Dimitris Nanopoulos

Griechische Wissenschaftler

Greek-American theoretical physicist (13.9-1948 Athens, Greece), the youngest member elected to the Academy of Athens' Natural and Applied Sciences. He also became the first elected member who does not reside in Greece.

Dr. Nanopoulos' research interests include:

• high-energy physics
• construction of a unified model containing electromagnetic, weak, strong and gravitational interactions
• grand unified theories
• supersymmetry
• supergravity
• superstring theories
• astroparticle physics
• dark matter
• inflationary models
• biophysics

Dimitri Nanopoulos is a Distinguished Professor of Physics and holder of the Mitchell/Heep Chair in High Energy Physics at Texas A&M University, head of the Houston Advanced Research Center (HARC) Astroparticle Physics Group, and fellow and chair of Theoretical Physics, Academy of Athens in Greece. Professor Nanopoulos received his B.S. in 1971 from the University of Athens and his Ph.D. in 1973 from the University of Sussex, England. He has made several contributions to particle physics and cosmology. He works in string unified theories, fundamentals of quantum theory, astroparticle physics and quantum-inspired models of brain function. Nanopoulos is fellow of the American Physical Society and was a Curie Fellow at the Laboratoire de Physique Theorique de l'Ecole Normale Superieure in Paris (1975-76), Research Fellow Harvard University (1977-79); CERN staff member (1979-86), Professor of Physics, University of Wisconsin (1986-88) and joined Texas A&M University in 1989. He is author of more than 515 refereed articles, with an excess of 27000 citations, placing him as the fourth most cited High Energy Physicist of all time (in 2001). He has given more than 250 invited presentations at international conferences.

From a report by Patrice Pages:

Nanopoulos has established, along with other physicists, that the speed of light, instead of being the constant value of 186282 miles per second, might change. "If the speed of light proves not to be constant any more, even by a very small changeable amount, laws of physics - the theory of relativity included - will have to undergo significant changes," says Nanopoulos. He, Nikolaos Mavromatos of King's College in London and John Ellis of CERN discovered a new expression for the speed of light, which depends on its frequency. ”Through our calculations, we found that the speed of light is frequency-dependent. But a change in the usual speed of light value of 186282 miles per second is noticeable only for light coming from astronomical objects situated very far from Earth, which is why this frequency dependence has not been noticed so far. One way to experimentally test our hypothesis is to consider galaxies or other objects in the sky that are very far from us. Then we collect the photons (particles of light) simultaneously emitted by these sources, and we look at differences of arrival times in a detector on earth between photons of different frequencies. The photons of higher frequencies should come later." says Nanopoulos. The frequency-dependent expression of the speed of light depends on the gravitational constant, a quantity that is known since Newton established his law of gravitation. By using the differences in photon arrival times of six astronomical sources, Nanopoulos and his collaborators estimated an upper bound of the value of the gravitational constant from the data, and compared their results with the expected value. "We were amazed to see that if we use all these astronomical data, we find very reasonable values for the gravitational constant," says Nanopoulos. "That was our first surprise: the fact that, put together, a bunch of data that had nothing to do with the gravitational constant, gave us values so close to what we would expect to find." A second experimental encouraging result about the frequency-dependence of the speed of light was provided by the HEGRA (High Energy Gamma Ray Astronomy) experiment, which is detecting photons from outer space, and is situated in La Palma, Canary Islands. The frequency-dependent expression of the speed of light was used to solve a problem faced by three physicists: Tadashi Kifune, from the University of Tokyo in Japan, Ray Protheroe, from the University of Adelaide in Australia, and Hinrich Meyer, from the University of Wuppertal in Germany. The problem occurred when HEGRA physicists detected very energetic photons emitted by the galaxy Markarian 501. "The most energetic of these photons were expected to interact with other very low-energy photons from the infrared background radiation, which is a radiation present since the early universe," says Nanopoulos. "When a very energetic photon interacts with a low-energy photon, they have just the right quantity of energy to create an electron-antielectron pair. But physicists at HEGRA did not see any of the expected electron-antielectron pairs, but did observe very energetic photons instead. "By using the frequency-dependent expression of the speed of light, Kifune, Protheroe and Meyer found that the combined energy of each type of phton was not enough to create an electron-antielectron pair," adds Nanopoulos. "That is why no electron-antielectron pair has been observed." If by looking at more energetic photons, HEGRA never detects the expected electron-antielectron pairs, this would provide further support of the new hypothesis put forward by Nanopoulos and his collaborators. "This frequency-dependence of the speed of light changes drastically our view of the theory of relativity," Nanopoulos says. "It is also the first time that we have a window of opportunity to study quantum gravity, and thus scientifically study the origin of the Universe. It is a fantastic thing that we can experimentally magnify such a tiny effect." Nanopoulos says that if the frequency-dependence of the speed of light is further confirmed by other experiments, the theory of relativity would still be valid under certain circumstances. "There is nothing wrong with Einstein's theory of relativity. If the energy of an object is much smaller than 1019 proton masses or if the distance between two objects is smaller than millions of light-years, Einstein's equations are still valid," he says.