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Blog – Page 6524

A new laser that generates quantum particles can recycle lost energy for highly efficient, low threshold laser applications.

Scientists at KAIST have fabricated a laser system that generates highly interactive quantum particles at room temperature. Their findings, published in the journal Nature Photonics, could lead to a single microcavity laser system that requires lower threshold energy as its energy loss increases.

The system, developed by KAIST physicist Yong-Hoon Cho and colleagues, involves shining light through a single hexagonal-shaped microcavity treated with a loss-modulated silicon nitride substrate. The system design leads to the generation of a polariton laser at room temperature, which is exciting because this usually requires cryogenic temperatures.

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According to NASA, the solar storm is travelling towards Earth at a velocity of 1.6 million km/hr and the speed might even increase more.

The satellites in the Earth’s upper atmosphere are also expected to get impacted by the incoming flares. This will directly impact GPS navigation, mobile phone signal and satellite TV. The power grids can also be impacted due to the solar flares.

On the positive side, the solar flares will create an amplified view of Aurora lights in North or South Pole. The people living near the poles will get to experience these lights.

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A new pizzeria, called Pazzi, is staffed entirely by robots, which can handle everything from order-taking to prepping the dough, to boxing the finished meal.

The restaurant, found in the Beaubourg area of Paris, has taken eight years of research and development. Its creators are two inventors, Cyril Hamon and Sébastien Roverso – both passionate about robotics and electronics since childhood – who began designing the machines in a family garage. Their goal has been to reinvent the fast food experience with a fully automated system that is more convenient and empowering to customers, while maintaining the same or better quality food as conventional restaurants and also being environmentally sustainable.

Pazzi builds on the success of a pilot, tested at the Val d’Europe shopping centre in 2019. The 120m² establishment is more visible and centrally located than that earlier demonstration, being opposite the famous Pompidou centre, benefiting from a high attendance.

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Math about black holes:

If you’ve been following the arXiv, or keeping abreast of developments in high-energy theory more broadly, you may have noticed that the longstanding black hole information paradox seems to have entered a new phase, instigated by a pair of papers [1, 2] that appeared simultaneously in the summer of 2019. Over 200 subsequent papers have since appeared on the subject of “islands”—subleading saddles in the gravitational path integral that enable one to compute the Page curve, the signature of unitary black hole evaporation. Due to my skepticism towards certain aspects of these constructions (which I’ll come to below), my brain has largely rebelled against boarding this particular hype train. However, I was recently asked to explain them at the HET group seminar here at Nordita, which provided the opportunity (read: forced me) to prepare a general overview of what it’s all about. Given the wide interest and positive response to the talk, I’ve converted it into the present post to make it publicly available.

Well, most of it: during the talk I spent some time introducing black hole thermodynamics and the information paradox. Since I’ve written about these topics at length already, I’ll simply refer you to those posts for more background information. If you’re not already familiar with firewalls, I suggest reading them first before continuing. It’s ok, I’ll wait.

Continue reading “Islands behind the horizon” | >

A new analysis of black hole vibrational spectra identifies which frequencies are stable to perturbations—information pertinent for gravitational-wave analysis and quantum gravity modeling.

Are black holes stable when they are slightly perturbed? This question was answered 50 years ago by the physicist C. V. Vishveshwara with a numerical experiment: Vishveshwara imagined sending a wave packet toward a black hole and observing what came out [1]. He found that the scattered wave is a sum of damped sinusoids, whose frequencies and damping times are the free-vibration modes, or so-called quasinormal modes, of the black hole. The damping implies that black holes are stable—they settle back into a stationary state after being perturbed.

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