ShantanuT01/DACTYL-Pretraining huggingface dataset:
A systematic study of the ground state properties of transitional nuclei W, Os and Pt is conducted with the help of Skyrme Hartree-Fock-Bogoliubov theory. Different Skyrme interactions are employed in the study. Two different bases, harmonic oscillator and transformed harmonic oscillator, are used in our investigation. 2n-separation energy, charge radii, neutron and proton rms radii, neutron skin thickness and deformation parameter have been estimated. The results obtained are in good agreement with the available experimental values.
We investigate to what extent the theory of N\'eron models of jacobians and of abel-jacobi maps extends to relative curves over base schemes of dimension greater than 1. We give a necessary and sufficient criterion for the existence of a N\'eron model. We use this to show that, in general, N\'eron models do not exist even after making a modification or even alteration of the base. On the other hand, we show that N\'eron models do exist outside some codimension-2 locus.
We consider the sums $T_N=\sum_{n=1}^N F(S_n)$ where $S_n$ is a random walk on $\mathbb Z^d$ and $F:\mathbb Z^d\to \mathbb R$ is a global observable, that is, a bounded function which admits an average value when averaged over large cubes. We show that $T_N$ always satisfies the weak Law of Large Numbers but the strong law fails in general except for one dimensional walks with drift. Under additional regularity assumptions on $F$, we obtain the Strong Law of Large Numbers and estimate the rate of convergence. The growth exponents which we obtain turn out to be optimal in two special cases: for quasiperiodic observables and for random walks in random scenery.
We report a new changing-look quasar, WISE~J105203.55+151929.5 at $z=0.303$, found by identifying highly mid-IR variable quasars in the WISE/NEOWISE data stream. Compared to multi-epoch mid-IR photometry of a large sample of SDSS-confirmed quasars, WISE J1052+1519 is an extreme photometric outlier, fading by more than a factor of two at $3.4$ and $4.6 \mu$m since 2009. Swift target-of-opportunity observations in 2017 show even stronger fading in the soft X-rays compared to the ROSAT detection of this source in 1995, with at least a factor of fifteen decrease. We obtained second-epoch spectroscopy with the Palomar telescope in 2017 which, when compared with the 2006 archival SDSS spectrum, reveals that the broad H$\beta$ emission has vanished and that the quasar has become significantly redder. The two most likely interpretations for this dramatic change are source fading or obscuration, where the latter is strongly disfavored by the mid-IR data. We discuss various physical scenarios that could cause such changes in the quasar luminosity over this timescale, and favor changes in the innermost regions of the accretion disk that occur on the thermal and heating/cooling front timescales. We discuss possible physical triggers that could cause these changes, and predict the multiwavelength signatures that could distinguish these physical scenarios.
Deconfined quantum critical point was proposed as a second-order quantum phase transition between two broken symmetry phases beyond the Landau-Ginzburg-Wilson paradigm. However, numerical studies cannot completely rule out a weakly first-order transition because of strong violations of finite-size scaling. We demonstrate that the fidelity is a simple probe to study deconfined quantum critical point. We study the ground-state fidelity susceptibility close to the deconfined quantum critical point in a spin chain using the large-scale finite-size density matrix renormalization group method. We find that the finite-size scaling of the fidelity susceptibility obeys the conventional scaling behavior for continuous phase transitions, supporting the deconfined quantum phase transition is continuous. We numerically determine the deconfined quantum critical point and the associated correlation length critical exponent from the finite-size scaling theory of the fidelity susceptibility. Our results are consistent with recent results obtained directly from the matrix product states for infinite-size lattices using others observables. Our work provides a useful probe to study critical behaviors at deconfined quantum critical point from the concept of quantum information.
We study the mass accretion histories (MAHs) and density profiles of dark matter halos using N-body simulations of self-similar gravitational clustering from scale-free power spectra, $P(k)\propto k^n$. We pay particular attention to the density profile curvature, which we characterize using the shape parameter, $\alpha$, of an Einasto profile. In agreement with previous findings our results suggest that, despite vast differences in their MAHs, the density profiles of virialized halos are remarkably alike. Nonetheless, clear departures from self-similarity are evident: for a given spectral index, $\alpha$ increases slightly but systematically with "peak height", $\nu\equiv\delta_{sc}/\sigma(M,z)$, regardless of mass or redshift. More importantly, however, the "$\alpha-\nu$" relation depends on $n$: the steeper the initial power spectrum, the more gradual the curvature of both the mean MAHs and mean density profiles. These results are consistent with previous findings connecting the shapes of halo mass profiles and MAHs and imply that dark matter halos are not structurally self-similar but, through the merger history, retain a memory of the linear density field from which they form.
Did time begin at a Big Bang? Will the present expansion of the universe last for a finite or infinite time? These questions sound philosophical but are becoming, now in the twenty-first century, central to the scientific study of cosmology. The answers, which should become clarified in the next decade or two, could have profound implications for how we see our own role in the universe. Since the original publication of Stephen Hawking's {\it A Brief History of Time} in 1988, the answers to these questions have progressed as a result of research by the community of active theoretical physicists including myself. To present the underlying ideas requires discussion of a wide range of topics in cosmology, especially the make up of the energy content of the universe. A brief summary of my conclusions, that of three different possibilities concerning the history and future of time, the least likely is the conventional wisdom (time began and will never end) and most likely is a cyclic model (time never begins or ends), is in the short final Chapter which could be read first. To understand the reasoning leading to my conclusions could encourage reading of my entire book. My hope in writing this, my first popular book, is that it will engender reflection about time. Many a non-scientist may already hold a philosophical opinion about whether time begins and ends. This book's aim is to present some recently discovered scientific facts which can focus the reader's consideration of the two short questions in my title.
We analyze the instability of an unpolarized uniform quantum plasma consisting of two oppositely charged fermionic components with varying mass ratios, against charge and spin density waves (CDWs and SDWs). Using density functional theory, we treat each component with the local spin density approximation and a rescaled exchange-correlation functional. Interactions between different components are treated with a mean-field approximation. In both two- and three-dimensions, we find leading unstable CDW modes in the second-order expansion of the energy functional, which would induce the transition to quantum liquid crystals. The transition point and the length of the wave-vector are computed numerically. Discontinuous ranges of the wave-vector are found for different mass ratios between the two components, indicating exotic quantum phase transitions. Phase diagrams are obtained and a scaling relation is proposed to generalize the results to two-component fermionic plasmas with any mass scale. We discuss the implications of our results and directions for further improvement in treating quantum plasmas.
One dimensional (1D) quantum wires exhibit a conductance feature near 0.7 x 2e^2/h in connection with many-body interactions involving the electron spin. With the possibility of exploiting this effect for novel spintronic device applications, efforts have focused on uncovering a complete microscopic theory to explain this conductance anomaly. Here we present conductance calculations based on a simple phenomenological model for a gate-dependent spin gap that are in excellent agreement with experimental data taken on ultra-low-disorder quantum wires. Taken together the phenomenology and experimental data indicate that the 0.7 feature depends strongly on the potential profile of the contact region, where the reservoirs meet the 1D wire. Microscopic explanations that may under-pin the phenomenological description are also discussed.
Let \sigma(n) be the sum of divisors of a positive integer n. Robin's theorem states that the Riemann hypothesis is equivalent to the inequality \sigma(n)<e^\gamma n\log\log n for all n>5040 (\gamma is Euler's constant). It is a natural question in this direction to find a first integer, if exists, which violates this inequality. Following this process, we introduce a new sequence of numbers and call it as extremely abundant numbers. In this paper we show that the Riemann hypothesis is true, if and only if, there are infinitely many of these numbers. Moreover, we investigate some of their properties together with superabundant and colossally abundant numbers.
During five decades astronomers have been puzzled by the presence of strong absorption features including metal lines, observed in the optical and ultraviolet spectra of quasars, signalling in- and outflowing gas winds with relative velocities up to several thousands of km/sec. In particular the location of these winds - close to the quasar, further out in its host galaxy, or in its direct environment - and the possible impact on their surroundings have been issues of intense discussion and uncertainty. Using our Herschel Space Observatory data, we report a tendency for this so-called associated metal absorption to occur along with prodigious star formation in the quasar host galaxy, indicating that the two phenomena are likely to be interrelated, that the gas winds likely occur on the kiloparsec scale and would then have a strong impact on the interstellar medium of the galaxy. This correlation moreover would imply that the unusually high cold dust luminosities in these quasars are connected with ongoing star formation. Given that we find no correlation with the AGN strength, the wind feedback which we establish in these radio-loud objects is most likely associated with their host star formation rather than with their black hole accretion.
This article presents a simple characterization for entangled vectors in a finite dimensional Hilbert space $H$. The characterization is in terms of the coefficients of an expansion of the vector relative to an orthonormal basis for $H$. This simple necessary and sufficient condition contains a restriction and we also present a more complicated condition that is completely general. Although these characterizations apply to bipartite systems, we show that generalizations to multipartite systems are also valid.
A scenario for stabilization of axionic moduli fields in the context of type IIB Calabi-Yau flux compactifications is discussed in detail. We consider the case of a Calabi-Yau orientifold with h^{1,1}_- \neq 0 which allows for the presence of B_2 and C_2-moduli. In an attempt to generalize the KKLT and the Large Volume Scenario, we show that these axions can also be stabilized - some already at tree level, and others when we include perturbative \alpha'-corrections to the Kaehler potential K and nonperturbative D3-instanton contributions to the superpotential W. At last, we comment on the possible influence of worldsheet instantons on the process of moduli stabilization.
Quiescent filaments are usually affected by internal and/or external perturbations triggering oscillations of different kinds. In particular, external large-scale coronal waves can perturb remote quiescent filaments leading to large-amplitude oscillations. Observational reports have indicated that the activation time of oscillations coincides with the passage of a large-scale coronal wavefront through the filament, although the disturbing wave is not always easily detected. Aiming to contribute to understand how -- and to what extent -- coronal waves are able to excite filament oscillations, here we modelled with 2.5 MHD simulations a filament floating in a gravitationally stratified corona disturbed by a coronal shock wave. This simplified scenario results in a two-coupled oscillation pattern of the filament which is damped in a few cycles, enabling a detailed analysis. A parametric study was accomplished varying parameters of the scenario such as height, size and mass of the filament. An oscillatory analysis reveals a general tendency where periods of oscillations, amplitudes and damping times increase with height, whereas filaments of larger radius exhibit shorter periods and smaller amplitudes. The calculation of forces exerted on the filament shows that the main restoring force is the magnetic tension.
Nonzero neutrino masses are required by the existence of flavour oscillations, with values of the order of at least 50 meV. We consider the gravitational clustering of relic neutrinos within the Milky Way, and used the $N$-one-body simulation technique to compute their density enhancement factor in the neighbourhood of the Earth with respect to the average cosmic density. Compared to previous similar studies, we pushed the simulation down to smaller neutrino masses, and included an improved treatment of the baryonic and dark matter distributions in the Milky Way. Our results are important for future experiments aiming at detecting the cosmic neutrino background, such as the Princeton Tritium Observatory for Light, Early-universe, Massive-neutrino Yield (PTOLEMY) proposal. We calculate the impact of neutrino clustering in the Milky Way on the expected event rate for a PTOLEMY-like experiment. We find that the effect of clustering remains negligible for the minimal normal hierarchy scenario, while it enhances the event rate by 10 to 20% (resp. a factor 1.7 to 2.5) for the minimal inverted hierarchy scenario (resp. a degenerate scenario with 150 meV masses). Finally we compute the impact on the event rate of a possible fourth sterile neutrino with a mass of 1.3 eV.
We consider the standard model (SM) quark flavor sector. We study its structure in a spurionic, symmetry oriented approach. The SM picture of flavor and CP violation is now experimentally verified, hence strong bounds on beyond the SM flavor structure follow. We show how to parametrically derive such bounds, in a model independent manner, via minimal flavor violation power counting. This min-review summarizes lectures given at the ISSCSMB '08 international school. It aims to give basic tools to understand how flavor and CP violation occur in the SM and its extensions. It should be particularly useful for non-expert students who have mastered other aspects of the SM dynamics.
The most general model-independent analysis of the rare $B$ decay, $\Bsll$, is presented. There are ten independent local four-Fermi interactions which may contribute to this process. The branching ratio, the forward-backward asymmetry, and the double differential rate are written as functions of the Wilson coefficients of the ten operators. We also study the correlation between the branching ratio and the forward-backward asymmetry by changing each coefficient. This procedure tells us which types of operator contribute to the process, and it will be very useful to pin down new physics systematically, once we have the experimental data with high statistics and the deviation from the Standard Model is found.
Merger-remnant galaxies with kpc-scale separation dual active galactic nuclei (AGNs) should be widespread as a consequence of galaxy mergers and triggered gas accretion onto supermassive black holes, yet very few dual AGNs have been observed. Galaxies with double-peaked narrow AGN emission lines in the Sloan Digital Sky Survey are plausible dual AGN candidates, but their double-peaked profiles could also be the result of gas kinematics or AGN-driven outflows and jets on small or large scales. To help distinguish between these scenarios, we have obtained spatial profiles of the AGN emission via follow-up long-slit spectroscopy of 81 double-peaked narrow-line AGNs in SDSS at 0.03 < z < 0.36 using Lick, Palomar, and MMT Observatories. We find that all 81 systems exhibit double AGN emission components with ~kpc projected spatial separations on the sky, which suggests that they are produced by kpc-scale dual AGNs or kpc-scale outflows, jets, or rotating gaseous disks. In addition, we find that the subsample (58%) of the objects with spatially compact emission components may be preferentially produced by dual AGNs, while the subsample (42%) with spatially extended emission components may be preferentially produced by AGN outflows. We also find that for 32% of the sample the two AGN emission components are preferentially aligned with the host galaxy major axis, as expected for dual AGNs orbiting in the host galaxy potential. Our results both narrow the list of possible physical mechanisms producing the double AGN components, and suggest several observational criteria for selecting the most promising dual AGN candidates from the full sample of double-peaked narrow-line AGNs. Using these criteria, we determine the 17 most compelling dual AGN candidates in our sample.
Magnetic fields lines are trapped in black hole event horizons by accreting plasma. If the trapped field lines are lightly loaded with plasma, then their motion is controlled by their footpoints on the horizon and thus by the spin of the black hole. In this paper, we investigate the boundary layer between lightly loaded polar field lines and a dense, equatorial accretion flow. We present an analytic model for aligned prograde and retrograde accretion systems and argue that there is significant shear across this "jet-disk boundary" at most radii for all black hole spins. Specializing to retrograde aligned accretion, where the model predicts the strongest shear, we show numerically that the jet-disk boundary is unstable. The resulting mixing layer episodically loads plasma onto trapped field lines where it is heated, forced to rotate with the hole, and permitted to escape outward into the jet. In one case we follow the mass loading in detail using Lagrangian tracer particles and find a time-averaged mass-loading rate ~ 0.01 Mdot.
In this talk I shall introduce our recent works on general pairing interactions and pair truncation approximations for fermions in a single-j shell, including the spin zero dominance, features of eigenvalues of fermion systems in a single-j shell interacting by a $J-$pairing interaction.
A phylogenetic network is a graph-theoretical tool that is used by biologists to represent the evolutionary history of a collection of species. One potential way of constructing such networks is via a distance-based approach, where one is asked to find a phylogenetic network that in some way represents a given distance matrix, which gives information on the evolutionary distances between present-day taxa. Here, we consider the following question. For which~$k$ are unrooted level-$k$ networks uniquely determined by their distance matrices? We consider this question for shortest distances as well as for the case that the multisets of all distances is given. We prove that level-$1$ networks and level-$2$ networks are reconstructible from their shortest distances and multisets of distances, respectively. Furthermore we show that, in general, networks of level higher than~$1$ are not reconstructible from shortest distances and that networks of level higher than~$2$ are not reconstructible from their multisets of distances.
We present cosmological results from the final galaxy clustering data set of the Baryon Oscillation Spectroscopic Survey, part of the Sloan Digital Sky Survey III. Our combined galaxy sample comprises 1.2 million massive galaxies over an effective area of 9329 deg^2 and volume of 18.7 Gpc^3, divided into three partially overlapping redshift slices centred at effective redshifts 0.38, 0.51, and 0.61. We measure the angular diameter distance DM and Hubble parameter H from the baryon acoustic oscillation (BAO) method after applying reconstruction to reduce non-linear effects on the BAO feature. Using the anisotropic clustering of the pre-reconstruction density field, we measure the product DM*H from the Alcock-Paczynski (AP) effect and the growth of structure, quantified by f{\sigma}8(z), from redshift-space distortions (RSD). We combine measurements presented in seven companion papers into a set of consensus values and likelihoods, obtaining constraints that are tighter and more robust than those from any one method. Combined with Planck 2015 cosmic microwave background measurements, our distance scale measurements simultaneously imply curvature {\Omega}_K =0.0003+/-0.0026 and a dark energy equation of state parameter w = -1.01+/-0.06, in strong affirmation of the spatially flat cold dark matter model with a cosmological constant ({\Lambda}CDM). Our RSD measurements of f{\sigma}_8, at 6 per cent precision, are similarly consistent with this model. When combined with supernova Ia data, we find H0 = 67.3+/-1.0 km/s/Mpc even for our most general dark energy model, in tension with some direct measurements. Adding extra relativistic species as a degree of freedom loosens the constraint only slightly, to H0 = 67.8+/-1.2 km/s/Mpc. Assuming flat {\Lambda}CDM we find {\Omega}_m = 0.310+/-0.005 and H0 = 67.6+/-0.5 km/s/Mpc, and we find a 95% upper limit of 0.16 eV/c^2 on the neutrino mass sum.
Quasi-periodic oscillation (QPO) detected in the X-ray radiation of black hole X-ray binaries (BHXBs) is thought to originate from dynamical processes in the close vicinity of the black holes (BHs), and thus carries important physical information therein. Such a feature is extremely rare in active galactic nuclei (AGNs) with supermassive BHs. Here we report on the detection of a possible X-ray QPO signal with a period of 3800\,s at a confidence level $>99.99\%$ in the narrow-line Seyfert 1 galaxy (NLS1) 1H~0707-495 in one data set in 0.2-10\,keV taken with {\it XMM-Newton}. The statistical significance is higher than that of most previously reported QPOs in AGNs. The QPO is highly coherent (quality factor $Q=\nu/\Delta\nu \geqslant 15$) with a high rms fractional variability ($\sim15\%$). A comprehensive analysis of the optical spectra of this AGN is also performed, yielding a central BH mass $5.2\times10^6\,M_{\odot}$ from the broad emission lines based on the scaling relation. The QPO follows closely the known frequency-BH mass relation, which spans from stellar-mass to supermassive BHs. The absence of the QPO in other observations of the object suggests it a transient phenomenon. We suggest that the (high-frequency) QPOs tend to occur in highly accreting BH systems, from BHXBs to supermassive BHs. Future precise estimation of the BH mass may be used to infer the BH spin from the QPO frequency.
In this paper we show that it is possible to switch the spin polarization of the photocurrent signal obtained from a single self-assembled quantum dot photodiode under the effect of elliptically polarized light by just increasing the light intensity. In the nonlinear mechanism treated here, intense elliptically polarized light creates an effective exchange interaction between the exciton spin states through the biexciton state. This effect can be used as a dynamical switch to invert the spin-polarization of the extracted photocurrent. We further show that the effect persists in realistic ensembles of dots, making this a powerful technique to dynamically generate spin-polarized electrons.