NPAC (Nuclear/Particle/Astro/Cosmo) Forum

Host: 
Gary Shiu
Speaker: Paul Steinhardt Princeton University

 

Available Downloads:

Room and Building: 
4274
At zero chemical potential, the finite temperature transition of QCD is known to be a smooth crossover from lattice simulations. The conjectured first order phase transition and its critical point at finite density is of great theoretical and experimental interest.
I will review the status of the lattice calculation with grand canonical approach and present an algorithm in the canonical approach. The preliminary results on the identification of a first order transition and the determination of the critical point with the help of Maxwell construction will be reported.
Speaker: Keh-Fei Liu University of Kentucky

 

Available Downloads:

Room and Building: 
5280 Chamberlin
will address the role of chiral symmetry and parity invariance in the properties of hot and dense quark-gluon matter. The possibility of parity-odd effects in this matter will be discussed. Local parity violation can manifest itself in heavy ion collisions at RHIC through the spatial separation of positive and negative particles with respect to the reaction plane. The charge separation induces the electric dipole moment of the produced hot quark-gluon matter; it stems from the interplay of strong magnetic field in the early stage of the heavy ion collision and the presence of topological configurations in hot matter ("the chiral magnetic effect"). There is a recent experimental evidence for local parity violation at RHIC. The effect has interesting implications for the cosmology of the Early Universe, and has analogs in condensed matter physics (quantum wires, graphene, and topological insulators), and in astrophysics (particle acceleration in cosmic strings).
Speaker: Dmitri Kharzeev Brookhaven National Laboratory

 

Available Downloads:

Room and Building: 
4274 Chamberlin
We present a solution to the cosmological constant, the zero-point energy, and the quantum gravity problems within a single comprehensive framework.We show that in quantum theories of gravity in which the zero-point energy density of the gravitational field is well-defined, the cosmological
constant and zero-point energy problems solve each other by mutual
cancellation between the cosmological constant and the matter and
gravitational field zero-point energy densities. Because of this
cancellation, regulation of the matter field zero-point energy density is not needed, and thus does not cause any trace anomaly to arise. We exhibit our results in two theories of gravity that are well-defined quantum-mechanically. Both of these theories are locally conformal invariant, quantum Einstein gravity in two dimensions and Weyl-tensor-based quantum conformal gravity in four dimensions (a fourth-order derivative quantum theory of the type that Bender and Mannheim have recently shown to be ghost-free and unitary). Central to our approach is the requirement that any and all departures of the geometry from Minkowski are to be brought about by quantum mechanics alone. Consequently, there have to be no fundamental classical fields, and all mass scales have to be generated by dynamical condensates. In such a situation the trace of the matter field energy-momentum tensor is zero, a constraint that obliges its cosmological constant and zero-point contributions to cancel each other identically, no matter how large they might be. Quantization of the gravitational field is caused by its coupling to quantized matter fields, with the gravitational field not needing any independent quantization of its own. With there being no a priori classical curvature, one does not have to make it compatible with quantization.
Speaker: Philip Mannheim University of Connecticut

 

Available Downloads:

Room and Building: 
5280 Chamberlin
Due to their outstanding property to be storable and hence observable for long periods of time (several hundreds of seconds) in suitable material or magnetic traps, ultra-cold neutrons (UCN)with energies around 100 neV are an unique tool to study fundamental properties of the free neutron. Their properties and production are described in detail. Selected experiments with ultra-cold neutrons (UCN) - the measurement of its lifetime and the search for an electric dipole moment - performed at the instrument "Physique Fondamentale 2 (PF2)" of the Institut Laue-Langevinn (ILL) are highlighted. For particles to have electric dipole moments, the forces concerned in their structure must be asymmetric with regard to space-parity (P) and time reversal (T). P violation is a well-known intrinsic feature of the weak interaction which is responsible for the beta-decay of the free neutron. T violation turns out to be necessary to explain the survival of matter at the expense of antimatter after the Big Bang. By searching for an EDM of the free neutron hypothetical new channels of T-violation can be investigated. The experiments at the ILL will be compared to competing EDM projects worldwide. The measurement of the lifetime of the free neutron together with the determination of one of the correlation parameters characterizing neutron decay allows tests of the Standard Model. Furthermore, the neutron lifetime plays an important role in Big-Bang Nucleosynthesis cosmology. Up to 180 s after the big-bang nuclei with more than one nucleon are unstable. The neutron lifetime determines how many neutrons have decayed up to this moment and hence the relative helium abundance in the universe. The different methods to measure the lifetime of the free neutron are reviewed and the latest experiments using storage of UCN at the ILL are described in detail. A brief outlook on future projects worldwide will be given.
Host: 
Michael Ramsey-Musolf
Speaker: Peter Geltenbort Institute Laue-Langevin, Grenoble

 

Available Downloads:

Room and Building: 
4274 Chamberlin
I will discuss electroweak baryogenesis (EWBG) in supersymmetric
U(1)' models. Unlike the usual wisdom, a spontaneous CP violation
plays a key role in this picture. This makes the EWBG in the U(1)'
models be very different from what happens in the minimal
supersymmetric standard model. I will also show that a successful
EWBG and an acceptable neutralino dark matter relic density can be
simultaneously achieved in our models.
Host: 
Michael Ramsey-Musolf
Speaker: Tao Liu University of Chicago

 

Available Downloads:

Room and Building: 
4274 Chamberlin
Host: 
Segev BenZvi
Speaker: Petra Huentemeyer Michigan Technological University

 

Available Downloads:

Room and Building: 
4274 Chamberlin
Host: 
Timbie
Speaker: Ted Bunn University of Richmond

 

Available Downloads:

Room and Building: 
4274 Chamberlin Hall
Recent cosmic ray data, notably from the Pamela and Fermi satellites, indicate that previously unaccounted-for powerful sources in the Galaxy inject high-energy electrons and positrons. Interestingly, this new source class might be related to new fundamental particle physics, and specifically to pair-annihilation or decay of galactic dark matter. I will
discuss how this exciting scenario is constrained by Fermi gamma-ray observations, and which astrophysical source counterparts could also be responsible for the high-energy electron-positron excess. In particular, I will review the case for nearby mature pulsars, and the impact of newly
discovered radio-quiet pulsars that pulsate in gamma rays. While
high-energy electron-positron measurements sample local (closer than 1 kpc) cosmic rays, diffuse radio and gamma-ray emission informs us about the global galactic cosmic ray population. I will thus offer a few thoughts on recent claims involving the detection of diffuse radio ("WMAP haze") and gamma-ray ("Fermi haze") emissions and on implications for the quest for New Physics
Host: 
Michael Ramsey-Musolf
Speaker: Stefano Profumo U.C. Santa Cruz

 

Available Downloads:

Room and Building: 
4274 Chamberlin
Host: 
Baha Balantekin
Speaker: Fedor Simkovic Comenius University

 

Available Downloads:

Room and Building: 
4274 Chamberlin

Pages

©2013 Board of Regents of the University of Wisconsin System