1,479 research outputs found
Nuclides as a liquid phase of chiral perturbation theory I: emergence of pion-less SU(2) PT
The Standard Model of particle physics, augmented with neutrino mixing, is at
least very nearly the complete theory of interactions of known particles at
energies accessible to Nature on Earth. Candidate effective theories of nuclear
structure must therefore reflect SM symmetries, especially the chiral global
symmetry of two-massless-quark QCD. For ground-state
nuclei, SU(2) chiral perturbation theory (XPT) enables perturbation in inverse
powers of , with analytic operators renormalized to
all loop orders. We show that pion-less "Static Chiral Nucleon Liquids" (SXNL)
emerge as a liquid phase of SU(2) XPT of protons, neutrons and 3
Nambu-Goldstone boson pions. Far-IR pions decouple from SXNL, simplifying the
derivation of saturated nuclear matter and microscopic liquid drops
(ground-state nuclides). We trace to the global symmetries of
two-massless-quark QCD the power of pion-less SU(2) XPT to capture experimental
ground-state properties of certain nuclides with even parity, spin zero, even
proton number Z, and neutron number N.
We derive the SXNL effective SU(2) XPT Lagrangian, including all order
operators. These include: all 4-nucleon
operators that survive Fierz rearrangement in the non-relativistic limit, and
effective Lorentz-vector iso-vector neutral "-exchange" operators. SXNL
motivate nuclear matter as non-topological solitons at zero pressure: the
Nuclear Liquid Drop Model and Bethe-Weizsacker Semi-Empirical Mass Formula
emerge in an explicit Thomas-Fermi construction provided in the companion
paper. For chosen nuclides, nuclear Density Functional and Skyrme models are
justified to order . We conjecture that inclusion of
higher order operators will result in accurate "natural" Skyrme, No-Core-Shell,
and neutron star models
Macro Dark Matter
Dark matter is a vital component of the current best model of our universe,
CDM. There are leading candidates for what the dark matter could be
(e.g. weakly-interacting massive particles, or axions), but no compelling
observational or experimental evidence exists to support these particular
candidates, nor any beyond-the-Standard-Model physics that might produce such
candidates. This suggests that other dark matter candidates, including ones
that might arise in the Standard Model, should receive increased attention.
Here we consider a general class of dark matter candidates with characteristic
masses and interaction cross-sections characterized in units of grams and
cm, respectively -- we therefore dub these macroscopic objects as Macros.
Such dark matter candidates could potentially be assembled out of Standard
Model particles (quarks and leptons) in the early universe. A combination of
Earth-based, astrophysical, and cosmological observations constrain a portion
of the Macro parameter space. A large region of parameter space remains, most
notably for nuclear-dense objects with masses in the range g and
g, although the lower mass window is closed
for Macros that destabilize ordinary matter.Comment: 13 pages, 1 table, 4 figures. Submitted to MNRAS. v3: corrected small
errors and a few points were made more clear, v4: included CMB bounds on dark
matter-photon coupling from Wilkinson et al. (2014) and references added.
Final revision matches published versio
Liquid Phases in SU(3) Chiral Perturbation Theory: Drops of Strange Chiral Nucleon Liquid & Ordinary Chiral Heavy Nuclear Liquid
Chiral SU(3) Perturbation Theory (SU3XPT) identifies hadrons as the building
blocks of strongly interacting matter at low densities and temperatures. We
show that it admits two co-existing chiral nucleon liquid phases at zero
external pressure with well-defined surfaces: 1) ordinary microscopic chiral
heavy nuclear liquid drops (XNL) and 2) a new Strange Chiral Nucleon Liquid
(SXNL) phase with both microscopic and macroscopic drop sizes. Liquid drops of
both XNL and SXNL are simultaneously solutions to the SU3XPT semi-classical
equations of motion and obey all relevant CVC and PCAC equations. Axial-vector
currents are conserved inside macroscopic drops of SXNL, a new form of baryonic
matter with zero electric charge density, which is by nature "dark". The
numerical values of all SU3XPT coefficients are used to fit current scattering
experiments and ordinary XNL drops (identified with the ground state of
ordinary even-even spin-zero spherical closed-shell nuclei). SXNL then also
emerges (i.e. without new adjustable parameters). For certain SU3XPT
coefficients, finite microscopic and macroscopic drops of SXNL may be the
ground state of a collection of nucleons: ordinary heavy nuclei may be
meta-stable, while oceans of SXNL may force qualitative and experimentally
observable changes to the neutron star equation of state
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