Mark Trodden

Fay R. and Eugene L. Langberg Professor of Physics and Department Chair
Co-Director for the Penn Center for Particle Cosmology

University of Pennsylvania

Fay R. and Eugene L. Langberg Professor of Physics and Co-Director: Center for Particle Cosmology, 2009 - present

Editor, Journal of Cosmology and Astroparticle Physics (2010-)

Editor, Physics Letters B. (2009-)

Visiting Professor, Cornell University (Fall 2008)

Editorial Advisory Board member, Multiversal Journeys Series, Springer (2007 -)

Editor, New Journal of Physics (2006 -)

Editorial Board member, The Gravitational Lens (2005-2007)

Co-Chair, Working Group on Cosmological Connections, American Linear Collider Physics Group (2003-2006)

Visitor, Kavli Institute for Theoretical Physics, Santa Barbara (Fall 2003)

  • Syracuse University
    Professor of Physics, 2000 - 2009
  • Case Western Reserve University
    Visiting Assistant Professor, 1999 - 2000
  • Case Western Reserve University
    Research Associate, 1997 - 1999
  • Massachusetts Institute of Technology
    Research Associate, 1995 - 1997



Brown University

  • Physics (M.Sc., Ph.D), 1992 - 1995
  • University of Cambridge
    Mathematics (Cert. Adv. Study), 1990 - 1991
  • University of Cambridge
    Mathematics (M.A.), 1987 - 1990


Research Interests: 

In recent years, rapid advances in observational cosmology have revealed a universe that provides support for some of our most speculative ideas about the early cosmos, while raising entirely new questions about its late-time evolution.

The recent and surprising discovery of cosmic acceleration has joined other fundamental unsolved problems - the nature of dark matter, the origin of the baryon asymmetry, and the fundamental origin of inflation or other physics of the early universe. Taken together, these puzzles of modern cosmology provide some of the most compelling reasons for and insights into the nature of physics beyond the remarkably successful theories of the standard model of particle physics and general relativity.

I am actively engaged in the construction and investigation of models that may shed light on the fundamental physics origin of some or all of these currently unsolved problems. The goal is to use the clues contained in cosmological data to guide the construction of models of new physics. Such models must, of course, explain current observations and make clear predictions for upcoming experiments. I am also interested in the role that cosmological data can play in constraining models of particle physics beyond the standard model. Such constraints can often provide complementary information about fundamental physics to that provided through terrestrial experiments such as those performed at colliders.

My work within these areas has been broad, spanning approaches to dark energy and dark matter; extra dimensional models of particle physics and cosmology; the baryon asymmetry of the universe; inflation and its problems and alternatives; topological defects in cosmology; and the BPS structure of intersecting branes in supersymmetric theories.

I have worked broadly in both cosmology and particle physics, in work ranging from the structure of inflationary spacetimes to the BPS structure of intersecting branes in supersymmetric theories. The majority of his work is firmly on the particle physics-cosmology border, and includes the development of the modified gravity approach to cosmic acceleration, approaches to dark energy and dark matter; extra dimensional models of particle physics and cosmology; the baryon asymmetry of the universe; inflation and its features; and topological defects in cosmology.

Much of my research program over the last several years has been concerned with trying to map out the space of viable models of the accelerating universe. This has included investigating the microphysical implications of exotic dark energy models, and proposing one of the most-studied approaches to the idea that a modification of general relativity may explain cosmic acceleration. In this area I have carried out some of the careful analyses of structure formation in these models, which have demonstrated how the resulting scale-dependent growth factor yields testable predictions even when the cosmic expansion history precisely mimics that of Lambda-CDM. 


Selected Publications: 


  • Agarwal, N., Bean, R., Khoury, J. and Trodden, M., “Cascading Cosmology,'' Phys. Rev. D81, 084020 (2010).
  • Silvestri, A. and Trodden, M., “Non-Gaussian Signatures from the Post-inflationary Early Universe,'' Phys. Rev. Lett. 103, 251301 (2009).
  • Bean, R., Flanagan, E. and Trodden, M., “Adiabatic instability in coupled dark energy-dark matter models,” Phys. Rev. D78, 023009 (2008).
  • Toharia, M. and Trodden, M., “Metastable Kinks in the Orbifold,” Phys. Rev. Lett. 100, 041602 (2008).
  • Bean, R., Bernat, D., Pogosian, L., Silvestri, A. and Trodden, M., “Dynamics of Linear Perturbations in f(R) Gravity,” Phys. Rev. D75, 064020 (2007).
  • Carroll, S.M., De Felice, A., Duvvuri, V., Easson, D.A., Trodden, M. and Turner, M.S., “The cosmology of generalized modified gravity models,” Phys. Rev. D71, 063513 (2005).
  • Carroll, S.M., Duvvuri, V., Trodden, M. and Turner, M.S., “Is cosmic speed-up due to new gravitational physics?” Phys. Rev. D70, 043528 (2004).
  • Carroll, S.M., Hoffman, M. and Trodden, M., “Can the dark energy equation-of-state parameter w be less than -1?” Phys. Rev. D68, 023509 (2003).
  • Melchiorri, A., Mersini-Houghton, L., Odman, C.J. and Trodden, M., “The state of the dark energy equation of state,” Phys. Rev. D68, 043509 (2003).
  • Kaloper, N., March-Russell, J., Starkman, G.D. and Trodden, M., “Compact hyperbolic extra dimensions: Branes, Kaluza-Klein modes and cosmology” Phys. Rev. Lett. 85, 928 (2000).
  • Carroll, S.M., Hellerman, S. and Trodden, M., “Domain wall junctions are 1/4-BPS states,” Phys. Rev. D61, 065001 (2000).
  • Vachaspati, T. and Trodden, M., “Causality and cosmic inflation,” Phys. Rev. D61, 023502 (2000).
  • Krauss, L.M. and Trodden, M., “Baryogenesis below the electroweak scale,” Phys. Rev. Lett. 83, 1502 (1999).
  • Riotto, A. and Trodden, M., “Recent progress in baryogenesis,” Ann. Rev. Nucl. Part. Sci. 49, 35-75 (1999).
  • Trodden, M., “Electroweak baryogenesis,” Rev. Mod. Phys. 71, 1463-1499 (1999).
  • Davis, S.C., Davis, A.C. and Trodden, M., “N = 1 supersymmetric cosmic strings,” Phys. Lett. B405, 257-264 (1997).
  • Brandenberger, R.H., Carter, B., Davis, A.C. and Trodden, M., “Cosmic vortons and particle physics constraints,” Phys. Rev. D54, 6059-6071 (1996).