Miracle-dz/UniFAR-FTUs huggingface dataset:
Constraints on string networks with junctions

We consider the constraints on string networks with junctions in which the strings may all be different, as may be found, for example, in a network of (p,q) cosmic superstrings. We concentrate on three aspects of junction dynamics. First we consider the propagation of small-amplitude waves across a static three-string junction. Then, generalizing our earlier work, we determine the kinematic constraints on two colliding strings with different tensions. As before, the important conclusion is that strings do not always reconnect with a third string; they can pass straight through one another (or in the case of non-Abelian strings become stuck in an X configuration), the constraint depending on the angle at which the strings meet, on their relative velocity, and on the ratios of the string tensions. For example, if the two colliding strings have equal tensions, then for ultrarelativistic initial velocities they pass through one another. However, if their tensions are sufficiently different they can reconnect. Finally, we consider the global properties of junctions and strings in a network. Assuming that, in a network, the incoming waves at a junction are independently randomly distributed, we determine the root-mean-square (r.m.s.) velocities of strings and calculate the average speed at whichmore » a junction moves along each of the three strings from which it is formed. Our findings suggest that junction dynamics may be such as to preferentially remove the heavy strings from the network leaving a network of predominantly light strings. Furthermore the r.m.s. velocity of strings in a network with junctions is smaller than 1/{radical}(2), the result for conventional Nambu-Goto strings without junctions in Minkowski space-time. « less
3D spinfoam quantum gravity: matter as a phase of the group field theory

An effective field theory for matter coupled to three-dimensional quantum gravity was recently derived in the context of spinfoam models (Freidel and Livine 2006 Phys. Rev. Lett. 96 221301 (Preprint hep-th/0512113)). In this paper, we show how this relates to group field theories and generalized matrix models. In the first part, we realize that the effective field theory can be recast as a matrix model where couplings between matrices of different sizes can occur. In a second part, we provide a family of classical solutions to the three-dimensional group field theory. By studying perturbations around these solutions, we generate the dynamics of the effective field theory. We identify a particular case which leads to the action of Freidel and Livine (2006 Phys. Rev. Lett. 96 221301 (Preprint hep-th/0512113)) for a massive field living in a flat non-commutative spacetime. The most general solutions lead to field theories with nonlinear redefinitions of the momentum which we propose to interpret as living on curved spacetimes. We conclude by discussing the possible extension to four-dimensional spinfoam models.
On-resonance material fast light

We theoretically revisit the problem of the propagation of coherent light pulses through a linear medium when the carrier frequency of the pulses coincides with the minimum of a narrow dip in the medium transmission. Considering realistic contrasts between the maximum and minimum transmission of the medium and incident pulses of strictly finite duration, we combine temporal and spectral approaches to obtain analytical expressions of the transmitted pulse that reproduce the main features of the exact numerical solutions derived by fast Fourier transform. A special attention is paid to the advance of the pulse maximum over that of a pulse covering the same distance in vacuum and the ratio of this advance to the pulse duration (fractional advance) is optimized.
Complex response and polariton-like dispersion splitting in periodic metal nanoparticle chains

We show that guiding of optical signals in chains of metal nanoparticles is subject to a surprisingly complex dispersion relation. Retardation causes the dispersion relation to split in two anticrossing branches, as common for polaritons. While huge radiation losses occur above the light line, just below the light line the micron-sized loss lengths are much longer than expected. The anticrossing allows to create highly localized energy distributions in finite arrays that can be tuned via the illumination wavelength. Our results apply to all linear chains of coupled resonant scatterers.
Redshift-Distance Survey of Early-Type Galaxies. I. Sample Selection, Properties, and Completeness

This is the first in a series of papers describing the recently completed all-sky redshift-distance survey of Early-type NEARby galaxies (ENEAR) carried out for peculiar velocity analysis. The sample is divided into two parts and consists of 1607 elliptical and lenticular galaxies with cz ≤ 7000 km s-1 and with blue magnitudes brighter than mB = 14.5 (ENEARm) and of galaxies in clusters (ENEARc). Galaxy distances based on the Dn-σ and fundamental plane (FP) relations are now available for 1359 and 1107 ENEARm galaxies, respectively, with roughly 80% based on new data gathered by our group. The Dn-σ and FP template distance relations are derived by combining 569 and 431 galaxies in 28 clusters, respectively, of which about 60% are based on our new measurements. To date the ENEAR survey has accumulated 2200 R-band images yielding photometric parameters for 1398 galaxies and 2300 spectra yielding 1745 measurements of central velocity dispersions and spectral line indices for 1210 galaxies. In addition, there are some 1834 spectra of early-type galaxies available in the Southern Sky Redshift Survey (SSRS+SSRS2) database, out of which roughly 800 galaxies yield high-quality measurements of velocity dispersions and spectral line indices, bringing the total number of galaxies with available spectral information to about 2000. Combined with measurements publicly available, a catalog has been assembled comprising ∼4500 measurements of central velocity dispersions for about 2800 galaxies, ∼3700 measurements of photometric parameters for about 2000 galaxies, and distances for about 1900 galaxies. This extensive database provides information on galaxies with multiple observations from different telescope/instrument configurations and from different authors. These overlapping data are used to derive relations to transform all available measurements into a common system, thereby ensuring the homogeneity of the database. The ENEARm redshift-distance survey extends the earlier work of the 7S and the recent Tully-Fisher surveys sampling a comparable volume. In subsequent papers of this series we intend to use the ENEAR sample by itself or in combination with the I-band field spiral (SFI) Tully-Fisher survey to analyze the properties of the local peculiar velocity field and to test how sensitive the results are to the different sampling of the galaxy distribution and to the distance relation used. We also anticipate that the homogeneous database assembled will be used for a variety of other applications and serve as a benchmark for similar studies at high redshift.
A numerical study of non-Gaussianity in the curvaton scenario

We study the curvaton scenario using gauge-invariant second order perturbation theory and solving the governing equations numerically. Focusing on large scales we calculate the non-linearity parameter fNL in the two-fluid curvaton model and compare our results with previous analytical studies employing the sudden decay approximation. We find good agreement of the two approaches for large curvaton energy densities at curvaton decay, Ωσdec, but significant differences of up to 10% for small Ωσdec.
Strain-induced incommensurate phases in hexagonal manganites

An incommensurate phase refers to a solid state in which the period of a superstructure is incommensurable with the primitive unit cell. Recently the incommensurate phase is induced by applying an in-plane strain to hexagonal manganites, which demonstrates single chiral modulation of six domain variants. Here we employ Landau theory in combination with the phase-field method to investigate the incommensurate phase in hexagonal manganites. It is shown that the equilibrium wave length of the incommensurate phase is determined by temperature and the magnitude of the applied strain, and a temperature-strain phase diagram is constructed for the stability of the incommensurate phase. Temporal evolution of domain structures reveals that the applied strain not only produces the force pulling the vortices and anti-vortices in opposite directions, but also results in the creation and annihilation of vortex-antivortex pairs.
D-brane probes on La,b,c superconformal field theories

We study supersymmetric embeddings of D-brane probes of different dimensionality in the AdS5 × La,b,c background of type IIB string theory. In the case of D3-branes, we recover the known three-cycles dual to the dibaryonic operators of the gauge theory and we also find a new family of supersymmetric embeddings. Supersymmetric configurations of D5-branes, representing fractional branes, and of spacetime filling D7-branes (which can be used to add flavor) are also found. Stable non supersymmetric configurations corresponding to fat strings and domain walls are found as well.
Structure formation in the Deser-Woodard nonlocal gravity model: a reappraisal

In this work, we extend previous analyses of the structure formation in the f(□−1R) model of nonlocal gravity proposed by Deser and Woodard (DW), which reproduces the background expansion of ΛCDM with no need of a cosmological constant nor of any dimensional constant beside Newton's one. A previous analysis based on redshift-space distortions (RSD) data concluded that the model was ruled out. In this work we revisit the issue and find that, when recast in a localized model, the DW model is not ruled out and actually gives a better fit to RSD data than ΛCDM. In fact, the DW model presents a suppressed growth of matter perturbations with respect to ΛCDM and a slightly lower value of σ8, as favored by observations. We also produce analytical approximations of the two modified gravity functions, i.e. the anisotropic stress η and the relative change of Newton's constant Y, and of fσ8(z) as a function of redshift. Finally, we also show how much the fit depends on initial conditions when these are generalized with respect to a standard matter-dominated era.
The Crab pulsar: ion-proton plasma and high-frequency radio spectrum

Salient features of the remarkable band structure seen in the high-frequency interpulse of the Crab pulsar are summarized. It is argued that its source must lie in a current sheet, probably coincident with the open-closed magnetosphere separatrix, and that the mechanism is a form of one-pass free-electron laser. An outward moving electron component in the current sheet interacts with the longitudinal electric field of an inward directed ion-proton Lamgmuir mode. The band structure is then a natural consequence of the differing charge-to-mass ratios of the ions, which are a return current component of those accelerated, as in almost all pulsars, from the polar cap to the light cylinder.
Geometry, Kinematics, and Magnetization of Simulated Prestellar Cores

We utilize the more than 100 gravitationally bound dense cores formed in our three-dimensional, turbulent MHD simulations reported in Chen & Ostriker to analyze structural, kinematic, and magnetic properties of prestellar cores. Our statistical results disagree with the classical theory of star formation in which cores evolve to be oblate with magnetic fields parallel to the minor axes. Instead, we find that cores are generally triaxial, although the core-scale magnetic field is still preferentially most parallel to the core’s minor axis and most perpendicular to the major axis. The internal and external magnetic field directions are correlated, but the direction of integrated core angular momentum is misaligned with the core’s magnetic field, which is consistent with recent observations. The ratio of rotational/total kinetic and rotational/gravitational energies are independent of core size and consistent in magnitude with observations. The specific angular momentum also follows the observed relationship L/M ∝ R3/2, indicating that rotation is acquired from ambient turbulence. With typical , rotation is not the dominant motion when cores collapse.
Towards commissioning the Fermilab Muon G-2 Experiment

Starting this summer, Fermilab will host a key experiment dedicated to the search for signals of new physics: The Fermilab Muon g-2 Experiment. Its aim is to precisely measure the anomalous magnetic moment of the muon. In full operation, in order to avoid contamination, the newly born secondary beam is injected into a 505 m long Delivery Ring (DR) wherein it makes several revolutions before being sent to the experiment. Part of the commissioning scenario will execute a running mode wherein the passage from the DR will be skipped. With the aid of numerical simulations, we provide estimates of the expected performance.
A comparison between semi-analytical gas cooling models and cosmological hydrodynamical simulations

We compare the mass cooling rates and cumulative cooled-down masses predicted by several semi-analytical (SA) cooling models with cosmological hydrodynamical simulations performed using the AREPO code (ignoring processes such as feedback and chemical enrichment). The SA cooling models are the new GALFORM cooling model introduced in Hou et al. (2017), along with two earlier GALFORM cooling models and the L-GALAXIES and MORGANA cooling models. We find that the predictions of the new GALFORM cooling model are generally in best agreement with the simulations. For halos with Mhalo ≲ 3 × 1011 M⊙, the SA models predict that the timescale for radiative cooling is shorter than or comparable to the gravitational infall timescale. Even though SA models assume that gas falls onto galaxies from a spherical gas halo, while the simulations show that the cold gas is accreted through filaments, both methods predict similar mass cooling rates, because in both cases the gas accretion occurs on similar timescales. For halos with Mhalo ≳ 1012 M⊙, gas in the simulations typically cools from a roughly spherical hot gas halo, as assumed in the SA models, but the halo gas gradually contracts during cooling, leading to compressional heating. SA models ignore this heating, and so overestimate mass cooling rates by factors of a few. At low redshifts halo major mergers or a sequence of successive smaller mergers are seen in the simulations to strongly heat the halo gas and suppress cooling, while mergers at high redshifts do not suppress cooling, because the gas filaments are difficult to heat up. The new SA cooling model best captures these effects.
Suppressed Far-UV Stellar Activity and Low Planetary Mass Loss in the WASP-18 System

WASP-18 hosts a massive, very close-in Jupiter-like planet. Despite its young age (<1 Gyr), the star presents an anomalously low stellar activity level: the measured activity parameter lies slightly below the basal level; there is no significant time-variability in the value; there is no detection of the star in the X-rays. We present results of far-UV observations of WASP-18 obtained with COS on board of Hubble Space Telescope aimed at explaining this anomaly. From the star’s spectral energy distribution, we infer the extinction ( ≈ 0.01 mag) and then the interstellar medium (ISM) column density for a number of ions, concluding that ISM absorption is not the origin of the anomaly. We measure the flux of the four stellar emission features detected in the COS spectrum (C ii, C iii, C iv, Si iv). Comparing the C ii/C iv flux ratio measured for WASP-18 with that derived from spectra of nearby stars with known age, we see that the far-UV spectrum of WASP-18 resembles that of old (>5 Gyr), inactive stars, in stark contrast with its young age. We conclude that WASP-18 has an intrinsically low activity level, possibly caused by star–planet tidal interaction, as suggested by previous studies. Re-scaling the solar irradiance reference spectrum to match the flux of the Si iv line, yields an XUV integrated flux at the planet orbit of 10.2 erg s−1 cm−2. We employ the rescaled XUV solar fluxes to models of the planetary upper atmosphere, deriving an extremely low thermal mass-loss rate of 10−20 MJ Gyr−1. For such high-mass planets, thermal escape is not energy limited, but driven by Jeans escape.
Seyfert 2 Galaxies with Spectropolarimetric Observations

We present a compilation of radio, infrared, optical, and hard X-ray (2-10 keV) data for a sample of 90 Seyfert 2 galaxies (Sy2s) with spectropolarimetric observations (41 Sy2s with detection of polarized broad lines [PBLs] and 49 without PBLs). Compared to Sy2s without PBLs, Sy2s with PBLs tend to be earlier type spirals and show warmer midinfrared color and significant excess of emissions (including the hard X-ray [2-10 keV], [O III] λ5007, infrared [25 μm], and radio). Our analyses indicate that the majority of Sy2s without PBLs are those sources having less powerful active galactic nucleus (AGN) activities, most likely caused by a low accretion rate. It implies that the detectability of the polarized broad emission lines in Sy2s may depend on their central AGN activities in most cases. Based on the available data, we find no compelling evidence for the presence of two types of Sy2s; one of which has been proposed to be intrinsically different from Sy2s claimed in the unification model.
THE VALUE FUNCTION REPRESENTING HAMILTON-JACOBI EQUATION WITH HAMILTONIAN DEPENDING ON VALUE OF SOLUTION

In the paper we investigate the regularity of the value function representing Hamilton- Jacobi equation: �Ut + H(t,x,U,�Ux) = 0 with a final condition: U(T,x )= g(x). Hamilton-Jacobi equation, in which the Hamiltonian H depends on the value of solution U, is represented by the value function with more complicated structure than the value function in Bolza problem. This function is described with the use of some class of Mayer problems related to the optimal control theory and the calculus of variation. In the paper we prove that absolutely continuous functions that are solutions of Mayer problem satisfy the Lipschitz condition. Using this fact we show that the value function is a bilateral solution of Hamilton-Jacobi equation. Moreover, we prove that continuity or the local Lipschitz condition of the function of final cost g is inherited by the value function. Our results allow to state the theorem about existence and uniqueness of bilateral solutions in the class of functions that are bounded from below and satisfy the local Lipschitz condition. In proving the main results we use recently derived necessary optimality conditions of Loewen-Rockafellar (P.D. Loewen and R.T. Rockafellar, SIAM J. Control Optim. 32 (1994) 442-470; P.D. Loewen and R.T. Rockafellar, SIAM J. Control Optim. 35 (1997) 2050-2069).
M75, A Globular Cluster with a Trimodal Horizontal Branch. I. Color-Magnitude Diagram

Deep UBVI photometry for a large field covering the distant globular cluster M75 (NGC 6864) is presented. We confirm a previous suggestion that M75 possesses a bimodal horizontal branch (HB) bearing striking resemblance to the well-known case of NGC 1851. In addition, we detect a third, smaller grouping of stars on the M75 blue tail, separated from the bulk of the blue HB stars by a gap spanning about 0.5 mag in V. Such a group of stars may correspond to the upper part of a very extended, though thinly populated, blue tail. Thus M75 appears to have a trimodal HB. The presence of the "Grundahl jump" is verified using the broadband U filter. We explore the color-magnitude diagram of M75 with the purpose of deriving the cluster's fundamental parameters and find a metallicity of [Fe/H] = -1.03 ± 0.17 dex and -1.24 ± 0.21 in the Carretta & Gratton and Zinn & West scales, respectively. We discuss earlier suggestions that the cluster has an anomalously low ratio of bright red giants to HB stars. A differential age analysis with respect to NGC 1851 suggests that the two clusters are essentially coeval.
Terahertz Spectroscopy and Global Analysis of the Rotational Spectrum of Doubly Deuterated Amidogen Radical ND2

The deuteration mechanism of molecules in the interstellar medium is still being debated. Observations of deuterium-bearing species in several astronomical sources represent a powerful tool to improve our understanding of the interstellar chemistry. The doubly deuterated form of the astrophysically interesting amidogen radical could be a target of detection in space. In this work, the rotational spectrum of the ND2 radical in its ground vibrational and electronic state has been investigated between 588 and 1131 GHz using a frequency modulation millimeter/submillimeter-wave spectrometer. The ND2 molecule has been produced in a free-space glass absorption cell by discharging a mixture of ND3 and Ar. Sixty-four new transition frequencies involving J values from 2 to 5 and Ka values from 0 to 4 have been measured. A global analysis including all the previous field-free pure rotational data has been performed, allowing for a more precise determination of a very large number of spectroscopic parameters. Accurate predictions of rotational transition frequencies of ND2 are now available from a few gigahertz up to several terahertz.
What Confines the Rings of Saturn?

The viscous spreading of planetary rings is believed to be counteracted by satellite torques, through either an individual resonance or overlapping resonances. For the A ring of Saturn, it has been commonly believed that the satellite Janus alone can prevent the ring from spreading, via its 7:6 Lindblad resonance. We discuss this common misconception and show that, in reality, the A ring is confined by the contributions from the group of satellites Pan, Atlas, Prometheus, Pandora, Janus, Epimetheus, and Mimas, whose cumulative torques from various resonances gradually decrease the angular momentum flux transported outward through the ring via density and bending waves. We further argue that this decrease in angular momentum flux occurs through “flux reversal. ” Furthermore, we use the magnitude of the satellites’ resonance torques to estimate the effective viscosity profile across the A ring, showing that it decreases with radius from ∼50 cm2 s−1 to less than ∼10 cm2 s−1. The gradual estimated decrease of the angular momentum flux and effective viscosity are roughly consistent with results obtained by balancing the shepherding torques from Pan and Daphnis with the viscous torque at the edges of the Encke and Keeler gaps, as well as the edge of the A ring. On the other hand, the Mimas 2:1 Lindblad resonance alone seems to be capable of confining the edge of the B ring, and contrary to the situation in the A ring, we show that the effective viscosity across the B ring is relatively constant at ∼24–30 cm2 s−1.