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Dedication of the Umbilic Torus  
The dedication ceremony of the Umbilic Torus, by Heleman Ferguson, has been held on October 26. Professor Tony Phillips (Department of Mathematics) introduced the speakers, including President Stanley, Marilyn and Jim Simons, and Heleman and Claire Ferguson. A reception and a lecure by the Ferguson's followed in the Simons Center.

The project was supported by the Simons Foundation. The statue was built in Baltimore over the last two years by a team led by the artist. The construction involved, among other things, the creation of a robot that shaped the sandstone forms for the casting of the silicon bronze structure. Photos about the installation and the dedication ceremony are here, username: public, password: photos.

Of all the twisty shapes that one can imagine, this one is special, because it relates to the solutions of the cubic equation, x3+bx2+cx+d=0. Here is a physicists interpretation of the math behind the satutue. (Thanks to John Morgan, who gave an excellent lecture about the subject. Apologies for the oversimplifications and missing some of the beautiful math. --LM)

If we pick the parameters b, c and d randomly, and we solve the eqaution, chances are that we have either one solution or three solutions (assuming we look at real numbers only). For example x3 - 3x2 + x - 3 = 0 has only one solution, x=3. On the other hand, x3 - 6x2 + 11x - 6 = 0 has three solutions: x=1, x=2 and x=3.

We can imagine that the the parameters b, c and d are the axes of a Cartesian coordinate system. In this three-dimensional space every point has well defined b, c and d, and therefore every point corresponds to a cubic equation. We solve the equation, but we do not care about the actual values of x. All we care about is the number of solutions: either one or three, as we have seen above. Now we color each point in the space of b, c and d according to the number of the solutions. For example, we give "blue" color to the points where there are three solutions, and we color "red" the points that yield one solution.

The Umbilical Torus is related to (topologically equivalent to) the surface that separates the blue and the red regions in the three dimensional space of b, c and d. The surface of the Torus itself correspond to the parameters when two of the three solutions happen to be equal. The "rim" or "edge" that runs around and performs a 120o twist (coming back to itself after three full rotations) correspond to the special case when all three solutions are equal (for example, in x3 - 6x2 + 12x - 8 = 0).

The animated gif images on the right hand side were created with the free softwares K3DSurf and Cropper. Here are links to the parametric equations describing the forms: umbilic1.k3ds, umbilic2.k3ds and umbilic3.k3ds


Umbilical torus generated by the free software K3DSurf. Click on the image to see a larger version.


Other variations of the twisted form that do not have the deeper interpretation of the Umbilical Torus.
2012-10-26
Building new ferroelectrics layer by layer  
Ferroelectric materials possess extremely useful functional properties, such as a switchable electronic polarization, and high dielectric constants and piezoresponse. Matt Dawber's group , supported by the Ceramics program of the National Science Foundation through a CAREER award, is leading a research program to develop new and improved ferroelectric materials by depositing different perovskite oxide materials in extremely fine layers, one on top of another.

In a recent paper (Phys. Rev. Lett. 109, 067601 (2012)) they describe results on combining a ferroelectric material, lead titanate, and a material that is normally metallic, strontium ruthenate. As the strontium ruthenate layers are very thin, the conductivity in the new artificial material is very low in the direction of the ferroelectric polarization. The new material thus behaves like a ferroelectric, but one that has a strong preference for one polarization direction over another. This effect is driven by a breaking of symmetry across the interfaces of the material. In addition to the polarization effect, the symmetry breaking also has the potential to allow coupling between ferroelectricity and magnetism. Compounds with this property are called "multiferroic" materials. An essential part of this work was a strong collaboration with the theory group of Marivi Fernandez-Serra , also in the Dept of Physics and Astronomy at Stony Brook.

Even more recently another publication from the group (Phys. Rev. Lett. 109, 167601 (2012)) showcased a different material system with quite different properties. Although the ferroelectric component in this system was again lead titanate, the other material was calcium titanate, chosen because it was hoped that it would induce polarization rotation and an associated enhancement of the piezoresponse and dielectric constant. By a detailed experimental study, this was shown to be the case, and a new pathway to piezoelectric materials has been opened by this work.

Both projects made extensive use of user facilities at nearby Brookhaven National Laboratory, particularly the National Synchrotron Light Source, which was used to identify structural changes in the materials by x-ray diffraction, and the Center for Functional Nanomaterials, where Dong Su performed electron microscopy which was critical to the success of both projects.


Click on the image to see a a schematic representation of a ferroelectric crystal.
2012-10-20
Discovery of the Higgs boson  
Physicists on the ATLAS and CMS experiments at the Large Hadron Collider (LHC) announced on July 4 that they have observed a new particle. This is generally considered as the discovery of the Higgs boson, but whether the particle has the properties of the predicted Higgs boson remains to be seen.

More than 1,700 people from U.S. institutions - including 89 American universities and seven U.S. Department of Energy (DOE) national laboratories - helped design, build and operate the LHC accelerator and its four particle detectors. The United States, through DOE’s Office of Science and the National Science Foundation, provides support for research and detector operations at the LHC and also supplies computing for the ATLAS and CMS experiments. Stony Brook University is represented at ATLAS by P&A faculty members Rod Engelman, John Hobbs, Robert L. McCarthy, Michael Rijssenbeek and Dmitri Tsybychev, together with posdocs and graduate students from the Department.

The CMS and ATLAS experiments announced last year seeing tantalizing hints of a new particle in their hunt for the Higgs. Since resuming data-taking in March 2012, the experiments have more than doubled their collected data, leading to the latest announcment. The result is consistent with the limits on the Higgs boson mass reported on July 2 by another large collaboration at Fermilab's Tevatron. Faculty from our Department, led by Paul Grannis, played a key role in the DZero experiment at Fermilab and more than 25 Ph.D. students did thesis research there .

The Standard Model of particle physics has proven to explain correctly the elementary particles and forces of nature through more than four decades of experimental tests. But it cannot, without the Higgs boson, explain how most of these particles acquire their mass, a key ingredient in the formation of our universe.


Click on the image to see a candidate Higgs Decay to four muons recorded by ATLAS in 2012. (Image credit: ATLAS WEB site.)
2012-07-05
Probing an ultracold-atom crystal using atomic matter maves  
This week, an article by Dominik Schneble's group (Ultracold atoms, Gadway et al.) is prominently featured on the main WEB page of Nature Physics. By "shining" a one-dimensional Bose gas (probe) onto a Mott insulator (target), Domink's group observed Bragg diffraction peaks that reveal the spatial ordering and localization of atoms on individual lattice sites. For weak confinement, they observe inelastic excitations of atoms in the target, which connect to a quantum "Newton's cradle" in the free-atom limit. They also use atomic de Broglie waves to detect forced antiferromagnetic ordering in an atomic spin mixture.

See the group's WEB page or the Nature Physics paper, or read the press release by the University.


Click on the image to see, on left side: Diffraction of a matter wave (red) from an atomic crystal (blue). Right: For a crystal with weak confinement, the Bragg peaks give way to inelastic excitations.
2012-05-22
Anomalous Quantum Effect in the Thermal Expansion of Ice  
A team of researchers from the Department, along with colleagues from the Universidad Autonoma de Madrid (UAM) in Spain, explain a puzzling water anomaly in a paper published in the May 9 edition of Physical Review Letters entitled, "Anomalous Nuclear Quantum Effects in Ice". Marivi Fernandez-Serra, Phil Allen, Peter Stephens, and PhD student Betul Pamuk, in collaboration with three UAM professors show that the volume of water (H2O) ice depends on the quantum zero-point motion of the H and O atoms in an opposite way from "normal" materials. The theoretical model proposed, which is backed by careful computational modeling and an X-ray diffraction experiment at Brookhaven National Laboratory’s National Synchrotron Light Source, attributes the effect to the peculiar nature of the hydrogen bond. See more at Mariv's WEB page, and at the University's WEB site.
2012-05-10
Neutron star in Cassiopeia A has a core made of superfluid neutrons  
Jim Lattimer and coworkers found that the temperature of a neutron star in our Galaxy is dropping faster than can be explained by standard cooling theories, matching researchers' expectations for a neutron star on its way to superfluidity. The results are published in Phys. Rev. Letters and featured in Nature. Cassiopeia A is 11,000 light years from Earth and at 330 years old it is the youngest neutron star known in our Galaxy.

All four authors of the Physical Review Letters paper have significant ties to Stony Brook University. Dany Page, of the National Autonomous University in Mexico, received his Ph.D. from SBU in 1989. Co-author Madappa Prakash, of Ohio University, is a former SBU faculty member. Andrew Steiner, of Michigan State University, received his Ph.D. from SBU in 2002.


Click on the image to see Cassiopea A. (Image credit: O. Krause et al., Steward Observatory, Spitzer Science Center, Caltech's Jet Propulsion Laboratory and NASA.)
2012-02-22

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