Piazza is a learning management system which allows students to ask questions in a forum-type format. Instructors are able to moderate the discussion, along with endorsing accurate answers. The software was invented by Pooja Nath in 2009 in order to speed response times and create a commonplace where students could engage in discussion outside of the classroom. Utilizing an extensive notification system and a simple layout, the response time on Piazza averages approximately 14 minutes. Instructors also have the ability to allow students to post anonymously, encouraging more in-depth discussion. The word Piazza comes from the Italian word for plaza—a common city square where people can come together to share ideas and knowledge.
Context. Recent observations with the James Webb Space Telescope (JWST) have revealed the presence of young massive clusters (YMCs) as building blocks of the first galaxies during the first billion years of the Universe. They are not only important constituents of the galaxies, but also potential birthplaces of very massive stars (VMSs) and black hole (BH) seeds. Aims. In this paper, we investigate whether runaway stellar collisions in extremely dense clusters inevitably lead to the formation of VMSs and BH seeds. We focus on clusters with initial half-mass densities of rho(h) greater than or similar to 10(8) M-circle dot pc(-3) at very low metallicity (Z = 10(-4)), using idealized initial conditions that assume a fully formed, gas-free, monolithic stellar system. Our goal is to follow their early internal evolution and quantify the efficiency of collisional growth. Methods. We use NBODY6++GPU and MOCCA, including the latest updates of the single stellar evolution (SSE) and binary stellar evolution (BSE), along with specific routines to handle the formation, growth through collisions, and dynamical evolution of VMSs. Results. Our direct N-body and Monte Carlo simulations show that VMSs form rapidly and unavoidably through repeated collisions, reaching final masses of similar to 5 x 10(3) to 4 x 10(4) M-circle dot, before collapsing into BH seeds of similar mass in less than 4 Myr. These results confirm the existence of a critical mass scale at which collisional growth becomes highly efficient, enabling the formation of VMSs and potentially intermediate-mass BHs. Conclusions. We identify a critical mass-density threshold beyond which clusters undergo runaway collisions, leading to efficient BH-seed formation. For YMCs detected with JWST, we expect efficiencies up to similar to 10%, corresponding to BH masses as large as 10(5) M-circle dot. We predict a BH mass-cluster mass scaling relation of log(M-BH / M-circle dot) = -0.76 + 0.76 log(M / M-circle dot). Frequent VMS formation in this regime may also provide a natural explanation for the strong nitrogen enrichment observed in some high-redshift galaxies.
Abstract We construct a new class of smooth, horizonless, non-supersymmetric solutions in five-dimensional minimal supergravity, which we call rotating topological stars. Built from a Kerr-Taub-bolt geometry embedded in five dimensions, they constitute the first rotating generalization of the topological star compatible with both smoothness in the interior and standard Kaluza-Klein asymptotics, S1 × ℝ1,3. The solutions carry angular momentum, magnetic and electric charges, and form a discrete tower of states labeled by a primary quantum number controlling the spin. Remarkably, despite lying outside the black-hole extremality bound, they can approach arbitrarily closely (in conserved charges) the Kerr black string with a large boost along the fifth dimension, making them relevant prototypes for rotating and astrophysical black-hole microstates. We analyze their geometry in detail, including their gravitational multipoles that can significantly deviate from those of black holes and the presence of an ergoregion, and show that both geodesics and scalar perturbations separate, paving the way for analyzing their dynamics in future work.
The ultraviolet(UV) continuum slope of galaxies, beta, is a powerful diagnostic of the metallicity and ages of stars, nebular gas properties, dust content, and the escape of Lyman continuum (LyC) photons. In this study, we present beta measurements for 395 spectroscopically confirmed galaxies at 5 < z < 14.3 selected primarily from JADES, using high-quality JWST (James Webb Space Telescope) NIRSpec/PRISM spectra. We find a median beta = -2.15, finding a mild increase in blueness of beta with increasing redshift and fainter UV magnitudes. Interestingly, we find evidence for reddening of the average beta at z > 9.5, deviating from the trend observed at z < 9.5. Using stacked spectra in bins of redshift and beta, we derive trends between beta and dust attenuation, metallicity, ionization parameter, and stellar age indicators, finding a lack of dust attenuation to be the dominant driver of bluer beta-values. We furtherreport five galaxies with beta <=-2.9, which show a range of spectroscopic properties and signs of significant LyC photon leakage. Finally, we show that the redder beta-values at z > 9.5 may require rapid build-up of dust reservoirs in the very early Universe or a significant contribution from the nebular continuum emission to the observed UV spectra, with the nebular continuum fraction depending on the gas temperatures and densities. We show that in the absence of dust, nebular emission at ne > 10 000 cm-3 can reproduce the range of red beta that we see in our sample. Higher gas densities can also redden the nebular continuum emission, potentially explaining the observed beta-values.
The phase space of hadron collider events spans hundreds of dimensions, generating an intricate geometry that we are just starting to explore. The number of possible new physics signals is exponential in the number of dimensions and detecting all of them is currently impossible for any human or artificial intelligence. In this work we introduce a method to search for new physics model-independently in this high-dimensional space. It is based on the measurement of the most basic property of the manifold of collider events, its dimensionality. Our proposed technique does not suffer from a look-elsewhere effect that grows exponentially with the number of dimensions of the dataset, and by construction is insensitive to energy scale uncertainties. We illustrate its potential by finding new physics in simulated events with hundreds of phase space dimensions, taking as input single particles rather than jets. This study sets the stage for new model-independent search strategies based on global properties of collider data manifolds.
This paper seeks to understand whether what has been labeled the “twin transition”, a flagship EU policy, emerges as a new endogenous technological trajectory involving the convergence of green and digital technologies, or whether this policy is in fact having little impact. Embracing an evolutionary approach to technology, we first identify the set of relevant technologies defined as “green” and then analyze their evolution in terms of the dominant blocks within the green technology sector and their intertwining with digital technologies, drawing on 560,720 patents granted by the US Patent Office from 1976 to 2024. Three dominant blocks emerge as relevant in defining the direction of innovation, namely energy, transport, and production processes. We assess the technological concentration and underlying complexity of the dominant blocks, interpreting this through the construction of counterfactual scenarios. We find hardly any evidence for a pattern of actual endogenous convergence of green and digital technologies in the period under analysis. On the whole, for the time being, the “twin transition” appears to be a flagship policy in name only, rather than an endogenous technological trajectory driving structural change.
