Office: Goodbody Hall 120

Phone: (812) 855-2541

*See also:* Professor Hagar's homepage

- Ph.D., Philosophy, University of British Columbia, Vancouver, 2004

**Foundations of quantum and statistical mechanics**

*Quantum Information and the Foundations of Quantum Theory*

I tend to resist the current hype around quantum information theory, inasmuch as it is portrayed as shedding new light on the foundational problems that saturate non relativistic quantum mechanics, and in recent papers I have exposed some fatal flaws in arguments to this end. What I do believe is that technological progress in the field of quantum information theory may clarify these foundational problems, and may even serve as basis to yet another case of experimental metaphysics, by allowing us to test decoherence based approaches against genuine collapse theories.

*The Origins of Probability in Statistical Mechanics*

I am intrigued by some old problems that the founding fathers of statistical mechanics (e.g., Maxwell, Boltzmann, Clausius) pondered with when they struggled to construct dynamical models that describe thermal phenomena. While it has become clear to them (first to Maxwell, and later also to Boltzmann and Clausius) that the thermal phenomena cannot be given a description in terms of Hamiltonian mechanics alone, and that additional probabilistic assumptions were needed, they were still ambigiuous with respect to the interpretation of these probabilistic assumptions. In a recent paper I have argued that contrary to a vocal view in the literature that regards the problem of irreversibility as the main problem in the foundations of statistical mechanics, the problem of probability, i.e., the attempt to underpin the probabilistic assumption that are necessary for the reduction of thermodynamics to statistical mechanics, is still open.

**Physical Computational Complexity and Quantum Computing**

*What Is Quantum In Quantum Computing?*

Quantum computing has by now become a small industry, and one of the most fascinating domains of quantum mechanics today. Apart from writing an entry on this subject to the Stanford Online Encyclopedia of Philosophy, I am interested in the conceptual problems that this field raises, which touch upon the foundations of quantum theory, the applicability of mathematics to physics, and the philosophy of mind. Together with Alex Korolev from UBC, I have argued against recent attempts to "solve" recursive-theoretic undecidable problems with the quantum adiabatic algorithm. Currently I am writing a paper on another quantum halting problem which, to my mind, havily constrains the alleged superiority of quantum algorithms over their classical counterparts.

**Constructing the Principles: Historical and Philosophical Lessons for Future Theoretical Physics**

In this monograph I am using Maxwell's and Poincare's famous distinction (adopted by Einstein) between constructive and principle theories in order to draw some historical and philosophical lessons from the development of the special theory of relativity and statistical mechanics to modern scenarios such as quantum information theory and quantum gravity.

**Ph.D. Thesis: Chance and Time**

In my PhD thesis, which was also published in Israel as an expository book on the philosophy of physics, I try to show how the problem of irreversibility in the foundations of statistical mechanics and the quantum emasurement problems are actually two facets of the general philosophical problem of explaining unobserved predictions. this problem arises from the conjunction of a philosophical stance, namely that our theories describe the world, and an undisputable fact, namely that some phenomena that are predicted by our theories remain nevertheless mostly unobserved. I characterize different solutions to this problem using another philosophical problem, namely the problem of probability, and suggest a possible experimental scenario in which these solutions may be tested.