As active galactic nuclei (AGN) `turn on', some stars end up embedded in accretion disks around supermassive black holes (SMBHs) on retrograde orbits. Such stars experience strong headwinds, aerodynamic drag, ablation and orbital evolution on short timescales. Loss of orbital angular momentum in the first $\sim 0.1$~Myr of an AGN leads to a heavy rain of stars (`starfall') into the inner disk and onto the SMBH. A large AGN loss cone ($θ_{\rm AGN,lc}$) can result from binary scatterings in the inner disk and yield tidal disruption events (TDEs). Signatures of starfall include optical/UV flares that rise in luminosity over time, particularly in the inner disk. If the SMBH mass is $M_{\rm SMBH} \ge 10^{8}M_{\odot}$, flares truncate abruptly and the star is swallowed. If $M_{\rm SMBH}<10^{8}M_{\odot}$, and if the infalling orbit lies within $θ_{\rm AGN,lc}$, the flare is followed by a TDE which can be prograde or retrograde relative to the AGN inner disk. Retrograde AGN TDEs are over-luminous and short-lived as in-plane ejecta collide with the inner disk and a lower AGN state follows. Prograde AGN TDEs add angular momentum to inner disk gas and so start off looking like regular TDEs
Optical transport network operators typically follow a pay-as-you-grow strategy for their network deployment. We propose a proactive multi-period planning approach based on heuristic network planning, supporting this deployment strategy while enabling efficient network utilization through next-generation technology. We report 60% less provisioned lightpaths.
We numerically investigate joint pilot-aided phase recovery for frequency comb-based long-haul wideband transmission. We report net information rate gains by optimizing the pilot overhead and phase estimation algorithm, outperforming per-channel processing at lower complexity.
Continued cost- and power-efficient capacity scaling in optical networks is imperative to keep pace with ever-increasing traffic demands. In this paper, we investigate multi-wavelength transponders as a potential way forward. Suitable system architectures and realistic specifications of multi-wavelength transponders are identified and analyzed in terms of transmit OSNR penalties and spectral constraints. We investigate the performance for different specifications as compared to single-wavelength transponders in a network planning study on two network topologies, developing guidelines for multi-wavelength transponders specifications and their potential benefits. The studies show a reduction in the number of required lasers of up to 83% at the expense of a slight increase in number of lightpaths, demonstrating the potential for significant cost savings and efficiency improvements.
Based on suitable system architectures and realistic specifications, transmit OSNR penalties and spectral constraints of multi-wavelength transponders are identified and analyzed in a network study. We report up to 70% less required lasers at the expense of a slight increase in number of lightpaths.
JWST has revealed dramatic differences between the dawn and dusk regions of the scorching exoplanet WASP-121 b。 Fierce winds appear to carry heat from the planet’s permanent dayside, making the evening side hotter and more expanded。 Scientists also found signs that water is being broken apart by extreme temperatures and that mysterious mineral clou
A new theory suggests the universe is constantly recording its own history in the fabric of spacetime。 If correct, this cosmic memory could help solve some of the biggest puzzles in physics, from black holes to dark matter and the universe’s ultimate fate
The race to build data centers in space is gaining momentum as AI drives unprecedented demand for computing power。 Orbital facilities could tap into abundant solar energy and avoid many of the environmental challenges faced on Earth。 Yet space remains a harsh and expensive place to operate, with major hurdles including cooling, maintenance, radiati
Crypto Clipper spreads over USB and communicates over Tor
Scientists found that transfer learning can make the search for new physics in the universe much faster, slashing the need for expensive simulations。 Yet the approach can backfire when AI relies too heavily on familiar patterns, potentially missing evidence of something truly new
Researchers developed a Wordle-solving strategy that succeeds 99% of the time by focusing on information gain rather than likely answers。 The method uses Shannon entropy to identify guesses that reveal the most about the hidden word。 Each guess is designed to slash uncertainty and narrow the possibilities faster
Oxford physicists have created an entirely new type of Schrödinger’s cat-like quantum state using components that are themselves highly quantum in nature。 The advance could open new possibilities for more resilient quantum computers and deeper insights into the strange rules that govern the quantum universe
What if our biggest idea about reality is built on a hidden misunderstanding。 A new philosophical look at space-time challenges the popular view that the past, present, and future all exist together in a timeless "block universe。" The argument suggests that physicists may be blurring the difference between things that exist and things that merely o
Physicists have solved a long-standing problem involving systems that appear to violate Newton’s third law, such as bird flocks and bacterial swarms。 By adding carefully designed “imaginary partners” to their models, they can now simulate these complex systems with unprecedented accuracy