Monthly Archives: June 2022

This Monday, July 4, 2022, is remarkable for a number of reasons. It happens to be aphelion: the day where the Earth is at its most distant from the Sun as it revolves through the Solar System in its elliptical orbit. Its the 246th anniversary of when the United States officially declared independence from, and war on, Britain. And it marks the annual date where the wealthiest nation in the world sets off more explosivesin the form of fireworksthan any other.

Whether youre an amateur hobbyist, a professional installer, or simply a spectator, fireworks showsare driven by the same laws of physicsthat govern all of nature. Individual fireworks all contain the same four component stages: launch, fuse, burst charges, and stars. Without quantum physics, not a single one of them would be possible. Heres the science behind how every component of these spectacular shows works.

The anatomy of a firework consists of a large variety of elements and stages. However, the same four basic elements are the same across all types and styles of fireworks: the lift charge, the main fuse, a burst charge, and stars. Variations in the diameter of the launch tube, the length of the time-delay fuse, and the height of the fireworks are all necessary to ignite the stars with the proper conditions during the break.

The start of any firework is the launch aspect: the initial explosion that causes the lift. Ever sincefireworks were first inventedmore than a millennium ago, the same three simple ingredients have been at the heart of them: sulfur, charcoal, and a source of potassium nitrate. Sulfur is a yellow solid that occurs naturally in volcanically active locations, while potassium nitrate is abundant in natural sources like bird droppings or bat guano.

Charcoal, on the other hand, isnt the briquettes we commonly use for grilling, but the carbon residue left over from charring (or pyrolyzing) organic matter, such as wood. Once all the water has been removed from the charcoal, all three ingredients can be mixed together with a mortar and pestle. The fine, black powder that emerges is gunpowder, already oxygen-rich from the potassium nitrate.

The three main ingredients in black powder (gunpowder) are charcoal (activated carbon, at left), sulfur (bottom right) and potassium nitrate (top right). The nitrate portion of the potassium nitrate contains its own oxygen, which means that fireworks can be successfully launched and ignited even in the absence of external oxygen; they would work just as well on the Moon as they do on Earth.

With all those ingredients mixed together, theres a lot of stored energy in the molecular bonds holding the different components together. But theres a more stable configuration that these atoms and molecules could be rearranged into. The raw ingredientspotassium nitrate, carbon, and sulfurwill combust (in the presence of high-enough temperatures) to form solids such as potassium carbonate, potassium sulfate, and potassium sulfide, along gases such as carbon dioxide, nitrogen, and carbon monoxide.

All it takes to reach these high temperatures is a small heat source, like a match. The reaction is a quick-burning deflagration, rather than an explosion, which is incredibly useful in a propulsion device. The rearrangement of these atoms (and the fact that the fuel contains its own oxygen) allows the nuclei and electrons to rearrange their configuration, releasing energy and sustaining the reaction. Without the quantum physics of these rearranged bonds, there would be no way to release this stored energy.

The Macys Fourth of July fireworks celebration that takes place annually in New York City displays some of the largest and highest fireworks you can find in the United States of America and the world. This iconic celebration, along with all the associated lights and colors, is only possible because of the inescapable rules of quantum mechanics.

When that first energy release occurs, conventionally known as the lift charge, it has two important effects.

The upward acceleration needs to give your firework the right upward velocity to get it to a safe height for explosion, and the fuse needs to be timed appropriately to detonate at the peak launch height. A small fireworks show might have shells as small as 2 inches (5 cm) in diameter, which require a height of 200 feet (60 m), while the largest shows (like the one by the Statue of Liberty in New York) have shells as large as 3 feet (90 cm) in diameter, requiring altitudes exceeding 1000 feet (300 m).

Different diameter shells can produce different sized bursts, which require being launched to progressively higher altitudes for safety and visibility reasons. In general, larger fireworks must be launched to higher altitudes, and therefore require larger lift charges and longer fuse times to get there. The largest fireworks shells exceed even the most grandiose of the illustrations in this diagram.

The fuse, on the other hand, is the second stage and will be lit by the ignition stage of the launch.Most fusesrely on a similar black powder reaction to the one used in a lift charge, except the burning black powder core is surrounded by wrapped textile coated with either wax or lacquer. The inner core functions via the same quantum rearrangement of atoms and electron bonds as any black powder reaction, but the remaining fuse components serve a different purpose: to delay ignition.

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The textile material is typically made of multiple woven and coated strings. The coatings make the device water resistant, so they can work regardless of weather. The woven strings control the rate of burning, dependent on what theyre made out of, the number and diameter of each woven string, and the diameter of the powder core. Slow-burning fuses might take 30 seconds to burn a single foot, while fast-burning fuses can burn hundreds of feet in a single second.

The three main configurations of fireworks, with lift charges, fuses, burst charges and stars all visible. In all cases, a lift charge launches the firework upward from within a tube, igniting the fuse, which then burns until it ignites the burst charge, which heats and distributes the stars over a large volume of space.

The third stage, then, is the burst charge stage, which controls the size and spatial distribution of the stars inside. In general the higher you launch your fireworks and the larger-diameter your shells are, the larger your burst charge will need to be to propel the insides of the shell outward. In general, the interior of the firework will have a fuse connected to the burst charge, which is surrounded by the color-producing stars.

Theburst chargecan be as simple as another collection of black powder, such as gunpowder. But it could be far more complex, such as the much louder and more impressiveflash powder, or a multi-stage explosive that sends stars in multiple directions. By utilizing different chemical compounds that offer different quantum rearrangements of their bonds, you can tune your energy release, the size of the burst, and the distribution and ignition times of the stars.

Differently shaped patterns and flight paths are highly dependent on the configuration and compositions of the stars inside the fireworks themselves. This final stage is what produces the light and color of fireworks, and is where the most important quantum physics comes into play.

But the most interesting part is that final stage: where the stars ignite. The burst is what takes the interior temperatures to sufficient levelsto create the light and colorthat we associate with these spectacular shows. The coarse explanation is that you can take different chemical compounds, place them inside the stars, and when they reach a sufficient temperature, they emit light of different colors.

This explanation, though, glosses over the most important component: the mechanism of how these colors are emitted. When you apply enough energy to an atom or molecule, you can excite or even ionize the electrons that conventionally keep it electrically neutral. When those excited electrons then naturally cascade downward in the atom, molecule or ion, they emit photons, producing emission lines of a characteristic frequency. If they fall in the visible portion of the spectrum, the human eye is even capable of seeing them.

Whether in an atom, molecule, or ion, the transitions of electrons from a higher energy level to a lower energy level will result in the emission of radiation at a very particular wavelength. This produces the phenomenon we see as emission lines, and is responsible for the variety of colors we see in a fireworks display.

What determines which emission lines an element or compound possesses? Its simply the quantum mechanics of the spacing between the different energy levels inherent to the substance itself. For example, heated sodium emits a characteristic yellow glow, as it has two very narrow emission lines at 588 and 589 nanometers. Youre likely familiar with these if you live in a city, as most of those yellow-colored street lamps you see are powered by elemental sodium.

As applied to fireworks, there are a great variety of elements and compounds that can be utilized to emit a wide variety of colors. Different compounds of Barium, Sodium, Copper and Strontium can produce colors covering a huge range of the visible spectrum, and the different compounds inserted in the fireworks stars are responsible for everything we see. In fact,the full spectrum of colors can be achievedwith just a handful of conventional compounds.

The interior of this curve shows the relationship between color, wavelength, and temperature in chromaticity space. Along the edges, where the colors are most saturated, a variety of elements, ions, and compounds can be shown, with their various emission lines marked out. Note that many elements/compounds have multiple emission lines associated with them, and all of these are used in various fireworks. Because of how easy it is to create barium oxide in a combustion reaction, certain firework colors, such as forest green and ocean green, remain elusive.

Whats perhaps the most impressive about all of this is that the color we see with the human eye is not necessarily the same as the color emitted by the fireworks themselves. For example, if you were to analyze the light emitted by a violet laser, youd find that the photons emerging from it were of a specific wavelength that corresponded to the violet part of the spectrum.

The quantum transitions that power a laser always result in photons of exactly the same wavelength, and our eyes see them precisely as they are, with the multiple types of cones we possess responding to that signal in such a way that our brain responds to construct a signal thats commensurate with the light possessing a violet color.

A set of Q-line laser pointers showcase the diverse colors and compact size that now are commonplace for lasers. By pumping electrons into an excited state and stimulating them with a photon of the desired wavelength, you can cause the emission of another photon of exactly the same energy and wavelength. This action is how the light for a laser is first created: by the stimulated emission of radiation.

But if you look at that same color that appears as violet not from a monochromatic source like a laser, but from your phone or computer screen, youll find that there are no intrinsically violet photons striking your eyes at all! Instead,as Chad Orzel has noted in the past,

Our eyes construct what we perceive as color from the response of three types of cells in our retina, each sensitive to light of a particular range of colors. One is most sensitive to blue-ish light (short wavelength), one is most sensitive to red light (long wavelength), and the third to a sort of yellow-green. Based on how strongly each of these cells responds to incoming light, our brains construct our perception ofcolor.

In other words, the key to producing the fireworks display you want isnt necessarily to create light of a specific color that corresponds to a specific wavelength, but rather to create light that excites the right molecules in our body to cause our brain to perceive a particular color.

A violet laser emits photons of a very particular, narrow wavelength, as every photon carries the same amount of energy. This curve, shown in blue, emits violet photons only. The green curve shows how a computer screen approximates the same exact violet color by using a mix of different wavelengths of light. Both appear to be the same color to human eyes, but only one truly produces photons of the same color that our eyes perceive.

Fireworks might appear to be relatively simple explosive devices. Pack a charge into the bottom of a tube to lift the fireworks to the desired height, ignite a fuse of the proper length to reach the burst charge at the peak of its trajectory, explode the burst charge to distribute the stars at a high temperature, and then watch and listen to the show as the sound, light, and color washes over you.

Yet if we look a little deeper, we can understand how quantum physics underlies every single one of these reactions. Add a little bit extrasuch as propulsion or fuel inside each starand your colored lights can spin, rise, or thrust in a random direction. Make sure you enjoy your fourth of July safely, but also armed with the knowledge that empowers you to understand how the most spectacular human-made light show of the year truly works!

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Fireworks are only possible because of quantum physics - Big Think

June 30, 2022• Physics 15, 97

Science communicators had a field day with the 2012 Higgs discovery, as it offered a chance to energize the public about fundamental physics research.

This article is part of a series of pieces that Physics Magazine is publishing to celebrate the 10th anniversary of the Higgs boson discovery. See also (upcoming): Poem: Higgs Boson: The Visible Glyph; News Feature: The Era of Higgs Physics; Q&A: The Higgs Boson: A Theory, An Observation, A Tool; Podcast: The Higgs, Ten Years After; and Collection: The History of Observations of the Higgs Boson.

The Higgs discovery, announced on July 4, 2012, was a major happening in science but also in science communication. Rarely has so much effort been made to engage the public over a fundamental physics topic. Front-page headlines, best-selling books, public lectures, TV interviews, and feature-length films all tried to explain the Higgs bosona particle whose claim to fame is its association with the generation of mass. Ten years later, the Higgs may not be a household name, but the intense limelight on this fundamental entity did offer communicators an opportunity to tell a larger story about the scientific enterprise.

The Higgs boson is the capstone of the standard model of particle physics, says physicist Sean Carroll from the California Institute of Technology, who wrote about the Higgs in his 2012 book The Particle at the End of the Universe. Hes also helped to popularize the Higgs by giving public lectures, writing blogs, and making TV appearances. He believes the discovery was a watershed moment, as it showed that physicists were clearly on the right track with their understanding of the fundamental workings of the Universe. That kind of accomplishment should not go unrecognized, Carroll says.

So how have science communicators tried to make the Higgs boson famous? One of the earliest attempts was by the Nobel prize winner Leon Lederman, who wrote the 1993 popular science book The God Particle. In it, Lederman described the Higgs as the crucial but elusive piece to our understanding of the structure of matter. [The book] was spectacularly successful in that you literally cannot have a conversation with a person on the street about the Higgs without someone talking about the God particle, Carroll says. But many physicists regret the connection that was made between the Higgs and religion. Theres a lot of work to be done in undoing the damage, Carroll says.

Another early attempt at capturing the publics imagination came with the cocktail party analogy, which earned David Miller of the University College London a bottle of champagne from the UK science minister in 1993. Miller likened the Higgs fielda space-filling energy out of which the Higgs boson arisesto a bustling crowd of partygoers. When a celebrity tries to walk through the room, the crowd presses toward them, slowing their progress. In a similar way, the Higgs field can be drawn toward a particle, slowing its progress and giving it mass. The Higgs is more drawn, for example, to the top quark than to the up quark, hence the top is more massive than the up.

These types of metaphors offer a basic appreciation of the physics behind the Higgs boson and its field. But getting people to take the time to learn about the Higgs requires a more human approach, says Mark Levinsondirector of the 2013 film Particle Fever. If you really want to get the message out, if you want to engage a bigger audience, it needs to be personalized, he says. His award-winning filmwhich ran in theaters across the globe and was distributed on Netflixrecounts the efforts at CERN in Geneva leading up to the Higgs discovery, with Levinsons cameras following a handful of theorists and experimentalists during their day-to-day activities. It is interesting to show why people pursue these incredibly abstract ideas, he says.

When Levinson started shooting in 2008, he was not focused on the Higgs boson, as physicists had warned him that a discovery might take too long to materialize. But once promising signs showed up at CERNs Large Hadron Collider (LHC), Levinson and his editor Walter Murch retooled their films narrative to give a leading role to the Higgs. They even created a graphic with the Higgs in the centera representation that the physics community has come to embrace, Levinson says (Fig. 1). The movies big climactic scene is when LHC scientists revealed their data to a packed auditorium that included a visibly moved Peter Higgs, who began working in the 1960salong with other theoristson his namesake particle. Seeing an 80-year-old physicist tear up over a vindication of his lifes work, thats a great story, Levinson says.

The 2012 announcement was a media hit as well, with over 12,000 news reports on the Higgs boson, according to James Gillies, who was head of CERNs communication group when the discovery was announced (Fig. 2). Like Levinson, Gillies believes the Higgs was an easy sell to the public because the human effort surrounding the discovery was so immense. We cast fundamental science as the latest step in humankinds journey of exploration, he says.

Gillies admits that it can be difficult to assess whether the Higgs excitement had a lasting impact on the publics appreciation of fundamental science. Very little data has been collected on changes in scientific understanding following a big discovery. But theres no doubt in my mind that CERN, LHC, and Higgs are quite common currency these days, Gillies says. My experience has taught me that people are more curious about basic research than we tend to think.

Levinson agrees. Many people have said, I really didnt understand it, but I loved the film. The science, he says, is rather complicated, but the story about scientists and their passion is something that audiences can identify with. The Higgs is fundamental to the physics theory, but its bigger than that, Levinson says. Its more about our quest to understand the way the Universe works.

Theres no shortage of enthusiasm among the public to learn about the Higgs boson, Carroll says. He thinks science communicators can always do better, but I think the Higgs boson is something where we did take advantage of the excitement to teach people a little bit of physics. For his part, Carroll used the discovery to explain some of the quantum field theory that lies at the basis of the Higgs boson prediction. We might as well leverage our big, happy discoveries to better acquaint the public with how science works and what scientists are finding.

Michael Schirber

Michael Schirber is a Corresponding Editor forPhysics Magazine based in Lyon, France.

Using radioactive tritium, scientists improve laboratory constraints on the overdensity signal of cosmic relic neutrinos by a factor of 100, an advance that should improve the chances of spotting this elusive particle. Read More

New neutrino-oscillation data show no sign of an anomalous signal seen in previous studies, but the analyses cant yet fully rule out its presence. Read More

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A Particle is Born: Making the Higgs Famous - Physics

1:002:00 pm

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Please Join us:

Kyle Kawagoe's PhDThesisDefense

Tuesday, July 5 2022 at 1:00 PM CDT

MICROSCOPIC DEFINITIONS OF TOPOLOGICAL DATA

Condensed matter physics rests its foundation on the notion of phases of matter with universal properties. As it is not possible to understand the detailed motions of large collections of particles by tracking them individually, we must rely on the fact that, much of the time, these details are irrelevant to a comprehensive understanding of a macroscopic system. Rather, we must understand the collective behavior of materials via a small set of quantities which summarize this information. For topological phases of matter, which are realized in quantum many-body systems, we can understand their most basic properties from information called ``topological data." This topological data describes the phase of matter of these systems and carries with it a broad array of information about their behavior. Previously, the nature of this data was broadly understood, but in most cases was lacking a concrete interpretation in terms of the microscopic details of these systems.

In this talk, I will resolve this issue by giving concrete definitions of the topological data in terms of a small number of microscopic properties of these systems. These definitions serve not only as a tool to analyze these theories, but also bridge a conceptual gap between the abstract mathematical understanding of these phases of matter with the concrete physical models that physicists study. I will discuss two types of (2+1)D topological phases of matter: intrinsic topological phases (exemplified by fractional quantum Hall states) and symmetry protected topological phases (exemplified by topological insulators). For intrinsic topological order, I will describe data which can be derived from properties of their anyons.For symmetry protected topological phases, I will show how to extract the data from the properties of their edge modes.

Committee Members:

(Chair): Michael Levin

Dam T. Son

Arvind Murugan

Jonathan Simon

Kyle will be heading to The Ohio State University as a Postdoctoral Scholar in the Physics Department, advised by Brian Skinner and Yuan-Ming Lu, and as a PhD Lecturer in the Mathematics Department, teaching and doing research with David Penneys. In these dual roles, he will continue bridging the gap between the physical and mathematical perspectives of condensed matter physics and will remain dedicated to his passion for pedagogy.

Thesis Defense

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Kyle Kawagoe's PhD Thesis Defense | Department of Physics | The University of Chicago - University of Chicago

An artists impression of a black hole and its accretion disk. Illustration: XMM-Newton, ESA, NASA

Twenty-five years ago, in 1997, an Argentine physicist named Juan Martin Maldacena published what would become the most highly cited physics paper in history (more than 20,000 to date). In the paper, Maldacena described a bridge between two theories that describe how our world works, but separately, without meeting each other. These are the field theories that describe the behaviour of energy fields (like the electromagnetic fields) and subatomic particles, and the theory of general relativity, which deals with gravity and the universe at the largest scales.

Field theories have many types and properties. One of them is a conformal field theory: a field theory that doesnt change when it undergoes a conformal transformation i.e. one which preserves angles but not lengths pertaining to the field. As such, conformal field theories are said to be mathematically well-behaved.

In relativity, space and time are unified into the spacetime continuum. This continuum can exist in many possible spaces. Some of these spaces have the same curvature everywhere, and come in three forms (roughly, universes of certain shapes): de Sitter space, Minkowski space and anti-de Sitter space. de Sitter space has positive curvature everywhere like a sphere (but is empty of any matter). Minkowski space has zero curvature everywhere i.e. a flat surface. Anti-de Sitter space has negative curvature everywhere like a hyperbola.

Because these shapes are related to the way our universe looks and works, cosmologists have their own way to understand them. If the spacetime continuum exists in de Sitter space, the universe is said to have a positive cosmological constant. Similarly, Minkowski space implies a zero cosmological constant and anti-de Sitter space a negative cosmological constant. Studies by various space telescopes have found that our universe has a positive cosmological constant, meaning it is approximately a de Sitter space (but not exactly since our universe does have matter).

In 1997, Maldacena found evidence to suggest that a description of quantum gravity in anti-de Sitter space in N dimensions is the same as a conformal field theory in N 1 dimensions. This AdS/CFT correspondence was an unexpected but monumental discovery that connected two kinds of theories that had thus far refused to cooperate.

The Wire Science had a chance to interview Maldacena about his past and current work in 2018, in which he provided more insights on AdS/CFT as well.

In his paper, Maldacena showed that in a very specific case, quantum gravity in anti-de Sitter space in five dimensions was the same as a specific conformal field theory in four dimensions. He conjectured that this equivalence would hold not just for the limiting case but the full theories. So the correspondence is also called the AdS/CFT conjecture. Physicists have not proven this to be the case so far but there is circumstantial evidence from many results that indicate that the conjecture is true.

Nonetheless, the finding was hailed as a major mathematical victory for string theory as well. This theory is a leading contender for one that can unify quantum mechanics and general relativity. However, we have found no experimental evidence of string theorys many claims.

Nonetheless, thanks to the correspondence, (mathematical) physicists have found that some problems that are hard on the AdS side are much easier to crack on the CFT side, and vice versa all they had to do was cross Maldacenas bridge! This was another sign that the AdS/CFT correspondence wasnt just a mathematical trick but could be a legitimate description of reality.

So how could it be real?

The holographic principle

In 1997, Maldacena proved that a string theory in five dimensions was the same as a conformal field theory in four dimensions. However, gravity in our universe exists in four dimensions not five. So the correspondence came close to providing a unified description of gravity and quantum mechanics, but not close enough. Nonetheless, it gave rise to the possibility that an entity that exists in some number of dimensions could be described by another entity that exists in one fewer number of dimensions.

Actually, in fact, the AdS/CFT correspondence didnt give rise to this possibility but realised it mathematically. The awareness of the possibility had existed for many years until then, as the holographic principle. The Dutch physicist Gerardus t Hooft first proposed it and the American physicist Leonard Susskind in the 1990s brought it firmly into the realm of string theory. One way to state the holographic principle, in the words of physicist Matthew Headrick, is thus:

The universe around us, which we are used to thinking of as being three dimensional, is actually at a more fundamental level two-dimensional and that everything we see thats going on around us in three dimensions is actually happening in a two-dimensional space.

This two-dimensional space is the surface of the universe, located at an infinite distance from us, where information is encoded that describes everything happening within the universe. Its a mind-boggling idea. Information here refers to physical information, such as, to use one of Headricks examples, the positions and velocities of physical objects. In beholding this information from the infinitely faraway surface, we apparently behold a three-dimensional reality.

It bears repeating that this is a mind-boggling idea. We have no proof so far that the holographic principle is a real description of our universe we only know that it could describe our reality, thanks to the AdS/CFT correspondence. This said, physicists have used the holographic principle to study and understand black holes.

In 1915, Albert Einsteins general theory of relativity provided a set of complicated equations to understand how mass, the spacetime continuum and the gravitational force are related. Within a few months, physicists Karl Swarzschild and Johannes Droste, followed in subsequent years by Georges Lematre, Subrahmanyan Chandrasekhar, Robert Oppenheimer and David Finkelstein, among others, began to realise that one of the equations exact solutions (i.e. non-approximate) indicated the existence of a point mass around which space was wrapped completely, preventing even light from escaping from inside this space to outside. This was the black hole.

Because black holes were exact solutions, physicists assumed that they didnt have any entropy i.e. that its insides didnt have any disorder. If there had been such disorder, it would have appeared in Einsteins equations. It didnt, so QED. But in the early 1970s, the Israeli-American physicist Jacob Bekenstein noticed a problem: if a system with entropy, like a container of hot gas, was thrown into the black hole, and the black hole doesnt have entropy, where does the entropy go? It had to go somewhere; otherwise, the black hole would violate the second law of thermodynamics that the entropy of an isolated system, like our universe, cant decrease.

Bekenstein postulated that black holes must also have entropy, and that the amount of entropy is proportional to the black holes surface area, i.e. the area of the event horizon. Bekenstein also worked out that there is a limit to the amount of entropy a given volume of space can contain, as well as that all black holes could be described by just three observable attributes: their mass, electric charge and angular momentum. So if a black holes entropy increases because it has swallowed some hot gas, this change ought to manifest as a change in one, some or all of these three attributes.

Taken together: when some hot gas is tossed into a black hole, the gas would fall into the event horizon but the information about its entropy might appear to be encoded on the black holes surface, from the point of view of an observer located outside and away from the event horizon. Note here that the black hole, a sphere, is a three-dimensional object whereas its surface is a flat, curved sheet and therefore two-dimensional. That is, all the information required to describe a 3D black hole could in fact be encoded on its 2D surface.

Doesnt this remind you of the AdS/CFT correspondence? For example, consider a five-dimensional anti-de Sitter space inside which there is a black hole. We can use the correspondence to show that the entropy of the theory that describes the boundary of this space matches exactly with the entropy of the black hole itself. This would realise the conjecture of t Hooft and others except here, the information is encoded not on the event horizon but on the boundary of the five-dimensional space itself.

This is just one example of the wider context that the AdS/CFT correspondence inhabits. For more examples and other insights, do read Maldacenas interview with The Wire Science.

The author is grateful to Nirmalya Kajuri for discussion and feedback on this article.

Original post:

AdS/CFT: 25 Years of the 'Bridge' to an Unknowable Universe - The Wire Science

Posted on Jun 26, 2022 in Black Holes, Physics, Science

It has been said that Newton gave us answers; Stephen Hawking gave us questions. A trio of physicists appear one step closer to resolving the black-hole information paradox, one of the most intriguing physics mysteries of our time.

Spacetime seems to fall apart at a black hole, implying that space-time is not the root level of reality as suggested by the famous paradox that Stephen Hawking first described five decades ago, but emerges from something deeper, observes George Musser, author of Spooky Action at a Distance, for Quanta about Hawkings seminal theory that in a fiery marriage of relativity and quantum physics says that when a black hole forms and then subsequently evaporates away completely by emitting radiation, the information that went into the black hole cannot come back out and is inevitably lost, violating the laws of physics that insist unequivocally that information can never get totally lost.

Enter EinsteinThe Dissolution of Spacetime

In 2003, Hawking found a way that information might escape during the holes evaporation, but he did not prove that the information escapes, so the paradox continued, until now. They are not the eternal prisons they were once thought of, Hawking said. Things can get out of a black hole both on the outside and possibly to another universe.

Although Einstein conceived of gravity as the curved geometry of space-time, his theory also entails the dissolution of space-time, which is ultimately why information can escape its gravitational prison, adds Musser, summarizing a landmark series of calculations by three physicists that show that information does escape a black hole through the workings of ordinary gravity with a single layer of quantum effects, which seems impossible by definition based on new gravitational calculations that Einsteins theory permits, but that Hawking did not include.

The Most Exciting Thing Since Hawking

That is the most exciting thing that has happened in this subject, I think, since Hawking, said one of the co-authors, Donald Marolf of the University of California, Santa Barbara.

Its from that mysterious area where relativity and quantum mechanics dont quite mesh, that the question of what happens to information in a black hole emerges, says says researcher Henry Maxfield at the University of California, Santa Barbara in calculating the quantum information content of a black hole and its radiation.

The Big Question

Maxfield was co-author of a paper, co-written with physicists Ahmed Almheiri at the Institute for Advanced Study and MITs Netta Engelhardt and Marolf UC Santa Barbara in 2019, that takes us one step closer, says Maxfield, to resolving the black hole information paradox. The hope was, if we could answer this question if we could see the information coming out in order to do that we would have had to learn about the microscopic theory, said Geoff Penington of the University of California, Berkeley, alluding to a fully quantum theory of gravity.

Black Holes Gently Glow and Radiate

It goes back to this problem in the 1970s that Stephen Hawking discovered, Maxfield explained. Black holes those extremely dense, high-gravity voids in space-time arent completely black. They gently glow and radiate, he said. And as they do that, the black holes evaporate. But one element of Hawkings calculations, Maxfield continued, is that this state of Hawking radiation destroys information about the original quantum state of the material drawn into the hole.

This is very different from what quantum mechanics does, Maxfield said. In principle, the laws of physics are completely reversible. In other words, information about the materials original quantum state should exist in some form. So there was this conflict that quantum mechanics behaves one way and gravity seems to behave another way.

Tip of the Iceberg

We were interested in something closely related, which was trying to identify where the information is located, Maxfield said about the non-linear path to their calculation as a modification to Hawkings calculation broadening it to include a method for quantifying the information.

So theres that early radiation when the black hole is still young that doesnt really carry any information, Maxfield said about their calculation about how much information is stored in a black hole as it evaporates, and the finding that the amount of information indeed decreases over time.. But once the black hole has shrunk away to half its size it takes a very long time the quantum information starts coming out. This is what youd expect from quantum mechanics.

The calculation that Maxfield, Englehardt, Almheiri and Geoff Penington (who was concurrently doing very similar work at Stanford) made, reports UC Santa Barbara, is but a tip of the iceberg.

The Biggest Clue Weve Had

It doesnt mean that weve completely understood everything, Maxfield said. But it is the biggest clue weve had for a really long time as to how this tension gets resolved.

They found that the information is coming out, even if they didnt have all the reasons why it comes out, Marolf commented. But the idea is that this is a first step. If you have a way of performing that calculation, you should be able to open that calculation up and figure out what the physical mechanism is. This calculation is something we expect is going to give us insight into quantum processes in black holes and how information comes out of them.

Im very resistant to people who come in and say, Ive got a solution in just quantum mechanics and gravity, said a skeptical Nick Warner of the University of Southern California. Because its taken us around in circles before.

Max Goldberg via UC Santa Barbara and Quanta

Read more:

Information Can Escape a Black Hole Both On the Outside and Possibly to Another Universe (Stephen Hawkings - The Daily Galaxy --Great Discoveries...

Cannon Arm and the Arcade Quest (15A) is an offbeat documentary from Danish director Mads Hedegaard that follows Kim Kanoin (aka Cannon Arm) as he attempts to break the world record for playing the arcade video game Gyruss without a break.

The plan, which requires the help of all Kims arcade game-obsessed friends to work, is for Kim to play Gyruss for 100 hours a mind-boggling effort in prospect, although Kim has previously clocked up 47 hours straight. It all sounds like an exercise in Sisyphean futility: Kim is so good that he finds himself negotiating countless repetitions of a spaceship blasting enemies out of existence but the film is chock-a-block with fascinating characters.

Kim himself is a monosyllabic grandfather still sporting a 70s-style ponytail, and his friends are a diverse group whose specialisations poetry, engineering, Bach, quantum physics all play their part in Kims quest.

Its kinda like Rocky, observes one of the friends, alluding to Kims refusal to be beaten, and while its not remotely akin to anything like Rocky, Cannon Arm is still an absorbingly Quixotic story of enduring friendship.

(cinema release)

Go here to see the original:

Film Review: Cannon Arm and the Arcade Quest is a love letter to chasing high scores - Irish Examiner

If one watches India's prime-time debates on the television channels or the internet, or even if one only reads news articles posted online and elsewhere, one is quite frequently confronted with the word 'narrative'.

Those who oppose the incumbent powers firmly believe they are indulging in a massive rewriting of history, obscuring facts not palatable to them and highlighting figures and events conducive to their agenda.

On the contrary, those in support of the ruling dispensation claim that their emphasis is only on "correcting" historical wrongs, which involves highlighting facts hitherto un-published, and demeaning facts which they see as instances of "historical injustice".

To an objective observer, the best route to understand who is in the more rationally or perhaps ethically justified position is to understand how history is written.

Ideally, history is written by academicians and scholars, who go through a rigorous process of peer review of their theories and accounts before they get published. How clean and transparent this review process is determining how factual any historical narrative is. In other words, the scientific method of observation, experiment and cataloguing is what dictates the global narratives of history. This hasn't been the case throughout most of history. Before the scientific revolution, history was taught more through anecdotes, i.e. personal reflection on the part of the individual scholar, and stories, i.e. fictionalised accounts of historical memories and narratives, were the order of the day when it came to the accounts of history. That is precisely the reason why the Mahabharata has references to events and entities that are considered 'impossible' by today's scientific standards. In other words, the distinction between story and history is not as old as a nave observer may assume.

Returning to the present, the attempt to revise history must be seen in the light of how the scientific method of chronological record-making proceeds. For this, a brief exposition of the scientific method itself is necessary.

The scientific method, developed not by scientists so much as by philosophers like Karl Popper, Quine, etc., is based on experimental observation and validation. In other words, what cannot be validated through observation is not considered science. Measurement or observation is key to the process here. That which cannot be substantiated through references, citations, and archaeological proofs is not considered history today.

The historical accounts of figures like Lord Ram, Prophet Muhammad, Jesus Christ, the Buddha, Arjun, Bhim or other characters in some of the great Indian epics have not been conceived on these lines. Why is this so? Did the historians of yesteryears have some insight into observation and measurement that today's 'scientific-minded' historians lack? Or was society intellectually very backward in that era - even during the days of Nalanda and Taxila, that they couldn't distinguish between fact and fiction?

A key to solving this mystery is in understanding the word measurement - a euphemism for observation in textbooks of modern science, especially those of theoretical physics pertaining to the quantum or sub-atomic realm of matter. In modern science, according to the most popular and accepted Copenhagen Interpretation of quantum mechanics, introduced to the world by Neils Bohr and Werner Heisenberg, pioneers of quantum physics, measurement is not an act separate from the one who is observing. In other words, although not many people seem to be aware of this, an act of observation is dependent on the person observing. There are no facts independent of the person checking them, just as there is no person independent of the environment he is surrounded with.

This does not mean that we can alter things by looking at them. It means that any scientific knowledge or any perception for that matter shows us not what things are but only shows us how we see things. In simpler words, any theory or piece of knowledge we acquire tells us more about ourselves and our own manners of perception rather than the thing perceived by us. In most crude language, anything we see, hear, taste, smell, feel, touch, or perceive in any possible manner, does not show us reality, but rather it shows us our brains perceiving reality.

Bringing us back to History and the battle of narratives being fought out on our television sets, computer screens and smartphones, what is the measurement or observation of a historical fact? Are the individual historians observing or researching a fact and modifying it while checking it? Are the institutions of historical scholarship and academia co-creating facts when they peer-review each other's research and publish only what is personally acceptable to their club, so to speak?

It could indeed be that historians are subconsciously or perhaps consciously changing history while observing it and that the 'clubs' of academic scholarship are being run by those who wish to dictate historical narratives based on their own self-defined notions of academic superiority and scholarship, which would even dictate what counts as 'proof'.

BJP loyalists, pejoratively called 'Bhakts' and 'Andh-Bhakts' by their opponents, might actually have a point when they question the validity of the erstwhile mainstream historical narrative or account. It is just that they're firing their bullets at the wrong target. Instead of focusing on "rewriting" while peddling it as "rediscovering" history, it would be more suitable for them to question the validity of historical narratives as being objective per se, with an as unbiased and non-political approach as possible.

In other words, we are indeed living in a 'post-truth' world, as those who keep shouting the words 'false narrative' to counter another person's point of view might have realised. But the point of realising that truth or at least knowledge is subjective is not to challenge the other person's subjectivity with one's own subjectivity, whether one supports the left, right or centre. It is to realise that we all live in our own subjective perceptual fields, which should ideally make us respect our opponent's point of view more and try to listen and learn from it. The truth will only emerge from a discussion between those who oppose and respect each other. It will not emerge from realising on the one hand that knowledge is relative and subjective and then immediately imposing this subjectivity upon another who we also acknowledge as being equally subjective.

Democracy is based on disagreement and reconciliation, not in self-imposed intellectual contradiction and forced imposition of this ailment upon others. If that were so, then we would all be mentally ill, and the whole world would be a 19th-century lunatic asylum, with no one fully communicating with anyone else, except that, in this case, even the healers and nurses would be patients with us, which is not a fantasy many of us would like to indulge in.

(The author is a research scholar)

Disclaimer: The views expressed above are the author's own. They do not necessarily reflect the views of DH.

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Why is Sangh Parivar engaged in rewriting history? - Deccan Herald