Category Archives: Quantum Physics

by Holly Evarts|October 14, 2021

Scientists have for the first time documented areas in the deep earth where materials have undergone changes on a subatomic level. There, crushing pressures apparently are bringing about a long hypothesized but until now unproven quantum phase transition called a spin crossover, which affects the magnetic state of a key deep-earth mineral.

The interior of the earth is a mystery, especially at depths greater than about 650 kilometers, or some 400 miles. Researchers have only seismic tomographic images of this region; to interpret them, they need to measure or calculate the velocities of seismic waves passing through minerals in various layers. Direct measurements are challenging and rare but in the last two decades scientists have gotten around this to some degree by making quantum calculations. With these, they can create 3D maps and figure out the mineralogy and temperature of the observed regions. When a phase transition occurs in a mineral, such as a crystal structure change, scientists observe a velocity change, usually a sharp seismic velocity discontinuity.

In 2003, lab scientists observed a novel type of phase change in mineralsa spin change in iron in ferropericlase, the second most abundant component of the earths lower mantle. A spin change, or spin crossover, can happen in minerals like ferropericlase under an external stimulus, such as pressure or temperature. Over the next few years, experimental and theoretical groups confirmed this phase change in both ferropericlase and bridgmanite, the most abundant phase of the lower mantle. But no one was quite sure why or where this was happening.

Columbia Engineering professor Renata Wentzcovitch began investigating this question. Wenzcovitchs research focuses on computational quantum mechanical studies of materials at extreme conditions, in particular planetary materials. In 2006, she published her first paper on ferropericlase, providing a theory for the spin crossover. Her theory suggested it happened across a thousand kilometers in the lower mantle.

Visualization: Nicoletta Barolini/Columbia Engineering

Since then, Wentzcovitch, a professor in Columbias department of Applied Physics and Applied Mathematics, and the universitys Lamont-Doherty Earth Observatory, has published 13 papers with her group on the topic. In these, they investigated velocities in every possible situation of the spin crossover in ferropericlase and bridgmanite, and predicted properties of these minerals throughout this crossover. In 2014, they predicted how this spin change could be detected in seismic tomographic images, but seismologists still could not see it.

With a multidisciplinary team from the University of Oslo, the Tokyo Institute of Technology and Intel Co., Wenzcovitchs latest paper, in the journal Nature, details how they have now identified the ferropericlase spin crossover signal deep within the earths lower mantle. They achieved this by looking at specific regions in the mantle where ferropericlase is expected to be abundant.

This exciting finding, which confirms my earlier predictions, illustrates the importance of materials physicists and geophysicists working together to learn more about whats going on deep within the earth and other planets, said Wentzcovitch. Geodynamic simulations have shown that the spin crossover invigorates convection in the earths mantle and tectonic plate motion. So we think that this quantum phenomenon also increases the frequency of tectonic events such as earthquakes and volcanic eruptions.

Engineers commonly harness spin transition in materials like those used for magnetic recording. If you stretch or compress just a few nanometer-thick layers of a magnetic material, you can change the layers magnetic properties and improve the mediums recording properties. Wentzcovitchs new study shows that the same phenomenon happens across thousands of kilometers in the planets interior, taking this from the nano- to the macro-scale.

There are still many regions of the mantle researchers do not understand, and [studying] spin state change is critical to further progress, said Wentzcovitch. She is continuing to interpret seismic tomographic maps, and developing more accurate materials simulation techniques to predict seismic velocities and transport properties. In particular, she is looking at regions rich in molten or near-molten iron. Well be able to improve our analyses of 3D tomographic images of the earth and learn more about how the crushing pressures of the [interior] are indirectly affecting our lives above, she said.

Read more from the original source:

Quantum Phase Transition Is Detected on a Global Scale in the Deep Earth - State of the Planet

Emmanouil Michellis/Alamy

Garry Trethewey

Cherryville, South Australia

The temperature of a substance, whether solid, liquid, gas or plasma, is essentially related to the speed at which its particles are moving in relation to each other. There is an upper limit on speed the speed of light.

Vlatko Vedral

University of Oxford, UK

There are a number of arguments as to why there should be an upper bound on the value of temperature. The simplest is that temperature is related to energy (via Boltzmanns constant). So if we believe that the energy in the universe is finite (a reasonable supposition), then that gives us the highest temperature.

This can be estimated as follows: the mass of the visible universe is about 1054 kilograms. From this, the energy of the universe can be calculated using the equation, E = mc2, where energy (E) equals mass (m) multiplied by the square of the speed of light (c2). Then divide this sum by Boltzmanns constant to get the temperature. This comes out to about 1094 kelvin. While this is a large number, it certainly isnt infinite.

It is possible that neither the lowest nor highest temperature will ultimately have any fundamental significance

The second argument comes from quantum physics and gravity. They imply that there is a smallest possible distance that can be defined in the universe, known as the Planck length. This gives us the highest possible frequency, which when multiplied by the Planck constant gives us the highest possible quantum of energy. If you divide this by Boltzmanns constant, you get a temperature of 1032 kelvin. This is sometimes called the Planck temperature.

Another way of thinking about this concerns the Planck mass, thought to be the highest mass that a hypothetical elementary particle could have. Multiply this by c2 to get the energy of this particle, then divide by Boltzmanns constant and you again get the Planck temperature, 1032 kelvin. This is much smaller than the first estimate I presented, but some cosmological models take it to be the initial temperature of the universe.

However, temperature isnt a fundamental entity. It is really an emergent concept that tells us about the average chaotic kinetic energy of an object. In that sense, it is perfectly possible that neither the lowest nor the highest temperature will ultimately have any fundamental significance. Only time will tell.

To answer this question or ask a new one email lastword@newscientist.com.

Questions should be scientific enquiries about everyday phenomena, and both questions and answers should be concise. We reserve the right to edit items for clarity and style. Please include a postal address, daytime telephone number and email address.

New Scientist Ltd retains total editorial control over the published content and reserves all rights to reuse question and answer material that has been submitted by readers in any medium or in any format.

Terms and conditions apply.

Read the original:

Absolute zero is the lowest temperature but is there an upper limit? - New Scientist

8:0010:00 am

Ian MacCormacksPhDThesisDefense

Thursday, October 28, 2021, 8-10 AM CT

In-person Location: MCP 201

and Via Zoom

PROBING THE SPATIAL DISTRIBUTION OF ENTANGLEMENT IN MANY-BODY QUANTUM SYSTEMS

Entanglement is the most unique and distinguishing feature of quantum mechanics, and is of fundamental importance not only to the theory of quantum information, but to the study of quantum phases of matter. While much work has been done to study the entanglement in the ground states of familiar systems like conformal field theories and gapped topological phases, slightly less attention has been paid to dynamical quantum systems and systems that lack translational invariance.

In this talk, I will first introduce some basic formalism and intuition related to entanglement in many-body quantum systems. I will then discuss an elegant means of calculating entanglement entropy and other measures in strongly interacting CFTs on curved backgrounds via the Ryu/Takyanagi formula. Next, I will introduce a general formula for the calculation of the entanglement contour, a well-behaved entanglement density function. The contour will be shown to be particularly useful for probing the dynamics of out-of-equilibrium quantum systems. With these dynamical systems in mind, I will present results from calculations of multipartite operator entanglement a state-independent entanglement measure in a many-body localized system.

Finally, I will conclude with a brief overview of the possibilities of realizing and probing entangled quantum matter using near-term quantum computers.

Committee Members:

Shinsei Ryu (Chair)

Jeffrey Harvey

Michael Levin

Mark Oreglia

Ian will be joining Menten AI, a startup that uses advanced computing methods to design protein drugs. There, he will be developing and adapting algorithms for near-term quantum computers to aid in the design of complex protein molecules.

Thesis Defense

Continued here:

Ian MacCormack's PhD Thesis Defense | Department of Physics | The University of Chicago - UChicago News

Scientists have just set a new record for the coldest temperature in a laboratory. By pouring magnetized gas 393 feet (120 metres) down a tower, they produced the bone-chilling temperature of 38 trillionths of a degree above -273.15 Celsius.

The German scientists were interested in the quantum properties of the fifth state of matter: The Bose-Einstein condensate (BEC) is a gas derivative that only exists at very low temperatures. In the BEC phase, matter begins to behave like a single gigantic atom, making it an intriguing topic for quantum physicists interested in the mechanics of subatomic particles.

Temperature is a measure of molecular vibration; the higher the aggregate temperature of a set of molecules, the faster they travel. Absolute zero, or minus 459.67 degrees Fahrenheit or -273.15 degrees Celsius, is the temperature at which all molecular motion ends. The Kelvin scale, with 0 Kelvin equal to absolute zero, was developed by scientists as a separate measure for freezing temperatures.

Light changes into a liquid that can be poured into a container, according to research published in the journal Nature Physics in 2017. Supercooled helium no longer feels friction at very low temperatures, according to a 2017 study published in the journal Nature Communications. NASAs Cold Atom Lab has even discovered atoms that are in two places at the exact moment.

Scientists used a magnetic field to trap a cloud of 100,000 gaseous rubidium atoms inside a vacuum container during the experiment. The chamber was then refrigerated to 2 billionths of a degree Celsius above absolute zero, which would have been a world record in and of itself.

However, to get much colder, the scientists needed to simulate deep-space conditions. So the crew travelled to the European Space Agencys Bremen drop tower, a microgravity research facility at the University of Bremen in Germany.

The rubidium atoms molecular speed was decreased next to nothing by dropping the vacuum chamber and rapidly switching the magnetic field on and off, allowing the BEC to float free of gravity. According to the study, the resulting BEC lasted around 38 picokelvins 38 trillionths of a Kelvin for about 2 seconds, creating an absolute minus record.

Scientists at the National Institute of Standards and Technology (NIST) in Boulder, Colorado, used specialised lasers to establish the previous record of 36 millionths of a Kelvin.

The Boomerang Nebula, 5,000 light-years from Earth, is the coldest known natural area in the universe. According to the European Space Agency, its average temperature is -272 C (approximately 1 Kelvin).

According to the new studys authors, they could sustain this temperature for up to 17 seconds in absolutely weightless environments, such as space. Freezing temperatures, according to MIT specialists, may help scientists in the construction of more powerful quantum computers.

More details can be found here.

See the original post here:

These Physicists Have Broken The Record For The Coldest Temperature Ever Measured In A Lab - Wonderful Engineering

In the beginning, there was well, maybe there was no beginning. Perhaps our universe has always existed and a new theory of quantum gravity reveals how that could work.

"Reality has so many things that most people would associate with sci-fi or even fantasy," said Bruno Bento, a physicist who studies the nature of time at the University of Liverpool in the U.K.

In his work, he employed a new theory of quantum gravity, called causal set theory, in which space and time are broken down into discrete chunks of space-time. At some level, there's a fundamental unit of space-time, according to this theory.

Bento and his collaborators used this causal-set approach to explore the beginning of the universe. They found that it's possible that the universe had no beginning that it has always existed into the infinite past and only recently evolved into what we call the Big Bang.

Related: Big Bang to civilization: 10 amazing origin events

Quantum gravity is perhaps the most frustrating problem facing modern physics. We have two extraordinarily effective theories of the universe: quantum physics and general relativity. Quantum physics has produced a successful description of three of the four fundamental forces of nature (electromagnetism, the weak force and the strong force) down to microscopic scales. General relativity, on the other hand, is the most powerful and complete description of gravity ever devised.

But for all its strengths, general relativity is incomplete. In at least two specific places in the universe, the math of general relativity simply breaks down, failing to produce reliable results: in the centers of black holes and at the beginning of the universe. These regions are called "singularities," which are spots in space-time where our current laws of physics crumble, and they are mathematical warning signs that the theory of general relativity is tripping over itself. Within both of these singularities, gravity becomes incredibly strong at very tiny length scales.

Related: 8 ways you can see Einstein's theory of relativity in real life

As such, to solve the mysteries of the singularities, physicists need a microscopic description of strong gravity, also called a quantum theory of gravity. There are lots of contenders out there, including string theory and loop quantum gravity.

And there's another approach that completely rewrites our understanding of space and time.

In all current theories of physics, space and time are continuous. They form a smooth fabric that underlies all of reality. In such a continuous space-time, two points can be as close to each other in space as possible, and two events can occur as close in time to each other as possible.

"Reality has so many things that most people would associate with sci-fi or even fantasy."

But another approach, called causal set theory, reimagines space-time as a series of discrete chunks, or space-time "atoms." This theory would place strict limits on how close events can be in space and time, since they can't be any closer than the size of the "atom."

Related: Can we stop time?

For instance, if you're looking at your screen reading this, everything seems smooth and continuous. But if you were to look at the same screen through a magnifying glass, you might see the pixels that divide up the space, and you'd find that it's impossible to bring two images on your screen closer than a single pixel.

This theory of physics excited Bento. "I was thrilled to find this theory, which not only tries to go as fundamental as possible being an approach to quantum gravity and actually rethinking the notion of space-time itself but which also gives a central role to time and what it physically means for time to pass, how physical your past really is and whether the future exists already or not," Bento told Live Science.

Causal set theory has important implications for the nature of time.

"A huge part of the causal set philosophy is that the passage of time is something physical, that it should not be attributed to some emergent sort of illusion or to something that happens inside our brains that makes us think time passes; this passing is, in itself, a manifestation of the physical theory," Bento said. "So, in causal set theory, a causal set will grow one 'atom' at a time and get bigger and bigger."

The causal set approach neatly removes the problem of the Big Bang singularity because, in the theory, singularities can't exist. It's impossible for matter to compress down to infinitely tiny points they can get no smaller than the size of a space-time atom.

So without a Big Bang singularity, what does the beginning of our universe look like? That's where Bento and his collaborator, Stav Zalel, a graduate student at Imperial College London, picked up the thread, exploring what causal set theory has to say about the initial moments of the universe. Their work appears in a paper published Sept. 24 to the preprint database arXiv. (The paper has yet to be published in a peer-reviewed scientific journal.)

The paper examined "whether a beginning must exist in the causal set approach," Bento said. "In the original causal set formulation and dynamics, classically speaking, a causal set grows from nothing into the universe we see today. In our work instead, there would be no Big Bang as a beginning, as the causal set would be infinite to the past, and so there's always something before."

Their work implies that the universe may have had no beginning that it has simply always existed. What we perceive as the Big Bang may have been just a particular moment in the evolution of this always-existing causal set, not a true beginning.

There's still a lot of work to be done, however. It's not clear yet if this no-beginning causal approach can allow for physical theories that we can work with to describe the complex evolution of the universe during the Big Bang.

"One can still ask whetherthis [causal set approach] can be interpreted in a 'reasonable' way, or what such dynamics physically means in a broader sense, but we showed that a framework is indeed possible," Bento said. "So at least mathematically, this can be done."

In other words, it's a beginning.

Originally published on Live Science.

View post:

What if the universe had no beginning? - Livescience.com

This study identified the content of the neural representations in the minds of physicists considering some of the classical and post-classical physics concepts that characterize their understanding of the universe. In this discussion, we focus on the representations of post-classical concepts, which are the most recent and most abstract and have not been previously studied psychologically. The neural representations of both the post-classical and classical concepts were underpinned by four underlying neurosemantic dimensions, such that these two types of concepts were located at opposite ends of the dimensions. The neural representations of classical concepts tended to be underpinned by underlying dimensions of measurability of magnitude, association with a mathematical formulation, having a concrete, non-speculative basis, and in some cases, periodicity. By contrast, the post-classical concepts were located at the other ends of these dimensions, stated initially here in terms of what they are not (e.g. they are not periodic and not concrete). Below we discuss what they are.

The main new finding is the underlying neural dimension of representation pertaining to the concepts presence (in the case of the classical concepts) or absence (in the case of the post-classical concepts) of a concrete, non-speculative basis. The semantic characterization of this new dimension is supported by two sources of converging evidence. First, the brain imaging measurement of each concepts location on this underlying dimension (i.e. the concepts factor scores) converged with the behavioral ratings of the concepts degree of association with this dimension (as we have interpreted it) by an independent group of physicists. (This type of convergence occurred for the other three dimensions as well.) Second, the two types of concepts have very distinguishable neural signatures: a classifier can very accurately distinguish the mean of the post-classical concepts signatures from the mean of the classical concepts within each participant, with a grand mean accuracy of 0.93, p<0.001.

As physicists ventured into conceptually new territory in the 20th century and developed new post-classical concepts, their brains organized the new concepts with respect to a new dimension that had not played a role in the representation of classical concepts.

To describe what mental processes might characterize the post-classical end of this new dimension, it is useful to consider what attributes of the post-classical concepts could have led to their being neurally organized as they are and what cognitive and neural processes might operate on these attributes. Previously mentioned was that post-classical concepts often involve their immeasurability and their lower likelihood of being strongly associated with a mathematical formulation and periodicity, both of which are attributes that are often absent from post-classical concepts.

More informative than the absent attributes are four types of cognitive processes evoked by the post-classical concepts: (1) Reasoning about intangibles, taking into account their separation from direct experience and their lack of direct observability; (2) Assessing consilience with other, firmer knowledge; (3) Causal reasoning about relations that are not apparent or observable; and (4) Knowledge management of a large knowledge organization consisting of a multi-level structure of other concepts.

In addition to enabling the decoding of the content of the participants thoughts, whether they were thinking of dark matter or tachyon for example, the brain activation patterns are also informative about the concomitant psychological processes that operate on the concepts, in particular, the four processes listed above are postulated to co-occur specifically with the post-classical concepts. The occurrence of these processes was inferred from those locations of the voxel clusters associated with (having high loadings on) the classical/post-classical factor, specifically the factor locations where the activation levels increased for the post-classical concepts. (These voxel clusters are shown in Fig. 4, and their centroids are included in Table 2). Inferring a psychological process based on previous studies that observed activation in that location is called reverse inference. This can be an uncertain inferential method because many different processes or tasks can evoke activation at the same location. What distinguishes the current study are several sources of independent converging evidence, in conjunction with the brain locations associated with a factor (and not simply observed activation), indicating a particular process.

The factor clusters are encircled and numbered for ease of reference in the text and their centroids are included in Table 2. These locations correspond to the four classes of processes evoked by the post-classical concepts.

First, a statistically reliable decoding model predicted the activation levels for each concept in the factor locations, based on independent ratings of the concepts with respect to the postulated dimension/factor. The activation levels of the voxels in the factor locations were systematically modulated by the stimulus set, with the post-classical concepts, a specific subset of the stimuli eliciting the highest activation levels in these locations, resulting in the highest factor scores for this factor. Thus these brain locations were associated with an activation-modulating factor, not with a stimulus or a task. Second, the processes are consistent with the properties participants reported to have associated with the post-classical concepts. These properties provide converging evidence for these four types of processes occurring. For example, the concept of multiverse evoked properties related to assessing consilience, such as a hypothetical way to explain away constants. Another example is that tachyons and quasars were attributed with properties related to reasoning about intangibles, such as quasi-stellar objects. Third, the processes attributed to the factor locations were based not simply on an occasional previous finding, but on the large-scale meta-analysis (the Neurosynth database, Yarkoni et al.10) using the association based test feature. The association between the location and the process was based on the cluster centroid locations; particularly relevant citations are included in the factor descriptions. Each of the four processes is described in more detail below.

The nature of many of the post-classical concepts entails the consideration of alternative possible worlds. The post-classical factor location in the right temporal area (shown in cluster 5 in Fig. 4) has been associated with hypothetical or speculative reasoning in previous studies. In a hypothetical reasoning task, the left supramarginal factor location (shown in cluster 8) was activated during the generation of novel labels for abstract objects11. Additionally, the right temporal factor location (shown in cluster 5) was activated during the assessment of confidence in probabilistic judgments12.

Another facet of post-classical concepts is that they require the unknown or non-observable to be brought into consilience with what is already known. The right middle frontal cluster (shown in cluster 2) has been shown to be part of a network for integrating evidence that disconfirms a belief13. This consilience process resembles the comprehension of an unfolding narrative, where a new segment of the narrative must be brought into coherence with the parts that preceded it. When readers of a narrative judge the coherence of a new segment of text, the dorsomedial prefrontal cortex location (shown in cluster 6) is activated14. This location is associated with a post-classical factor location, as shown in Fig. 4. Thus understanding the coherence of an unfolding narrative text might involve some of the same psychological and neural consilience-seeking processes as thinking about concepts like multiverse.

Thinking about many of the post-classical concepts requires the generation of novel types of causal inferences to link two events. In particular, the inherent role of the temporal relations in specifying causality between events is especially complex with respect to post-classical concepts. The temporal ordering itself of events is frame-dependent in some situations, despite causality being absolutely preserved, leading to counter-intuitive (though not counter-factual) conclusions. For example, in relativity theory the concept of simultaneity entails two spatially separated events that may occur at the same time for a particular observer but which may not be simultaneous for a second observer, and even the temporal ordering of the events may not be fixed for the second observer. Because the temporal order of events is not absolute, causal reasoning in post-classical terms must eschew inferencing on this basis, but must instead rely on new rules (laws) that lead to consilience with observations that indeed can be directly perceived.

Another example, this one from quantum physics, concerns a particle such as an electron that may be conceived to pass through a small aperture at some speed. Its subsequent momentum becomes indeterminate in such a way that the arrival location of the particle at a distant detector can only be described in probabilistic terms, according to new rules (laws) that are very definite but not intuitive. The perfectly calculable non-local wave function of the particle-like object is said to collapse upon arrival in the standard Copenhagen interpretation of quantum physics. Increasingly elaborate probing of physical systems with one or several particles, interacting alone or in groups with their environment, has for decades elucidated and validated the non-intuitive new rules about limits and alternatives to classical causality in the quantum world. The fact that new rules regarding causal reasoning are needed in such situations was described as the heart of quantum mechanics and as containing the only mystery by Richard Feynman15.

Generating causal inferences to interconnect a sequence of events in a narrative text evokes activation in a right temporal and right frontal location (shown in clusters 3 and 4) which are post-classical factor locations16,17,18 as shown in Fig. 4. Causal reasoning accompanying perceptual events also activates a right middle frontal location (shown in cluster 3) and a right superior parietal location (shown in cluster 1)19. Notably, the right parietal activation is the homolog of a left parietal cluster associated with causal visualization1 found in undergraduates physics conceptualizations, suggesting that post-classical concepts may recruit right hemisphere homologs of regions evoked by classical concepts. Additionally, a factor location in the left supramarginal gyrus (shown in cluster 8) is activated in causal assessment tasks such as determining whether the causality of a social event was person-based (being a hard worker) or situation based (danger)20.

Although we have treated post-classical concepts such as multiverse as a single concept, it is far more complex than velocity. Multiverse entails the consideration of the uncertainty of its existence, the consilience of its probability of existence with measurements of matter in the universe, and the consideration of scientific evidence relevant to a multiverse. Thinking about large, multi-concept units of knowledge, such as the schema for executing a complex multi-step procedure evokes activation in medial frontal regions (shown in cluster 6)21,22. Reading and comprehending the description of such procedures (read, think about, answer questions, listen to, etc.) requires the reader to cognitively organize diverse types of information in a common knowledge structure. Readers who were trained to self-explain expository biological texts activated an anterior prefrontal cortex region (shown in cluster 7 in Fig. 4) during the construction of text models and strategic processing of internal representations23.

This underlying cognitive function of knowledge management associated with the post-classical dimension may generate and utilize a structure to manage a complex array of varied information that is essential to the concept. This type of function has been referred to as a Managerial Knowledge Unit22. As applied to a post-classical concept such as a tachyon, this knowledge management function would contain links to information to evaluate the possibility of the existence of tachyons, hypothetical particles that would travel faster than light-speed in vacuum. The concept invokes a structured network of simpler concepts (mass, velocity, light, etc.) that compose it. This constitutes a knowledge unit larger than a single concept.

Although the discussion has so far focused on the most novel dimension (the classical vs. post-classical), all four dimensions together compose the neural representation of each concept, which indicates where on each dimension a given concept is located (assessed by the concepts factor scores). The bar graphs of Fig. 5 show how the concepts at the extremes of the dimensions can appear at either extreme on several dimensions. These four dimensions are:

the classical vs. post-classical dimension, as described above, which is characterized by contrasting the intangible but consilient nature of post-classical concepts versus the quantifiable, visualizable, otherwise observable nature of classical concepts.

the measurability of a magnitude associated with a concept, that is, the degree to which it has some well-defined extent in space, time, or material properties versus the absence of this property.

the periodicity or oscillation which describes how many systems behave over time versus the absence of periodicity as an important element.

the degree to which a concept is associated with a mathematical formulation that formalizes the rules and principles of the behavior of matter and energy versus being less specified by such formalizations.

A concept may have a high factor score for more than one factor; for example, potential energy appears as measurable, mathematical, and on the classical end of the post-classical dimension. In contrast, multiverse appears as non-measurable, non-periodic, and post-classical.

The locations of the clusters of voxels with high loadings on each of the factors are shown in Fig. 6.

Colors differentiate the factors and greater color transparency indicates greater depth. Sample concepts from the two ends of the dimensions are listed. The post-classical factor locations include those whose activations were high for post-classical concepts (their locations are shown in Fig. 4) as well as those locations whose activations were high for classical concepts.

Classical concepts with high factor scores on the measurability factor, such as frequency, wavelength, acceleration, and torque, are all concepts that are often measured, using devices such as oscilloscopes and torque wrenches, whereas post-classical concepts such as duality and dark matter have an uncertainty of boundedness and no defined magnitude resulting in factor scores at the other end of the dimension. This factor is associated with parietal and precuneus clusters that are often found to be activated when people have to assess or compare magnitudes of various types of objects or numbers24,25,26, a superior frontal cluster that exhibits higher activation when people are comparing the magnitudes of fractions as opposed to decimals27, and an occipital-parietal cluster (dorsolateral extrastriate V3A) that activates when estimating the arrival time of a moving object28. Additional brain locations associated with this factor include left supramarginal and inferior parietal regions that are activated during the processing of numerical magnitudes;26 and left intraparietal sulcus and superior parietal regions activated during the processing of spatial information29. This factor was not observed in a previous study that included only classical concepts and hence the factor would not have differentiated among the concepts1.

The mathematical formulation factor is salient for concepts that are clearly associated with a mathematical formalization. The three concepts that are most strongly associated with this factor, commutator, Lagrangian, and Hamiltonian, are mathematical functions or operators. Cluster locations that are associated with this factor include: parietal regions that tend to activate in tasks involving mathematical representations30,31 and right frontal regions related to difficult mental calculations32,33. The parietal regions associated with the factor, which extend into the precuneus, activate in arithmetic tasks34. While most if not all physics concepts entail some degree of mathematical formulation, post-classical concepts such as quasar, while being measurable, are typically not associated with an algebraic formulation.

The periodicity factor is salient for many of the classical concepts, particularly those related to waves: wave function, light, radio waves, and gamma rays. This factor is associated with right hemisphere clusters and a left inferior frontal cluster, locations that resemble those of a similarly described factor in a neurosemantic analysis of physics concepts in college students1. This factor was also associated with a right hemisphere cluster in the inferior frontal gyrus and bilateral precuneus.

For all four underlying semantic dimensions, the brain activation-based orderings of the physics concepts with respect to their dimensions were correlated with the ratings of those concepts along those dimensions by independent physics faculty. This correlation makes it possible for a linear regression model to predict the activation pattern that will be evoked by future concepts in physicists brains. When a new physics concept becomes commonplace, (such as a new particle category, say, magnetic monopoliae), it should be possible to predict the brain activation that will be the neural signature of the magnetic monopole concept, based on how that concept is rated along the four underlying dimensions.

The neurosemantic conceptual space defined by the four underlying dimensions includes regions that are currently sparsely populated by existing concepts, but these regions may well be the site of some yet-to-be theorized concepts. It is also possible that as future concepts are developed, additional dimensions of neural representation may emerge, expanding the conceptual space that underpins the concepts in the current study.

More here:

The neuroscience of advanced scientific concepts | npj Science of Learning - Nature.com

Science fiction novels and movies are packed with far-out ideas, most often as the springboard for an action-packed adventure rather than a serious attempt to predict future trends in science or technology. Some of the most common tropes, such as accelerating a spacecraft to fantastic speeds in a matter of seconds without crushing the occupants , are just plain impossible according to the laws of physics as we understand them. Yet those very same laws appear to permit other seemingly far-fetched sci-fi concepts, from wormholes to parallel universes. Here's a rundown of some of the sci-fi ideas that could really be done in theory, at least.

The idea of a wormhole a shortcut through space that allows almost instantaneous travel between distant parts of the universe sounds like it was created as a fictional story-driver. But under its more formal name of an Einstein-Rosen bridge, the concept has existed as a serious theoretical concept long before sci-fi writers got hold of it. It comes out of Albert Einstein's theory of general relativity, which views gravity as a distortion of space-time caused by massive objects. In collaboration with physicist Nathan Rosen, Einstein theorized in 1935 that points of extremely strong gravity, such as black holes, could be directly connected with each other. And so the idea of wormholes was born.

The forces around a black hole would destroy anyone that came close to it, so the idea of actually traveling through a wormhole wasn't given serious consideration until the 1980s, when astrophysicist Carl Sagan decided he was going to write a sci-fi novel. According to the BBC, Sagan encouraged fellow physicist Kip Thorne to come up with a feasible way to travel interstellar distances in a flash. Thorne duly devised a way possible in theory, but highly improbable in practice that humans might achieve interstellar travel by traversing a wormhole unscathed. The result found its way into Sagan's novel "Contact" (Simon and Schuster: 1985) which was subsequently adapted into a film with Jodie Foster in the lead role.

While it's highly unlikely that wormholes will ever become the simple and convenient methods of transportation portrayed in movies, scientists have now come up with a more viable way to construct a wormhole than Thorne's original suggestion. It's also possible that, if wormholes already exist in the universe, they could be located using the new generation of gravitational-wave detectors.

An essential prerequisite for most space-based adventure stories is the ability to get from A to B much faster than we can today. Wormholes aside, there are multiple stumbling blocks to achieving this with a conventional spaceship. There's the enormous amount of fuel required, the crushing effects of acceleration, and the fact that the universe has a strictly imposed speed limit. This is the speed at which light travels precisely one light-year per year, which in a cosmic context isn't very fast at all. Proxima Centauri, the second-closest star to Earth, is 4.2 light-years from the sun, while the center of the galaxy is a whopping 27,000 light-years away.

Fortunately, there's a loophole in the cosmic speed limit: It only dictates the maximum speed we can travel through space. As Einstein explained, space itself can be distorted, so perhaps it's possible to manipulate the space around a ship in such a way as to subvert the speed limit. The spaceship would still travel through the surrounding space at less than the speed of light, but the space itself would be moving faster than that.

This was what the writers of "Star Trek" had in mind when they came up with the concept of a "warp drive" in the 1960s. But to them it was just a plausible-sounding phrase, not real physics. It wasn't until 1994 that theoretician Miguel Alcubierre found a solution to Einstein's equations that produced a real warp drive effect, Live Science's sister site Space.com reported, contracting space in front of a spaceship and expanding it to the rear. To start with, Alcubierre's solution was no less contrived than Thorne's traversable wormhole, but scientists are attempting to refine it in the hope that it might one day be practical.

The concept of a time machine is one of the great sci-fi plot devices, allowing characters to go back and change the course of history for better or worse. But this inevitably raises logical paradoxes. In "Back to the Future," for example, would Doc have built his time machine if he hadn't been visited by the future Marty using that very same machine? It's because of paradoxes like these that many people assume time travel must be impossible in the real world and yet, according to the laws of physics, it really can occur.

Just like with wormholes and space warps, the physics that tells us it's possible to travel back in time comes from Einstein's theory of general relativity. This treats space and time as part of the same "space-time" continuum, with the two being inextricably linked. Just as we talk about distorting space with a wormhole or warp drive, time can be distorted as well. Sometimes it can get so distorted that it folds back on itself, in what scientists refer to as a "closed timelike curve" though it could just as accurately be called a time machine.

A conceptual design for such a time machine was published in 1974 by physicist Frank Tipler, according to physicist David Lewis Anderson, who describes the research on the Anderson Institute, a private research lab. Called a Tipler cylinder, it has to be big at least 60 miles (97 kilometers) long, according to Humble and extremely dense, with a total mass comparable to that of the sun. To get it to function as a time machine, the cylinder has to rotate fast enough to distort space-time to the point where time folds back on itself. It may not sound as simple as installing a flux capacitor in a DeLorean, but it does have the advantage that it really would work on paper, at least.

The archetypal sci-fi example of teleportation is the "Star Trek" transporter, which, as the name suggests, is portrayed simply as a convenient way to transport personnel from one location to another. But teleportation is quite unlike any other form of transport: Instead of the traveler moving through space from the starting point to the destination, teleportation results in an exact duplicate being created at the destination while the original is destroyed. Viewed in these terms and at the level of subatomic particles rather than human beings teleportation is indeed possible, according to IBM.

The real-world process is called quantum teleportation. This process copies the precise quantum state of one particle, such as a photon, to another that may be hundreds of miles away. Quantum teleportation destroys the quantum state of the first photon, so it does indeed look as though the photon has been magically transported from one place to another. The trick is based on what Einstein referred to as "spooky action at a distance," but is more formally known as quantum entanglement. If the photon that is to be "teleported" is brought into contact with one of a pair of entangled photons, and a measurement of the resulting state is sent to the receiving end where the other entangled photon is then the latter photon can be switched into the same state as the teleported photon.

It's a complicated process even for a single photon, and there's no way it could be scaled up to the kind of instant-transportation system seen in "Star Trek." Even so, quantum teleportation does have important applications in the real world, such as for hack-proof communications and super-fast quantum computing.

The universe is everything our telescopes reveal to us all the billions of galaxies expanding outward from the Big Bang. But is that all there is? Theory says maybe not: There might be a whole multiverse of universes out there. The idea of "parallel universes" is another familiar sci-fi theme, but when they're depicted on screen they typically differ from our own universe only in minor details. But the reality may be much weirder than that, with the basic parameters of physics in a parallel universe such as the strength of gravity or nuclear forces differing from our own. A classic portrayal of a genuinely different universe of this kind, and the creatures living in it, is Isaac Asimov's novel "The Gods Themselves" (Doubleday: 1972).

The key to the modern understanding of parallel universes is the concept of "eternal inflation." This pictures the infinite fabric of space in a state of perpetual, incredibly rapid expansion. Every now and then a localized spot in this space a self-contained Big Bang drops out of the general expansion and begins to grow at a more sedate pace, allowing material objects like stars and galaxies to form inside it. According to this theory, our universe is one such region, but there may be countless others.

As in Asimov's story, these parallel universes could have completely different physical parameters from our own. At one time scientists believed that only universes with virtually the same parameters as ours would be capable of supporting life, but recent studies suggest the situation may not be as restrictive as this, Live Science previously reported. So there's hope for Asimov's aliens yet though perhaps not for making contact with them, as happens in the novel. Nevertheless, the traces of other universes might be detectable to us by other means. It's even been suggested that the mysterious "cold spot" in the cosmic microwave background is the scar from a collision with a parallel universe, Ivan Baldry, a professor of astrophysics at Liverpool John Moores University in the U.K. wrote in The Conversation.

Originally published on Live Science.

Read the original here:

5 sci-fi concepts that are possible (in theory) - Livescience.com

The humble atom is the fundamental building block of all normal matter.

Hydrogen, where single electrons orbit individual protons, composes ~90% of all atoms.

Quantum mechanically, electrons only occupy specific energy levels.

Atomic and molecular transitions between those levels absorbs and/or releases energy.

Energetic transitions have many causes: photon absorption, molecular collisions, atomic bond breaking/forming, etc.

Chemical energy powers most human endeavors: through coal, oil, gas, wind, hydroelectric, and solar power.

The most energy-efficient chemical reactions convert merely ~0.000001% of their mass into energy.

However, atomic nuclei offer superior options.

Containing 99.95% of an atoms mass, bonds between protons and neutrons involve significantly greater energies.

Nuclear fission, for example, converts ~0.09% of the fissionable mass into pure energy.

Fusing hydrogen into helium achieves even greater efficiencies.

For every four protons that fuse into helium-4, ~0.7% of the initial mass is converted into energy.

Nuclear power universally outstrips electron transitions for energy efficiency.

Still, the atoms greatest source of energy is rest mass, extractable via Einsteins E = mc2.

Matter-antimatter annihilation is 100% efficient, converting mass completely into energy.

Practically unlimited energy is locked within every atom; the key is to safely and reliably extract it.

Mostly Mute Monday tells an astronomical story in images, visuals, and no more than 200 words. Talk less; smile more.

Read this article:

The 3 types of energy stored within every atom - Big Think

Mutual combatants.

I was a prosecutor for nearly 20 years and taught criminal law. But I must admit, Id missed that one and thus had to be, um, edified by the office of Kim Foxx, states attorney for Cook County, Ill., and thus responsible for enforcing the law on Chicagos murder-ravaged streets.

There was a gang firefight in Chicago recently. Well, okay, theres always a gang firefight in Chicago. This one seemed run-of-the-mill at first. There is internecine strife, Im sure youll be stunned to hear, in the Four Corner Hustlers street gang. As a result, rival factions shot it out. Not in the dark of night, but in mid-morning, as though a brisk daylight gunfight were as routine as a jog along the river (provided, of course, that you wear your flak jacket and matching N95 mask). When the dust settled, one young man was dead and two were wounded.

Windy City police rounded up five of the gangbangers and brought them to prosecutors, expecting that each would be charged with commensurately serious felonies, including first-degree murder. The cops, however, were stunned when Foxxs office released the suspects without any charges.

Why? Did the shooting not really happen? Oh, it happened all right. But theres apparently a new law non-enforcement standard in Chicago: No indictments, even in brutal crossfire between rival criminals, because those criminals are yes mutual combatants.

Theyre in gangs, get it? And if youre in a gang, this is what you sign up for. Next case.

You want to know why violent crime is surging in the nations urban centers? Why, as the latest FBI statistics indicate, murder was up an astonishing 30 percent year-over-year in 2020, a record increase? Look no further than the Progressive Prosecutors Project (as I branded it in a March 2020 Commentary essay). This is the radical lefts enterprise to reform the criminal justice system by pretending that we dont have criminals or, to get so very nuanced about it, to assign blame for all crime on our systemically racist society.

No, it is not the sociopaths committing the violence, the thinking goes. See, when you really consider it, its each of us, right?

Imagine if todays prosecutors didnt rationalize this way. Lets say they werent hypnotized under the spell of disparate impact analysts, who insist that racism, not crime, explains Americas prison population which, not coincidentally, has plummeted as felonies have surged.

Well, then theyd have to wrestle with what, and who, is responsible for the bloodshed. Progressive prosecutors would have to come to grips with the stubborn fact they and their media cheerleaders strain to avoid: patterns of offending.

By the metric of percentage composition of the overall population, young Black males account for a disproportionate amount of the incarcerated population because, as a demographic class, they commit a disproportionate amount of the crime. They account for an overwhelming number of the gang arrests in cities such as Chicago because they are shooting at each other; that means they also account for more of the victims. And shooting each other is something they are certain to do more of, if progressive prosecutors keep coming up with creative ways to resist charging them.

These novelties include declining to invoke the anti-gang sentencing enhancement provisions. Though state legislatures enact these laws, prosecutors are effectively and imperiously repealing them because they disproportionately punish African Americans (as if defendants were being prosecuted for being African American rather than for committing murder and mayhem).

Now, evidently, the do-not-prosecute trick bag also includes the flat-out refusal to prosecute on a mutual combatant theory the lunatic notion that killing and being killed is what gang members volunteer for, so who are we prosecutors to intrude?

Heres an interesting point: If arrests and prosecutions are explained by racism rather than criminal behavior, why rely on the statistics breaking down the races of prison inmates? Why not just say that police departments even though many are run and heavily staffed by minority officers are systematically racist, and therefore, must be blinded by bias in making arrests?

Because progressive prosecutors know that is not how things work.

In most cases, police do not witness crimes or theorize about who the suspects are. Crimes have victims, and victims file reports identifying the perps. Thats what police act on. And thats how we know although progressive prosecutors are preoccupied by their perception of racism against the criminals (which may reflect their own ingrained bias) it is African American communities that disproportionately bear the bruntof violent crime. Prosecutors like Kim Foxx exacerbate this tragedy when they invent reasons not to address it.

If you want to know why crime is up, you need to understand why it went down, dramatically, after the high-crime generation from the 1970s into the 90s.

Prosecutors and police back then grasped that crime rates were a function of expectations about the rule of law. When prosecutors set the tone by acting against quality-of-life crimes, it signaled to more serious criminals that the communitys laws would be enforced. When serious crimes were committed, police were not told the cases would be dismissed; they were encouraged to conduct interrogations and follow-up investigations that improved law enforcements intelligence data bank. That intelligence was carefully and continually studied so that police could be deployed in the places where crime trends were emerging. Order does not need to be re-established if you take pains not to lose it in the first place.

This is not quantum physics. Progressive prosecutors dereliction of their duty invites more crime. Professional criminals are recidivists, and if they are repeatedly returned to the streets, rather than prosecuted and imprisoned, they commit lots more crime. The only way to stop it is to stop it. That means enforcing the law, even or especially, I should say against the mutual combatants.

Former federal prosecutor Andrew C. McCarthy is a senior fellow atNational Review Institute, a contributing editor at National Review, a Fox News contributor and the author of several books, including Willful Blindness: A Memoir of the Jihad. Follow him on Twitter@AndrewCMcCarthy.

Read the original post:

What's behind rising violent crime? Progressive prosecutors' non-enforcement of the law | TheHill - The Hill

If a friend tells you Ive seen a UFO! what would you think? It might have been an alien spacecraftor perhaps the friend was mistaken. The first possibility requires numerous unproven assumptions about extraterrestrial life; the second is consistent with what we know about human fallibility. The 14th-century Franciscan friar William of Occam was never troubled by flying saucers, but he did see the importance of eliminating unnecessary assumptionsthe principle known as Occams Razor. It forms the central theme of Johnjoe McFaddens Life Is Simple, a tour through two millennia of scientific discovery.

Mr. McFadden is professor of molecular genetics at the University of Surrey in England. His interest in Occam was sparked by a daily commute which took him past the village of Ockham, where William was born, probably around 1287. Little is known about Williams early life, but by his thirties his writings on philosophy and theology were widely readand highly controversial.

Continued here:

Life Is Simple Review: A Blade to Shave Away Error - The Wall Street Journal