5 Most Important Breakthroughs That My Field of Research Needs -- Nathan Seiberg

Nathan Seiberg [photo courtesy: Institute for Advanced Study, Princeton]

[Our guest today in the feature ‘5-Breakthroughs’ is Nathan Seiberg, Professor at the Institute for Advanced Study in Princeton, NJ. Prof. Seiberg’s work has spanned a wide spectrum of research revolving around particle physics phenomenology, field theory, gauge theory, Matrix theory, string theory, and supersymmetry.

In early 1990s, he formulated the application of holomorphy to calculations in gauge theories with supersymmetry. In his famous 1994 article “Electric-Magnetic Duality in Supersymmetric Non-Abelian Gauge Theories” (Abstract link) he conjectured a new kind of Strong-Weak duality or S-duality relating two different supersymmetric QCDs which are not identical, but agree at low energies. This is now well-known as Seiberg duality.

Working with Edward Witten, he also devised a series of partial differential equations that simplified the classification of 4-dimensional manifolds. The invariants of such compact smooth 4-manifolds are now known as Seiberg–Witten invariants. Later, they analyzed the appearance of non-commutative geometry in theories containing open strings, and identified a low energy limit of open string dynamics as a noncommutative quantum field theory.

Prof. Seiberg also made pioneering contribution in Matrix Theory, M Theory and various subfields of particle physics. Here is link to his list of publications: Google Scholar.

He received his Ph.D from the Weizmann Institute of Science in Israel in 1982. Before joining the Institute for Advanced Study, he had been a Professor of Physics at the Weizmann Institute for Science and at Rutgers University.

Prof. Seiberg is a member of National Academy of Sciences and Fellow of American Academy of Arts and Sciences. He received The John D. and Catherine T. MacArthur Fellowship (Genius Grant) in 1996. In 1998, American Physical Society awarded Dannie Heineman Prize for Mathematical Physics to Nathan Seiberg and Ed Witten "for their decisive advances in elucidating the dynamics of strongly coupled supersymmetric field and string theories. The deep physical and mathematical consequences of the electric-magnetic duality they exploited have broadened the scope of Mathematical Physics (quote from the citation)."

It’s an honor and privilege on our part to present 5 most important breakthroughs that Prof. Seiberg would like to see in his fields of research.
— 2Physics.com ]

1. Origin of electroweak symmetry breaking. This will shed light on the origin of mass of elementary particles. An effective description of this phenomenon in terms of the Higgs mechanism is known. The Large Hadron Collider (LHC) will explore it in detail and perhaps will point to a deeper structure. One possibility is that the LHC will discover supersymmetry – a new kind of symmetry which extends our understanding of space and time. Alternatively, it will find new particles which might have a description in terms of new space dimensions. If only the Higgs particle is discovered, its mass might be set anthropically. Is this true?

2. Origin of the elementary particles. What determines the properties of the quarks and the leptons (their quantum numbers)? Why do they appear in 3 generations? Most of the parameters of the Standard Model of particle physics are associated with the quark and lepton masses. It is possible that the underlying structure which controls them exists at very high energies which will not be explored soon. One possible explanation of the properties of the quarks, the leptons, and their interactions is the idea of grand unification. Is this idea correct?

3. Dark matter and dark energy of the Universe. Is the dark matter weakly interacting massive particles? This question could be settled soon either by detecting these particles, or the product of their interactions, or by creating them at the LHC. Is the dark energy a cosmological constant? What sets the value of the cosmological constant today? Is it anthropic?

4. Inflation. It seems that in the past the Universe had a period of rapid expansion known as inflation, during which the cosmological constant was large. What is the detailed description of this phenomenon? The study of inflation naturally leads to the idea of a multiverse – the Universe is a lot larger than what we observe and different parts of the Universe have different physics. How should we think about physics in such a setup? What are the correct observables? What is the precise role of anthropic ideas in this context?

5. Theory of quantum gravity. The correct theory of quantum gravity appears to be string theory. At the moment we do not have a clear conceptual formulation of the theory, nor do we have clear experimentally verifiable predictions of string theory. Can we solve these problems? Presumably, a deeper understanding of string theory will show that space and time are emergent concepts which are not present in the fundamental formulation of the theory. This could have important implications for the mysteries of the Big Bang.

Accurate Measurement of Huge Pressures that Melt Diamond provides crucial data for Planetary Astrophysics and Nuclear Fusion

Marcus Knudson examines the focal point of his team's effort to characterize materials at extremely high pressures. The fortress-like box sitting atop its support will hold within it a so-called "flyer plate" that -- at speeds far faster than a rifle bullet -- will smash into multiple targets inserted in the two circular holes. An extensive network of tiny sensors and computers will reveal information on shock wave transmission, mass movement, plate velocity, and other factors. [Photo by: Randy Montoya]

In a recent paper in the journal 'Science' [1], researchers from Sandia National Laboratories (a multiprogram laboratory operated by Sandia Corporation for the U.S. Department of Energy’s National Nuclear Security Administration) reported ten times more accurate measurement of the enormous pressures needed to melt diamond to slush and then to a completely liquid state.

Researchers Marcus Knudson, Mike Desjarlais, and Daniel Dolan discovered a triple point at which solid diamond, liquid carbon, and a long-theorized but never-before-confirmed state of solid carbon called bc8 were found to exist together.

The high–energy density behavior of carbon has received much attention in recent times mainly due to its relevance to planetary astrophysics. The outer planets, Neptune and Uranus, are thought to contain large quantities of carbon (as much as 10-15% of the total planetary mass). In Neptune, for example, much of the atmosphere is composed of methane (CH4). Under high pressure, methane decomposes, liberating its carbon. One question for astrophysicists in theorizing the planet’s characteristics is knowing the form that carbon takes in the planet’s interior. At what precise pressure does simple carbon form diamond? Is the pressure eventually great enough to liquefy the diamond, or form bc8, a solid that has yet other characteristics?

“Liquid carbon is electrically conductive at these pressures, which means it affects the generation of magnetic fields,” says Desjarlais. “So, accurate knowledge of phases of carbon in planetary interiors makes a difference in computer models of the planet’s characteristics. Thus, better equations of state can help explain planetary magnetic fields that seem otherwise to have no reason to exist.”

Accurate knowledge of these changes of state are also essential to the effort to produce nuclear fusion at Lawrence Livermore National Laboratory’s National Ignition Facility (NIF) in California. In 2010, at NIF, 192 laser beams are expected to focus on isotopes of hydrogen contained in a little spherical shell that may be made of diamond. The idea is to bring enough heat and pressure to bear to evenly squeeze the shell, which serves as a containment capsule. The contraction is expected to fuse the nuclei of deuterium and tritium within.

The success of this reaction would give more information about the effects of a hydrogen bomb explosion, making it less likely the U.S. would need to resume nuclear weapons tests. It could also be a step in learning how to produce a contained fusion reaction that could produce electrical energy for humanity from seawater, the most abundant material on Earth.

For the reaction to work, the spherical capsule must compress evenly. But at the enormous pressures needed, will the diamond turn to slush, liquid, or even to the solid bc8? A mixture of solid and liquid would create uneven pressures on the isotopes, thwarting the fusion reaction, which to be effective must offer deuterium and tritium nuclei no room to escape.

That problem can be avoided if researchers know at what pressure point diamond turns completely liquid. One laser blast could bring the diamond to the edge of its ability to remain solid, and a second could pressure the diamond wall enough that it would immediately become all liquid, avoiding the slushy solid-liquid state. Or a more powerful laser blast could cause the solid diamond to jump past the messy triple point, and past the liquid and solid bc8 mixture, to enter a totally liquid state. This would keep coherent the pressure on the nuclei being forced to fuse within.

The mixed phase regions, says Dolan, are good ones to avoid for fusion researchers. The Sandia work provides essentially a roadmap showing where those ruts in the fusion road lie.

Sandia researchers achieved these results by dovetailing theoretical simulations with laboratory work. Simulation work led by Desjarlais used theory to establish the range of velocities at which projectiles, called flyer plates, should be sent to create the pressures needed to explore these high pressure phases of carbon and how the triple point would reveal itself in the shock velocities. The theory, called density functional theory, is a powerful method for solving Schrödinger’s equation for hundreds to thousands of atoms using today’s large computers.

[Image courtesy: Sandia National Laboratories] The solid and dotted lines in both graphs represent the same equation-of-state predictions for carbon by Sandia theorists. Jogs in the lines occur when the material changes state. Graph A's consistent red-diamond path, hugging the predicted graph lines, are Z's laboratory results. They confirm the theoretical predictions. The scattered data points of graph B represent lab results from various laser sites external to Sandia.

Using these results as guides, experimental results from fifteen flyer-plate flights — themselves powered by the extreme magnetic fields of Sandia’s Z machine — in work led by Knudson, then determined more exact change-of-state transition pressures than ever before determined. Even better, these pressures fell within the bounds set by theory, thus showing that the theory was accurate.

“These experiments are much more accurate than ones previously performed with laser beams [2,3],” says Knudson. “Our flyer plates, with precisely measured velocities, strike several large diamond samples, which enables very accurate shock wave velocity measurements.” Laser beam results, he says, are less accurate because they shock only very small quantities of material, and must rely on an extra step to infer the shock pressure and density.

Sandia’s magnetically driven plates measure about 4 cm by 1.7 cm cross section, are hundreds of microns thick, and impact three samples on each firing. Z-machine’s target diamonds are each about 1.9 carats, while laser experiments use about 1/100 of a carat.

“No, they’re not gemstones,” says Desjarlais about the Sandia targets. The diamonds in fact are created through industrial processes and have no commercial value, says Dolan, though their scientific value has been large!

Reference
[1] "Shock-Wave Exploration of the High-Pressure Phases of Carbon"
M. D. Knudson, M. P. Desjarlais, D. H. Dolan, Science, 322, 1822 - 1825 (2008). Abstract.
[2] "Hugoniot measurement of diamond under laser shock compression up to 2 TPa"
H. Nagao, K. G. Nakamura, K. Kondo, N. Ozaki, K. Takamatsu, T. Ono, T. Shiota, D. Ichinose, K. A. Tanaka, K. Wakabayashi, K. Okada, M. Yoshida, M. Nakai, K. Nagai, K. Shigemori, T. Sakaiya, K. Otani, Physics of Plasmas, 13, 052705 (2006). Abstract.
[3] "Laser-shock compression of diamond and evidence of a negative-slope melting curve"
Stéphanie Brygoo, Emeric Henry, Paul Loubeyre, Jon Eggert, Michel Koenig, Bérénice Loupias, Alessandra Benuzzi-Mounaix & Marc Rabec Le Gloahec, Nature Materials 6, 274 - 277 (2007), Abstract.

[We thank Media Relations, Sandia National Laboratories for materials used in this report]

Quantum Data Buffering

Alberto Marino

In a paper published in Feb. 12 issue of the journal Nature [1], a team of researchers at the Joint Quantum Institute (JQI) of the University of Maryland and National Institute of Standards and Technology (NIST) demonstrated the development of a "quantum buffer," a technique that could be used to control the data flow inside a quantum computer.

This new work follows up on the researchers' landmark creation in 2008 [2] of pairs of multi-pixel quantum images (past posting in 2Physics). A pair of quantum images is "entangled" which means that their properties are linked in such a way that they exist as a unit rather than individually. In this work, each quantum image is carried by a light beam and consists of up to 100 "pixels." A pixel in one quantum image displays random and unpredictable changes say, in intensity, yet the corresponding pixel in the other image exhibits identical intensity fluctuations at the same time, and these fluctuations are independent from fluctuations in other pixels. This entanglement can persist even if the two images are physically disconnected from one another.

[Image credit: A. Marino, JQI] Closeup of two "quantum images" created with the help of a "pump" laser beam. The two images are "entangled," so that if there is a change in the intensity in one region ("pixel") of the image, there would be an identical change in the intensity in the corresponding pixel in the second image. In this experiment, one of the images is delayed on its arrival to a detector, so that the correlations between the two images can be out of sync by up to 27 nanoseconds, something that is potentially useful for managing data to a future "quantum computer."

"If you want to set up some sort of communications system or a quantum information-processing system, you need to control the arrival time of one data stream relative to other data streams coming in," says JQI's Alberto Marino, lead author of the paper. "We can accomplish the delay in a compact setup, and we can rapidly change the delay if we want, something that would not be possible with usual laboratory apparatus such as beamsplitters and mirrors," he says.

By using a gas cell to slow down one of the light beams to 500 times slower than the speed of light, the group has demonstrated that they could delay the arrival time of one of the entangled images at a detector by up to 27 nanoseconds. The correlations between the two entangled images still occur—but they are out of sync. A flicker in the first image would have a corresponding flicker in the slowed-down image up to 27 nanoseconds later.

While such "delayed entanglement" has been demonstrated before, it has never been accomplished in information-rich quantum images. Up to now, the "spooky action at a distance" has usually been delayed in single-photon systems.

"What gives our system the potential to store lots of data is the combination of having multiple-pixel images and the possibility of each pixel containing 'continuous' values for properties such as the intensity," says co-author Raphael Pooser.

To generate the entanglement, the researchers use a technique known as four-wave mixing, in which incoming light waves are mixed with a "pump" laser beam in a rubidium gas cell to generate a pair of entangled light beams. In their experiment, the researchers then send one of the entangled light beams through a second cell of rubidium gas where a similar four-wave mixing process is used to slow down the beam. The beam is slowed down as a result of the light being absorbed and re-emitted repeatedly in the gas. The amount of delay caused by the gas cell can be controlled by changing the temperature of the cell (by modifying the density of the gas atoms) and also by changing the intensity of the pump beam for the second cell.

[Image credit: A. Marino, JQI] In this simplified representation of the experimental setup for a ‘quantum buffer,’ a cell containing rubidium gas is used to produce a pair of information-rich entangled images. One of the images goes through a second rubidium gas cell and slows down, which is potentially useful for feeding data at properly timed intervals to future quantum computers. The delay can be controlled such that, during the time it takes one image to travel a centimeter, the other image can travel up to 8 meters. The twisted loops illustrate the entanglement between the images.

This demonstration shows that this type of quantum buffer could be particularly useful for quantum computers, both in its information capacity and its potential to deliver data at precisely defined times. Quantum computers could potentially speed up or expand present capabilities in decrypting data, searching large databases, and other tasks.

References
[1] "Tunable Delay of Einstein-Podolsky-Rosen Entanglement"
A.M. Marino, R.C. Pooser, V. Boyer, and P.D. Lett, Nature, 457, 859-862 (2009), Abstract.
[2] "Entangled Images from Four-Wave Mixing"
V. Boyer, A. Marino, R. Pooser, and P. Lett, Science, 321, 544 - 547 (2008), Abstract.

[We thank NIST for materials used in this article, and Institut de Ciències Fotòniques, Barcelona for Alberto Marino's photo]

Upcoming Physics Conferences

[To add an upcoming physics conference to this list, please send an email to 2Physics@gmail.com ]

Feb 09-11: Dark Matter (Florence, Italy)
Mar 25-27: Intl Symposium on Quantum Interaction (Saarbruecken, Germany)
Mar 25-30: ISF Research Workshop on Random Matrices and Integrability: From Theory to Applications (Yad Hashmona, Judean Hills, Israel)
Apr 08-09: Quantum Physics and Logic (Oxford, UK)
Apr 12-19: International Conference: String Field Theory and Related Aspects (Moscow, Russia)
Apr 20-23: The Sun, The Stars, The Universe and General Relativity -- Intl conference in honor of Ya. B. Zeldovich 95th Anniversary (Minsk, Belarus)
Apr 27-May 01: Relativity in Astrometry (Virginia Beach, VA, USA)
May 03-17: PhD School on Quantum Information and Many-Body Systems (Cortona, Italy)
May 11-13: Workshop on Theory of Quantum Computation, Communication, and Cryptography (Waterloo, Canada)
May 11-13: Phenomenology 2009 Symposium: LHC Turn On (Madison, WI, USA)
May 11-15: Gravity: Where do we stand? (Como, Italy)
May 19-21: Relativistic Astrophysics (Atlanta, USA)
May 25-29: From the Planck Scale to the Electroweak Scale (Padova, Italy)
May 31-Jun 05: Cosmological Magnetic Fields (Ascona, Switzerland)
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Jun 18-19 Mathematical Relativity (Lisbon, Portugal)
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Aug 17-23: Astrophysics and Cosmology after Gamow: Recent progress and new horizons: 4-th Gamow International Conference and 9-th Gamow Summer School "Astronomy and beyond: Astrophysics, Cosmology, Radioastronomy, High Energy Physics and Astrobiology" (Odessa, Ukraine)
Aug 18-28: International Summer School on Astroparticle Physics (Nijmegen, Netherlands)
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Aug 30-Sep 03: Joint International Hadron Structure Conference (Tatranska Strba, Slovak Republic)
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Oct 08-09: Space, Time and Beyond (Golm, Germany)
Oct 11-14: 50 years of the Aharonov-Bohm Effect: Concepts and Applications (Tel Aviv, Israel)
Oct 26-30: Galileo - Xu Guangqi Meeting on the Sun, the Stars, the Universe and General Relativity (Shanghai, China)
Nov 29-Dec 04: Intl Conference on Hadron Spectroscopy (Tallahassee, FL, USA)
Nov 30-Dec 03: International Symposium on Computational Mechanics (Hong Kong and Macau, China)