20,728 research outputs found
Heavy-ion physics: freedom to do hot, dense, exciting QCD
In these two lectures I review the basics of heavy-ion collisions at
relativistic energies and the physics we can do with them. I aim to cover the
basics on the kinematics and observables in heavy-ion collider experiments, the
basics on the phenomenology of the nuclear matter phase diagram, some of the
model building and simulations currently used in the heavy-ion physics
community and a selected list of amazing phenomenological discoveries and
predictions.Comment: These lectures were given at the 2019 CERN Latin-American School of
High-Energy Physics in Cordoba, Argentina, 13 - 26 March 2019 and the notes
have been submitted to proceedings of CLASHEP 2019. These lecture notes are
based on previous Heavy-Ion and extreme QCD lectures given at CLASHEP by A.
Ayala (2017), E. Fraga (2015) and J. Takahashi (2013
The Dielectric Skyrme model
We consider a version of the Skyrme model where both the kinetic term and the
Skyrme term are multiplied by field-dependent coupling functions. For suitable
choices, this "dielectric Skyrme model" has static solutions saturating the
pertinent topological bound in the sector of baryon number (or topological
charge) but not for higher . This implies that higher charge
field configurations are unbound, and loosely bound higher skyrmions can be
achieved by small deformations of this dielectric Skyrme model. We provide a
simple and explicit example for this possibility. Further, we show that the
BPS sector continues to exist for certain generalizations of the model
like, for instance, after its coupling to a specific version of the BPS Skyrme
model, i.e., the addition of the sextic term and a particular potential.Comment: Latex file, 13 pages, no figure
High-Frequency Electron-Spin-Resonance Study of the Octanuclear Ferric Wheel CsFe
High-frequency ( = 190 GHz) electron paramagnetic resonance (EPR) at
magnetic fields up to 12 T as well as Q-band ( = 34.1 GHz) EPR were
performed on single crystals of the molecular wheel CsFe. In this molecule,
eight Fe(III) ions, which are coupled by nearest-neighbor antiferromagnetic
(AF) Heisenberg exchange interactions, form a nearly perfect ring. The
angle-dependent EPR data allow for the accurate determination of the spin
Hamiltonian parameters of the lowest spin multiplets with 4.
Furthermore, the data can well be reproduced by a dimer model with a uniaxial
anisotropy term, with only two free parameters and . A fit to the dimer
model yields = -15(2) cm and = -0.3940(8) cm. A rhombic
anisotropy term is found to be negligibly small, = 0.000(2) cm. The
results are in excellent agreement with previous inelastic neutron scattering
(INS) and high-field torque measurements. They confirm that the CsFe
molecule is an excellent experimental model of an AF Heisenberg ring. These
findings are also important within the scope of further investigations on this
molecule such as the exploration of recently observed magnetoelastic
instabilities.Comment: 21 pages, 8 figures, accepted for publication in Inorganic Chemistr
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