1,682 research outputs found
Twisted valence quarks and hadron interactions on the lattice
No full textAbstractWe consider QCD with valence and sea quarks obeying different boundary conditions. We point out that the energy of low lying two hadron states do not depend on the boundary condition of the sea quarks (up to exponentially small corrections). Thus, the advantages in using twisted boundary conditions on the lattice QCD extraction of nucleon–nucleon phase shifts can be gained without the need of new gauge configurations, even in fully unquenched calculations
A complex path around the sign problem
No full textWe review recent attempts at dealing with the sign problem in Monte Carlo calculations by deforming the region of integration in the path integral from real to complex fields. We discuss the theoretical foundations, the algorithmic issues and present some results for low dimensional field theories in both imaginary and real time
Estimativas do nível de mortalidade e de esperança de vida para o Estado de São Paulo, Brasil, em 1970 Estimatives of mortality rate and life expectance for the S. Paulo, State, Brazil, in 1970
No full textResultados preliminares do Censo Demográfico de 1970, são utilizados para a determinação do nível de mortalidade no Estado de São Paulo, Brasil. Através da teoria de populações estáveis e de tábuas de vida modelo, encontrou-se tábuas de sobrevivência para os sexos masculino e feminino. Acredita-se que estas tábuas refletem as condições de mortalidade vigentes nos períodos próximos a data censitária.Preliminary results of the 1970 Demographic Census in Brazil lead the author to determining the mortality level for the State of São Paulo, Brazil. Life Tables for males and females were found through stable population theory and model life tables. It is believed that those tables reflect mortality conditions of the State of S. Paulo during the period close to me Census date
Charged kaon condensation in high density quark matter
No full textAbstractWe show that at asymptotically high densities the “color-flavor-locked+neutral kaon condensate” phase of QCD develops a charged kaon condensate through the Coleman–Weinberg mechanism. At densities achievable in neutron stars a charged kaon condensate forms only for some (natural) values of the low energy constants describing the low-lying excitations of the ground state
Aharonov–Bohm effect and nucleon–nucleon phase shifts on the lattice
No full textAbstractWe propose a method for the lattice QCD computation of nucleon–nucleon low-energy interactions. It consists in simulating QCD in the background of a “electromagnetic” field whose potential is non-vanishing, but whose field strength is zero. By tuning the background field, phase-shifts at any (but small) momenta can be determined by measuring the shift of the ground state energy. Lattice sizes as small as 5 Fermi can be sufficient for the calculation of phase shifts up to momenta of order of mπ/2
Goldstone modes in the neutron star core
No full textAbstractWe studied the effect of the diverse Goldstone boson modes in the transport properties of dense neutron matter. The two Goldstone bosons associated with density oscillations of the neutron and electron + proton fluids, called superfluid phonons, mix and couple strongly to electrons reducing their mean free time and suppressing their contribution to transport coefficients. For typical neutron star temperatures in the range T=106–109 K, the Goldstone modes associated with rotational symmetry, called angulons, couple weakly to each other and to electrons and, consequently, have anomalously large mean free paths and can contribute to both diffusive and ballistic transport of heat and momentum. Still, their contribution is smaller that coming from the electrons on account of their smaller density. We speculate that long-wavelength superfluid phonons and angulons can play a role in neutron star seismology, and lead to interesting phenomenology especially since angulons couple to magnetic fields and have anisotropic dispersion relations
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