Special relativity (alternative formulations)

As formulated by Albert Einstein in 1905, the theory of special relativity was based on two main postulates:
There have been various alternative formulations of special relativity over the years. Some of these formulations are equivalent to the original formulation whereas others result in modifications.
"Single postulate" approaches.
"Equivalent to the original? Yes."
According to some references, the theory of special relativity can be derived from a single postulate: the principle of relativity. This claim can be misleading because actually these formulations rely on various unsaid assumptions such as isotropy and homogeneity of space. The question here is not about the exact number of postulates. The phrase "single postulate" is just used in comparison with the original "two postulate" formulation. The real question here is whether universal lightspeed can be deduced rather than assumed.
The Lorentz transformations, up to a nonnegative free parameter, can be derived without first postulating the universal lightspeed. Experiment rules out the validity of the Galilean transformations and this means the parameter in the Lorentz transformations is nonzero hence there is a finite maximum speed before anything has been said about light. Combining this with Maxwell's equations shows that light travels at this maximum speed. The numerical value of the parameter in these transformations is determined by experiment, just as the numerical values of the parameter pair "c" and the permittivity of free space are left to be determined by experiment even when using Einstein's original postulates. When the numerical values in both Einstein's and these other approaches have been found then these different approaches result in the same theory. So the end result of the interlocking trio of theory+Maxwell+experiment is the same either way. This is the sense in which universal lightspeed can be deduced rather than postulated.
For some historical information, see: History of special relativity#Spacetime physics and the section "Lorentz transformation without second postulate" for the approaches of Ignatowski and Frank/Rothe. However, according to Pauli (1921), Resnick (1967), and Miller (1981), those models were insufficient. But the constancy of the speed of light is contained in Maxwell's equations. That section includes the phrase "Ignatowski was forced to recourse to electrodynamics to include the speed of light.". So, the trio of "principle of relativity+Maxwell+numerical values from experiment" gives special relativity and this should be compared with "principle of relativity+second postulate+Maxwell+numerical values from experiment". Since Einstein's 1905 paper is all about electrodynamics he is assuming Maxwell's equations, and the theory isn't practically applicable without numerical values. When compared like with like, from the point of view of asking what is knowable, the second postulate can be deduced. If you restrict your attention to just the standalone theory of relativity then yes you need the postulate. But given all the available knowledge we don't need to postulate it. In other words, different domains of knowledge are overlapping and thus taken together have more information than necessary.
This can be summarized as follows:
There are references which discuss in more detail the principle of relativity
Lorentz ether theory.
"Equivalent to the original ? Yes."
Hendrik Lorentz and Henri Poincaré developed their version of special relativity in a series of papers from about 1900 to 1905. They used Maxwell's equations and the principle of relativity to deduce a theory that is mathematically equivalent to the theory later developed by Einstein.
Minkowski spacetime.
"Equivalent to the original ? Yes."
Minkowski space (or Minkowski spacetime) is a mathematical setting in which special relativity is conveniently formulated. Minkowski space is named for the German mathematician Hermann Minkowski, who around 1907 realized that the theory of special relativity (previously developed by Poincaré and Einstein) could be elegantly described using a four-dimensional spacetime, which combines the dimension of time with the three dimensions of space.
Mathematically there are a number of ways in which the four-dimensions of Minkowski spacetime are commonly represented: as a four-vector with 4 real coordinates, as a four-vector with 3 real and one complex coordinate, or using tensors.
Test theories of special relativity.
"Equivalent to the original ? No."
Test theories of special relativity are flat space-time theories which differ from special relativity by having a different postulate about light concerning one-way speed of light vs two-way speed of light. Different postulates on light result in different notions of time simultaneity. There is Robertson's test theory (1949) which predicts different experimental results from Einstein's special relativity, and then there is Edward's theory (1963) which cannot be called a test theory because it is physically equivalent to special relativity, and then there is the Mansouri-Sexl theory (1977) which is equivalent to Robertson's theory.
Curvilinear coordinates and non-inertial frames.
"Equivalent to the original ? Curvilinear is a generalization, but the original SR can be applied locally."
There can be misunderstandings over the sense in which SR can be applied to accelerating frames.
Special relativity cannot be used to describe a global frame for non-inertial i.e. accelerating frames. However general relativity implies that special relativity "can" be applied locally where the observer is confined to making local measurements. For example, an analysis of Bremsstrahlung does not require general relativity, SR is sufficient.
The key point is that you can use special relativity to describe all kinds of accelerated phenomena, and also to predict the measurements made by an accelerated observer who's confined to making measurements at one specific location only. If you try to build a complete frame for such an observer, one that is meant to cover all of spacetime, you'll run into difficulties (there'll be a horizon, for one).
The problem is that you cannot derive from the postulates of special relativity that an acceleration will not have a non-trivial effect. E.g. in case of the twin paradox, we know that you can compute the correct answer of the age difference of the twins simply by integrating the formula for time dilation along the trajectory of the travelling twin. This means that one assumes that at any instant, the twin on its trajectory can be replaced by an inertial observer that is moving at the same velocity of the twin. This gives the correct answer, as long as we are computing effects that are local to the travelling twin. The fact that the acceleration that distinguishes the local inertial rest frame of the twin and the true frame of the twin does not have any additional effect follows from general relativity (it has, of course, been verified experimentally).
In 1943, Moller obtained a transform between an inertial frame and a frame moving with constant acceleration, based on Einstein's vacuum eq and a certain postulated time-independent metric tensor, although this transform is of limited applicability as it does not reduce to the Lorentz transform when a=0.
Throughout the 20th century efforts were made in order to generalize the Lorentz transformations to a set of transformations linking inertial frames to non-inertial frames with uniform acceleration. So far, these efforts failed to produce satisfactory results that are both consistent with 4-dimensional symmetry and to reduce in the limit a=0 to the Lorentz transformations. Hsu and Hsu claim that they have finally come up with suitable transformations for constant linear acceleration (uniform acceleration). They call these transformations: Generalized Moller-Wu-Lee Transformations. They also say: "But such a generalization turns out not to be unique from a theoretical viewpoint and there are infinitely many generalizations. So far, no established theoretical principle leads to a simple and unique generalization."
de Sitter relativity.
"Equivalent to the original ? No."
According to the works of Cacciatori, Gorini and Kamenshchik, and Bacry and Lévi-Leblond and the references therein, if you take Minkowski's ideas to their logical conclusion then not only are boosts non-commutative but translations are also non-commutative. This means that the symmetry group of space time is a de Sitter group rather than the Poincaré group. This results in spacetime being slightly curved even in the absence of matter or energy. This residual curvature is caused by a cosmological constant to be determined by observation. Due to the small magnitude of the constant, then special relativity with the Poincaré group is more than accurate enough for all practical purposes, although near the Big Bang and inflation de Sitter relativity may be more useful due to the cosmological constant being larger back then. Note this is not the same thing as solving Einstein's field equations for general relativity to get a de Sitter Universe, rather the de Sitter relativity is about getting a de Sitter Group for special relativity which neglects gravity.
Taiji relativity.
"Equivalent to the original ? Yes."
This section is based on the work of Jong-Ping Hsu and Leonardo Hsu. They decided to use the word "Taiji" which is a Chinese word meaning the ultimate principles that existed before the creation of the world. In SI units, time is measured in seconds, but taiji time is measured in units of metres — the same units used to measure space. Their arguments about choosing what units to measure time in, lead them to say that they can develop a theory of relativity which is experimentally indistinguishable from special relativity, but without using the second postulate in their derivation. Their claims have been disputed.
The transformations that they derive involve the factor formula_2 where β is the velocity measured in metres per metre (a dimensionless quantity). This looks the same as (but should NOT be conceptually confused with) the velocity as a fraction of light v/c that appears in some expressions for the Lorentz transformations. Expressing time in metres has previously been done by other authors: Taylor and Wheeler in "Spacetime Physics" and Moore in "Six Ideas that Shaped Physics".
The transformations are derived using just the principle of relativity and have a maximal speed of 1, which is quite unlike "single postulate" derivations of the Lorentz transformations in which you end up with a parameter that may be zero. So this is not the same as other "single postulate" derivations. However the relationship of taiji time "w" to standard time "t" must still be found, otherwise it would not be clear how an observer would measure taiji time. The taiji transformations are then combined with Maxwell's equations to show that the speed of light is independent of the observer and has the value 1 in taiji speed (i.e. it has the maximal speed). This can be thought of as saying: a time of 1 metre is the time it takes for light to travel 1 metre. Since we can measure the speed of light by experiment in m/s to get the value c, we can use this as a conversion factor. i.e. we have now found an operational definition of taiji time: w=ct.
So we have: w metres = (c m/s) * t seconds
But it is not just due to the choice of units that there is a maximum speed. It is the principle of relativity, that Hsu & Hsu say, when applied to 4d spacetime, implies the invariance of the 4d-spacetime interval formula_3 and this leads to the coordinate transformations involving the factor formula_4 where beta is the magnitude of the velocity between two inertial frames. The difference between this and the spacetime interval formula_5 in Minkowski space is that formula_3 is invariant purely by the principle of relativity whereas formula_5 requires both postulates.
The "principle of relativity" in spacetime is taken to mean invariance of laws under 4-dimensional transformations.
Hsu & Hsu then explore other relationships between w and t such as w=bt where b is a function. They show that there are versions of relativity which are consistent with experiment but have a definition of time where the "speed" of light is not constant. They develop one such version called "common relativity" which is more convenient for performing calculations for "relativistic many body problems" than using special relativity.
Euclidean relativity.
"Equivalent to the original ? yes."
Euclidean relativity
 uses a Euclidean (++++) metric as opposed to the traditional Minkowski (+---) or (-+++) metric which is derived from the Minkowski metric by rewriting formula_8 into the equivalent formula_9. The roles of time t and proper time formula_10 have switched so that proper time formula_10 takes the role of the coordinate for the 4th spatial dimension. A universal velocity formula_12 for all objects in 4D space-time appears from the regular time derivative formula_13. The approach differs from the so-called Wick rotation or "complex" Euclidean relativity. In Wick rotation, time formula_14 is replaced by formula_15, which also leads to a positive definite metric but it maintains proper time formula_10 as the Lorentz invariant value whereas in Euclidean relativity formula_10 becomes a coordinate. Because formula_13 implies that photons travel at the speed of light in the subspace {x, y, z} and baryonic matter that is at rest in {x, y, z} travels normal to photons along formula_19, a paradox arises on how photons can be propagated in a space-time. The possible existence of parallel space-times or parallel worlds shifted and co-moving along formula_10 is the approach of Giorgio Fontana. The Euclidean geometry is consistent with classical, Minkowski based relativity. The hyperbolic Minkowski geometry turns into a rotation in 4D circular geometry where length contraction and time dilation result from the geometric projection of 4D properties to 3D space.
Very special relativity.
"Equivalent to the original ? No"
Ignoring gravity, experimental bounds seem to suggest that special relativity with its Lorentz symmetry and Poincaré symmetry describes spacetime. Surprisingly, Cohen and Glashow
have demonstrated that a small subgroup of the Lorentz group is sufficient to explain all the current bounds.
The minimal subgroup in question can be described as follows: The stabilizer of a null vector is the special Euclidean group SE(2), which contains T(2) as the subgroup of parabolic transformations. This T(2), when extended to include either parity or time reversal (i.e. subgroups of the orthochronous and time-reversal respectively), is sufficient to give us all the standard predictions. Their new symmetry is called Very Special Relativity (VSR).
Doubly special relativity.
"Equivalent to the original ? No."
Doubly special relativity (DSR) is a modified theory of special relativity in which there is not only an observer-independent maximum velocity (the speed of light), but an observer-independent minimum length (the Planck length).
The motivation to these proposals is mainly theoretical, based on the following observation: The Planck length is expected to play a fundamental role in a theory of Quantum Gravity, setting the scale at which Quantum Gravity effects cannot be neglected and "new" phenomena are observed. If Special Relativity is to hold up exactly to this scale, different observers would observe Quantum Gravity effects at different scales, due to the Lorentz–FitzGerald contraction, in contradiction to the principle that all inertial observers should be able to describe phenomena by the same physical laws.
A drawback of the usual doubly special relativity models is that they are valid only at the energy scales where ordinary special relativity is supposed to break down, giving rise to a patchwork relativity. On the other hand, de Sitter relativity is found to be invariant under a simultaneous re-scaling of mass, energy and momentum, and is consequently valid at all energy scales.


Muon

The muon (; from the Greek letter mu (μ) used to represent it) is an elementary particle similar to the electron, with an electric charge of −1 "e" and a spin of 1/2, but with a much greater mass. It is classified as a lepton. As with other leptons, the muon is not known to have any sub-structure – that is, it is not thought to be composed of any simpler particles.
The muon is an unstable subatomic particle with a mean lifetime of , much longer than many other subatomic particles. As with the decay of the non-elementary neutron (with a lifetime around 15 minutes), muon decay is slow (by subatomic standards) because the decay is mediated only by the weak interaction (rather than the more powerful strong interaction or electromagnetic interaction), and because the mass difference between the muon and the set of its decay products is small, providing few kinetic degrees of freedom for decay. Muon decay almost always produces at least three particles, which must include an electron of the same charge as the muon and two types of neutrinos.
Like all elementary particles, the muon has a corresponding antiparticle of opposite charge (+1 "e") but equal mass and spin: the antimuon (also called a "positive muon"). Muons are denoted by and antimuons by . Formerly, muons were called ""mu mesons", but are not classified as mesons by modern particle physicists (see ), and that name is no longer used by the physics community.
Muons have a mass of , which is approximately 207 times that of the electron, "m". More precisely, it is .
Due to their greater mass, muons accelerate more slowly than electrons in electromagnetic fields, and emit less bremsstrahlung (deceleration radiation). This allows muons of a given energy to penetrate far deeper into matter because the deceleration of electrons and muons is primarily due to energy loss by the bremsstrahlung mechanism. For example, so-called "secondary muons", created by cosmic rays hitting the atmosphere, can penetrate the atmosphere and reach Earth's land surface and even into deep mines.
Because muons have a greater mass and energy than the decay energy of radioactivity, they are not produced by radioactive decay. However they are produced in great amounts in high-energy interactions in normal matter, in certain particle accelerator experiments with hadrons, and in cosmic ray interactions with matter. These interactions usually produce pi mesons initially, which almost always decay to muons.
As with the other charged leptons, the muon has an associated muon neutrino, denoted by , which differs from the electron neutrino and participates in different nuclear reactions.
History.
Muons were discovered by Carl D. Anderson and Seth Neddermeyer at Caltech in 1936, while studying cosmic radiation. Anderson noticed particles that curved differently from electrons and other known particles when passed through a magnetic field. They were negatively charged but curved less sharply than electrons, but more sharply than protons, for particles of the same velocity. It was assumed that the magnitude of their negative electric charge was equal to that of the electron, and so to account for the difference in curvature, it was supposed that their mass was greater than an electron but smaller than a proton. Thus Anderson initially called the new particle a "mesotron", adopting the prefix "meso-" from the Greek word for "mid-". The existence of the muon was confirmed in 1937 by J. C. Street and E. C. Stevenson's cloud chamber experiment.
A particle with a mass in the meson range had been predicted before the discovery of any mesons, by theorist Hideki Yukawa:
It seems natural to modify the theory of Heisenberg and Fermi in the following way. The transition of a heavy particle from neutron state to proton state is not always accompanied by the emission of light particles. The transition is sometimes taken up by another heavy particle.
Because of its mass, the mu meson was initially thought to be Yukawa's particle and some scientists, including Niels Bohr, originally named it the yukon. Yukawa's predicted particle, the pi meson, was finally identified in 1947 (again from cosmic ray interactions), and was shown to differ from the mu meson by having the properties of a particle that mediated the nuclear force.
With two particles now known with the intermediate mass, the more general term "meson" was adopted to refer to any such particle within the correct mass range between electrons and nucleons. Further, in order to differentiate between the two different types of mesons after the second meson was discovered, the initial mesotron particle was renamed the "mu meson" (the Greek letter "μ" ["mu"] corresponds to "m"), and the new 1947 meson (Yukawa's particle) was named the pi meson.
As more types of mesons were discovered in accelerator experiments later, it was eventually found that the mu meson significantly differed not only from the pi meson (of about the same mass), but also from all other types of mesons. The difference, in part, was that mu mesons did not interact with the nuclear force, as pi mesons did (and were required to do, in Yukawa's theory). Newer mesons also showed evidence of behaving like the pi meson in nuclear interactions, but not like the mu meson. Also, the mu meson's decay products included both a neutrino and an antineutrino, rather than just one or the other, as was observed in the decay of other charged mesons.
In the eventual Standard Model of particle physics codified in the 1970s, all mesons other than the mu meson were understood to be hadrons – that is, particles made of quarks – and thus subject to the nuclear force. In the quark model, a "meson" was no longer defined by mass (for some had been discovered that were very massive – more than nucleons), but instead were particles composed of exactly two quarks (a quark and antiquark), unlike the baryons, which are defined as particles composed of three quarks (protons and neutrons were the lightest baryons). Mu mesons, however, had shown themselves to be fundamental particles (leptons) like electrons, with no quark structure. Thus, mu "mesons" were not mesons at all, in the new sense and use of the term "meson" used with the quark model of particle structure.
With this change in definition, the term "mu meson" was abandoned, and replaced whenever possible with the modern term "muon", making the term "mu meson" only a historical footnote. In the new quark model, other types of mesons sometimes continued to be referred to in shorter terminology (e.g., "pion" for pi meson), but in the case of the muon, it retained the shorter name and was never again properly referred to by older "mu meson" terminology.
The eventual recognition of the muon as a simple "heavy electron", with no role at all in the nuclear interaction, seemed so incongruous and surprising at the time, that Nobel laureate I. I. Rabi famously quipped, "Who ordered that?"
In the Rossi–Hall experiment (1941), muons were used to observe the time dilation (or, alternatively, length contraction) predicted by special relativity, for the first time.
Muon sources.
Muons arriving on the Earth's surface are created indirectly as decay products of collisions of cosmic rays with particles of the Earth's atmosphere.
When a cosmic ray proton impacts atomic nuclei in the upper atmosphere, pions are created. These decay within a relatively short distance (meters) into muons (their preferred decay product), and muon neutrinos. The muons from these high-energy cosmic rays generally continue in about the same direction as the original proton, at a velocity near the speed of light. Although their lifetime "without" relativistic effects would allow a half-survival distance of only about 456 meters at most (as seen from Earth) the time dilation effect of special relativity (from the viewpoint of the Earth) allows cosmic ray secondary muons to survive the flight to the Earth's surface, since in the Earth frame the muons have a longer half-life due to their velocity. From the viewpoint (inertial frame) of the muon, on the other hand, it is the length contraction effect of special relativity which allows this penetration, since in the muon frame its lifetime is unaffected, but the length contraction causes distances through the atmosphere and Earth to be far shorter than these distances in the Earth rest-frame. Both effects are equally valid ways of explaining the fast muon's unusual survival over distances.
Since muons are unusually penetrative of ordinary matter, like neutrinos, they are also detectable deep underground (700 meters at the Soudan 2 detector) and underwater, where they form a major part of the natural background ionizing radiation. Like cosmic rays, as noted, this secondary muon radiation is also directional.
The same nuclear reaction described above (i.e. hadron-hadron impacts to produce pion beams, which then quickly decay to muon beams over short distances) is used by particle physicists to produce muon beams, such as the beam used for the muon "g"−2 experiment.
Muon decay.
Muons are unstable elementary particles and are heavier than electrons and neutrinos but lighter than all other matter particles. They decay via the weak interaction. Because leptonic family numbers are conserved in the absence of an extremely unlikely immediate neutrino oscillation, one of the product neutrinos of muon decay must be a muon-type neutrino and the other an electron-type antineutrino (antimuon decay produces the corresponding antiparticles, as detailed below).
Because charge must be conserved, one of the products of muon decay is always an electron of the same charge as the muon (a positron if it is a positive muon). Thus all muons decay to at least an electron, and two neutrinos. Sometimes, besides these necessary products, additional other particles that have no net charge and spin of zero (e.g., a pair of photons, or an electron-positron pair), are produced.
The dominant muon decay mode (sometimes called the Michel decay after Louis Michel) is the simplest possible: the muon decays to an electron, an electron antineutrino, and a muon neutrino. Antimuons, in mirror fashion, most often decay to the corresponding antiparticles: a positron, an electron neutrino, and a muon antineutrino. In formulaic terms, these two decays are:
The mean lifetime, = /, of the (positive) muon is  . The equality of the muon and antimuon lifetimes has been established to better than one part in 104.
Prohibited decays.
Certain neutrino-less decay modes are kinematically allowed but are, for all practical purposes, forbidden in the Standard Model, even given that neutrinos have mass and oscillate. Examples forbidden by lepton flavour conservation are:
and
To be precise: in the Standard Model with neutrino mass, a decay like → + is technically possible, for example by neutrino oscillation of a virtual muon neutrino into an electron neutrino, but such a decay is astronomically unlikely and therefore should be experimentally unobservable: Less than one in 1050 muon decays should produce such a decay.
Observation of such decay modes would constitute clear evidence for theories beyond the Standard Model. Upper limits for the branching fractions of such decay modes were measured in many experiments starting more than years ago. The current upper limit for the → + branching fraction was measured 2009–2013 in the MEG experiment and is 4.2 × 10−13.
Theoretical decay rate.
The muon decay width which follows from Fermi's golden rule has dimension of energy, and must be proportional to the square of the amplitude, and thus the square of Fermi's coupling constant (formula_1), with over-all dimension of inverse fourth power of energy. By dimensional analysis, this leads to Sargent's rule of fifth-power dependence on ,
where formula_3, and
The decay distributions of the electron in muon decays have been parameterised using the so-called Michel parameters. The values of these four parameters are predicted unambiguously in the Standard Model of particle physics, thus muon decays represent a good test of the spacetime structure of the weak interaction. No deviation from the Standard Model predictions has yet been found.
For the decay of the muon, the expected decay distribution for the Standard Model values of Michel parameters is
where formula_6 is the angle between the muon's polarization vector formula_7 and the decay-electron momentum vector, and formula_8 is the fraction of muons that are forward-polarized. Integrating this expression over electron energy gives the angular distribution of the daughter electrons:
The electron energy distribution integrated over the polar angle (valid for formula_10) is
Because the direction the electron is emitted in (a polar vector) is preferentially aligned opposite the muon spin (an axial vector), the decay is an example of non-conservation of parity by the weak interaction. This is essentially the same experimental signature as used by the original demonstration. More generally in the Standard Model, all charged leptons decay via the weak interaction and likewise violate parity symmetry.
Muonic atoms.
The muon was the first elementary particle discovered that does not appear in ordinary atoms.
Negative muon atoms.
"Negative" muons can, however, form muonic atoms (previously called mu-mesic atoms), by replacing an electron in ordinary atoms. Muonic hydrogen atoms are much smaller than typical hydrogen atoms because the much larger mass of the muon gives it a much more localized ground-state wavefunction than is observed for the electron. In multi-electron atoms, when only one of the electrons is replaced by a muon, the size of the atom continues to be determined by the other electrons, and the atomic size is nearly unchanged. However, in such cases the orbital of the muon continues to be smaller and far closer to the nucleus than the atomic orbitals of the electrons.
Muonic helium is created by substituting a muon for one of the electrons in helium-4. The muon orbits much closer to the nucleus, so muonic helium can therefore be regarded like an isotope of helium whose nucleus consists of two neutrons, two protons and a muon, with a single electron outside. Colloquially, it could be called "helium 4.1", since the mass of the muon is slightly greater than 0.1 amu. Chemically, muonic helium, possessing an unpaired valence electron, can bond with other atoms, and behaves more like a hydrogen atom than an inert helium atom.
Muonic heavy hydrogen atoms with a negative muon may undergo nuclear fusion in the process of muon-catalyzed fusion, after the muon may leave the new atom to induce fusion in another hydrogen molecule. This process continues until the negative muon is captured by a helium nucleus, and cannot escape until it decays.
Negative muons bound to conventional atoms can be captured (muon capture) through the weak force by protons in nuclei, in a sort of electron-capture-like process. When this happens, nuclear transmutation results: The proton becomes a neutron and a muon neutrino is emitted.
Positive muon atoms.
A "positive" muon, when stopped in ordinary matter, cannot be captured by a proton since the two positive charges can only repel. The positive muon is also not attracted to the nucleus of atoms. Instead, it binds a random electron and with this electron forms an exotic atom known as muonium (mu) atom. In this atom, the muon acts as the nucleus. The positive muon, in this context, can be considered a pseudo-isotope of hydrogen with one ninth of the mass of the proton. Because the mass of the electron is much smaller than the mass of both the proton and the muon, the reduced mass of muonium, and hence its Bohr radius, is very close to that of hydrogen. Therefore this bound muon-electron pair can be treated to a first approximation as a short-lived "atom" that behaves chemically like the isotopes of hydrogen (protium, deuterium and tritium).
Both positive and negative muons can be part of a short-lived pi-mu atom consisting of a muon and an oppositely charged pion. These atoms were observed in the 1970s in experiments at Brookhaven and Fermilab.
Use in measurement of the proton charge radius.
The experimental technique that is expected to provide the most precise determination of the root-mean-square charge radius of the proton is the measurement of the frequency of photons (precise "color" of light) emitted or absorbed by atomic transitions in muonic hydrogen. This form of hydrogen atom is composed of a negatively charged muon bound to a proton. The muon is particularly well suited for this purpose because its much larger mass results in a much more compact bound state and hence a larger probability for it to be found inside the proton in muonic hydrogen compared to the electron in atomic hydrogen. The Lamb shift in muonic hydrogen was measured by driving the muon from a 2s state up to an excited 2p state using a laser. The frequency of the photons required to induce two such (slightly different) transitions were reported in 2014 to be 50 and 55 THz which, according to present theories of quantum electrodynamics, yield an appropriately averaged value of for the charge radius of the proton.
The internationally accepted value of the proton's charge radius is based on a suitable average of results from older measurements of effects caused by the nonzero size of the proton on scattering of electrons by nuclei and the light spectrum (photon energies) from excited atomic hydrogen. The official value updated in 2014 is (see orders of magnitude for comparison to other sizes).
The expected precision of this result is inferior to that from muonic hydrogen by about a factor of fifteen, yet they disagree by about 5.6 times the nominal uncertainty in the difference (a discrepancy called 5.6  in scientific notation). A conference of the world experts on this topic led to the decision to exclude the muon result from influencing the official 2014 value, in order to avoid hiding the mysterious discrepancy.
This "proton radius puzzle" remained unresolved as of late 2015, and has attracted much attention, in part because of the possibility that both measurements are valid, which would imply the influence of some "new physics".
Anomalous magnetic dipole moment.
The anomalous magnetic dipole moment is the difference between the experimentally observed value of the magnetic dipole moment and the theoretical value predicted by the Dirac equation. The measurement and prediction of this value is very important in the precision tests of QED (quantum electrodynamics). The E821 experiment at Brookhaven National Laboratory (BNL) and the Muon g-2 experiment at Fermilab studied the precession of the muon spin in a constant external magnetic field as the muons circulated in a confining storage ring. The Muon g-2 collaboration reported in 2021:
The prediction for the value of the muon anomalous magnetic moment includes three parts:
The difference between the "g"-factors of the muon and the electron is due to their difference in mass. Because of the muon's larger mass, contributions to the theoretical calculation of its anomalous magnetic dipole moment from Standard Model weak interactions and from contributions involving hadrons are important at the current level of precision, whereas these effects are not important for the electron. The muon's anomalous magnetic dipole moment is also sensitive to contributions from new physics beyond the Standard Model, such as supersymmetry. For this reason, the muon's anomalous magnetic moment is normally used as a probe for new physics beyond the Standard Model rather than as a test of QED. Muon "g"−2, a new experiment at Fermilab using the E821 magnet improved the precision of this measurement.
In 2020 an international team of 170 physicists calculated the most accurate prediction for the theoretical value of the muon's anomalous magnetic moment.
Electric dipole moment.
The current experimental limit on the muon electric dipole moment, |dμ| < 1.9 × 10−19e·cm set by the E821 experiment at the Brookhaven Laboratory, is orders of magnitude above the Standard Model prediction. The observation of non-zero a muon electric dipole moment would provide an additional source of CP violation. An improvement in sensitivity by two orders of magnitude over the Brookhaven limit is expected from the experiments at Fermilab.
Muon radiography and tomography.
Since muons are much more deeply penetrating than X-rays or gamma rays, muon imaging can be used with much thicker material or, with cosmic ray sources, larger objects. One example is commercial muon tomography used to image entire cargo containers to detect shielded nuclear material, as well as explosives or other contraband.
The technique of muon transmission radiography based on cosmic ray sources was first used in the 1950s to measure the depth of the overburden of a tunnel in Australia and in the 1960s to search for possible hidden chambers in the Pyramid of Chephren in Giza. In 2017, the discovery of a large void (with a length of 30 metres minimum) by observation of cosmic-ray muons was reported.
In 2003, the scientists at Los Alamos National Laboratory developed a new imaging technique: "muon scattering tomography". With muon scattering tomography, both incoming and outgoing trajectories for each particle are reconstructed, such as with sealed aluminum drift tubes. Since the development of this technique, several companies have started to use it.
In August 2014, Decision Sciences International Corporation announced it had been awarded a contract by Toshiba for use of its muon tracking detectors in reclaiming the Fukushima nuclear complex. The Fukushima Daiichi Tracker (FDT) was proposed to make a few months of muon measurements to show the distribution of the reactor cores.
In December 2014, Tepco reported that they would be using two different muon imaging techniques at Fukushima, "Muon scanning method" on Unit 1 (the most badly damaged, where the fuel may have left the reactor vessel) and "Muon scattering method" on Unit 2.
The International Research Institute for Nuclear Decommissioning IRID in Japan and the High Energy Accelerator Research Organization KEK call the method they developed for Unit 1 the muon permeation method; 1,200 optical fibers for wavelength conversion light up when muons come into contact with them. After a month of data collection, it is hoped to reveal the location and amount of fuel debris still inside the reactor. The measurements began in February 2015.


Mario Garavaglia

Mario Garavaglia (born 1937) is an Argentine physicist.
Biography.
He was born in Junín (Buenos Aires Province, Argentina) in 1937.
In 1999 the International Commission for Optics awarded him the "Galileo Galilei Award" by unanimous vote for his work on lasers and their applications in industry, medicine and biology and for promoting optics in Latin America.
In 2004 he received the Houssay Career Award.


Arthur Hafford Cooke

Arthur Hafford Cooke, MBE (13 December 1912; 31 July 1987) was an English academic administrator at the University of Oxford.
Cooke was educated at Wyggeston Grammar School and Christ Church, Oxford He became a Research Lecturer at Christ Church in 1939. During World War Two he conducted Radar research for the Admiralty. He was a Fellow of New College, Oxford from 1946 to 1976; University Lecturer in Physics from 1944 to 1971; Reader in Physics from 1971 to 1976; and Warden of New College from 1976 to 1985.


Dynamitron

The Dynamitron is an electrostatic particle accelerator invented by Marshal Cleland in 1956 at Washington University and manufactured by IBA Industrial (formerly Radiation Dynamics).
 It is similar to a Cockcroft-Walton accelerator, using a series capacitor-diode ladder network to generate a high DC voltage on an electrode, which accelerates particles through an evacuated beam tube between the electrode and a target at ground potential. However instead of being powered at one end as in the CW, the capacitive ladder is charged in parallel electrostatically by a high frequency oscillating voltage applied between two long cylindrical electrodes on either side of the ladder column, which induce voltage in semicircular corona rings attached to each end of the diode rectifier tubes. in combination with an inductor this structure forms a resonant tank circuit for the oscillator providing the voltage, at a frequency of 100 kHz. The alternating voltage across the diodes pumps charge in one direction up the series stack of diodes to the high voltage electrode as in the Cockcroft-Walton circuit. The advantage of this design is that it can produce higher beam currents than the Cockcroft-Walton design, up to hundreds of milliamperes, and the high frequency reduces the ripple on the accelerating voltage. The accelerator stack is inside a tank of pressurized sulfur hexafluoride gas for insulation. It can accelerate either electrons or positive ions, and tandem versions have been built.
The Dynamitron is made in several models with output energies from 0.5 to 5 MeV and beam power from 50 to 200 kW. Its main use is in industrial irradiation applications; the most common are polymer crosslinking for production of heat shrink tubing, and shrink wrap plastic film for food packaging, sterilization, and curing of plastic foam and tire components. Around 200 units are in operation, primarily in the US. A number have been installed in university research settings including the University of Birmingham in the UK and Tohoku University in Japan A modern research application for Dynamitrons is as a high intensity neutron source. They are particularly suited for neutron production via the Lithium (p,n) reaction with potential applications in neutron imaging, activation analysis and Boron Neutron Capture Therapy.


Riccardo Betti

Riccardo Betti (Rome, Italy on July 29, 1963) is the Robert L. McCrory professor of Mechanical Engineering and Physics and Astronomy at the University of Rochester, in Rochester, NY. Since 2004, he has also acted as the Director of the Fusion Science Center at the Laboratory for Laser Energetics. He received is Ph.D. from the Department of Nuclear Engineering at the Massachusetts Institute of Technology (Cambridge, MA) in 1992. Prior to that he studied at the University of Rome (Italy), where he graduated with honors with a degree in Nuclear Engineering in 1987.
Honors and awards.
Dr. Betti is the Chair of the American Physical Society's Division of Plasma Physics (November, 2014-October 2015).
Dr. Betti was a 2012 recipient of the U.S. Department of Energy's Ernest O. Lawrence Award for "a series of impactful theoretical discoveries in the physics of inertial confinement fusion including seminal transformative work on thermonuclear ignition, hydrodynamic instabilities and implosion dynamics, and the development of innovative approaches to ignition and energy gains."
In 2010, he was given a Leadership Award from Fusion Power Associates "for the leadership he has been providing to the U.S. and world inertial fusion efforts, including his contributions to the search for efficient methods of igniting fusion targets, contributions to the emerging field of high energy density physics, and his advisory role in the DOE's Fusion Energy Sciences Advisory Committee."
In 2009, Dr. Betti was awarded the Edward Teller Medal from the American Nuclear Society "for seminal contributions to the theory and understanding of hydrodynamic instabilities, implosion dynamics and thermonuclear ignition in inertial confinement fusion."
He has been a Fellow at the American Physical Society since 2001. In 2010, he was appointed to the Board of Physics and Astronomy of the National Academy of Sciences. He was Vice Chair of the Fusion Energy Science Committee of the Department of Energy.
On October 29, 2009, Dr Betti gave a statement to the U.S. House of Representative's Committee on Science and Technology Subcommittee on Energy and Environment on the "Next Generation of Fusion Energy Research."


Detection of internally reflected Cherenkov light

In particle detectors a detection of internally reflected Cherenkov light (DIRC) detector measures the velocity of charged particles and is used for particle identification. It is a design of a ring imaging Cherenkov detector where Cherenkov light that is contained by total internal reflection inside the solid radiator has its angular information preserved until it reaches the light sensors at the detector perimeter.
A charged particle travelling through a material (for instance fused silica) with a speed greater than c/n (n refractive index, c vacuum speed of light) emits Cherenkov radiation. If the light angle on the surface is sufficiently shallow, this radiation is contained inside and transmitted through internal reflections to an expansion volume, coupled to photomultipliers (or other types of photon detectors), to measure the angle. Preserving the angle requires a precise planar and rectangular cross section of the radiator. Knowledge of the angle at which the radiation was produced, combined with the track angle and the particle's momentum (measured in a tracking detector like a drift chamber) may be used to calculate the particle's mass.
A DIRC was first proposed by Blair Ratcliff as a tool for particle identification at a B-Factory, and the design was first used by the BaBar collaboration at SLAC. Since the successful operation in the BaBar experiment next-generation DIRC-type detectors have been designed for several new particle physics experiments, including Belle-II, PANDA, and GlueX. The DIRC differs from earlier RICH and CRID Cherenkov light detectors in that the quartz bars used as radiators also transmit the light.


Kendal Nezan

Kendal Nezan is a French-Kurdish nuclear physicist and president of the Kurdish Institute of Paris. He was born in Turkey. He is also a board member of the Washington Kurdish Institute.
In 1975, Nezan established the France-Kurdistan Society, which included the leading French intellectual Jean-Paul Sartre.
Nezan maintains close relations with numerous European governments and the European Parliament.


Helmholtz Institute Jena

The Helmholtz Institute Jena was founded as an outstation of the GSI Helmholtzzentrum für Schwerionenforschung on June 25, 2009 and is located on the campus of the Friedrich Schiller University (FSU) in the city of Jena, Germany. Its purpose is to unite the research activities of the FSU in the fields of high intensity laser physics and x-ray spectroscopy with the expertise of the Deutsches Elektronen-Synchrotron (DESY), GSI Helmholtzzentrum für Schwerionenforschung and Helmholtz-Zentrum Dresden-Rossendorf in the fields of accelerator physics, laser physics and x-ray technology.
The research profile of the Helmholtz Institute Jena is focused on the physics occurring at the border between conventional particle-acceleration technology and the fast-evolving field of laser-induced particle acceleration. ("e.g." wakefield accelerator). It is concerned with advancing these new laser-induced accelerator concepts, as well as with the production and investigation of intense photon and particle beams, including their interaction with matter. Therefore the main activities of the institute are emphasized on the development of high intensity lasers, new concepts for laser-driven particle acceleration, x-ray spectroscopy and strong-field quantum electrodynamics, as well as on the physics of hot dense plasmas. Apart from that the Helmholtz Institute Jena aims to contribute to the further development of the research facilities at the Helmholtz center GSI, especially the future project FAIR (Facility for Antiproton and Ion Research), and DESY with the free-electron laser (FEL) photon sources FLASH and XFEL (European XFEL).
In cooperation with the FSU Jena a completely diode-pumped laser system of the high energy petawatt class (HEPW) with the POLARIS laser is realized in the building of the Helmholtz Institute Jena. First measurements are done since 2008. Due to the missing last amplifier stage the pulse strength of 1 PW couldn't be reached yet.
The graduate school "Research School for Advanced Photon Science" (RS-APS) was established at the Helmholtz Institute Jena in July 2012. The RS-APS supports up to 25 PhD students and provides a structured graduation program in cooperation with facilities of the FSU Jena and the Helmholtz Graduate School for Hadron and Ion Research (HGS-HIRe).


James Robert Milne

Dr James Robert Milne PRSSA FRSE (c.1880–3 February 1961) was a 20th-century Scottish physicist. He served as President of the Royal Scottish Society of Arts from 1923 to 1925.
Life.
He graduated with a BSc from the University of Edinburgh in 1899.
He was an early radio engineer and ran the Edinburgh and District Radio Society from around 1900.
In 1904 he was elected a Fellow of the Royal Society of Edinburgh. His proposers were James Gordon MacGregor, Cargill Gilston Knott, William Peddie, and George Chrystal. He lived at 11 Melville Crescent in Edinburgh's West End.
In 1908 he was elected a Fellow of the Royal Scottish Society of Arts. In 1923 he succeeded Richard Stanfield as President of the society. In 1925 he was succeeded in turn by Robert Stuart Pilcher.
From 1912 to 1946 he lectured in physics at the University of Edinburgh.
He died in Edinburgh on 3 February 1961.


Gordon D. Love

Gordon D Love is an optics researcher and Professor of Physics at Durham University. He is noted for work in Adaptive Optics.
He is a Council Member of the Institute of Physics and past board member of the European Optical Society.
Education.
Love earned both his Bachelor of Science and doctorate from Durham University. He was an undergraduate at Van Mildert College.


James Kakalios

James Kakalios (born December 27, 1958) is a physics professor at the University of Minnesota. Known within the scientific community for his work with amorphous semiconductors, granular materials, and 1/f noise, he is known to the general public as the author of the book "The Physics of Superheroes", which considers comic book superheroes from the standpoint of fundamental physics.
Work.
Kakalios, who earned PhD from the University of Chicago in 1985, began his comic book collection as a graduate student as a way to relieve stress. At Minnesota, he taught a freshman seminar that focused on the physics of superheroes as a way to motivate students to think about physics. This course gained great popularity as an enticing alternative to the typical inclined planes and pulleys of physics.The seminar was a great success, leading to articles in popular magazines including "People", lectures on the subject, and publication of "The Physics of Superheroes". In his talks, favorite examples are the death of Gwen Stacy (Spider-Man's girlfriend), "can Superman jump over tall buildings and what does this tell us about Krypton?", the high-velocity actions of The Flash, and the shrinking problem of the Atom. His analysis of Gwen Stacy's death eventually became integral to the plot of a new Spider-Man comic.
Kakalios is of the opinion that the most unrealistic aspect of the comic-book universe is often the sociology. He notes that pedestrians do not usually provide running monologues describing everything around them. There is one aspect of the story of the Atom that he does not question, however. The Atom begins as a physics professor, who encounters a chunk of white dwarf star and picks it up. "By a conservative estimate, he is lifting about 5000 metric tons. This is not unreasonable. We physics professors are just that strong."
He provides content on the DVD of the film "Watchmen". Under extras, he is filmed discussing the physics of superheroes. As one of the film's lead scientific consultants of the 2012 film "The Amazing Spider-Man", Kakalios designed the film's "decay rate algorithm", which was inspired by the real-life Gompertz–Makeham law of mortality.
Kakalios has been nominated by the University of Minnesota to be one of the USA Science and Engineering Festival's Nifty Fifty Speakers who will speak about his work and career to middle and high school students in October 2010.
James Kakalios was awarded an Honorary Doctor of Science degree from the University of Lincoln, UK (2017).


Fausto Cattaneo

Fausto Cattaneo is an Italian physicist, currently at University of Chicago and an Elected Fellow of the American Physical Society.


List of early third generation computers

This list of early third generation computers, tabulates those computers using monolithic integrated circuits (ICs) as their primary logic elements, starting from small-scale integration CPUs (SSI) to large-scale integration CPUs (LSI). Computers primarily using ICs first came into use about 1961 for military use. With the availability of reliable low cost ICs in the mid 1960s commercial third generation computers using ICs started to appear.
The fourth generation computers began with the shipment of CPS-1, the first commercial microprocessor microcomputer in 1972 and for the purposes of this list marks the end of the "early" third generation computer era. Note that third generation computers were offered well into the 1990s.
The list is organized by delivery year to customers or production/operational date. In some cases only the first computer from any one manufacturer is listed. Computers announced, but never completed, are not included. Computers without documented manual input (keyboard/typewriter/control unit) are also not included.
Aerospace & military computers (1961-1972).
1961
1962
1963
1965
1967
1970
1971
Commercial computers (1965-1972).
This table of commercial 3rd generation computers has been constructed by merging of several lists of computers offered from February 1965, the date of the shipment of the first commercial 3rd generation computer, thru 1971 inclusive and then finding reliable sources as to the generation of the models listed and the associated dates.


Rapid radiative transfer model

The Rapid Radiative Transfer Model (RRTM) is a validated, correlated k-distribution band model for the calculation of solar and thermal-infrared atmospheric radiative fluxes and heating rates. The Rapid Radiative Transfer Model for GCMs (RRTM-G) is an accelerated version of RRTM that provides improved efficiency with minimal loss of accuracy for application to general circulation models. The latter divides the solar spectrum into 14 bands within which a total of 112 pseudo-monochromatic calculations are performed, and in the thermal infrared 16 bands are used within which 140 pseudo-monochromatic calculations are performed. RRTM-G is used in a number of general circulation models worldwide, such as that of the European Centre for Medium-Range Weather Forecasts.


Optofluidics

Optofluidics is a research and technology area that combines the advantages of fluidics (in particular microfluidics) and optics. Applications of the technology include displays, biosensors, lab-on-chip devices, lenses, and molecular imaging tools and energy.
History.
The idea of fluid-optical devices can be traced back at least as far as the 18th century, when spinning pools of mercury were proposed (and eventually developed) as liquid-mirror telescopes. In the 20th century new technologies such as dye lasers and liquid-core waveguides were developed that took advantage of the tunability and physical adaptability that liquids provided to these newly emerging photonic systems. The field of optofluidics formally began to emerge in the mid-2000s as the fields of microfluidics and nanophotonics were maturing and researchers began to look for synergies between these two areas. One of the primary applications of the field is for lab-on-a-chip and biophotonic products.
Companies and technology transfer.
Optofluidic and related research has led to the formation of a number of new products and start-up companies. Varioptic specializes in the development of electrowetting based lenses for numerous applications. Optofluidics, Inc. was launched in 2011 from Cornell University in order to develop tools for molecular trapping and disease diagnosis based on photonic resonator technology. Liquilume from UC Santa Cruz specializes in molecular diagnostics based on arrow waveguides.
In 2012, the European Commission has launched a new COST framework that is concerned solely with optofluidic technology and their application.


Ned Goldwasser

Ned Goldwasser (born Edwin L. Goldwasser, March 9, 1919 — December 14, 2016) was an American physicist and Co-Founder of the Fermi National Accelerator Laboratory and the field of particle physics. He was a Professor of Physics Emeritus and former Vice Chancellor of Academic Affairs at the University of Illinois, as well as the first Deputy Director of Fermilab National Accelerator Laboratory. His interests were photons, cosmic rays, charged particles and elementary particles. He was Fellow to the American Association for the Advancement of Science and American Physical Society (elected in 1961). He was a Guggenheim Fellow for the academic year 1957–1958.
Life and career.
Ned was born in Manhattan, attending the Horace Mann school and later graduating at Harvard, majoring in physics and graduating in 1940. His first job was in the Navy, working as a civilian physicist for the Bureau of Ordnance


Kristin Persson

Kristin A. Persson is a Swedish American physicist and chemist. She is a Faculty Staff Scientist at Lawrence Berkeley National Laboratory and Professor of Materials Science and Engineering at University of California, Berkeley. Currently, she is also the Director of the Molecular Foundry, a national user facility managed by the US Department of Energy at Lawrence Berkeley National Laboratory. Persson is the Director and Co-Founder of the Materials Project, a multi-national effort to compute the properties of all inorganic materials.
Education.
Persson holds a Master of Science in Engineering Physics from Lund Institute of Technology in Sweden and completed a Ph.D. in Theoretical Physics from Royal Institute of Technology (KTH) in Sweden in 2001, under the supervision of . After her Ph.D., she joined the Massachusetts Institute of Technology as a postdoctoral associate from 2001 to 2007.


Domain wall (optics)

A domain wall is a term used in physics which can have similar meanings in optics, magnetism, or string theory. These phenomena can all be generically described as topological solitons which occur whenever a discrete symmetry is spontaneously broken.
As of 2009, a phase-locked dark-dark vector soliton was observed only in fiber lasers of positive dispersion while a phase-locked dark-bright vector soliton was obtained in fiber lasers of either positive or negative dispersion. Numerical simulations confirmed the experimental observations, and further showed that the observed vector solitons are the two types of phase-locked polarization domain-wall solitons theoretically predicted. Another novel type of domain wall soliton is the vector dark domain wall, consisting of stable localized structures separating the two orthogonal linear polarization eigenstates of the laser emission, with a dark structure that is visible only when the total laser emission is measured.


Paolo Giubellino

Paolo Giubellino (born November 9, 1960) is an experimental particle physicist working on High-Energy Nuclear Collisions. Currently he is the joint Scientific Managing Director of the Facility for Antiproton and Ion Research (FAIR) and the GSI Helmholtz Centre for Heavy Ion Research (GSI) and Professor at the Institute of Nuclear Physics of the Technische Universität Darmstadt.
Until December 31, 2016, Giubellino was Spokesperson of the , an international collaboration of more than 1300 people from 163 scientific institutions from 40 countries.
He has carried several responsibility positions in the ALICE Collaboration since its creation in the early nineties, to be eventually elected Deputy Spokesperson from 2004 to 2010 and Spokesperson from 1 January 2011. On July 17, 2013, he was elected for a second term as Spokesperson of ALICE.
Giubellino has dedicated most of his scientific life to the physics of high-energy heavy ion collisions, in which quark–gluon plasma a state of ultra dense and hot matter, as it prevails in the first microseconds of the life of our universe. Moreover, he has participated in numerous experimental projects first at the CERN Super Proton Synchrotron and, since the beginning of the program, at the Large Hadron Collider.
Early life and education.
Paolo Giubellino, Italian, born in 1960, graduated in Physics at the University of Torino in 1983 with 110/110 cum laude and special honorable mention and continued his studies as a
Fulbright fellow at the University of California, Santa Cruz. In 2000 he was awarded the title of Doctor in Physics and Mathematics (Habilitation) by the Dubna Academic Council (Russia). He is married and has one son.
Research career.
Paolo Giubellino has dedicated most of his scientific life to the Physics of High-Energy Heavy-Ion collisions, first in HELIOS, then in NA50, in the ALICE experiment and finally at GSI and FAIR.
He joined the Torino branch of the Italian National Institute for Nuclear Physics (INFN) in 1985. In 2006 he was promoted to "research director", the highest in the three-level INFN career. Giubellino has been responsible for several scientific programs within INFN and for NATO, INTAS and EU grants. From 1990 to 1996 he was coordinator of the Group II (one of the five sections in which INFN research is organized) of the Torino branch of the INFN. From 1995 to 2000 and since 2007 he was responsible for the involvement of the Torino group in the ALICE Inner Tracking System project.
Giubellino has participated in CERN heavy-ion programme from the early days of his career. He was in charge of the design, construction and operation of the SCI-PAD detector for the NA34/1 experiment as well as for the NA34/2 silicon pad detectors for the Ring Counters.
In 1988 he joined the NA50 collaboration and worked in one of the fixed-target experiments. He was responsible in NA50 for the design, construction and commissioning of the silicon multiplicity detectors (MD).
During his entire career, Giubellino has participated in several R&D projects directed to the development of silicon detectors and radiation tolerant electronics. He is also one of the founding fathers of the microelectronics group at INFN Torino
Giubellino has been involved in ALICE from the very first feasibility studies, and has later carried a number of responsibilities in the experiment, including Project Leader for the Inner Tracking System, Chair of Conference Committee, Upgrade Coordinator and, for six years, Deputy Spokesperson (July 2000 - September 2002 and August 2006 - December 2010). He was elected Spokesperson of the ALICE Collaboration for the first time in March 2010 and re-elected in July 2013. During this period he led the ALICE Collaboration to the preparation of an Upgrade proposal for experiment, spanning the years 2018 to 2025. The upgrade project, which will involve 163 Institutions from 40 countries, has been approved by the Large Hadron Collider Committee in September 2012.
On January 1, 2017, Paolo Giubellino became the first joint scientific managing director of Facility for Antiproton and Ion Research in Europe GmbH (FAIR GmbH) and GSI Helmholtzzentrum für Schwerionenforschung GmbH in Darmstadt. In addition, he has taken over the position of spokesperson of the management of FAIR and GSI. In September 2016, the FAIR Council and the GSI Supervisory Board announced their decision to appoint Giubellino. Since January 1, 2017 Giubellino is Professor at the Institute of Nuclear Physics of the Technische Universität Darmstadt.
Science Management and Review Committees.
Paolo Giubellino serves in many scientific committees and panels in France, Germany, Russia, the United States, Mexico, Spain, the Czech Republic, the Republic of Korea and South Africa. He has been active in International collaboration, and has promoted and had key roles in several programs funded by the European Union, NATO and numerous bilateral agreements.
Paolo Giubellino is also member of the International Advisory Committee of numerous International Conferences, including the International Conference on High-Energy Physics, ICHEP, and all major conferences in High-Energy Nuclear Physics (Quark Matter, Hard Probes, Strange Quark Matter, ICPAQGP). He has served as referee for several major international Physics Journals, among which Physical Review Letters, Physical Review, Nuclear Physics, Physics Letters and Nuclear Instruments and Methods.
Finally he has been referee for the selection and evaluation of projects for, among others, INTAS, Several European Programs, the Italian Ministry of Education and Research, The Russian Ministry of Education, the Government of the Czech Republic, the Ministry of Economy and Innovation of Spain, the National Research Foundation of the Republic of South Korea and the National Research Foundation of South Africa.
Invited lectures and outreach.
Paolo Giubellino is frequently invited to give public lectures on experimental particle physics at the LHC. He has delivered about 50 talks at international conferences and many invited seminars and colloquia about the results of his scientific work, including the closing plenary talk at the 2002 Quark Matter Conference and the plenary talk dedicated to Heavy Ion Physics at the 25th International Nuclear Physics Conference (INPC 2013) in June 2013, and chaired sessions in numerous international conferences. In May 2015, he delivered a talk about the work done at at the first Italian Conference of Physics Students.
Giubellino has played a significant role in developing collaboration between Europe and Latin American institutes. His support led to Mexico’s involvement in ALICE, particularly in the successful construction of the V0 detector and the Cosmic Ray detector. As a recognition of these efforts he has been the first European to be awarded the medal of the Mexican Physical Society.
Giubellino has also taught short courses at various international schools, among which the instrumentation schools of the ICFA and the International school "Enrico Fermi" and for PhD and Master students at Torino University.


Rowan Thomson

Rowan Thomson is a professor in the Department of Physics at Carleton University and Assistant Dean (Equity, Diversity and Inclusion) in the Faculty of Science. She is a Canada Research Chair in Radiotherapy Physics.
Background and Education.
Thomson received a Double BSc degree in Honours Mathematics and Physics from Carleton University. She earned her PhD from Perimeter Institute and the University of Waterloo in 2007 where she studied Superstring Theory.


Canonical divergence


Fred Gilman

Fred Gilman is an American physicist, currently the Buhl Professor at Carnegie Mellon University and formerly the Dean.
Biography.
Gilman received his BS from Michigan State University and his PhD from Princeton University under the supervision of Marvin Leonard Goldberger, and held a postdoctoral position at Caltech. He was a professor at SLAC, deputy director of the Superconducting Super Collider, and Dean of the Mellon College of Science at Carnegie Mellon University.
In 1985, Gilman was elected a Fellow of the American Physical Society "for highly original and timely contributions to the phenomenolgy of elementary particle reactions, especially for his creative interplay with the experimental program at SLAC, including the elucidation of scaling behavior in deeply inelastic scattering".


Ronald E. Mickens

Ronald Elbert Mickens (born February 7, 1943) is an American physicist and mathematician who is the Fuller E. Callaway Professor of Physics at Clark Atlanta University. His research focuses on nonlinear dynamics and mathematical modeling, including applications of these tools to modeling the dynamics of disease. He also has an interest in the history of science and has written on the history of black scientists. He is a fellow of the American Physical Society and served as the historian of the National Society of Black Physicists. He has made significant contributions to the theory of nonlinear oscillations and numerical analysis.
Early life and education.
Ronald Elbert Mickens was born February 7, 1943 in Petersburg, Virginia, to Joseph P. Mickens, a general construction worker, and Daisy Brown Williamson Mickens who was a part-time domestic worker. The eldest of three children, Mickens was raised primarily by his maternal grandparents. It was through discussions with his grandfather, James Williamson, that Mickens was inspired to become a scientist at age six and has credited his grandfather with his early interest in science. Mickens attended Fisk University as an undergraduate and graduated in 1964 with degrees in mathematics and physics. He received his Ph.D. in theoretical physics in 1968 from Vanderbilt University and subsequently worked as a postdoctoral fellow at MIT. His studies at Vanderbilt were supported by fellowships from the Danforth Foundation and the Woodrow Wilson Foundation. Continuing his research efforts, he received a National Science Foundation Postdoctoral Fellowship to investigate elementary particle physics at the Massachusetts Institute of Technology.
Academic career.
Mickens returned to Fisk University as a faculty member in 1970 and later worked at the Joint Institute for Laboratory Astrophysics, from which he was recruited to what was then Atlanta University in 1981. He became a Callaway Professor in 1986. Mickens was elected a Fellow of the American Physical Society in 1999, with the citation "For his sustained service to the physics community and his original contributions on the applications of mathematics to the study of physical systems."
Mickens is African-American and has had an interest in the history of science, and specifically the history of black scientists, throughout his academic career. He has served as the historian of the National Society of Black Physicists and has published histories of black physicists – most notably Edward Bouchet, widely recognized as the first African-American to receive a Ph.D. in the United States – as well as biographies of black women in science. Mickens was also a co-founder of the National Conference of Black Physics Students and he was a member of the founding council of the Edward Bouchet Abdus Salam Institute, an organization founded in 1988 by Nobel laureate in physics Abdus Salam to encourage collaboration between African and American physicists, where he continues to serve as a council member. Mickens' work earned him recognition by Mathematically Gifted & Black as a Black History Month 2017 Honoree.
Mickens' papers are held by the Amistad Research Center at Tulane University.


International Centre for Theoretical Sciences

The International Centre for Theoretical Sciences (ICTS), a centre of the Tata Institute of Fundamental Research, is a research institute based in Bengaluru, India. Founded in 2007, ICTS has grown from a fledgling institution to a global centre of activity in various areas of science. Prof. Spenta R. Wadia was the founding director of the institute and served till 2015, after which he was succeeded by Rajesh Gopakumar as the Director.
Mission.
ICTS is a multi and interdisciplinary venture that brings together various subjects such as mathematics, physics, biology, computer science and earth sciences. It is envisaged as a place where researchers from around the world meet and interact for critical periods of time in a relaxed and collaborative atmosphere. ICTS hopes to attract the best researchers from around the world to organize and participate in programs that stimulate progress in science. It is also involved in high level education and training and in reaching out to the larger society by serving as a node for scientific information and values.
The activities at ICTS fall under the following broad categories
Research.
ICTS aims to have a high quality permanent faculty of modest size together with a large floating population of visitors, postdoctoral fellows and graduate students. The faculty members work in various areas of theoretical sciences. ICTS also has a wide group of Associated Faculty, who are deeply involved in various activities of the Centre.
ICTS has a vigorous Ph.D. students’ program. The students are stationed in Bangalore and their course requirements for a degree from TIFR are partly fulfilled by arrangements with various institutions in Bangalore. A strong post-doctoral program has also been initiated.
The scientific questions that drive the current ICTS faculty research are from the broad areas of "Astrophysical Relativity, Data Assimilation and Dynamical Systems, Condensed matter and Statistical Physics, Physical Biology and String Theory and Interdisciplinary/Exploratory mathematics".
Programs.
ICTS provides a platform along with resources for researchers working on diverse subjects to congregate during high-quality programs of varying durations. Cross-disciplinary immersions are encouraged at ICTS.
Long duration programs have a large educational component. They aim to provide an introduction to current problems in an emerging research area. There is a fair balance of international and national participation. The lecturers are carefully chosen and are often distinguished scientists. The participants are mainly graduate students, postdocs, and young faculty.
Short programs are focused discussion meetings on a recent exciting development in a given field. They are also often organized around a leading lecturer on a theme related to her/his work. These meetings usually include a research-oriented participation and are frequently organized in conjunction with one of the following three lecture series: "Chandrasekhar" (Physical Sciences), "Ramanujan" (Mathematics) and "Turing" (Biology, Computer Science and Engineering).
ICTS also organizes programs in collaboration with other international research institutes. Examples include the `ICTP-ICTS Biology Program’ and the `Asian Winter School in Strings, Particles and Cosmology’.
Anyone holding a faculty position at any research and educational institution can apply for organizing a program at the ICTS. However, until the ICTS campus comes up, its programs must be organized at other places in India. For this reason, at present, it is preferable to have at least one of the organizers from an existing institution in India. A typical proposal for organizing a program is expected to have two or more organizers.
Outreach.
ICTS regularly organizes Public Lectures given by eminent visitors. Another aspect that contributes to ICTS outreach is the freely available proceedings of its activities in various formats on the ICTS website and on YouTube as well as on DVDs and CDs. ICTS is the India node for "Mathematics of Planet Earth", a global initiative for mathematics programs and outreach. As part of this program, ICTS, in collaboration with other scientific institutes in Bangalore, organized a hands-on math exhibition in Bangalore that saw over 32,000 visitors in a span of 10 days.
Campus.
The new ICTS campus is located in north Bangalore and spread over 78,000 square metres. The campus has been designed to provide office space and on-site accommodation for more than 150 academic members, including 75 visitors.
Formerly ICTS functioned out of the TIFR and Raman buildings in the Indian Institute of Science, Bangalore.
Organisation.
ICTS is guided, nurtured and managed by three committees – the International Advisory Board, the Management Board and the Program Committee.


Spatial dispersion

In the physics of continuous media, spatial dispersion is a phenomenon where material parameters such as permittivity or conductivity have dependence on wavevector. Normally, such a dependence is assumed to be absent for simplicity, however spatial dispersion exists to varying degrees in all materials.
Spatial dispersion can be compared to temporal dispersion, the latter often just called dispersion. Temporal dispersion represents memory effects in systems, commonly seen in optics and electronics. Spatial dispersion on the other hand represents spreading effects and is usually significant only at microscopic length scales. Spatial dispersion contributes relatively small perturbations to optics, giving weak effects such as optical activity. Spatial dispersion and temporal dispersion may occur in the same system.
Origin: nonlocal response.
The origin of spatial dispersion is nonlocal response, where response to a force field appears at many locations, and can appear even in locations where the force is zero. This usually arises due to a spreading of effects by the hidden microscopic degrees of freedom.
As an example, consider the current formula_1 that is driven in response to an electric field formula_2, which is varying in space (x) and time (t). Simplified laws such as Ohm's law would say that these are directly proportional to each other, formula_3, but this breaks down if the system has memory (temporal dispersion) or spreading (spatial dispersion). The most general linear response is given by:
where formula_5 is the "nonlocal" conductivity function.
If the system is invariant in time (time translation symmetry) and invariant in space (space translation symmetry), then we can simplify because formula_6 for some convolution kernel formula_7. We can also consider plane wave solutions for formula_8 and formula_9 like so:
which yields a remarkably simple relationship between the two plane waves' complex amplitudes:
where the function formula_13 is given by a Fourier transform of the space-time response function:
The conductivity function formula_13 has spatial dispersion if it is dependent on the wavevector "k". This occurs if the spatial function formula_16 is not pointlike (delta function) response in "x-x' ".
Spatial dispersion in electromagnetism.
In electromagnetism, spatial dispersion plays a role in a few material effects such as optical activity and doppler broadening. Spatial dispersion also plays an important role in the understanding of electromagnetic metamaterials. Most commonly, the spatial dispersion in permittivity "ε" is of interest.
Crystal optics.
Inside crystals there may be a combination of spatial dispersion, temporal dispersion, and anisotropy. The constitutive relation for the polarization vector can be written as:
i.e., the permittivity is a wavevector- and frequency-dependent tensor.
Considering Maxwell's equations, one can find the plane wave normal modes inside such crystals. These occur when the following relationship is satisfied for a nonzero electric field vector formula_18:
Spatial dispersion in formula_20 can lead to strange phenomena, such as the existence of multiple modes at the same frequency and wavevector direction, but with different wavevector magnitudes.
Nearby crystal surfaces and boundaries, it is no longer valid to describe system response in terms of wavevectors. For a full description it is necessary to return to a full nonlocal response function (without translational symmetry), however the end effect can sometimes be described by "additional boundary conditions" (ABC's).
In isotropic media.
In materials that have no relevant crystalline structure, spatial dispersion can be important.
Although symmetry demands that the permittivity is isotropic for zero wavevector, this restriction does not apply for nonzero wavevector. The non-isotropic permittivity for nonzero wavevector leads to effects such as optical activity in solutions of chiral molecules. In isotropic materials without optical activity, the permittivity tensor can be broken down to transverse and longitudinal components, referring to the response to electric fields either perpendicular or parallel to the wavevector.
For frequencies nearby an absorption line (e.g., an exciton), spatial dispersion can play an important role.
Landau damping.
In plasma physics, a wave can be collisionlessly damped by particles in the plasma whose velocity matches the wave's phase velocity. This is typically represented as a spatially dispersive loss in the plasma's permittivity.
Permittivity–permeability ambiguity at nonzero frequency.
At nonzero frequencies, it is possible to represent all magnetizations as time-varying polarizations. Moreover, since the electric and magnetic fields are directly related by formula_21, the magnetization induced by a magnetic field can be represented instead as a polarization induced by the electric field, though with a highly dispersive relationship.
What this means is that at nonzero frequency, any contribution to permeability "μ" can instead be alternatively represented by a spatially dispersive contribution to permittivity "ε". The values of the permeability and permittivity are different in this alternative representation, however this leads to no observable differences in real quantities such as electric field, magnetic flux density, magnetic moments, and current.
As a result, it is most common at optical frequencies to set "μ" to the vacuum permeability "μ"0 and only consider a dispersive permittivity "ε". There is some discussion over whether this is appropriate in metamaterials where effective medium approximations for "μ" are used, and debate over the reality of "negative permeability" seen in negative index metamaterials.
Spatial dispersion in acoustics.
In acoustics, especially in solids, spatial dispersion can be significant for wavelengths comparable to the lattice spacing, which typically occurs at very high frequencies (gigahertz and above).
In solids, the difference in propagation for transverse acoustic modes and longitudinal acoustic modes of sound is due to a spatial dispersion in the elasticity tensor which relates stress and strain. For polar vibrations (optical phonons), the distinction between longitudinal and transverse modes can be seen as a spatial dispersion in the restoring forces, from the "hidden" non-mechanical degree of freedom that is the electromagnetic field.
Many electromagnetic wave effects from spatial dispersion find an analogue in acoustic waves. For example, there is acoustical activity — the rotation of the polarization plane of transverse sound waves — in chiral materials, analogous to optical activity.


Ivan Bardin

Ivan Pavlovich Bardin (Russian: Иван Павлович Бардин) (1883–1960) was a Soviet metallurgist and active participant in solving the main engineering issues of the domestic ferrous metallurgical industry. He was also an Academician of USSR AS (1932), vice-president of USSR AS (from 1942), Hero of Socialist Labor (1945), and winner of the Lenin (1958) and State prizes (1942, 1949). His scientific interests were designing new powerful completely mechanized steel works; creating advanced typical metallurgical aggregates; intensifying metallurgical processes, especially by means of oxygen; elaborating and introducing the basic oxygen process; and assimilation and multi-purpose utilization of new kinds of metallurgical raw materials.
Career.
He was chair of economics and management (1943–1959) of the Moscow Institute of Steel and Alloys (Moscow, Russia)(MISIS).
Since 1910 after graduation from the Kiev Polytechnic Institute he worked at the steel works of the Russia South (Yuzovka, Yenakiyevo) and in the US. In 1929—1936 I. P. Bardin was one of the construction managers of the Kuznetsk integrated iron-and-steel works (Novokuznetsk Iron and Steel Plant). Since 1937 he held leading positions in ferrous metallurgy (engineer in chief of the central directorate, chairman of the Technical Council of the People's Commissariat, deputy People's Commissar (minister) for ferrous metallurgy.
From 1939 he was director of the Institute of Metallurgy of the USSR AS and since 1944 director of the Central research institute of ferrous metallurgy that has borne his name since 1960. Since 1942 he was made vice-president of USSR AS and from 1937 a Delegate of the USSR Supreme Soviet of the 1st-5th convocations.
Awards.
USSR State prizes:
Lenin prize:


Cockcroft Institute

The Cockcroft Institute is an international centre for Accelerator Science and Technology (AST) in the UK. It was proposed in September 2003 and officially opened in September 2006. It is a joint venture of Lancaster University, the University of Liverpool, the University of Manchester, the Science and Technology Facilities Council, and the Northwest Regional Development Agency. The Institute is located in a purpose-built building on the Sci-Tech Daresbury campus, and in centres in each of the participating universities.
The Institute's aim is to provide the intellectual focus, educational infrastructure, and the essential scientific and technological facilities for Accelerator Science and Technology research and development, which will enable UK scientists and engineers to take a major role in accelerator design, construction, and operation for the foreseeable future. The Institute is named after the Nobel prizewinner Sir John Cockcroft FRS.
The present director of the Cockcroft Institute is Peter Ratoff, who replaced the previous directors Swapan Chattopadhyay and John Dainton.


Fritz Reiche

Fritz Reiche (July 4, 1883 – January 14, 1969) was a German physicist, a student of Max Planck and a colleague of Albert Einstein, who was active in, and made important contributions to the early development of quantum mechanics including co-authoring the Thomas-Reiche-Kuhn sum rule.
Fritz Reiche was born in 1883 in Berlin, Germany. In 1901 and 1902, he attended the University of Munich and he attended the University of Berlin from 1902 to 1907, where he received his PhD. From 1913 to 1920 as privatdozent he worked and taught under Planck in Berlin. Reiche published more than 55 scientific papers and books including "The Quantum Theory".
He became a professor in 1921 at the University of Breslau and then was dismissed as a Jew from his academic position in 1933. Eventually, with the help of Ladenburg, Einstein, and the Emergency Committee in Aid of Displaced Foreign Scholars, Reiche emigrated with his family to the United States in 1941 and went on to work with NASA and the United States Navy on projects related to supersonic flow.


Arnold William Reinold

Arnold William Reinold (19 June 1843 – 11 April 1921) was an English physicist.
Born in Hull, the son of shipbroker John Henry Arnold Reinold, he received his early education at the St Peter's School, York. In 1863 he matriculated to Brasenose College, Oxford where he studied mathematics. He became a fellow of Merton College, Oxford in December, 1866; a position which he resigned in 1869 upon marrying Marian Owen—the couple would have one daughter and three sons. In 1869 he was appointed the first "Lee's Reader in Physics" at Christ Church, and was awarded an M.A. in 1870.
In 1871 he was named Examiner in Physics at Oxford. When the Royal Naval College, Greenwich was established in 1873, he was appointed Professor of Physics there; a post he would hold for the next 35 years. During most of his period at Greenwich he was a lecturer at Guy's Hospital. Between 1877–93, he collaborated with English physicist Arthur William Rucker on series of papers about the properties of thin films. He was named a fellow of the Royal Society in 1883. During 1874–88 he was honorable secretary for the Physical Society of London, whereupon he was elected as president of the body.


J. Thomas Dickinson

J. Thomas Dickinson is an American physicist and astronomer.
H earned a B.A. degree in physics from Western Michigan University in 1963, and a PhD degree in chemical physics from the University of Michigan in 1968. He went directly to Washington State University and was appointed Paul A. Anderson Professor and Regents Professor, positions he held until his retirement in 2017. His field research involved laser-materials relations, nanotribology and tribochemistry.
He is a Fellow of the American Association for the Advancement of Science, American Vacuum Society and American Physical Society.
Education.
He graduated from Western Reserve University with a B.A. in Physics in 1963 and followed with a PhD in chemical physics from University of Michigan in 1968.


John Dowell

John Derek Dowell FRS (born 6 January 1935) is a British physicist, emeritus professor at University of Birmingham.
Born in Leicestershire, he was educated at Coalville Grammar School and the University of Birmingham (BSc, PhD).
He worked as a Research fellow at Birmingham University (1958-1960) before moving to be a Research associate at the European Organization for Nuclear Research near Geneva (1960-1962}. He then returned to Birmingham as lecturer (1962-1970), senior lecturer (1970-1974) and reader (1974-1980). In 1980 he was appointed Professor of Elementary Particle Physics and finally retired as professor emeritus in 2002.
He published results from CERN’s SPS accelerator which included the first observation in Europe of the J/psi particle, which consists of charmed quarks, supporting the theory that matter is composed of quarks. After research at the Hadron-Electron Ring Accelerator (HERA) at DESY in Hamburg, he helped develop detectors for the Large Hadron Collider (LHC) at Geneva and was involved in the ATLAS experiment which discovered the Higgs boson. He won the 1988 Rutherford Medal and Prize.
He was elected a Fellow of the Royal Society in 1986 and a Fellow of the American Physical Society in 2003
In July 2002, a symposium was held in his honour, as he retired in September of that year.


Harold A. Wilson (physicist)

Dr Harold Albert Wilson FRS FRSE (1 December 1874 – 1964) was an English physicist.
Early life.
Wilson was born in York, the son of Albert William Wilson, a goods manager with the North British Railway.5|url=https://www.royalsoced.org.uk/cms/files/fellows/biographical_index/fells_indexp2.pdf}}</ref> His mother, Anne Gill, was the daughter of a farmer and innkeeper from Topcliffe.
Wilson was educated at St Olave's Grammar School. He then studied science at Victoria University College in Leeds and then at University College, London, graduating BSc in 1896. He then went to Cambridge University and gained a BA and DSc.
Career.
In 1896 he became a colleague of English physicist J. J. Thomson at Cambridge University, and performed one of the earliest measurements of the electron's charge. He was awarded his Doctor of Science degree from London in 1900, and was elected Fellow of Trinity College, Cambridge in October 1901. From 1901 to 1904, he held a James Clerk Maxwell fellowship at the Cavendish Laboratory. He became a lecturer in Physics at King's College London, then professor at the college in 1905. In 1906 he was elected a Fellow of the Royal Society of London (FRS).
In 1909 he accepted a role as professor of Physics at McGill University in Montreal in Canada, staying there three years.
He joined the Rice Institute located in Houston, Texas in 1912, becoming the first chair of the physics department. He was one of the original 12 founding professors.
He returned to Britain in 1924, spending a year at the University of Glasgow. In 1925 he was elected a Fellow of the Royal Society of Edinburgh. His proposers were Charles Glover Barkla, Frederick Orpen Bower, John Walter Gregory and Sir John Graham Kerr.
In 1925 he returned to Rice University in Houston (also working as a consultant to an oil company) and continued there until retiral in 1947.
He died in a hospital in Houston on 13 October 1964.
Family.
In 1912 he married Marjorie Patterson Smyth.
Harold had one sister, Lilian, who would marry Sir Owen W. Richardson.
Recognition.
The Wilson Award at Rice University is named after him.


Robert Roland Hughes

Robert Roland Hughes MB ChB MD FRCP (1911 – 18 March 1991) was a British neurologist and pioneer of Electroencephalography and neurology. He studied medicine at Liverpool University and spent the bulk of his life as a consultant in the Liverpool and North Wales area, particularly in the Liverpool Royal Infirmary and the Royal Southern Hospital.
Career.
Hughes began his career as an apprentice printer in his father's business, and entered medicine somewhat later than was usual. He served in the Royal Army Medical Corps during World War II, rising to the rank of Major, during which time he was instrumental in setting up the Allied field hospital at D-Day.
He took up a post in under Lord Cohen at the Royal Southern Hospital after being demobilised. He also worked at Walton Neurological Unit, Clatterbridge, HM Stanley and Boddelwyddan. Dr Hughes wrote the landmark book "An introduction to clinical electro-encephalography" (1961) which is used as a textbook and authority on the subject. As his reputation became established, he did a substantial amount of work as a private medico-legal consultant.
Dr Hughes' son, Dr Simon H C Hughes, is a medical physicist whose work on CT and MRI scanners helped reduce their cost, making such equipment more available and widespread.


William George Harter

William George Harter (born July 18, 1943) is an American physicist at the University of Arkansas.
Harter was born in Lancaster, Pennsylvania and studied at Hiram College (AB, 1964) and the University of California, Irvine (Ph.D, 1967).
He was appointed assistant professor of physics at the University of Southern California, Los Angeles, (1969-1973) and associate professor at the University of Campinas, Sao Paulo, Brazil (1974-1977). He was visiting fellow at the Joint Institute for Laboratory Astrophysics at the University of Colorado, Boulder in 1977-1978 and professor at the Georgia Institute of Technology, Atlanta from 1979 to 1984, and the University of Arkansas, Fayetteville since 1985. He has also been visiting fellow at the Harvard–Smithsonian Center for Astrophysics, Cambridge, Massachusetts from 1993.
He was awarded the status of Fellow in the American Physical Society, after they were nominated by their Division of Atomic, Molecular & Optical Physics in 1994, for "the development of novel and semiclassical and graphical theories which contributed to better understanding, analysis and prediction of complex electronic spectra of atoms and molecules, and high resolution rotation-vibration of symmetric polyatomic molecules."


U-70 (synchrotron)

U-70 () is a proton synchrotron with a final energy of 70 GeV, built in 1967 at the Institute for High Energy Physics in Protvino (near Serpukhov, Russia). The accelerator held the world record in beam energy at the time of its construction, and it still is the highest energy accelerator in Russia. In 1970, the U-70 scientists team was awarded the Lenin Prize for the development and commissioning of the synchrotron.
Description of the accelerator complex.
The complex operates in pulsed mode. Protons are accelerated to 30 MeV by linear accelerator URAL-30. Then they are injected into the fast-cyclic booster synchrotron U-1.5 having 100-m perimeter, where protons are accelerated to 1.32 GeV. Then the protons are injected to the U-70. After this, an acceleration cycle takes place for 9 seconds, when protons are accelerated to the maximum energy of 76 GeV, and then, they are extracted from the ring to the secondary beams in the experimental halls. U-70 has perimeter about 1.5 km. Focusing structure type is FODO (strong focusing). The total weight of the magnetic system of over 20 000 t.
The prior injection of U-70 was a 100 MeV linear accelerator I-100 (until 1985).
A project for the UNK accelerator-storage complex, a proton-proton collider with an energy of 3 × 3 TeV, started in the mid 1980s. It was planned that U-70 becomes an injector for the collider ring, but the project was stopped because of the dissolution of the Soviet Union.
Accident.
In 1978, Anatoli Bugorski stuck his head into the synchrotron to check a piece of malfunctioning equipment, when the safety mechanism failed and he got hit in the head with a proton beam. He reportedly saw "a flash brighter than a thousand suns", although no pain was reported. Though he ultimately survived he did receive lifelong injuries to the left side of his face and experienced irregular bouts of epileptic seizures.


Optical path

The path that a light ray follows as it passes through an optical medium or system is often called the optical path. The physical length of an optical device can be reduced to less than the length of the optical path by using folded optics. The optical path length as defined in optics is the length of the path multiplied by the refractive index of the medium.
Factors affecting optical path.
Path of light in medium, or between two media is affected by the following:
Simple materials used.
‘change in optical length is equal to wavelength of light passed’


Kurdyumov Institute of Metal Physics

The G. V. Kurdyumov Institute for Metal Physics (IMP) of the National Academy of Sciences of Ukraine () is one of the oldest research institutions of physical science within the Academy.
The research institute was established in 1945 as a laboratory of the Black Metallurgy (Ferrous Metallurgy) Institute. In 1955 it was turned into a separate research institute.
Currently, the Institute employs more than 250 researchers (together with several Full Members and Corresponding Members of the NASU) and around 150 peoples of supporting personnel. It has more than 20 scientific units (including the state-of-the-art hardware) which are grouped around several research programs.
Traditionally, the Institute is focused on fundamental research. At the same time, applied research on metals, their alloys, and related nanotechnologies strengthen the Institute's activities.
The IMP is consistently ranked at the top of national academic institutions ranking. Besides, international reputation of IOP is growing constantly as prominent scientists from the Institute expand their activity to leading foreign research centers and universities.


G. V. Skrotskii

George V. Skrotskii (January 11, 1915 – July 13, 1992) was a Russian physicist.
Skrotskii realized that electromagnetic field equations in a curved spacetime can be written in a non-covariant form formally equivalent to Maxwell's equations in a macroscopic medium in flat spacetime.