My Research Interests
My research interests center on pursuing two deep mysteries of
fundamental physics, the nature of the Origin of Mass of elementary particles
and the nature of the Dark Energy accelerating the Universe's expansion.
I try to connect my theoretical work to
the comprehensive and exciting experimental/observational programs underway
to understand these questions.
The backdrop for the first mystery is
the beautiful and very successful Standard Model of particle physics,
written in the grammar of quantum mechanics and special relativity. The
Higgs sector is the least tested part of the Standard Model and yet one of
the most important: it is responsible for generating masses via a process
known as electroweak symmetry breaking for all
elementary particles! The problem is that quantum effects have the
tendency of making these masses either too large (by many orders of magnitude)
or vanish altogether. So the first mystery concerns the question of what
types of new physics might resolve this puzzle. I have work on several
of the major proposals, Supersymmetry, Extra Spacetime
Dimensions and Non-perturbative Strong Dynamics. In particular, many of the
ideas I work on resonate with or originate with String Theories of quantum
gravity (although I would not label myself a string theorist). For
example, a lot of my present work thinking about how the Higgs sector might
manifest in the pathbreaking
new experiments starting soon at the Large Hadron Collider
(at CERN, Geneva) is governed by one of the central
insights from string theory known as the AdS/CFT correspondence,
relating extra dimensions and strong dynamics. I also talk to particle
experimentalists
at Hopkins and elsewhere about how they might go about testing these ideas.
The backdrop for the second mystery is again another extremely successful
and beautiful theory, that of Big Bang cosmology and our
understanding of our universe on the largest distance scales.
A variety of recent high precision obervational measurements have made a
crisis out of an ancient puzzle. They have resolved that not only is the
Universe expanding, a nearly century-old discovery, but this expansion
is speeding up! Part of the puzzle is that familiar forms of
matter and energy can only result in a decelerating expansion. The mysterious
agent of accelerating expansion has been dubbed "dark energy". The second
part of the puzzle is that there is a candidate for dark energy, sometimes
called a "cosmological constant" or sometime "vacuum energy". But quantum
effects tend (as in the Higgs sector) to overshoot, they tend to
give a vacuum energy many orders of magnitude too large to account for the
small but now observed dark energy. This puzzle has few if any broadly
accepted proposals. I have been working on a proposal for several years
to see if modifications of gravity at short distances including the
coupling to ordinary matter can mute the large quantum effects. I have
proposed in this connection that a likely experimental signal of such
a modification would be the breakdown of Newton's Inverse Square Law at
a distance of tens of microns. Such signals are presently being sought.
I continue to work on firming up this theoretical proposal. Again I value
and take advantage of
the strong presence at Hopkins in experimental cosmology, in particular
the area of dark energy.
While the above two mysteries drive a lot of my research, some amount
of my research is independent of these, sometimes
a case of sharpening or inventing new theoretical tools that may only
gain an application later, sometimes a case of understanding
some physical phenomenon from already established physical laws but
through a subtle derivation, new approximation, or other insight.
The central theoretical tools I use in my work are Quantum Field Theory
and General Relativity, with much inspiration from String Theory. My work also
relies heavily on thinking through the implications of the large
body of detailed experimental data, often as massaged and made
digestible by others.
Useful Links for Students interested in Particle Physics
The Microphysical Origin of Mass by Hopkins Professor Jonathan Bagger.
FourDcube
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