3,677 research outputs found
Locating the critical end point using the linear sigma model coupled to quarks
We use the linear sigma model coupled to quarks to compute the effective
potential beyond the mean field approximation, including the contribution of
the ring diagrams at finite temperature and baryon density. We determine the
model couplings and use them to study the phase diagram in the baryon chemical
potential-temperature plane and to locate the Critical End Point.Comment: 8 pages, 2 figures, conference paper from ISMD 201
Optimization of the investment casting process
Rapid prototyping is an important technique for manufacturing. This work refers to the manufacture of hollow patterns made of polymeric materials by rapid prototyping technologies for its use in the preparation of ceramic molds in the investment casting process. This work is focused on the development of a process for manufacturing patterns different from those that currently exist due to its hollow interior design, allowing its direct use in the fabrication of ceramic molds; avoiding cracking and fracture during the investment casting process, which is an important process for the foundry industry
Optimiranje postupka kalupljenja u ljevaÄkom procesu
Rapid prototyping is an important technique for manufacturing. This work refers to the manufacture of hollow patterns made of polymeric materials by rapid prototyping technologies for its use in the preparation of ceramic molds in the investment casting process. This work is focused on the development of a process for manufacturing patterns different from those that currently exist due to its hollow interior design, allowing its direct use in the fabrication of ceramic molds; avoiding cracking and fracture during the investment casting process, which is an important process for the foundry industry.Brzo razvijanje prototipa važna je proizvodna tehnika. Ovaj se rad odnosi na proizvodnju Å”upljih kalupa izraÄenih od polimerskih materijala pomoÄu tehnologija brzog razvijanja prototipa za uporabu u izradi keramiÄkih modela u postupku kalupljenja ljevaÄkog procesa. Ovaj rad je usmjeren na razvijanje postupka za proizvodnju kalupa drukÄijih od onih kakvi trenutno postoje i to zbog svoje Å”uplje unutarnje izvedbe Äime se omoguÄava izravna uporaba u izradi keramiÄkih modela te se izbje gava pucanje i lom tijekom postupka kalupljenja ljevaÄkog procesa koji predstavlja važan postupak u ljevaoniÄkoj industriji
On the critical end point in a two-flavor linear sigma model coupled to quarks
We use the linear sigma model coupled to quarks to explore the location of
the phase transition lines in the QCD phase diagram from the point of view of
chiral symmetry restoration at high temperature and baryon chemical potential.
We compute analytically the effective potential in the high- and
low-temperature approximations up to sixth order, including the contribution of
the ring diagrams to account for the plasma screening properties. We determine
the model parameters, namely, the couplings and mass-parameter, from conditions
valid at the first order phase transition at vanishing temperature and, using
the Hagedorn limiting temperature concept applied to finite baryon density, for
a critical baryochemical potential of order of the nucleon mass. We show that
when using the set of parameters thus determined, the second order phase
transition line (our proxy for the crossover transition) that starts at finite
temperature and zero baryon chemical potential converges to the line of first
order phase transitions that starts at zero temperature and finite baryon
chemical potential to determine the critical end point to lie in the region
5.02<\mu_B^{\mbox{CEP}}/T_c<5.18, 0.14, where
is the critical transition temperature at zero baryon chemical potential.Comment: 11 pages, 3 figures, discussion extended, explicit calculations
included in appendices and version accepted for publication in EPJ
Inverse magnetic catalysis from the properties of the QCD coupling in a magnetic field
We compute the vacuum one-loop quark-gluon vertex correction at zero
temperature in the presence of a magnetic field. From the vertex function we
extract the effective quark-gluon coupling and show that it grows with
increasing magnetic field strength. The effect is due to a subtle competition
between the color charge associated to gluons and the color charge associated
to quarks, the former being larger than the latter. In contrast, at high
temperature the effective thermo-magnetic coupling results exclusively from the
contribution of the color charge associated to quarks. This produces a decrease
of the coupling with increasing field strength. We interpret the results in
terms of a geometrical effect whereby the magnetic field induces, on average, a
closer distance between the (electrically charged) quarks and antiquarks. At
high temperature, since the effective coupling is proportional only to the
color charge associated to quarks, such proximity with increasing field
strength makes the effective coupling decrease due to asymptotic freedom. In
turn, this leads to a decreasing quark condensate. In contrast, at zero
temperature both the effective strong coupling and the quark condensate
increase with increasing magnetic field. This is due to the color charge
associated to gluons dominating over that associated to quarks, with both
having the opposite sign. Thus, the gluons induce a kind of screening of the
quark color charge, in spite of the quark-antiquark proximity. The implications
of these results for the inverse magnetic catalysis phenomenon are discussed.Comment: Expanded discussion, references added. Version to appear in Phys.
Lett.
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