25,555 research outputs found
Quantum Chemistry, Anomalous Dimensions, and the Breakdown of Fermi Liquid Theory in Strongly Correlated Systems
We formulate a local picture of strongly correlated systems as a Feynman sum
over atomic configurations. The hopping amplitudes between these atomic
configurations are identified as the renormalization group charges, which
describe the local physics at different energy scales. For a metallic system
away from half-filling, the fixed point local Hamiltonian is a generalized
Anderson impurity model in the mixed valence regime. There are three types of
fixed points: a coherent Fermi liquid (FL) and two classes of self-similar
(scale invariant) phases which we denote incoherent metallic states (IMS). When
the transitions between the atomic configurations proceed coherently at low
energies, the system is a Fermi liquid. Incoherent transitions between the low
energy atomic configurations characterize the incoherent metallic states. The
initial conditions for the renormalization group flow are determined by the
physics at rather high energy scales. This is the domain of local quantum
chemistry. We use simple quantum chemistry estimates to specify the basin of
attraction of the IMS fixed points.Comment: 12 pages, REVTE
The Gravothermal Instability at all scales: from Turnaround Radius to Supernovae
The gravitational instability, responsible for the formation of the structure
of the Universe, occurs below energy thresholds and above spatial scales of a
self-gravitating expanding region, when thermal energy can no longer
counterbalance self-gravity. I argue that at sufficiently-large scales, dark
energy may restore thermal stability. This stability re-entrance of an
isothermal sphere defines a turnaround radius, which dictates the maximum
allowed size of any structure generated by gravitational instability. On the
opposite limit of high energies and small scales, I will show that an ideal,
quantum or classical, self-gravitating gas is subject to a high-energy
relativistic gravothermal instability. It occurs at sufficiently-high energy
and small radii, when thermal energy cannot support its own gravitational
attraction. Applications of the phenomenon include neutron stars and
core-collapse supernovae. I also extend the original Oppenheimer--Volkov
calculation of the maximum mass limit of ideal neutron cores to the non-zero
temperature regime, relevant to the whole cooling stage from a hot
proto-neutron star down to the final cold state.Comment: Minor amendments to match published versio
Optical Potentials Derived from Nucleon-Nucleon Chiral Potentials at N4LO
Background: Elastic scattering is probably the main event in the interactions
of nucleons with nuclei. Even if this process has been extensively studied in
the last years, a consistent description, i.e., starting from microscopic two-
and many-body forces connected by the same symmetries and principles, is still
under development. Purpose: In a previous paper we derived a theoretical
optical potential from NN chiral potentials at fourth order (N3LO). In the
present work we use NN chiral potentials at fifth order (N4LO), with the
purpose to check the convergence and to assess the theoretical errors
associated with the truncation of the chiral expansion in the construction of
an optical potential. Methods: The optical potential is derived as the
first-order term within the spectator expansion of the nonrelativistic multiple
scattering theory and adopting the impulse approximation and the optimum
factorization approximation. Results: The pp and np Wolfenstein amplitudes and
the cross section, analyzing power, and spin rotation of elastic proton
scattering from 16O, 12C, and 40Ca nuclei are presented at an incident proton
energy of 200 MeV. The results obtained with different versions of chiral
potentials at N4LO are compared. Conclusions: Our results indicate that
convergence has been reached at N4LO. The agreement with the experimental data
is comparable with the agreement obtained in our previous work. We confirm that
building an optical potential within chiral perturbation theory is a promising
approach for describing elastic proton-nucleus scattering.Comment: Physical Review C, in prin
Quantum Mott Transition and Multi-Furcating Criticality
Phenomenological theory of the Mott transition is presented. When the
critical temperature of the Mott transition is much higher than the quantum
degeneracy temperature, the transition is essentially described by the Ising
universality class. Below the critical temperature, phase separation or
first-order transition occurs. However, if the critical point is involved in
the Fermi degeneracy region, a marginal quantum critical point appears at zero
temperature. The originally single Mott critical point generates subsequent
many unstable fixed points through various Fermi surface instabilities induced
by the Mott criticality characterized by the diverging charge susceptibility or
doublon susceptibility. This occurs in marginal quantum-critical region.
Charge, magnetic and superconducting instabilitites compete severely under
these critical charge fluctuations. The quantum Mott transition triggers
multi-furcating criticality, which goes beyond the conventional concept of
multicriticality in quantum phase transitions. Near the quantum Mott
transition, the criticality generically drives growth of inhomogeneous
structure in the momentum space with singular points of flat dispersion on the
Fermi surface. The singular points determine the quantum dynamics of the Mott
transition by the dynamical exponent . We argue that many of
filling-control Mott transitions are classified to this category. Recent
numerical results as well as experimental results on strongly correlated
systems including transition metal oxides, organic materials and He layer
adsorbed on a substrate are consistently analyzed especially in two-dimensional
systems.Comment: 28 pages including 2 figure
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