221,279 research outputs found
Persistent Challenges of Quantum Chromodynamics
Unlike some models whose relevance to Nature is still a big question mark,
Quantum Chromodynamics will stay with us forever. Quantum Chromodynamics (QCD),
born in 1973, is a very rich theory supposed to describe the widest range of
strong interaction phenomena: from nuclear physics to Regge behavior at large
E, from color confinement to quark-gluon matter at high densities/temperatures
(neutron stars); the vast horizons of the hadronic world: chiral dynamics,
glueballs, exotics, light and heavy quarkonia and mixtures thereof, exclusive
and inclusive phenomena, interplay between strong forces and weak interactions,
etc. Efforts aimed at solving the underlying theory, QCD, continue. In a
remarkable entanglement, theoretical constructions of the 1970s and 1990s
combine with today's ideas based on holographic description and strong-weak
coupling duality, to provide new insights and a deeper understanding.Comment: Julius Edgar Lilienfeld Prize Lecture at the April Meeting of APS,
Dallas, TX, April 22-25, 2006; v.2: reference added; v.3: reference adde
Experimental Challenges for Quantum Gravity
The existence of a new fundamental scale may lead to modified dispersion
relations for particles at high energies. Such modifications seem to be
realized with the Planck scale in certain descriptions of quantum gravity. We
apply effective field theory to this problem and identify dimension 5 operators
that would lead to cubic modifications of dispersion relations for Standard
Model particles. We also discuss other issues related to this approach
including various experimental bounds on the strength of these interactions.
Further we sketch a scenario where mixing of these operators with dimensions 3
and 4 due to quantum effects is minimal.Comment: QTS3 proceedings; review of hep-ph/0301124 plus extended discussio
Interdisciplinary and physics challenges of Network Theory
Network theory has unveiled the underlying structure of complex systems such
as the Internet or the biological networks in the cell. It has identified
universal properties of complex networks, and the interplay between their
structure and dynamics. After almost twenty years of the field, new challenges
lie ahead. These challenges concern the multilayer structure of most of the
networks, the formulation of a network geometry and topology, and the
development of a quantum theory of networks. Making progress on these aspects
of network theory can open new venues to address interdisciplinary and physics
challenges including progress on brain dynamics, new insights into quantum
technologies, and quantum gravity.Comment: (7 pages, 4 figures
Quantum Internet: from Communication to Distributed Computing!
In this invited paper, the authors discuss the exponential computing speed-up
achievable by interconnecting quantum computers through a quantum internet.
They also identify key future research challenges and open problems for quantum
internet design and deployment.Comment: 4 pages, three figures, invited pape
Comments on Challenges for Quantum Gravity
We examine radiative corrections arising from Lorentz violating dimension
five operators presumably associated with Planck scale physics as recently
considered by Myers and Pospelov. We find that observational data result in
bounds on the dimensionless parameters of the order . These represent
the most stringent bounds on Lorentz violation to date
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