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Blog – Page 6499

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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Adding absorbent nanoparticles to polymer membranes simplifies desalination.

University of California, Berkeley, chemists have discovered a way to simplify the removal of toxic metals. like mercury and boron. during desalination to produce clean water, while at the same time potentially capturing valuable metals, such as gold.

Desalination — the removal of salt — is only one step in the process of producing drinkable water, or water for agriculture or industry, from ocean or waste water. Either before or after the removal of salt, the water often has to be treated to remove boron, which is toxic to plants, and heavy metals like arsenic and mercury, which are toxic to humans. Often, the process leaves behind a toxic brine that can be difficult to dispose of.

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Experiment opens up field for new physics, say Fermilab, UChicago scientists.

The news that muons have a little extra wiggle in their step sent word buzzing around the world this spring.

The Muon g-2 experiment hosted at Fermi National Accelerator Laboratory announced on April 7 that they had measured a particle called a muon behaving slightly differently than predicted in their giant accelerator. It was the first unexpected news in particle physics in years.

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World Economic Forum Founder Klaus Schwab opens Cyber Polygon 2021 with a warning: “A lack of cybersecurity has become a clear and immediate danger to our society worldwide.”

Giving the welcoming remarks at Cyber Polygon for the second year in a row, Schwab spoke at length about the World Economic Forum’s (WEF) desire to tackle cybersecurity by bringing together a closer merger of corporations, small businesses, and governments.

Last year, Schwab warned, “We all know, but still pay insufficient attention to, the frightening scenario of a comprehensive cyber attack, which would bring a complete halt to the power supply, transportation, hospital services, our society as a whole.”

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Transportable tiny homes are complex operations, to say the least. Designing them to be sustainable makes building them that much more of an intricate process. First Light Studio, a New Zealand-based architecture group built their own tiny home with help from a local company Build Tiny, Ohariu, checking all of the above boxes. Built to be net-zero through several sustainable features and compact enough to meet all NZTA regulations for mobile homes.

Ohariu was built by First Light Studio and Build Tiny from a client’s brief calling for, “a refined tramping lodge on wheels.” That’s code for hiking, for all us Americans. Since the tiny home would primarily be used for hiking trips and traveling throughout the outdoors, Ohariu was built to be adaptable and versatile above all else. Inside, the living spaces are described by the architects at First Light Studio as being, “more a large and very detailed piece of furniture than a traditional house build, the fit-out [focusing] on the things that are important and necessary.”

Catering to the necessities and casual family pastimes, the tiny home is doused in modular and multifunctional design that’s surrounded by creamy poplar plywood walls and silvery fittings that add a touch of refinement to an otherwise bare interior. Each furniture piece inside Ohariu doubles as storage to maintain an open, clutter-free interior where the tiny home’s family would bond over pastimes like cooking, playing card games, and enjoying the surrounding landscape. Featuring a chef’s kitchen, Ohariu comes with plenty of prep space for cooking and integrates tilt-up tabletops to make even more for when there’s company. Outside, Ohariu is coated in a stealthy ebony corrugate to match its lightweight mobility, supported by aluminum joinery, lights, and utilities that were given the same ebony finish. Ohariu’s roof is asymmetrical with six solar panels lined up on its longer side and a mezzanine bedroom cozying up beneath its sloped short side.

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Researchers from Skoltech and their colleagues from the UK have managed to create a stable giant vortex in interacting polariton condensates, addressing a known challenge in quantized fluid dynamics. The findings open possibilities in creating uniquely structured coherent light sources and exploring many-body physics under unique extreme conditions. The paper was published in the journal Nature Communications.

In fluid dynamics, a vortex is a region where a fluid revolves around a point (2D) or a line (3D); you’ve clearly seen one in your sink or may have felt one in the form of turbulence while flying. The quantum world also has vortices: the flow of a quantum fluid can create a zone where the particles revolve persistently around some point. The prototypical signature of such quantum vortices is their singular phase at the core of the vortex.

Skoltech Professors Natalia Berloff and Pavlos Lagoudakis and colleagues studied vortices created by polaritons – odd hybrid quantum particles that are half-light (photon) and half-matter (electrons) – forming a quantum fluid under the right conditions. They were looking for a way to create vortices in these polariton fluids with high values of angular momentum (i.e., getting them to rotate fast). These vortices, also known as giant vortices, are generally very hard to obtain as they tend to break apart into many smaller vortices with low angular momentum in other systems.

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