10,870 research outputs found

### ERG and Schwinger-Dyson Equations - Comparison in formulations and applications --

The advantageous points of ERG in applications to non-perturbative analyses
of quantum field theories are discussed in comparison with the Schwinger-Dyson
equations. First we consider the relation between these two formulations
specially by examining the large N field theories. In the second part we study
the phase structure of dynamical symmetry breaking in three dimensional QED as
a typical example of the practical applications.Comment: 13 pages, 6 figures, references are added. Invited talk presented at
Second Conference on the Exact RG, Sept 18 - 22, 2000, Rome, Ital

### Enhancement of field renormalization in scalar theories via functional renormalization group

The flow equations of the Functional Renormalization Group are applied to the
O(N)-symmetric scalar theory, for N=1 and N=4, in four Euclidean dimensions,
d=4, to determine the effective potential and the renormalization function of
the field in the broken phase. In our numerical analysis, the infrared limit,
corresponding to the vanishing of the running momentum scale in the equations,
is approached to obtain the physical values of the parameters by extrapolation.
In the N=4 theory a non-perturbatively large value of the physical
renormalization of the longitudinal component of the field is observed. The
dependence of the field renormalization on the UV cut-off and on the bare
coupling is also investigated.Comment: 20 pages, 7 figures. To appear in Physical Review

### Two-dimensional Lattice Gross-Neveu Model with Wilson Fermion Action at Finite Temperature and Chemical Potential

We investigate the phase structure of the two-dimensional lattice Gross-Neveu
model formulated with the Wilson fermion action to leading order of 1/N
expansion. Structural change of the parity-broken phase under the influence of
finite temperature and chemical potential is studied. The connection between
the lattice phase structure and the chiral phase transition of the continuum
theory is clarified.Comment: 42 pages, 20 EPS figures, using REVTe

### Roles of axial anomaly on neutral quark matter with color superconducting phase

We investigate effects of the axial anomaly term with a chiral-diquark
coupling on the phase diagram within a two-plus-one-flavor Nambu-Jona-Lasinio
(NJL) model under the charge-neutrality and $\beta$-equilibrium constraints. We
find that when such constraints are imposed, the new anomaly term plays a quite
similar role as the vector interaction does on the phase diagram, which the
present authors clarified in a previous work. Thus, there appear several types
of phase structures with multiple critical points at low temperature $T$,
although the phase diagrams with intermediate-$T$ critical point(s) are never
realized without these constraints even within the same model Lagrangian. This
drastic change is attributed to an enhanced interplay between the chiral and
diquark condensates due to the anomaly term at finite temperature; the u-d
diquark coupling is strengthened by the relatively large chiral condensate of
the strange quark through the anomaly term, which in turn definitely leads to
the abnormal behavior of the diquark condensate at finite $T$, inherent to the
asymmetric quark matter. We note that the critical point from which the
crossover region extends to zero temperature appears only when the strength of
the vector interaction is larger than a critical value. We also show that the
chromomagnetic instability of the neutral asymmetric homogenous two-flavor
color superconducting(2CSC) phase is suppressed and can be even completely
cured by the enhanced diquark coupling due to the anomaly term and/or by the
vector interaction.Comment: 15 pages, 5 figures, typos corrected, new references and some
statements adde

### Nuclear Physics in a Susy Universe

We refine a previous zeroth order analysis of the nuclear properties of a
supersymmetric (susy) universe with standard model particle content plus
degenerate susy partners. No assumptions are made concerning the Higgs
structure except we assume that the degenerate fermion/sfermion masses are
non-zero. This alternate universe has been dubbed Susyria and it has been
proposed that such a world may exist with zero vacuum energy in the string
landscape.Comment: 8 pages, 1 figur

### Full QCD Light Hadron Spectrum and Quark Masses: Final Results from CP-PACS

We present the final results of the CP-PACS calculation of the light hadron
spectrum and quark masses with two flavors of dynamical quarks. Simulations are
made with a renormalization-group improved gauge action and a mean-field
improved clover quark action for sea quark masses corresponding to $m_{\rm
PS}/m_{\rm V} \approx 0.8$--0.6 and the lattice spacing $a=0.22$--0.11 fm. For
the meson spectrum in the continuum limit a clearly improved agreement with
experiment is observed compared to the quenched case, demonstrating the
importance of sea quark effects. For light quark masses we obtain
$m_{ud}^{\bar{MS}}(2GeV)=3.44^{+0.14}_{-0.22}$ MeV and
$m_s^{\bar{MS}}(2GeV)=88^{+4}_{-6}$ MeV ($K$-input) and
$m_s^{\bar{MS}}(2GeV)=90^{+5}_{-11}$ MeV ($\phi$-input), which are reduced by
about 25% compared to the values in quenched QCD.Comment: Lattice 2000 (Spectrum), 4 pages, 3 figure

### Renormalization flow of QED

We investigate textbook QED in the framework of the exact renormalization
group. In the strong-coupling region, we study the influence of
fluctuation-induced photonic and fermionic self-interactions on the
nonperturbative running of the gauge coupling. Our findings confirm the
triviality hypothesis of complete charge screening if the ultraviolet cutoff is
sent to infinity. Though the Landau pole does not belong to the physical
coupling domain owing to spontaneous chiral symmetry breaking (chiSB), the
theory predicts a scale of maximal UV extension of the same order as the Landau
pole scale. In addition, we verify that the chiSB phase of the theory which is
characterized by a light fermion and a Goldstone boson also has a trivial
Yukawa coupling.Comment: 4 pages, 1 figur

### Non-Perturbative Determination of $c_{\rm SW}$ in Three-flavor Dynamical QCD

We present a fully non-perturbative determination of the $O(a)$ improvement
coefficient $c_{\rm SW}$ in three-flavor dynamical QCD for the RG improved as
well as the plaquette gauge actions, using the Schr\"odinger functional scheme.
Results are compared with one-loop estimates at weak gauge coupling.Comment: 3 pages, 6 figures, Lattice2002(Improvement and Renormalization),
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