Many young clusters possess extended main sequences, a phenomenon commonly ascribed to stellar rotation. However, the mechanism behind their very wide stellar rotation distributions remains unclear. A proposed explanation is that magnetic star–disk interaction can regulate stellar rotation, i.e., protostars with longer disk lifetimes will eventually evolve into slow rotators, and vice versa. To examine this hypothesis, we took the star-forming region NGC 2264, as a test bed. We have studied its high-mass pre-main-sequence and zero-age main-sequence (ZAMS) stars. We find that, on average, diskless pre-main-sequence stars rotate faster than their disk-bearing counterparts. The stellar rotation distribution of the ZAMS stars is similar to evolved young clusters. We conclude that disk-locking may play a crucial role in the rotational velocity distribution of intermediate-mass early-type stars. We suggest that the observed wide stellar rotation distributions in many young clusters can occur in their early stages.
Exoplanetary systems hosting multiple low-mass planets are thought to have experienced dynamical instability, during which planet–planet collisions and mergers occur; these collisions can impart a substantial amount of angular momentum to the merger remnants, changing the obliquities of the resulting planets significantly. In this work, we carry out a series of N -body experiments to investigate the spin magnitude (∣ S ∣) and obliquity ( θ _SL ) distributions of low-mass exoplanets that have gone through planetary collisions. In our fiducial super-Earth (with m = 3 M _⊕ , R = 1.3 R _⊕ ) and mini-Neptune systems (with m = 9 M _⊕ , R = 2.5 R _⊕ ), the collision products follow a nearly uniform distribution in $\cos {\theta }_{{\rm{SL}}}$ , and the spin magnitude distribution is approximately linear in ∣ S ∣. Parameter studies and theoretical analysis show that increasing planetary radii or masses, or decreasing the initial planet–planet mutual inclinations, tend to polarize the obliquity distribution toward alignment or antialignment (i.e., excess probability near $\cos {\theta }_{{\rm{SL}}}=\pm 1$ ). Experiments with initially two-planet and three-planet systems produce qualitatively similar outcomes, suggesting that the trends in this study may generalize to systems with higher planetary multiplicities.
Abstract Motivated by the impact of the phantom field (or anti-Maxwell field) on the structure of three-dimensional black holes in the presence of the cosmological constant, we present the first extraction of solutions for the phantom BTZ (A)dS black hole. In this study, we analyze the effect of the phantom field on the horizon structure. Furthermore, we compare the BTZ black holes in the presence of both the phantom and Maxwell fields. Additionally, we calculate the conserved and thermodynamic quantities of the phantom BTZ black holes, demonstrating their compliance with the first law of thermodynamics. Subsequently, we assess the effects of the electrical charge and the cosmological constant on the local stability in the canonical ensemble by considering these fields with respect to the heat capacity. We then investigate the global stability area of the BTZ black holes with phantom and Maxwell fields within the grand canonical ensemble using Gibbs free energy. In this analysis, we evaluate the influence of the electrical charge and the cosmological constant on this area.
Astrophysics, Nuclear and particle physics. Atomic energy. Radioactivity
Abstract We study the $$B^+ \rightarrow D^{*-}D^+K^+$$ B + → D ∗ - D + K + reaction, showing that a peak in the $$D^+K^+$$ D + K + mass distribution around $$2834 \text { MeV}$$ 2834 MeV reported by LHCb could be associated with a theoretical exotic state with that mass, a width of $$19 \text { MeV}$$ 19 MeV and $$J^P=2^+$$ J P = 2 + , stemming from the interaction of the $$D^{*+}K^{*+}$$ D ∗ + K ∗ + and $$D^{*+}_s \rho ^+$$ D s ∗ + ρ + channels, which is a partner of the $$0^+$$ 0 + $$T_{c{\bar{s}}}(2900)$$ T c s ¯ ( 2900 ) . We show that the data is compatible with this assumption, but also see that the mass distribution itself cannot discriminate between the spins $$J=0$$ J = 0 , 1, 2 of the state. Then we evaluate the momenta of the angular mass distribution and show that they are very different for each of the spin assumptions, and that the momenta coming from interference terms have larger strength at the resonant energy than the peaks seen in the angular integrated mass distribution. We make a call for the experimental determination of these magnitudes, which has already been used by the LHCb in related decay reactions.
Astrophysics, Nuclear and particle physics. Atomic energy. Radioactivity
Shun Inoue, Wataru Buz Iwakiri, Teruaki Enoto
et al.
The Monitor of All-sky X-ray Image (MAXI) detected a superflare, releasing 5 × 10 ^37 erg in 2−10 keV, of the RS CVn-type star IM Peg at 10:41 UT on 2023 July 23 with its Gas Slit Camera (2−30 keV). We conducted X-ray follow-up observations of the superflare with the Neutron Star Interior Composition Explorer (NICER; 0.2−12 keV) starting at 16:52 UT on July 23 until 06:00 UT on August 2. NICER X-ray spectra clearly showed emission lines of the Fe xxv He α and Fe xxvi Ly α for ∼1.5 days since the MAXI detection. The Fe XXV He α line was blueshifted with its maximum Doppler velocity reaching −2200 ± 600 km s ^−1 , suggesting an upward-moving plasma during the flare, such as a coronal mass ejection (CME) and/or chromospheric evaporation. This is the first case that the Fe xxv He α line is blueshifted during a stellar flare, and its velocity overwhelmingly exceeds the escape velocity of the star (−230 km s ^−1 ). One hour before the most pronounced blueshift detection, a signature of the reheating of the flare plasma was observed. We discuss the origin of the blueshift, a CME, or high-velocity chromospheric evaporation.
Mark J. Avara, Julian H. Krolik, Manuela Campanelli
et al.
While supermassive binary black holes (SMBBHs) inspiral toward merger they may also accrete matter from a surrounding disk. To study the dynamics of this system requires simultaneously describing the evolving spacetime and the magnetized plasma. We present the first relativistic calculation simulating two equal-mass, nonspinning black holes as they inspiral from a 20 M ( G = c = 1) initial separation almost to merger. Our results imply important observational consequences: for instance, the accretion rate $\dot{M}$ onto the black holes first decreases and then plateaus, dropping by only a factor of ∼3 despite the rapid inspiral. An estimated bolometric light curve follows the same profile, suggesting some merging SMBBHs may be significantly luminous past the predicted circumbinary disk decoupling. The minidisks are nonstandard: Reynolds, not Maxwell, stresses dominate, and they oscillate between two states. In one part of the cycle, “sloshing” streams transfer mass between minidisks, carrying kinetic energy at a rate sometimes as high as the peak minidisk bolometric luminosity. We also discover that episodic accretion drives time-varying minidisk tilts. These complex dynamics all contribute to unique cyclical behavior in the light curves of late-time inspiraling SMBBHs. The poloidal magnetic flux on the black holes is roughly constant at a dimensionless level ϕ ∼ 2–3, but doubles just before merger; for significant black hole spin, this flux predicts powerful jets with variability driven by binary dynamics, another potentially unique electromagnetic signature. This simulation is the first to employ our multipatch infrastructure P atchwork MHD, decreasing the computational expense to ∼3% of conventional single-grid methods’ cost.
Ray Garner III, Robert Kennicutt Jr., Laurie Rousseau-Nepton
et al.
The variations of oxygen abundance and ionization parameter in H ii regions are usually thought to be the dominant factors that produced variations seen in observed emission-line spectra. However, if and how these two quantities are physically related is hotly debated in the literature. Using emission line data of NGC 628 observed with SITELLE as part of the Star formation, Ionized Gas, and Nebular Abundances Legacy Survey (SIGNALS), we use a suite of photoionization models to constrain the abundance and ionization parameters for over 1500 H ii regions throughout its disk. We measure an anticorrelation between these two properties, consistent with expectations, although with considerable scatter. Secondary trends with dust extinction and star formation rate surface density potentially explain the large scatter observed. We raise concerns throughout regarding various modeling assumptions and their impact on the observed correlations presented in the literature.
We rederive the possible dependence of the redshift with a very-high-energy (VHE) γ -ray photon index. The results suggest that the universe to VHE γ -rays is becoming more transparent than expected. We introduce the extragalactic background light (EBL) and photon to axion-like particle (ALP) oscillations to explain this phenomenon. We concentrate our analysis on 70 blazars up to redshift z ≃ 1. Assuming this correlation is solely the result of photon-photon absorption of VHE photons with the EBL, with deviations between the predictions and observations, especially at redshifts 0.2 < z < 1. We then discuss the implications of photon-ALP oscillations for the VHE γ -ray spectra of blazars. Strong evidence shows that (1) the results of the EBL attenuation show that the VHE γ -ray photon index increases nonlinearly at the ranges of redshift 0.03 < z < 0.2 and (2) the photon-ALP oscillation results in an attractive characteristic in the VHE γ -ray photon index at the ranges of redshift 0.2 < z < 1. We suggest that both EBL absorption and photon-ALP oscillation can influence the propagation of VHE γ -rays from distant blazars.
Abstract This paper presents a search for hypothetical massive, charged, long-lived particles with the ATLAS detector at the LHC using an integrated luminosity of 139 fb −1 of proton–proton collisions at s $$ \sqrt{s} $$ = 13 TeV. These particles are expected to move significantly slower than the speed of light and should be identifiable by their high transverse momenta and anomalously large specific ionisation losses, dE/dx. Trajectories reconstructed solely by the inner tracking system and a dE/dx measurement in the pixel detector layers provide sensitivity to particles with lifetimes down to O $$ \mathcal{O} $$ (1) ns with a mass, measured using the Bethe–Bloch relation, ranging from 100 GeV to 3 TeV. Interpretations for pair-production of R-hadrons, charginos and staus in scenarios of supersymmetry compatible with these particles being long-lived are presented, with mass limits extending considerably beyond those from previous searches in broad ranges of lifetime.
Nuclear and particle physics. Atomic energy. Radioactivity
Abstract We present improved methods for calculating confidence intervals and p values in situations where standard asymptotic approaches fail due to small sample sizes. We apply these techniques to a specific class of statistical model that can incorporate uncertainties in parameters that themselves represent uncertainties (informally, “errors on errors”) called the Gamma Variance Model. This model contains fixed parameters, generically denoted by $$\varepsilon $$ ε , that represent the relative uncertainties in estimates of standard deviations of Gaussian distributed measurements. If the $$\varepsilon $$ ε parameters are small, one can construct confidence intervals and p values using standard asymptotic methods. This is formally similar to the familiar situation of a large data sample, in which estimators for all adjustable parameters have Gaussian distributions. Here we address the important case where the $$\varepsilon $$ ε parameters are not small and as a consequence the first-order asymptotic distributions do not represent a good approximation. We investigate improved test statistics based on the technology of higher-order asymptotics (modified likelihood root and Bartlett correction). The effective application of higher-order corrections removes an important computational barrier to the use of the Gamma Variance Model.
Astrophysics, Nuclear and particle physics. Atomic energy. Radioactivity
Abstract Liquid xenon time projection chambers are promising detectors to search for neutrinoless double beta decay (0 $$\nu \beta \beta $$ ν β β ), due to their response uniformity, monolithic sensitive volume, scalability to large target masses, and suitability for extremely low background operations. The nEXO collaboration has designed a tonne-scale time projection chamber that aims to search for 0 $$\nu \beta \beta $$ ν β β of $$^{136}$$ 136 Xe with projected half-life sensitivity of $$1.35\times 10^{28}$$ 1.35 × 10 28 yr. To reach this sensitivity, the design goal for nEXO is $$\le $$ ≤ 1% energy resolution at the decay Q-value ( $$2458.07\pm 0.31$$ 2458.07 ± 0.31 keV). Reaching this resolution requires the efficient collection of both the ionization and scintillation produced in the detector. The nEXO design employs Silicon Photo-Multipliers (SiPMs) to detect the vacuum ultra-violet, 175 nm scintillation light of liquid xenon. This paper reports on the characterization of the newest vacuum ultra-violet sensitive Fondazione Bruno Kessler VUVHD3 SiPMs specifically designed for nEXO, as well as new measurements on new test samples of previously characterised Hamamatsu VUV4 Multi Pixel Photon Counters (MPPCs). Various SiPM and MPPC parameters, such as dark noise, gain, direct crosstalk, correlated avalanches and photon detection efficiency were measured as a function of the applied over voltage and wavelength at liquid xenon temperature (163 K). The results from this study are used to provide updated estimates of the achievable energy resolution at the decay Q-value for the nEXO design.
Astrophysics, Nuclear and particle physics. Atomic energy. Radioactivity
Abstract Geomagnetically induced current (GIC) in utility systems such as electric power grids occurring during extreme geomagnetic storms can exceed the tolerance limit of the systems, which can cause serious system damages. It has therefore been important to evaluate the GIC levels in the utility systems. This study presents the simulation and analysis of GIC levels in the Shandong 500 kV power grid system consisting of 34 substations under a variety of uniform induced geoelectric fields. The line type, substation grounding resistance, and other influencing factors are included in the simulations. The results show that the GIC level varies largely in the 34 substations. In 11 substations, the GIC exceeds 100 A and it reaches up to ∼200 A in two substations for an assumed 1 V/km induced electric field. The changes in the GIC distribution are found consistent with the direction changes of the electric field. Utilizing the directional sensitivity, we calculate the maximum GIC level for the optimum direction for all substations. By combining this information with statistical tools, we propose a method for identifying the key substations which are most vulnerable. The result can provide suggestions for GIC disaster prevention and mitigation, substation site selection, monitoring equipment installation, and so on, in Shandong province.
Stefano Giusto, Rodolfo Russo, Alexander Tyukov
et al.
Abstract We provide strong evidence that all tree-level 4-point holographic correlators in $$\hbox {AdS}_3 \times S^3$$ AdS3×S3 are constrained by a hidden 6D conformal symmetry. This property has been discovered in the $$\hbox {AdS}_5 \times S^5$$ AdS5×S5 context and noticed in the tensor multiplet subsector of the AdS$$_3 \times S^3$$ 3×S3 theory. Here we extend it to general AdS$$_3 \times S^3$$ 3×S3 correlators which contain also the chiral primary operators of spin zero and one that sit in the gravity multiplet. The key observation is that the 6D conformal primary field associated with these operators is not a scalar but a self-dual 3-form primary. As an example, we focus on the correlators involving two fields in the tensor multiplets and two in the gravity multiplet and show that all such correlators are encoded in a conformal 6D correlator between two scalars and two self-dual 3-forms, which is determined by three functions of the cross ratios. We fix these three functions by comparing with the results of the simplest correlators derived from an explicit supergravity calculation.
Astrophysics, Nuclear and particle physics. Atomic energy. Radioactivity
Moriah B. Bostian, Cinzia Daraio, Rolf Färe
et al.
Network models provide a general representation of inter-connected system dynamics. This ability to connect systems has led to a proliferation of network models for economic productivity analysis, primarily estimated non-parametrically using Data Envelopment Analysis (DEA). While network DEA models can be used to measure system performance, they lack a statistical framework for inference, due in part to the complex structure of network processes. We fill this gap by developing a general framework to infer the network structure in a Bayesian sense, in order to better understand the underlying relationships driving system performance. Our approach draws on recent advances in information science, machine learning and statistical inference from the physics of complex systems to estimate unobserved network linkages. To illustrate, we apply our framework to analyze the production of knowledge, via own and cross-disciplinary research, for a world-country panel of bibliometric data. We find significant interactions between related disciplinary research output, both in terms of quantity and quality. In the context of research productivity, our results on cross-disciplinary linkages could be used to better target research funding across disciplines and institutions. More generally, our framework for inferring the underlying network production technology could be applied to both public and private settings which entail spillovers, including intra- and inter-firm managerial decisions and public agency coordination. This framework also provides a systematic approach to model selection when the underlying network structure is unknown.
Information theory provides a powerful framework to analyse the representation of sensory stimuli in neural population activity. However, estimating the quantities involved such as entropy and mutual information from finite samples is notoriously hard and any direct estimate is known to be heavily biased. This is especially true when considering large neural populations. We study a simple model of sensory processing and show through a combinatorial argument that, with high probability, for large neural populations any finite number of samples of neural activity in response to a set of stimuli is mutually distinct. As a consequence, the mutual information when estimated directly from empirical histograms will be equal to the stimulus entropy. Importantly, this is the case irrespective of the precise relation between stimulus and neural activity and corresponds to a maximal bias. This argument is general and applies to any application of information theory, where the state space is large and one relies on empirical histograms. Overall, this work highlights the need for alternative approaches for an information theoretic analysis when dealing with large neural populations.
This article summarizes the work presented at the workshop “The Power of Faraday Tomography: towards 3D mapping of cosmic magnetic fields”, held in Miyazaki, Japan, in Spring 2018. We place the various oral and poster presentations given at the workshop in a broader perspective and present some highlight results from every presenter.
A search is presented for the production of vector-like quark pairs, TT‾ or YY‾, with electric charge of 2/3 (T) or −4/3 (Y), in proton–proton collisions at s=13TeV. The data were collected by the CMS experiment at the LHC in 2016 and correspond to an integrated luminosity of 35.8fb−1. The T and Y quarks are assumed to decay exclusively to a W boson and a b quark. The search is based on events with a single isolated electron or muon, large missing transverse momentum, and at least four jets with large transverse momenta. In the search, a kinematic reconstruction of the final state observables is performed, which would permit a signal to be detected as a narrow mass peak (≈7% resolution). The observed number of events is consistent with the standard model prediction. Assuming strong pair production of the vector-like quarks and a 100% branching fraction to bW, a lower limit of 1295 GeV at 95% confidence level is set on the T and Y quark masses. Keywords: CMS, Physics, Vector-like quarks