ShantanuT01/DACTYL-Pretraining huggingface dataset:
We present a set of gas-dynamical simulations of galaxy groups and clusters aimed at exploring the effect of non-gravitational heating. We use GASOLINE, a parallel Tree+SPH code, to simulate the formation of four cosmic halos with temperature 0.5<T<8 keV. Non-gravitational heating is implemented in two different ways: (1) by imposing a minimum entropy floor at a given redshift, 1<z<5; (2) by gradually heating gas, proportionally to the SN rate expected from semi-analytical modeling of galaxy formation. Our main results are the following. (a) An extra heating energy of about 1 keV per gas particle is required to reproduce the observed Lx-T relation, independent of whether it is provided so as to create an entropy floor of 50-100 keV cm^2, or is modulated in redshift; our SN feedback recipe provides only 1/3 keV/part. (b) The M-T relation is almost unaffected by non-gravitational heating and follows the M T^{3/2} scaling, with a normalization ~40% higher than observed, independent of the heating scheme. The inclusion of cooling in a run of a small group has the effects of increasing T_ew by ~30%, possibly reconciling simulated and observed M-T relations, and of decreasing Lx by ~40%. In spite of the inclusion of SN feedback energy, almost 40% of the gas becomes cold, in excess of current observational estimates. (abridged)
The experimental observation of sizable transverse components for B-> phi K^* decay is in strong contrast to all other VV modes, and poses a challenge to our understanding of B decay dynamics. Observing that the gluon emitted from b-> sg^{(*)} chromodipole transition is transverse, we give a heuristic model where the transverse phi descends from the emitted gluon, hence similar phenomena should occur for B-> omega K^* but not for B-> rho^0 K^*. New physics in bsg chromodipole coupling, perhaps needed for the \bar B -> phi K_S CP violation anomaly, may lead to different patterns of CP and T violation in transverse components of \bar B -> phi \bar K^*, omega \bar K^* decays.
The compound, Ca3CoRhO6, containing magnetic Co-Rh chains intervened by Ca ions, has been known to be one of the few exhibiting partially disordered antiferromagnetic structure (PDA) due to geometrical frustration. Here, we report the influence of partial replacement of Ca by Y on the magnetic anomalies by investigating the solid solution, Ca(3-x)Y(x)CoRhO6 by bulk measurements. There are profound changes in the magnetic behavior, the most notable one being that the features attributable to spin-chain magnetism and PDA structure get suppressed dramatically by a small replacement of Ca by Y (x= 0.15), despite the fact that the magnetic chain is not disrupted. This finding suggests that this compound is on the verge of PDA-structural-instability.
We aim at studying automorphic forms of bounded analytic conductor in the division quaternion algebra setting. We prove the equidistribution of the universal family with respect to an explicit and geometrically meaningful measure. It leads to answering the Sato-Tate conjectures in this case, and contains the counting law of the universal family, with a power savings error term in the totally definite case.
Equilibrium molecular dynamics (EMD) simulations through Green-Kubo formula (GKF) have been widely used in the study of thermal conductivity of various materials. However, there exist controversial simulation results which have huge discrepancies with experimental ones in literatures. In this paper, we demonstrate that the fluctuation in calculated thermal conductivity is due to the uncertainty in determination of the truncation time, which is related to the ensemble and size dependent phonon relaxation time. We thus propose a new scheme in the direct integration of heat current autocorrelation function (HCACF) and a nonzero correction in the double-exponential-fitting of HCACF to describe correctly the contribution to thermal conductivity from low frequency phonons. By using crystalline Silicon (Si) and Germanium (Ge) as examples, we demonstrate that our method can give rise to the values of thermal conductivity in an excellent agreement with experimental ones.
We present Chandra observations of the cool cluster A168, for which previous X-ray imaging and optical studies indicated a merger of two subclusters nearly in the plane of the sky. We derive a temperature map for A168, which shows that the merger has proceeded beyond the core passage and is near subcluster turnaround. It also reveals an unusual feature -- the gas core of one of the subclusters forms a tongue-like structure extending ahead (in the direction of motion) of the subcluster center. The coolest cluster gas is found in a crescent-shaped region at the tip of this tongue, and forms a cold front in pressure equilibrium with the external gas. In contrast with this feature's forward location, previously observed merger cold fronts (e.g., A3667, 1E0657--56) lagged behind their host subclusters, as expected in the presense of ram pressure. We propose that A168 illustrates a much later stage in the evolution of a cold front, when its host subcluster approaches the apocenter of the merger orbit where the ram pressure on its gas drops sharply. As a result, a large chunk of the subcluster gas ``slingshots'' past the dark matter center, becomes unbound from the subcluster and expands adiabatically, as seen in some recent hydrodynamic simulations.
Spin-waves e.g. magnons are the conventional elementary excitations of ordered magnets. However, other possibilities exist. For instance, magnon bound-states can arise due to attractive magnon-magnon interactions and drastically impact the static and dynamic properties of materials. Here, we demonstrate a zoo of distinct multi-magnon quasiparticles in the frustrated spin-1 triangular antiferromagnet FeI$_2$ using time-domain terahertz spectroscopy. The energy-magnetic field excitation spectrum contains signatures of one-, two-, four- and six-magnon bound-states, which we analyze using an exact diagonalization approach for a dilute gas of interacting magnons. The two-magnon single-ion bound states occur due to strong anisotropy and the preponderance of even higher order excitations arises from the tendency of the single-ion bound states to themselves form bound states due to their very flat dispersion. This menagerie of tunable interacting quasiparticles provides a unique platform in a condensed matter setting that is reminiscent of the few-body quantum phenomena central to cold-atom, nuclear, and particle physics experiments.
We investigate, both analytically and by computer simulation, the kinetics of a microscopic model of hard rods adsorbing on a linear substrate. For a small, but finite desorption rate, the system reaches the equilibrium state very slowly, and the long-time kinetics display three successive regimes: an algebraic one where the density varies as $1/t$, a logarithmic one where the density varies as $1/ln(t)$, followed by a terminal exponential approach. A mean-field approach fails to predict the relaxation rate associated with the latter. We show that the correct answer can only be provided by using a systematic description based on a gap-distribution approach.
We study the signatures of rotational and phase symmetry breaking in small rotating clouds of trapped ultracold Bose atoms by looking at rigorously defined condensate wave function. Rotational symmetry breaking occurs in narrow frequency windows, where the ground state of the system has degenerated with respect to the total angular momentum, and it leads to a complex wave function that exhibits vortices clearly seen as holes in the density, as well as characteristic vorticity. Phase symmetry (or gauge symmetry) breaking, on the other hand, is clearly manifested in the interference of two independent rotating clouds.
We use ZENS data at low redshift to study the dependence of the quenched satellite fraction and of the morphological mix of these quenched satellites, on three different environmental parameters: group halo mass, halo-centric distance and large-scale structure over-density. The fraction of quenched satellites is independent of halo mass and the surrounding large-scale overdensity, but increases towards the centres of the haloes, as previously found. The morphological mix is, however, constant with radial position, indicating that the well-known morphology-density relation results from the increasing fraction of quenched galaxies towards the centres of haloes. The constancy of the morphological outcome suggests that mass-quenching and satellite quenching have the same effect on the morphologies of the galaxies. The quenched satellites have larger B/T and smaller half-light radii than the star-forming satellites. These are mostly due to differences in the disks. The bulges in quenched satellites have very similar luminosities and surface brightness profiles, and any mass growth of the bulges associated with quenching cannot greatly change these quantities. The quenched disks are fainter and have smaller scale lengths than in star-forming satellites. This can be explained either by a differential fading of the disks or if disks were generally smaller in the past, both of which are expected in an inside-out growth of disks. At least at low redshifts, the structure of massive quenched satellites is produced by processes that operate before quenching takes place. A comparison with semi-analytic models argues for a reduction in the efficiency of group halos in quenching their disk satellites and for mechanisms to increase the B/T of low mass quenched satellites. [abridged]
A model for strangelets at finite temperature is built, in which the quark masses are dynamically generated. The dynamical chiral symmetry breaking inside strangelets at finite temperature is investigated. It is found that the chiral symmetry is going to break spontaneously inside the strangelets at some finite temperature, and then the masses of strange quarks inside the strangelets increase as the temperature rises. The phenomenon that strange quark mass increases with temperature after the chiral symmetry breaks spontaneously is illustrated by some typical numerical examples.
We present a derivation of a generalized optimally-weighted estimator for the weak lensing magnification signal, including a calculation of errors. With this estimator, we present a local method for optimally estimating the local effects of magnification from weak gravitational lensing, using a comparison of number counts in an arbitrary region of space to the expected unmagnified number counts. We show that when equivalent lens and source samples are used, this estimator is simply related to the optimally-weighted correlation function estimator used in past work and vice-versa, but this method has the benefits that it can calculate errors with significantly less computational time, that it can handle overlapping lens and source samples, and that it can easily be extended to mass-mapping. We present a proof-of-principle test of this method on data from the CFHTLenS, showing that its calculated magnification signals agree with predictions from model fits to shear data. Finally, we investigate how magnification data can be used to supplement shear data in determining the best-fit model mass profiles for galaxy dark matter haloes. We find that at redshifts greater than z ~ 0.6, the inclusion of magnification can often significantly improve the constraints on the components of the mass profile which relate to galaxies' local environments relative to shear alone, and in high-redshift, low- and medium-mass bins, it can have a higher signal-to-noise than the shear signal.
We combine dust, atomic (HI) and molecular (H$_{2}$) hydrogen mass measurements for 176 galaxies in the Herschel Reference Survey to investigate the effect of environment on the gas-to-dust mass ($M_{\rm gas}/M_{\rm dust}$) ratio of nearby galaxies. We find that, at fixed stellar mass, the average $M_{\rm gas}/M_{\rm dust}$ ratio varies by no more than a factor of $\sim$2 when moving from field to cluster galaxies, with Virgo galaxies being slightly more dust rich (per unit of gas) than isolated systems. Remarkably, once the molecular and atomic hydrogen phases are investigated separately, we find that \hi-deficient galaxies have at the same time lower $M_{\rm HI}/M_{\rm dust}$ ratio but higher $M_{\rm H_{2}}/M_{\rm dust}$ ratio than \hi-normal systems. In other words, they are poorer in atomic but richer in molecular hydrogen if normalized to their dust content. By comparing our findings with the predictions of theoretical models, we show that the opposite behavior observed in the $M_{\rm HI}/M_{\rm dust}$ and $M_{\rm H_{2}}/M_{\rm dust}$ ratios is fully consistent with outside-in stripping of the interstellar medium (ISM), and is simply a consequence of the different distribution of dust, \hi\ and H$_{2}$ across the disk. Our results demonstrate that the small environmental variations in the total $M_{\rm gas}/M_{\rm dust}$ ratio, as well as in the gas-phase metallicity, do not automatically imply that environmental mechanisms are not able to affect the dust and metal content of the ISM in galaxies.
In this paper, we study the formulae for a product of two product Euler polynomials.   From this study, we derive some formulae for the integral of the product of two or more Ruler polynomials.
The ultimate aim of quantum key distribution (QKD) is improving the performance of transmission distance and key generation speed. Unfortunately, it is believed to be limited by the secret-key capacity of quantum channel without quantum repeater. Recently, a novel twin-field QKD (TFQKD) [Nature 557, 400 (2018)] is proposed to break through the limit, where the key rate is proportional to the square-root of channel transmittance. Here, by using the vacuum and one-photon state as a qubit, we show that the TF-QKD can be regarded as a measurement-device-independent QKD (MDI-QKD) with single-photon Bell state measurement. Therefore, the MDI property of TF-QKD can be understood clearly. Importantly, the universal security proof theories can be directly used for the TF-QKD, such as BB84, six-state and reference-frame-independent schemes. Furthermore, we propose a feasible experimental scheme for the proof-of-principle experimental demonstration.
Probably the most fundamental characteristic of the quasar-AGN power house, the mass of the central black hole, is the least well known. I review the three main classes of mass estimation methods---broad emission-line kinematics, X-ray variability and accretion-disk modeling, and the masses they give in terms of the Eddington ratio, $L/L_{\rm Edd}$. The broad emission lines are probably the best probe of the central mass. They provide mass estimates that suggest a narrow spread for the Eddington ratio - 1--2 orders of magnitude over more than six orders of magnitude in continuum luminosity, possibly indicating a universal $M/L$ ratio for AGN. However, other methods give a larger spread and possibly a luminosity- dependent Eddington ratio. Potential sources of errors and bias are discussed.
Let $I$ be a finite alphabet and $\aS\subset I$ be a nonempty strict subset. The sequences in $I^\ZZ$ are organized into connected regions which always start with a symbol in $\aS$. The regions are labelled by types $C(s)$, thus a region starting at $s'\in C(s)$ has the same type as one starting at $s$. Let $(\aP_s: s\in \aS)$ be a family of distributions on $I^\NN$ where each $\aP_s$ charges sequences starting with the symbol $s$. We can define a natural distribution $\PP$ on $I^\NN$, that counts the number of visits to the states from $\aP_s$, properly weighted. A dynamics of interest is such that at the first occurrence of $s'\in \aS\setminus C(s)$ the law regenerates with distribution $\aP_{s'}$. In this case we are able to find simple conditions for $\PP$ to be stationary. In addition, we study the following more complex model: once a symbol $s'\in \aS\setminus C(s)$ has been encountered, there is a decision to be made, either a new region of type $C(s')$ governed by $\aP_{s'}$ starts or the region continues to be a $C(s)$ region. This decision is modeled as random and depends on $s'$. In this setting a similar distribution to $\PP$ can be constructed and the conditions for stationarity are supplied. These models are inspired by genomic sequences where $I$ is the set of codons, the classes $(C(s): s\in \aS)$ group codons defining similar genomic classes, e.g. in bacteria there are two classes corresponding to the start and stop codons, and the random decision to continue a region or to begin a new region of a different class reflects the well-known fact that not every appearance of a start codon marks the beginning of a new coding region.
We study the perception of Hawking radiation by different observers outside a black hole. The analysis is done in terms of an effective-temperature function that varies along the trajectory of each observer. The vacuum state of the radiation field is chosen to be non-stationary, so as to mimic the switching-on of Hawking radiation that would appear in a real black hole collapse. We analyse how this vacuum is perceived by observers staying at a fixed radius, by observers coming in free-fall from radial infinity at different times, and by observers in free-fall released from finite radial positions. Results found have a compelling physical interpretation. One main result, at first unexpected, is that in general free-falling observers do perceive particle emission by the black hole when crossing the event horizon. This happens because of a diverging Doppler shift at the event horizon.
In this paper, we develop an iterative scheme to enable the explicit calculation of an arbitrary post-Newtonian order for a relativistic body that reduces to the Maclaurin spheroid in the appropriate limit. This scheme allows for an analysis of the structure of the solution in the vicinity of bifurcation points along the Maclaurin sequence. The post-Newtonian expansion is solved explicitly to the fourth order and its accuracy and convergence are studied by comparing it to highly accurate numerical results.
These are the notes corresponding to the course given at the IAS-Park City graduate summer school in July 2007.
The electronic structure of Mott insulators continues to be a major unsolved problem in physics despite more than half-century of intense research efforts. Well-developed momentum-resolved spectroscopies such as photoemission or neutron scattering cannot probe the full Mott gap. We report observation of dispersive charge excitations across the Mott gap in a high Tc parent cuprate Ca2CuO2Cl2 using high resolution resonant inelastic x-ray scattering shedding light on the anisotropy of Mott-gap. The results provide direct support for the Hubbard model to describe charge excitations across the Mott gap.
Recent theoretical studies [Chen et al., Phys. Rev. B 82, 174440 (2010), Ishizuka et al., Phys. Rev. B 90, 184422 (2014)] for the magnetic Mott insulator Ba2NaOsO6 have proposed a low-temperature order parameter that breaks lattice rotational symmetry without breaking time reversal symmetry leading to a nematic phase just above magnetic ordering temperature. We present high-resolution calorimetric and magnetization data of the same Ba2NaOsO6 single crystal and show evidence for a weakly field-dependent phase transition occurring at a temperature of Ts ~ 9.5K, above the magnetic ordering temperature of Tc ~ 7.5K. This transition appears as a broadened step in the low-field temperature dependence of the specific heat. The evolution of the phase boundary with applied magnetic field suggests that this phase coincides with the phase of broken local point symmetry seen in high field NMR experiments [Lu et al., Nat.\ Comm. 8 14407 (2017)]. Furthermore, the magnetic field dependence of the specific heat provides clear indications for magnetic correlations persisting at temperatures between Tc and Ts where long-range magnetic order is absent giving support for the existence of the proposed nematic phase.
Starting from a covariant and background independent definition of normal ordered vertex operators we give an alternative derivation of the KPZ relation between conformal dimensions and their gravitational dressed partners. With our method we are able to study for arbitrary genus the dependence of N-point functions on all dimensionful parameters. Implications for the interpretation of gravitational dressed dimensions are discussed.
One may consider cross-correlation routines applied to stellar spectra as a way to determine not only the radial velocities but also to assess the properties of stellar atmospheres. We show that this is not the case. High value of the cross-correlation coefficient between the observed and a template spectrum does not mean that the template corresponds to correct values of stellar temperature, gravity or metallicity. Cross-correlation operates in normalized space, so it is not sensitive to scaling or shifting of stellar flux. It is argued that cross-correlation is useful to efficiently determine the velocity shift between the observed and the template spectrum. But minimal distance methods need to be used to determine which template gives the best match to the observed spectrum, and so derive values of physical parameters. To illustrate the point we use data from the RAVE project which are being obtained at very similar spectral resolution and wavelength domain as will be the case for GAIA's RVS.
Most of the low-energy effective descriptions of spin-orbit driven Mott insulators consider spin orbit coupling (SOC) as a second order perturbation to electron-electron interactions. However, when SOC is comparable to anisotropic Hund's coupling, such as in Ir, validity of this formally weak-SOC approach is not a priori known. Depending on the relative strength of SOC and anisotropic Hund's coupling, different descriptions of the multiplet structure should be employed in the weak and strong SOC limits, \textit{viz.} \textit{LS} and \textit{jj} coupling schemes, respectively. We investigate the implications of both the coupling schemes on the low-energy effective $t-J$ model and calculate the angle resolved photoemission (ARPES) spectra using self-consistent Born approximation. In particular, we obtain the ARPES spectra of quasi-two-dimensional square-lattice iridate ${\rm Sr_2IrO_4}$ in both weak and strong SOC limits. The differences in the limiting cases are understood in terms of the composition and relative energy splittings of the multiplet structure. Our results indicate that the LS coupling scheme yields better agreement with the experiment, thus providing an indirect evidence for the validity of LS coupling scheme for iridates. We also discuss the implications for other metal ions with strong SOC.
The mechanical effects in finite two-dimensional electron systems (quantum dots or droplets) in a strong perpendicular magnetic field are studied. It is shown that, due to asymmetry of the cyclotron dynamics, an additional in-plane electric field causes a ground state transition accompanied by a change in the average total angular momentum of the system, unless the lateral confining potential is exactly parabolic. A precise mechanical experiment is proposed in which a macroscopic angular momentum of a dense matrix of quantum dots could be measured and used to detect and estimate anharmonicity of the confinement.
The Glauber theory has been used to investigate the reaction cross section of proton-rich nucleus $^{23}$Al. A core plus a proton structure is assumed for $^{23}$Al. HO-type density distribution is used for the core while the density distribution for the valence proton is calculated by solving the eigenvalue problem of Woods-Saxon potential. The transparency function in an analytical expression is obtained adopting multi-Gaussian expansion for the density distribution. Coulomb correction and finite-range interaction are introduced. This modified Glauber model is apt for halo nuclei. A dominate s-wave is suggested for the last proton in $^{23}$Al from our analysis which is possible in the RMF calculation.