ShantanuT01/DACTYL-Pretraining huggingface dataset:
Dualities of M-theory are used to determine the exact dependence on the coupling constant of the D^6R^4 interaction of the IIA and IIB superstring effective action. Upon lifting to eleven dimensions this determines the coefficient of the D^6R^4 interaction in eleven-dimensional M-theory. These results are obtained by considering the four-graviton two-loop scattering amplitude in eleven-dimensional supergravity compactified on a circle and on a two-torus -- extending earlier results concerning lower-derivative interactions. The torus compactification leads to an interesting SL(2,Z)-invariant function of the complex structure of the torus (the IIB string coupling) that satisfies a Laplace equation with a source term on the fundamental domain of moduli space. The structure of this equation is in accord with general supersymmetry considerations and immediately determines tree-level and one-loop contributions to D^6R^4 in perturbative IIB string theory that agree with explicit string calculations, and two-loop and three-loop contributions that have yet to be obtained in string theory. The complete solution of the Laplace equation contains infinite series' of single D-instanton and double D-instanton contributions, in addition to the perturbative terms. General considerations of the higher loop diagrams of eleven-dimensional supergravity suggest extensions of these results to interactions of higher order in the low energy expansion.
This paper studies the lower bound for the blow-up time $T^{*}$ of the heat equation $u_t=\Delta u$ in a bounded convex domain $\Omega$ in $\mathbb{R}^{N}(N\geq 2)$ with positive initial data $u_{0}$ and a local nonlinear Neumann boundary condition: the normal derivative $\partial u/\partial n=u^{q}$ on partial boundary $\Gamma_1\subseteq\partial\Omega$ for some $q>1$, while $\partial u/\partial n=0$ on the other part. For any $\alpha<\frac{1}{N-1}$, we obtain a lower bound for $T^{*}$ which is of order $|\Gamma_{1}|^{-\alpha}$ as $|\Gamma_{1}|\rightarrow 0^{+}$, where $|\Gamma_{1}|$ represents the surface area of $\Gamma_{1}$. As $|\Gamma_{1}|\rightarrow 0^{+}$, this result significantly improves the previous lower bound $\ln\big(|\Gamma_1|^{-1}\big)$ and is almost optimal in dimension $N=2$, since the existing upper bound is of order $|\Gamma_{1}|^{-1}$ as $|\Gamma_{1}|\rightarrow 0^{+}$. In addition, the optimal asymptotic order of the lower bound for $T^{*}$ on $q$ (as $q\rightarrow 1^{+}$) and on $M_{0}$ (as $M_{0}\rightarrow 0^{+}$) are obtained, where $M_{0}$ denotes the maximum of $u_{0}$.
The Chiral Quark-Soliton model provides the quark and antiquark substructure of the nucleon, which is embedded in nuclear matter. This provides a new way to asses the effects of the nuclear medium on the nucleon. We calculate nuclear binding and saturation, describe the European Muon Collaboration (EMC) effect consistently with Drell-Yan experiments, and predict modifications to the polarized parton distributions. We also calculate the electromagnetic form factors of a bound proton, and find significant modifications of the electromagnetic form factors in the nuclear environment. In every case, the properties of the sea of quark-antiquark pairs in the nucleon are very important, and serve to mitigate the valence quark effect. The changes in the sea quarks when the nucleon is immersed in the nuclear medium are the primary mode by which consistency is maintained with experimental constraints (Drell-Yan data, magnetic moment), while still maintaining a significant effect needed to explain the deep inelastic scattering and polarization transfer data.
Amplification of optical or microwave fields is often achieved by strongly driving a medium to induce population inversion such that a weak probe can be amplified through stimulated emission. Here we strongly couple a superconducting qubit, an artificial atom, to the field in a semi-infinite waveguide. When driving the qubit strongly on resonance such that a Mollow triplet appears, we observe a 7\% amplitude gain for a weak probe at frequencies in-between the triplet. This amplification is not due to population inversion, neither in the bare qubit basis nor in the dressed-state basis, but instead results from a four-photon process that converts energy from the strong drive to the weak probe. We find excellent agreement between the experimental results and numerical simulations without any free fitting parameters. The device demonstrated here may have applications in quantum information processing and quantum-limited measurements.
We present new observations of near-infrared molecular hydrogen (H2) line emission in a sample of 18 Class I and flat-spectrum low mass protostars, primarily in the Tau- Aur and {\rho} Oph dark clouds. The line emission is extended by up to several arcseconds (several hundred AU) for most objects, and there is little night-to-night variation in line strength coincident with the continuum point source. Flux ratios of H2 v = 2 - 1 S(1) and v = 1 - 0 S(1) lines are consistent with this emission arising in jets or winds in many objects. However, most objects have only small offsets (under 10 km s-1) between their H2 and photospheric radial velocities. No objects have line ratios which are clearly caused solely by UV excitation, but the H2 emission of several objects may be caused by UV or X-ray excitation in the presence of circumstellar dust. There are several objects in the sample whose observed velocities and line fluxes suggest quiescent, non-mechanical origins for their molecular hydrogen emissions. Overall we find the H2 emission properties of these protostars to be similar to the T Tauri stars studied in previous surveys.
We study the non-radial oscillations of relativistic neutron stars, in particular the (fundamental) f-modes, which are believed to be the most relevant for the gravitational wave emission of perturbed isolated stars. The expected frequencies of the f-modes are compared to the sensitivity range of Mario Schenberg, the Brazilian gravitational wave spherical detector.
We discuss entanglement evolution of a multi-qubit system when one of its qubits is subjected to a general noisy channel. For such a system, an evolution equation of entanglement for a lower bound for multi-qubit concurrence is derived. Using this evolution equation, the entanglement dynamics of an initially mixed three-qubit state composed of a GHZ and a W state is analyzed if one of the qubits is affected by a phase, an amplitude or a generalized amplitude damping channel.
We investigate the interplay of many-body and band structure effects of interacting Weyl semimetals (WSM). Attractive and repulsive Hubbard interactions are studied within a model for a time-reversal-breaking WSM with tetragonal symmetry, where we can approach the limit of weakly coupled planes and coupled chains by varying the hopping amplitudes. Using a slab geometry, we employ the variational cluster approach to describe the evolution of WSM Fermi arc surface states as a function of interaction strength. We find spin and charge density wave instabilities which can gap out Weyl nodes. We identify scenarios where the bulk Weyl nodes are gapped while the Fermi arcs still persist, hence realizing a quantum anomalous Hall state.
Type-I X-ray burst oscillations are powered by thermonuclear released on the neutron star (NS) surface in low mass X-ray binaries (LMXBs), where the burst oscillation frequencies are close to the NS spin rates. In this work, we report the detection of oscillation at 584.65 Hz during the cooling tail of a type-I X-ray bursts observed from the accreting NS LMXB 4U~1730--22 in 2022 March 20, by the \textit{ Neutron star Interior Composition Explorer} (\textit{NICER}) telescope. The oscillation signal showed a strong Leahy power, $P_{\rm m}\sim54.04$, around 584.65 Hz, which has single trial and multiple trials confidence levels of $7.05\sigma$ and $4.78\sigma$, respectively. The folded pulse profile of the oscillation in the 0.2--10 keV band showed a sinusoidal shape with the fraction amplitude rms of $(12.5\pm1.8)\%$. We found the oscillation frequency showed insignificant upward drifting, i.e., less than 0.3 Hz, during the cooling tail, similar as the behavior appearing in accreting millisecond X-ray pulsars (AMXP), and indicate the source could be an AMXP spinning at 1.71 ms.
In this work, the nucleation and growth mechanism of aluminum oxide (Al2O3) in the early stages of the direct atomic layer deposition (ALD) on monolayer epitaxial graphene (EG) on silicon carbide (4H-SiC) has been investigated by atomic force microscopy (AFM) and Raman spectroscopy. Contrary to what is typically observed for other types of graphene, a large and uniform density of nucleation sites was observed in the case of EG and ascribed to the presence of the buffer layer at EG/SiC interface. The deposition process was characterized by Al2O3 island growth in the very early stages, followed by the formation of a continuous Al2O3 film (2.4 nm thick) after only 40 ALD cycles due to the islands coalescence, and subsequent layer-by-layer growth. Raman spectroscopy analyses showed low impact of the ALD process on the defects density and doping of EG. The EG strain was also almost unaffected by the deposition in the regime of island growth and coalescence, whereas a significant increase was observed after the formation of a compact Al2O3 film. The obtained results can have important implications for device applications of epitaxial graphene requiring the integration of ultra-thin high-k insulators.
Classical novae are powered by thermonuclear runaways that occur on the white dwarf component of close binary systems. During these violent stellar events, whose energy release is only exceeded by gamma-ray bursts and supernova explosions, about 10-4 10-5 Msun of material is ejected into the interstellar medium. Because of the high peak temperatures attained during the explosion, Tpeak ~ (1-4)x10+8 K, the ejecta are enriched in nuclear-processed material relative to solar abundances, containing significant amounts of 13C, 15N, and 17O and traces of other isotopes. The origin of these metal enhancements observed in the ejecta is not wellknown and has puzzled theoreticians for about 40 years. In this paper, we present new 2-D simulations of mixing at the core-envelope interface. We show that Kelvin-Helmholtz instabilities can naturally lead to self-enrichment of the solar-like accreted envelopes with material from the outermost layers of the underlying white dwarf core, at levels that agree with observations.
We consider the problem of determining an unaccessible part of the boundary of a conductor by mean of thermal measurements. We study a problem of corrosion where a Robin type condition is prescribed on the damaged part and we prove logarithmic stability estimate.
Spin transport of indirect excitons in GaAs/AlGaAs coupled quantum wells was observed by measuring the spatially resolved circular polarization of exciton emission. Exciton spin transport over several microns originates from a long spin relaxation time and long lifetime of indirect excitons.
Facial expression recognition (FER) is a topic attracting significant research in both psychology and machine learning with a wide range of applications. Despite a wealth of research on human FER and considerable progress in computational FER made possible by deep neural networks (DNNs), comparatively less work has been done on comparing the degree to which DNNs may be comparable to human performance. In this work, we compared the recognition performance and attention patterns of humans and machines during a two-alternative forced-choice FER task. Human attention was here gathered through click data that progressively uncovered a face, whereas model attention was obtained using three different popular techniques from explainable AI: CAM, GradCAM and Extremal Perturbation. In both cases, performance was gathered as percent correct. For this task, we found that humans outperformed machines quite significantly. In terms of attention patterns, we found that Extremal Perturbation had the best overall fit with the human attention map during the task.
The Large Area Telescope on board the Fermi Gamma-ray Space Telescope detected a strong gamma-ray flare on 2011 May 15 from a source identified as 4C 49.22, a flat spectrum radio quasar also known as S4 1150+49. This blazar, characterised by a prominent radio-optical-X-ray jet, was in a low gamma-ray activity state during the first years of Fermi observations. Simultaneous observations during the quiescent, outburst and post-flare gamma-ray states were obtained by Swift, Planck and optical-IR-radio telescopes (INAOE, Catalina CSS, VLBA, Metsahovi). The flare is observed from microwave to X-ray bands with correlated variability and the Fermi, Swift and Planck data for this FSRQ show some features more typical of BL Lac objects, like the synchrotron peak in the optical band that outshines the thermal blue-bump emission, and the X-ray spectral softening. Multi-epoch VLBA observations show the ejection of a new component close in time with the GeV gamma-ray flare. The radio-to-gamma-ray spectral energy distribution is modeled and fitted successfully for the outburst and the post-flare epochs using either a single flaring blob with two emission processes (synchrotron self Compton, and external-radiation Compton), and a two-zone model with SSC-only mechanism.
We study the CP-violating terms of the spin-spin correlations in chargino production e+e- -> chi^+/-_1 chi^-/+_2, and their subsequent two-body decays into sneutrinos plus leptons. We propose novel CP-sensitive observables with the help of T-odd products of the spin-spin terms. These terms depend on the polarizations of both charginos, with one polarization perpendicular to the production plane. We identify two classes of CP-sensitive observables; one requires the reconstruction of the production plane, the other not. Our framework is the Minimal Supersymmetric Standard Model with complex parameters.
We study a two-dimensional tight-binding lattice for excitons with on-site disorder, coupled to a thermal environment at infinite temperature. The disorder acts to localise an exciton spatially, while the environment generates dynamics which enable exploration of the lattice. Although the steady state of the system is trivially uniform, we observe a rich dynamics and uncover a dynamical phase transition in the space of temporal trajectories. This transition is identified as a localisation in the dynamics generated by the bath. We explore spatial features in the dynamics and employ a generalisation of the inverse participation ratio to deduce an ergodic timescale for the lattice.
Two giant plasma lobes, known as the Fermi Bubbles, extend 10 kpc above and below the Galactic Center. Since their discovery in X-rays in 2003 (and in gamma-rays in 2010), the Bubbles have been recognized as a new morphological feature of our Galaxy and a striking example of energetic feedback from the nuclear region. They remain the subject of intense research and their origin via AGN activity or nuclear star formation is still debated. While imaging at gamma-ray, X-ray, microwave, and radio wavelengths has revealed their morphology and energetics, spectroscopy at radio and UV wavelengths has recently been used to study the kinematics and chemical abundances of outflowing gas clouds embedded in the Bubbles (the nuclear wind). Here we identify the scientific themes that have emerged from the spectroscopic studies, determine key open questions, and describe further observations needed in the next ten years to characterize the basic physical conditions in the nuclear wind and its impact on the rest of the Galaxy. Nuclear winds are ubiquitous in galaxies, and the Galactic Center represents the best opportunity to study the constitution and structure of a nuclear wind in close detail.
Showing that the Ramsey property holds for a class of finite structures can be an extremely challenging task and a slew of sophisticated methods have been proposed in literature. In this paper we propose a new strategy to show that a class of structures has the Ramsey property. The strategy is based on a relatively simple result in category theory and consists of establishing a pre-adjunction between the category of structures which is known to have the Ramsey property, and the category of structures we are interested in. This strategy was implicitly used already in 1981 by H.J. Pr\"omel and B. Voigt in their proof of the Ramsey property for the class of finite linearly ordered graphs. We demonstrate the applicability of this strategy by providing short proofs of three important well known results: we show the Ramsey property for the category of all finite linearly ordered posets with embeddings, for the category of finite convexly ordered ultrametric spaces with embeddings, and for the category of all finite linearly ordered metric spaces (rational metric spaces) with embeddings.
Let X be a general complex Fano threefold of genus 8. We prove that the moduli space of rank two semistable sheaves on X with Chern numbers c_1=1, c_2=6 and c_3=0 is isomorphic to the Fano surface F(X) of conics on X. Inside F(X), the non-locally free sheaves are parameterized by a smooth curve of genus 26 isomorphic to the base of the family of lines on X.
Stellar evolution theory predicts that asymptotic giant branch stars undergo a series of short thermal pulses that significantly change their luminosity and mass on timescales of hundreds to thousands of years. Secular changes in these stars resulting from thermal pulses can be detected as measurable changes in period if the star is undergoing Mira pulsations. The American Association of Variable Star Observers (AAVSO) International Database currently contains visual data for over 1500 Mira variables. Light curves for these stars span nearly a century in some cases, making it possible to study the secular evolution of the pulsation behavior on these timescales. In this paper, we present the results of our study of period change in 547 Mira variables using data from the AAVSO. We find non-zero rates of period change, dlnP/dt, at the 2-sigma significance level in 57 of the 547 stars, at the 3-sigma level in 21 stars, and at the level of 6-sigma or greater in eight of the 547. The latter eight stars have been previously noted in the literature, and our derived rates of period changes largely agree with published values. The largest and most statistically significant dlnP/dt are consistent with the rates of period change expected during thermal pulses on the AGB. A number of other stars exhibit non-monotonic period changes on decades-long timescales, the cause of which is not yet known.
The correlation, found in nearby galaxies, between black hole mass and stellar bulge mass implies that the formation of these two components must be related. Here we report submillimeter photometry of eight x--ray absorbed active galactic nuclei which have luminosities and redshifts characteristic of the sources that produce the bulk of the accretion luminosity in the universe. The four sources with the highest redshifts are detected at 850 microns, with flux densities between 5.9 and 10.1 milliJanskies, and hence are ultraluminous infrared galaxies. Interpreting the submillimeter flux as emission from dust heated by starbursts, these results suggest that the majority of stars in spheroids were formed at the same time as their central black holes built up most of their mass by accretion, accounting for the observed demography of massive black holes in the local universe. The skewed rate of submillimeter detection with redshift is consistent with a high redshift epoch of star formation in radio quiet active galactic nuclei, similar to that seen in radio galaxies.
Let $r$ be a positive integer, $h(X)\in\Bbb F_{q^2}[X]$, and $\mu_{q+1}$ be the subgroup of order $q+1$ of $\Bbb F_{q^2}^*$. It is well known that $X^rh(X^{q-1})$ permutes $\Bbb F_{q^2}$ if and only if $\text{gcd}(r,q-1)=1$ and $X^rh(X)^{q-1}$ permutes $\mu_{q+1}$. There are many ad hoc constructions of permutation polynomials of $\Bbb F_{q^2}$ of this type such that $h(X)^{q-1}$ induces monomial functions on the cosets of a subgroup of $\mu_{q+1}$. We give a general construction that can generate, through an algorithm, {\em all} permutation polynomials of $\Bbb F_{q^2}$ with this property, including many which are not known previously. The construction is illustrated explicitly for permutation binomials and trinomials.
Using the Polyakov-Nambu-Jona-Lasinia (PNJL) model, we study the spinodal instability of a baryon-rich quark-gluon plasma in the linear response theory. We find that the spinodal unstable region in the temperature and density plane shrinks with increasing wave number of the unstable mode and is also reduced if the effect of Polyakov loop is not included. In the small wave number or long wavelength limit, the spinodal boundaries in both cases of with and without the Polyakov loop coincide with those determined from the isothermal spinodal instability in the thermodynamic approach. Also, the vector interactions among quarks is found to suppress unstable modes of all wave numbers. Moreover, the growth rate of unstable modes initially increases with the wave number but is reduced when the wave number becomes large. Including the collisional effect from quark scattering via the linearized Boltzmann equation, we further find that it decreases the growth rate of unstable modes of all wave numbers. Relevance of these results to relativistic heavy ion collisions is discussed.
Recently Kleides et al [IJMPA \textbf{11}, 1697 (2008)] found a growing rate for magnetic fields in ideal plasma cosmologies by making use of general relativistic Friedmann model. This growth rate of $\frac{{\delta}B}{B}\sim{{(\frac{t}{t_{H}})}^{{1/4}}}$ indicates the presence of a slow dynamo in the universe. More recently Hasseein [Phys Plasmas (2009)] have also investigate Beltrami magnetic fields in plasma universe. Here general relativistic(GR) MHD dynamo equation, recently given by Clarkson and Marklund [Monthly Not Roy Astr Soc (2005)] is used to investigate the relation between collapsing of the isotropic universe and dynamo action in ideal and dissipative cosmologies. Dynamo action can be supported in these phases as long as the kinetic helicity overcomes universe diffusion effects. A cosmological Beltrami flow in 3D shows that helicities may act constructively on gravitational collapse and enhance dynamo action. A slow dynamo action is found in the static Einstein universe also filled with a Beltrami flow. A rotating, shear-free Bianchi type-IX universe, is obtained, by magnetically perturbing the Einstein static model inducing slow dynamos in the model. Magnetic field growth of $B\approx{t}$, which is stronger than Harrison estimate of $B\approx{t^{{4/5}}}$ is obtained. CMB limits on the expansion, global rotation and slow dynamos are given and a less slower dynamo than the one obtained by Kleides et al, is found with $\frac{{\delta}B}{B}\sim{|{\Theta}|t}$.
We report the site-specific probing of charge-transfer dynamics in a prototype system for organic photovoltaics (OPV) by picosecond time-resolved X-ray photoelectron spectroscopy. A layered system consisting of approximately two monolayers of C$_{60}$ deposited on top of a thin film of Copper-Phthalocyanine (CuPC) is excited by an optical pump pulse and the induced electronic dynamics are probed with 590 eV X-ray pulses. Charge transfer from the electron donor (CuPC) to the acceptor (C$_{60}$) and subsequent charge carrier dynamics are monitored by recording the time-dependent C 1$s$ core level photoemission spectrum of the system. The arrival of electrons in the C$_{60}$ layer is readily observed as a completely reversible, transient shift of the C$_{60}$ associated C 1$s$ core level, while the C 1$s$ level of the CuPC remains unchanged. The capability to probe charge transfer and recombination dynamics in OPV assemblies directly in the time domain and from the perspective of well-defined domains is expected to open additional pathways to better understand and optimize the performance of this emerging technology.