Fotini Markopoulou-Kalamara

Fotini G. Markopoulou-Kalamara (Greek: Φωτεινή Μαρκοπούλου-Καλαμαρά; born April 3, 1971) is a Greek theoretical physicist interested in foundational mathematics and quantum mechanics. She was a faculty member at Perimeter Institute for Theoretical Physics and was an adjunct professor at the University of Waterloo.

Career

Markopoulou received her Ph.D. from Imperial College London in 1998 and held postdoctoral positions at the Albert Einstein Institute, Imperial College, and Penn State University. She shared First Prize in the Young Researchers competition at the Ultimate Reality Symposium in Princeton, New Jersey.^[1]

She has been influenced by researchers such as Christopher Isham who call attention to the unstated assumption in most modern physics that physical properties are most naturally calibrated by a real-number continuum. She, and others, attempt to make explicit some of the implicit mathematical assumptions underpinning modern theoretical physics and cosmology.

In her interdisciplinary paper "The Internal Description of a Causal Set: What the Universe Looks Like from the Inside", Markopoulou instantiates some abstract terms from mathematical category theory to develop straightforward models of space-time. It proposes simple quantum models of space-time based on category-theoretic notions of a topos and its subobject classifier (which has a Heyting algebra structure, but not necessarily a Boolean algebra structure).

For example, hard-to-picture category-theoretic "presheaves" from topos theory become easy-to-picture "evolving (or varying) sets" in her discussions of quantum spacetime. The diagrams in Markopoulou's papers (including hand-drawn diagrams in one of the earlier versions of "The Internal Description of a Causal Set") are straightforward presentations of possible models of space-time. They are intended as meaningful and provocative, not just for specialists but also for newcomers.

In May 2006, Markopoulou published a paper with Lee Smolin that further popularized this Causal Dynamical Triangulation (CDT) Theory by explaining time slicing of the Ambjorn–Loll CDT model as result of gauge fixing. Their approach relaxed the definition of the Ambjorn–Loll CDT model in 1 + 1 dimensions to allow for a varying lapse.

Quantum graphity

In 2008, Markopoulou, Tomasz Konopka and Simone Severini initiated the study of a new background independent model of evolutionary space called quantum graphity.

In the quantum graphity model, points in spacetime are represented by nodes on a graph connected by links that can be on or off.^[2] This indicates whether or not the two points are directly connected as if they are next to each other in spacetime. When they are on the links have additional state variables which are used to define the random dynamics of the graph under the influence of quantum fluctuations and temperature. At high temperature the graph is in Phase I where all the points are randomly connected to each other and no concept of spacetime as we know it exists. As the temperature drops and the graph cools, it is conjectured to undergo a phase transition to a Phase II where spacetime forms. It will then look like a spacetime manifold on large scales with only near-neighbour points being connected in the graph.

The hypothesis of quantum graphity is that this geometrogenesis models the condensation of spacetime in the big bang. A second model, related to ideas around quantum graphity, has been published.^[3]

References

External links

• Fotini Markopoulou, The Internal Description of a Causal Set: What the Universe Looks Like from the Inside (1999)
• Related seminar (1998)
• Gefter, Amanda (11 November 2002). "Throwing Einstein for a Loop". Scientific American. Retrieved 10 November 2012. 
• Creating Spacetime - a lecture presented by Fotini Markopoulou at the Quantum to Cosmos festival.