Miracle-dz/UniFAR-FTUs huggingface dataset:
Holographic Fermi surfaces and bulk dipole couplings

Non-Fermi liquids can be studied using holographic duality. The low energy physics of a holographic Fermi surface is controlled by an emergent scale invariance. After reviewing these developments, we generalize the holographic calculation to include in the bulk action the leading irrelevant operator, which is a dipole coupling between the spinor field and the background gauge field. We find that this dipole coupling changes the attainable low-energy scaling dimensions, and changes the locations of the Fermi surfaces in momentum space. The structure of the holographic framework for non-Fermi liquids is, however, robust under this deformation.
Streamwise oscillation of spanwise velocity at the wall of a channel for turbulent drag reduction

Steady forcing at the wall of a channel flow is studied via direct numerical simulation to assess its ability of yielding reductions in turbulent friction drag. The wall forcing consists of a stationary distribution of spanwise velocity that alternates in the streamwise direction. The idea behind the forcing builds on the existing technique of the spanwise wall oscillation and exploits the convective nature of the flow to achieve an unsteady interaction with turbulence. The analysis takes advantage of the equivalent laminar flow, which is solved analytically to show that the energetic cost of the forcing is unaffected by turbulence. In a turbulent flow, the alternate forcing is found to behave similarly to the oscillating wall; in particular an optimal wavelength is found which yields a maximal reduction in turbulent drag. The energetic performance is significantly improved, with more than 50% of maximum friction saving at large intensities of the forcing, and a net energetic saving of 23% for smaller int.
redMaPPer II: X-RAY AND SZ PERFORMANCE BENCHMARKS FOR THE SDSS CATALOG

We evaluate the performance of the Sloan Digital Sky Survey (SDSS) DR8 redMaPPer photometric cluster catalog by comparing it to overlapping X-ray- and Sunyaev-Zeldovich (SZ)-selected catalogs from the literature. We confirm that the redMaPPer photometric redshifts are nearly unbiased (〈Δz〉 ⩽ 0.005), have low scatter (σz ≈ 0.006–0.02, depending on redshift), and have a low catastrophic failure rate (≈1%). Both the TX–λ and Mgas–λ scaling relations are consistent with a mass scatter of σln M|λ ≈ 25%, albeit with a ≈1% outlier rate due to projection effects (λ is the cluster richness estimated employed by redMaPPer). This failure rate is somewhat lower than that expected for the full cluster sample but is consistent with the additional selection effects introduced by our reliance on X-ray and SZ selected reference cluster samples. Where the redMaPPer DR8 catalog is volume-limited (z ⩽ 0.35), the catalog is 100% complete above TX ≳ 3.5 keV, and LX ≳ 2 × 1044 erg s−1, decreasing to 90% completeness at LX ≈ 1043 erg s−1. All rich (λ ≳ 100), low-redshift (z ≲ 0.25) redMaPPer clusters are X-ray-detected in the ROSAT All Sky Survey, and 86% of the clusters are correctly centered. Compared to other SDSS photometric cluster catalogs, redMaPPer has the highest completeness and purity, and the best photometric redshift performance, though some algorithms do achieve comparable performance to redMaPPer in subsets of the above categories and/or in limited redshift ranges. The redMaPPer richness is clearly the one that best correlates with X-ray temperature and gas mass. Most algorithms (including redMaPPer) have very similar centering performance as tested by comparing against X-ray centers, with only one exception which performs worse.
SHOCKS, SEYFERTS, AND THE SUPERNOVA REMNANT CONNECTION: A CHANDRA OBSERVATION OF THE CIRCINUS GALAXY

We analyze new Chandra observations of the nearest (D = 4 Mpc) Seyfert 2 active galaxy, Circinus, and match them to pre-existing radio, infrared, and optical data to study the kpc-scale emission. The proximity of Circinus allows us to observe in striking detail the structure of the radio lobes, revealing for the first time edge-brightened emission in both X-rays and radio. After considering various other possible scenarios, we show that this extended emission in Circinus is most likely caused by a jet-driven outflow, which is driving shells of strongly shocked gas into the halo of the host galaxy. In this context, we estimate Mach numbers –3.6 and –5.3 for the W and E shells, respectively. We derive temperatures of 0.74+0.06−0.05 keV and 0.8–1.8 keV for the W and E shells and an expansion velocity of ∼900–950 km s−1. We estimate that the total energy (thermal and kinetic) involved in creating both shells is ∼2 × 1055 erg, and their age is ∼106 yr. Comparing these results with those we previously obtained for Centaurus A, NGC 3801, and Mrk 6, we show that these parameters scale approximately with the radio power of the parent active galactic nucleus (AGN). The spatial coincidence between the X-ray and edge-brightened radio emission in Circinus resembles the morphology of some supernova remnant shocks. This parallel has been expected for AGNs but has never been observed before. We investigate what underlying mechanisms both types of systems may have in common, arguing that, in Circinus, the edge-brightening in the shells may be accounted for by a B field enhancement caused by shock compression but do not preclude some local particle acceleration. These results can be extrapolated to other low-power systems, particularly those with late-type hosts.
NO EVIDENCE FOR PROTOPLANETARY DISK DESTRUCTION BY OB STARS IN THE MYStIX SAMPLE

Hubble Space Telescope images of proplyds in the Orion Nebula, as well as submillimeter/radio measurements, show that the dominant O7 star θ 1 ? > Ori C photoevaporates nearby disks around pre-main-sequence stars. Theory predicts that massive stars photoevaporate disks within distances of the order of 0.1 pc. These findings suggest that young, OB-dominated massive H ii regions are inhospitable to the survival of protoplanetary disks and, subsequently, to the formation and evolution of planets. In the current work, we test this hypothesis using large samples of pre-main-sequence stars in 20 massive star-forming regions selected with X-ray and infrared photometry in the MYStIX survey. Complete disk destruction would lead to a deficit of cluster members with an excess in JHKS and Spitzer/IRAC bands in the vicinity of O stars. In four MYStIX regions containing O stars and a sufficient surface density of disk-bearing sources to reliably test for spatial avoidance, we find no evidence for the depletion of inner disks around pre-main-sequence stars in the vicinity of O-type stars, even very luminous O2–O5 stars. These results suggest that massive star-forming regions are not very hostile to the survival of protoplanetary disks and, presumably, to the formation of planets.
Laboratory measurement of optical constants of solid SiO and application to circumstellar dust

Context. Silicate minerals belong to the most abundant solids that form in cosmic environments. Their formation requires that a suffi cient number of oxygen atoms per silicon atom is freely available. For the standard cosmic element mixture this can usually be taken for granted, but this becomes a problem at the transition from the oxygen rich chemistry of M-stars to the carbon rich chemistry of C-stars. In the intermediate type S-stars most of the oxygen and carbon is consumed by formation of CO and SiO molecules, and left-over oxygen to build SiO4-tetrahedrons in solids becomes scarce. Under such conditions SiO molecules from the gas phase may condense into solid SiO. The infrared absorption spectrum of solid SiO differs from that of normal silicates by the absence of Si-O-Si bending modes around 18µm while the absorption band due to Si-O bond stretching modes at about 10µm is present. Recently it has been reported (Hony et al. 2009) that exactly this particula r characteristics is observed in a number of S-star spectra. Aims. We demonstrate that this observation may be explained by the formation of solid SiO as a major dust component at C/O abundance ratios close to unity. Methods. The infrared absorption properties of solid SiO are determined by laboratory transmission measurements of thin films of SiO produced by vapour deposition on a Si(111) wafer. From the measured spectra the dielectric function of SiO is derived by using a Brendel-oscillator model, particularly suited for the rep resentation of optical properties of amorphous materials. The results are used in model calculations of radiative transfer in circumstell ar dust shells with solid SiO dust in order to determine the spectral features due to SiO dust. Results. Comparison of synthetic and observed spectra shows that reasonable agreement is obtained between the main spectral characteristics of emission bands due to solid silicon monoxide and an emission band centred on 10µm, but without accompanying 18µm band, observed in some S-stars. We propose that solid SiO is the carrier material of this 10µm spectral feature.
Holographic Nucleons

Recent developments in holography have provided a new vista to the nucleon composition. A strongly coupled core nucleon tied with vector mesons emerge in line with the Cheshire cat principle. The cat is found to hide in the holographic direction. We discuss the one, two and many baryon problem in this context and point at the striking similarities between the holographic results and recent lattice simulations at strong coupling. To appear in Festschrift for Gerry Brown, Ed. Sabine Lee, World Scientific 1 Dedication This paper is dedicated to Gerry Brown who has been my mentor and colleague for the past three decades. I have met Gerry while in graduate school way back at MIT, in Feshbach’s office on a sunny fall morning. After the meeting, Gerry asked me when I would graduate as he was prepared to hire me for the next three years. I did the following spring and have been with Gerry since then. Gerry is an outstanding scientist and humanist that has contributed immensely to our field. I thank him for his guidance and friendship, and wish him well for the years to come. 2 Introduction Back in the eighties, quark bag models were proposed as models for hadrons that capture the essentials of asymptotic freedom through weakly interacting quarks and gluons within a bag, and the tenets of nuclear physics through strongly interacting mesons at the boundary. The delineation or bag radius was considered as a fundamental and physically measurable scale that separates ultraviolet from infrared QCD. Two competing pictures emerged: The original MIT bag model with a large radius surrounded by a bare vacuum and the Stony-Brook bag model with a small radius surrounded by pions [1]. In fact, at low energy this delineation is unphysical as stated in the Cheshire cat principle [2]. Quantum effects and anomalies cause most of the charges (fermionic, axial, etc.) to leak making the bag boundary immaterial [3], much like the smile of the Cheshire cat in ”Alice in wonderland” [4]. The Skyrme model typifies the extreme realization of the Cheshire cat principle whereby the immaterial bag radius is reduced to zero size [5]. The Skyrme model realizes QCD baryons as chiral solitons in the limit of large number of colors Nc. Recently, the same model was found to emerge from holographic QCD in the dual limit of large Nc and strong coupling t’Hooft coupling λ = g Nc [6, 7]. In the holographic construction, the Skyrmion is the holonomy of a flavor instanton tied to Witten’s vertex in bulk [8]. Baryon number at the boundary is dual to instanton number in bulk. Although the exact holographic dualities are only known for a restricted set of string theories in bulk with mostly conformal field theories at the boundary [9], we will assume that such a correspondence holds for holographic QCD which is not conformal. The present paper review some aspects of the holographic baryons following recent work in [10]. It is dedicated to Gerry Brown. In section 3, we review the holographic baryon construction from a bulk instanton, and emphasize the emergence of the Cheshire cat principle.
EVIDENCE FOR A PHOTOSPHERIC COMPONENT IN THE PROMPT EMISSION OF THE SHORT GRB 120323A AND ITS EFFECTS ON THE GRB HARDNESS–LUMINOSITY RELATION

The short GRB 120323A had the highest flux ever detected with the Gamma-Ray Burst Monitor on board the Fermi Gamma-Ray Space Telescope. Here we study its remarkable spectral properties and their evolution using two spectral models: (1) a single emission component scenario, where the spectrum is modeled by the empirical Band function (a broken power law), and (2) a two-component scenario, where thermal (a Planck-like function) emission is observed simultaneously with a non-thermal component (a Band function). We find that the latter model fits the integrated burst spectrum significantly better than the former, and that their respective spectral parameters are dramatically different: when fit with a Band function only, the Epeak of the event is unusually soft for a short gamma-ray burst (GRB; 70 keV compared to an average of 300 keV), while adding a thermal component leads to more typical short GRB values (Epeak ∼ 300 keV). Our time-resolved spectral analysis produces similar results. We argue here that the two-component model is the preferred interpretation for GRB 120323A based on (1) the values and evolution of the Band function parameters of the two component scenario, which are more typical for a short GRB, and (2) the appearance in the data of a significant hardness–intensity correlation, commonly found in GRBs, when we employee two-component model fits; the correlation is non-existent in the Band-only fits. GRB 110721A, a long burst with an intense photospheric emission, exhibits the exact same behavior. We conclude that GRB 120323A has a strong photospheric emission contribution, observed for the first time in a short GRB. Magnetic dissipation models are difficult to reconcile with these results, which instead favor photospheric thermal emission and fast cooling synchrotron radiation from internal shocks. Finally, we derive a possibly universal hardness–luminosity relation in the source frame using a larger set of GRBs (), which could be used as a possible redshift estimator for cosmology.
Structural, Electronic, Magnetic, and Mechanical Properties of Co<sub>2-<italic>x</italic></sub>V<sub><italic>x</italic></sub>FeSi Heusler Alloys

The influence of V substitution for Co on the structural, electronic, magnetic, and mechanical properties of quaternary Heusler alloys Co2−x VxFeSi (x = 0, 0.25, 0.50, 0.75, and 1) has been systematically investigated. The microstructural and the scanning profile using energy-dispersive X-ray analysis suggests the single-phase behavior in all alloys except for x = 1. The X-ray diffraction analysis at room temperature reveals the L21 crystal structure promoting lattice expansion after V substitution. The low-temperature saturation magnetic moments, as determined from magnetization measurements, agree fairly well with our theoretical results and also obey the Slater–Pauling rule. Very high Curie temperature is also observed. The alloys are mechanically robust. First-principles calculation with the implementation of a Hubbard correction term (U) is observed to predict half-metallic behavior.
The 2D surfaces that generate Newtonian and general relativistic orbits with small eccentricities

Embedding diagrams prove to be quite useful when learning general relativity as they offer a way of visualizing spacetime curvature through warped two dimensional (2D) surfaces. In this manuscript we present a different 2D construct that also serves as a useful conceptual tool for gaining insight into gravitation, in particular, orbital dynamics - namely the cylindrically symmetric surfaces that generate Newtonian and general relativistic orbits with small eccentricities. Although we first show that no such surface exists that can exactly reproduce the arbitrary bound orbits of Newtonian gravitation or of general relativity (or, more generally, of any spherically symmetric potential), surfaces do exist that closely approximate the resulting orbital motion for small eccentricities; exactly the regime that describes the motion of the solar system planets. These surfaces help to illustrate the similarities, as well as the differences, between the two theories of gravitation (i.e. stationary elliptical orbits in Newtonian gravitation and precessing elliptical-like orbits in general relativity) and offer, in this age of 3D printing, an opportunity for students and instructors to experimentally explore the predictions made by each.
The galactic halo in mixed dark matter cosmologies

A possible solution to the small scale problems of the cold dark matter (CDM) scenario is that the dark matter consists of two components, a cold and a warm one. We perform a set of high resolution simulations of the Milky Way halo varying the mass of the WDM particle (mWDM) and the cosmic dark matter mass fraction in the WDM component (bar fW). The scaling ansatz introduced in combined analysis of LHC and astroparticle searches postulates that the relative contribution of each dark matter component is the same locally as on average in the Universe (e.g. fW,odot = bar fW). Here we find however, that the normalised local WDM fraction (fW,odot / bar fW) depends strongly on mWDM for mWDM < 1 keV. Using the scaling ansatz can therefore introduce significant errors into the interpretation of dark matter searches. To correct this issue a simple formula that fits the local dark matter densities of each component is provided.
Cosmological particle production in emergent rainbow spacetimes

We investigate cosmological particle production in spacetimes where Lorentz invariance emerges in the infrared limit, but is explicitly broken in the ultraviolet regime. Thus these models are similar to many (but not all) models of quantum gravity, where a breakdown of Lorentz invariance is expected for ultraviolet physics around the Planck/string scale. Our specific model focuses on the boost subgroup that supports CPT invariance and results in a momentum-dependent dispersion relation. Motivated by previous studies on spacetimes emerging from a microscopic substrate, we show how these modifications naturally lead to momentum-dependent rainbow metrics. Firstly, we investigate the possibility of reproducing cosmological particle production in spacetimes emerging from real Bose gases. Several papers have been written on the analogy between the kinematics of linearized perturbations in Bose–Einstein condensates and effective curved-spacetime quantum field theory. Recently we have studied the influence of nonperturbative ultraviolet corrections in time-dependent analog spacetimes, leading to momentum-dependent emergent rainbow spacetimes. We show that models involving a time-dependent microscopic interaction are suitable for mimicking quantum effects in FRW spacetimes. Within certain limits the analogy is sufficiently good to simulate relativistic quantum field theory in time-dependent classical backgrounds, and the quantum effects are approximately robust against the model-dependent modifications. Secondly, we analyze how significantly the particle production process deviates from the common picture. While very low-energy modes do not see the difference at all, some modes ‘re-enter the Hubble horizon’ during the inflationary epoch, and extreme ultraviolet modes are completely insensitive to the expansion. The analysis outlined here, because it is nonperturbative in the rainbow metric, exhibits features that cannot be extracted simply from the standard perturbative modification of particle dispersion relations. However, we also show how the final result, after many e-foldings, will approach a time-independent exponentially decaying particle spectrum.
Exact and approximate expressions of energy generation rates and their impact on the explosion properties of pair instability supernovae

Energetics of nuclear reaction is fundamentally important to understand the mechanism of pair instability supernovae (PISNe). Based on the hydrodynamic equations and thermodynamic relations, we derive exact expressions for energy conservation suitable to be solved in simulation. We also show that some formulae commonly used in the literature are obtained as approximations of the exact expressions. We simulate the evolution of very massive stars of ~100-320 Msun with zero- and 1/10 Zsun, and calculate further explosions as PISNe, applying each of the exact and approximate formulae. The calculations demonstrate that the explosion properties of PISN, such as the mass range, the 56Ni yield, and the explosion energy, are significantly affected by applying the different energy generation rates. We discuss how these results affect the estimate of the PISN detection rate, which depends on the theoretical predictions of such explosion properties.
DETECTION OF GRB 090618 WITH THE RT-2 EXPERIMENT ON BOARD THE CORONAS-PHOTON SATELLITE

We present the results of an analysis of the prompt gamma-ray emission from GRB 090618 using the RT-2 Experiment on board the Coronas-Photon satellite. GRB 090618 shows multiple peaks, and a detailed study of the temporal structure as a function of energy is carried out. As the gamma-ray burst (GRB) was incident at an angle of 77° to the detector axis, we have generated appropriate response functions of the detectors to derive the spectrum of this GRB. We have augmented these results using the publicly available data from the Swift Burst Alert Telescope detector and show that a combined spectral analysis can measure the spectral parameters quite accurately. We also attempt a spectral and timing analysis of individual peaks and find evidence for a systematic change in the pulse emission characteristics for the successive pulses. In particular, we find that the peak energy of the spectrum, Ep, is found to monotonically decrease with time, for the successive pulses of this GRB.
Imaging F region drifts using monostatic phased‐array incoherent scatter radar

We develop a technique for using monostatic, electronically steerable incoherent scatter radar (ISR) to generate 2‐D estimates of F region flow fields. Tikhonov regularization is used to achieve robustness in the presence of spatial variation. The regularization functional imposes partial incompressibility on the medium and is therefore physically justified. Although the estimator has difficulty resolving sharp discontinuities, it performs well in regions of uniform flow. In order to characterize the effect of the regularization parameter, we test the performance of the operator in three simulated scenarios. We then analyze data from an experiment on the Poker Flat ISR. The experimental results are validated against coregistered all‐sky optical data and are found to be mostly consistent with these independent measurements. Namely, the radar‐derived estimates show a reduction of ion flow wherever the optical data indicates an auroral enhancement. The estimated flow is directed parallel to an arc boundary, consistent with an electric field directed toward the arc.