Why space has exactly three dimensions - physics-math - 26 September 2013 - New Scientist

Why space has exactly three dimensions - physics-math - 26 September 2013 - New Scientist: Quantum states are described not by 1D real numbers, which all lie on a single line, but by 2D complex numbers that represent points on a plane. The way these numbers interact to produce a complete description of objects such as photons that can be in more than one state at once naturally sketches out a 3D sphere describing all those possible states. Perhaps this result is just emphasising how the dimensionality of basic quantum objects and the dimensionality of space happen to be the same.

Müller thinks not: he thinks it points to an inextricable link between space's geometry and the degree of probability inherent in quantum theory. If so, the roots of relativity and quantum theory would be embedded in the way information is exchanged in the cosmos, suggesting where to look for any unifying theories. "It offers a clue that the notion of information will be an important part of quantum gravity," says Müller.

Physicists Discover Geometry Underlying Particle Physics | Simons Foundation

Physicists Discover Geometry Underlying Particle Physics | Simons Foundation: The amplituhedron looks like an intricate, multifaceted jewel in higher dimensions. Encoded in its volume are the most basic features of reality that can be calculated, “scattering amplitudes,” which represent the likelihood that a certain set of particles will turn into certain other particles upon colliding.

'Holographic Duality' Hints at Hidden Subatomic World - Wired Science

'Holographic Duality' Hints at Hidden Subatomic World - Wired Science; If strongly correlated matter is thought of as “living” on the 2-D surface of a pond, the holographic duality suggests that the extreme turbulence on that surface is mathematically equivalent to still waters in the interior. Physicists can get at the surface-level behavior by studying the parallel, but much simpler, situation below...

In the mathematical parlance of the holographic duality, certain strongly correlated matter in 2-D corresponds, in 3-D, to a black hole.... “These very complicated quantum mechanical collective effects are beautifully captured by black hole physics... For strongly correlated systems, if you put an electron into the system, it will immediately ‘disappear’ — you can no longer track it.” It’s like an object falling into a black hole.


To determine a formula for the conductivity of cuprates, Horowitz and Santos had to study how light would interact with the complicated horizon of their black hole... In the new work, they extended the calculation down to the temperature range in which cuprates become superconductive, or conduct electricity with no resistance, and again found a close match with experimental measurements of real cuprates.

Physicists Find a Backdoor Way to Do Experiments on Exotic Gravitational Physics

Physicists Find a Backdoor Way to Do Experiments on Exotic Gravitational Physics: But what about running the dualities in the other direction, using laboratory measurements of extreme materials to probe exotic gravitational physics?...
The experiments in question entail smashing gold or lead nuclei together to create plasmas of quarks and gluons...
The plasmas must actually be liquid...

They equated the viscosity of a fluid to gravitational waves caroming off a black hole in higher-dimensional space—which, even for a physicist, is not an analogy that springs to mind...

The answer: 1/4π, in the appropriate units. The viscosity measured by RHIC comes close. Water, some 400 times more viscous, is molasses in comparison.

Surprisingly, the minimum value is the same for all fluids, whatever they are made of. Through the logic of duality, this universality has a simple explanation: Viscosity is equivalent to a gravitational phenomenon, and according to Einstein’s general theory of relativity, gravitation is blind to compositional details.

Quantum Horse Races and Crystals of Light

Quantum Horse Races and Crystals of Light: Bloch’s team and others bring them to heel by cooling them to a temperature of nanokelvins and pouring them into an optical lattice, which, depending on your poetic frame of mind, you might call an optical egg crate or a crystal of light... The atoms are spaced perhaps 400 nanometers apart, so they reach a density of about 100 trillion atoms per cubic centimeter—which is a lot of atoms per cubic centimeter, but still only about a hundred-thousandth the density of hydrogen gas at room temperature and pressure. So these systems let physicists explore a domain they seldom otherwise enter, a frigid, sparse realm where quantum is king...

There are all sorts of other fun experiments you can do. Last year, Bloch’s team tracked the insulator-superfluid transition and showed that the system goes through a “hidden” phase of matter—a subtly patterned arrangement that conventional theory doesn’t capture...

Yet another experiment touches on the fundamental question of what determines the speed of events in the world... They began with an insulator, dialed up the interaction energy, and watched the atoms start to self-organize. A wave of activity spread though the system at twice the speed of sound. What governed the velocity was that atoms did not passively roll on the wave, but actively contributed to it. Some quantum gravity theorists have speculated that the speed of light represents the Lieb-Robinson bound of some underlying quantum system out of which space and time emerge.

String theorists squeeze nine dimensions into three

String theorists squeeze nine dimensions into three: In the simulation, the universe starts off as a tiny blob of strings that is symmetric in nine different dimensions. As the strings interact, a random energy fluctuation — provided by the quantum laws that govern these small scales — breaks the symmetry. Three dimensions balloon outward, leaving the other six stunted at a billionth of a trillionth of a trillionth of a centimeter, far too small to be detected.

Naked black-hole hearts live in the fifth dimension

Naked black-hole hearts live in the fifth dimension: Lehner has now proposed another situation where naked singularities might exist: in the extra dimensions proposed by string theory. The rub is that this time, they aren't unusual.

To understand why, think of black holes as points in the four dimensions we experience - three of space and one of time. These become "black strings" when extended into a fifth dimension of space (see diagram).

Black strings are unstable and break up into smaller black holes like a stream of water splitting into droplets. Lehner showed that at the point where a smaller black hole pinches off from the stream, the black hole's radius is zero, which means its density is infinite. In other words, it is a naked singularity. Lehner showed this will happen any time you have a black string.

Nuclear clock could steal atomic clock's crown - New Scientist - New Scientist

Nuclear clock could steal atomic clock's crown: A nuclear clock has not yet been made but the idea would be to use the atomic nucleus like a tuning fork. A nucleus will jump to a higher energy state, then fall back down, and jump up again, only if it is hit with a very specific frequency of light. Tuning a laser so that it prompts these jumps is a way to set its frequency with a phenomenal level of precision. The frequency can then be used like a clock's tick to keep time.

A similar method is used in atomic clocks, except it is the electrons orbiting the nucleus that make the energy jump...

A thorium clock controlled in this way would drift by just 1 second in 200 billion years...

Black holes and pulsars could reveal extra dimensions - space - 21 August 2011 - New Scientist

Black holes and pulsars could reveal extra dimensions: Black holes are predicted to fritter away their mass over time by emitting particles, a phenomenon called Hawking radiation. Without extra dimensions, this process is predicted to be agonisingly slow for run-of-the-mill black holes weighing a few times as much as the sun, making it impossible to measure.

Extra dimensions would give the particles more ways to escape, speeding up the process.

Einstein's theory applied to superconducting circuits

Einstein's theory applied to superconducting circuits: Horowitz and his research team found what could be called a gravitational model, or a gravitational dual — a dual description of a superconductor using gravity, black holes, and all of the traditional ingredients of general relativity. "This came as quite a surprise because this is a totally different area of physics, which is now being connected to this condensed matter area," said Horowitz.

Why 5, 8 and 24 Are the Strangest Numbers in the Universe: Scientific American

Why 5, 8 and 24 Are the Strangest Numbers in the Universe: Scientific American: "If string theory is right, the octonions are not a useless curiosity; on the contrary, they provide the deep reason why the universe must have 10 dimensions: in 10 dimensions, matter and force particles are embodied in the same type of numbers—the octonions."

Out Of The Fabric - Science News

Out Of The Fabric - Science News: Further study of spaceless theories may help solve serious problems confronting physicists today, Seiberg believes. String theory implies countless possible vacuum states — that is, spaces of differing physical properties — with no obvious method for determining which one the visible universe should have chosen. Knowing how space emerges from spacelessness might help explain why humans exist in one particular space from among the countless possibilities.

Doing away with time poses more difficult problems, Seiberg acknowledges. Basic notions in physics, such as that of causes preceding effects, or predicting the outcome of experiments before the experiment is done, seem to lose their meaning if there is no time to define before and after. So some physicists, Markopoulou for one, have suggested that even if space is emergent, time may remain fundamental. In fact, she conjectures, time is needed to allow quantum processes to create the illusion of space. Space may not have been around at the beginning, but that beginning would be stillborn without time to get reality going.

Black holes: a model for superconductors? | Engineering at Illinois

Black holes: a model for superconductors? | Engineering at Illinois: Since most condensed matter phenomena involve electron physics, Leigh, along with graduate student Juan Jottar, set out to investigate the sorts of interactions that electrons might have in classical gravity theories that arise in string theory. Since the Mott problem is an example of strongly interacting particles, Edalati, Leigh, and Philips then asked the question: “Is it possible to devise a theory of gravity that mimics a Mott insulator?” Indeed it is.

The researchers built on Maldacena’s mapping and devised a model for electrons moving in a curved space-time in the presence of a charged black hole that captures two of the striking features of the normal state of high-temperature superconductors: 1) the presence of a barrier for electron motion in the Mott state, and 2) the strange metal regime in which the electrical resistivity scales as a linear function of temperature, as opposed to the quadratic dependence exhibited by standard metals.

Atoms ripple in the periodic table of shapes - physics-math - 16 February 2011 - New Scientist

Atoms ripple in the periodic table of shapes: The shapes he is referring to aren't just any old triangles or squares, but smooth ones that don't have edges, more like spheres. These can be written as differential equations, allowing them to be described in terms of their "flow", says Coates. If a shape has a unique flow pattern that meets certain requirements then it is an atom. But if a shape's flow contains a number of these unique patterns, it is a molecule and can be broken down even further.

String Theory Fails Another Test, the “Supertest” � Not Even Wrong

String Theory Fails Another Test, the “Supertest” � Not Even Wrong: If you believe that string theory “predicts” low-energy supersymmetry, this is a serious failure. Completely independently of string theory, it’s a discouraging result for low-energy supersymmetry in general. The LHC has just dashed hopes that, at least for strongly-interacting particles, supersymmetry would show up just beyond the energy range accessible at the Tevatron.

String theory tackles strange metals : Nature News

String theory tackles strange metals : Nature News: The hope is that tricks from string theory can now be used to make progress on improving the FFL model. One of its problematic aspects is the prediction of a state of matter that still has some level of order (non-zero entropy) at absolute zero (0 Kelvin). This violates the third law of thermodynamics, which says that, for FFLs, entropy should tend to zero as the system is cooled to absolute zero. Sachdev says he always considered this a shortcoming of his theory, but other physicists took the view that it might instead be saying something profound about real materials. "We never knew whether it was a bug or a feature," says Polchinski.


In his latest work, Sachdev shows that the string theory version of the FFL model also violates the third law of thermodynamics at absolute zero. The emergence of the same problem in a totally different mathematical framework suggests it is pointing to something in the real world, Polchinski says. Sachdev says more work will be needed to establish that for certain.

String Theory Entangled - Science News

String Theory Entangled - Science News: In a paper published last year, the physicists noted that the string theory math describing black holes is surprisingly similar to the equations for a group of three entangled particles. The new study takes the analogy a step further, tackling the more difficult problem of how four pieces of quantum information, called qubits, behave when they’re entangled. Because experiments disagree, physicists aren’t sure about how many ways four qubits can be entangled. The answer, according to string theory, is 31.

Duff and his team can’t yet explain why the formulas apply to this system. “We don’t understand why it works,” he says. “At some deep level we’re mystified by it.”

Researchers Devise the First Experimental Test of Controversial, Confusing String Theory | Popular Science

Researchers Devise the First Experimental Test of Controversial, Confusing String Theory: Duff said he was at a conference in Tasmania when a colleague presented some mathematical formulas describing entanglement of multiple quantum bits. The equations looked familiar. Upon returning home, Duff checked his notebooks from a few years earlier, and realized the formulas were the same as those he developed to use string theory to describe black holes.

This is completely unexpected, he said. There is no obvious reason why the insanely complex mathematics underlying string theory can also be used to predict the behavior of entangled quantum systems.

“This may be telling us something very deep about the world we live in, or it may be no more than a quirky coincidence,” he said.

Physicists use offshoot of string theory to describe puzzling behavior of superconductors

Physicists use offshoot of string theory to describe puzzling behavior of superconductors: "Using gauge/gravity duality — the connection between quantum and gravitational mechanics — the MIT team identified a system that has the same unusual properties as strange metals, but could be explained by gravitational mechanics. In this case, the model they used was a gravitational system with a black hole. "It's a mathematical abstraction which we hope may shed light on the physics of the real system," says Liu. In their model, they can study behavior at high and low energy (determined by how the excitation energy of a single electron compares to the average energy of an electron in the system), and it turns out that at low energy, the black-hole model exhibits many of the same unusual traits seen in non-Fermi liquids such as cuprates."

Strings Link the Ultracold with the Superhot

Perfect liquids suggest theory’s math mirrors something real

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