\it et al.}, Phys. Rev. B {\bf 55}, 10869 (1997)]. In this article we propose a model which explains these states as transient excitonic states in metals. The physical background of transient excitons is the finite time a system needs to react to an external perturbation, in other words, the time which is needed to build up a polarization cloud. This process can be probed with modern ultra-short laser pulses. We calculate the time-dependent density-response function within the jellium model and for real Cu. From this knowledge it is possible within linear response theory to calculate the time needed to screen a positive charge distribution and -- on top of this -- to determine excitonic binding energies. Our results lead to the interpretation of the experimentally detected states as transient excitonic states.