19 research outputs found
Renormalized effective actions for the O(N) model at next-to-leading order of the 1/N expansion
A fully explicit renormalized quantum action functional is constructed for
the O(N)-model in the auxiliary field formulation at next-to-leading order
(NLO) of the 1/N expansion. Counterterms are consistently and explicitly
derived for arbitrary constant vacuum expectation value of the scalar and
auxiliary fields. The renormalized NLO pion propagator is exact at this order
and satisfies Goldstone's theorem. Elimination of the auxiliary field sector at
the level of the functional provides with order N^0 accuracy the renormalized
effective action of the model in terms of the original variables. Alternative
elimination of the pion and sigma propagators provides the renormalized NLO
effective potential for the expectation values of the N-vector and of the
auxiliary field with the same accuracy.Comment: RevTeX4, 19 pages, 3 figures. Version published Phys. Rev.
A renormalized large-n solution of the U(n) x U(n) linear sigma model in the broken symmetry phase
Dyson-Schwinger equations for the U(n) x U(n) symmetric matrix sigma model
reformulated with two auxiliary fields in a background breaking the symmetry to
U(n) are studied in the so-called bare vertex approximation. A large n solution
is constructed under the supplementary assumption so that the scalar components
are much heavier than the pseudoscalars. The renormalizability of the solution
is investigated by explicit construction of the counterterms.Comment: RevTeX4, 14 pages, 2 figures. Version published in Phys. Rev.
Renormalized O(N) model at next-to-leading order of the 1/N expansion: Effects of the Landau pole
Apparently convergent contributions of resummed perturbative series at the next-to-leading order of the 1/N expansion in the O(N) model are reanalyzed in terms of renormalizability. Compared to our earlier article [G. Fejős et al., Phys. Rev. D 80, 025015 (2009)], an additional subtraction is performed. We show numerically that this is indispensable for diminishing the cutoff sensitivity of some integrals below the scale of the Landau pole. Following the method of our earlier article, an improved counterterm Lagrangian is constructed in the two-particle irreducible formalism, with and without the use of an auxiliary field formulation
Renormalisability of the 2PI-Hartree approximation of multicomponent scalar models in the broken symmetry phase
Non-perturbative renormalisation of a general class of scalar field theories is performed at the Hartree level truncation of the 2PI effective action in the broken symmetry regime. Renormalised equations are explicitly constructed for the one- and two-point functions. The non-perturbative counterterms are deduced from the conditions for the cancellation of the overall and the subdivergences in the complete Hartree-Dyson-Schwinger equations, with a transparent method. The procedure proposed in the present paper is shown to be equivalent to the iterative renormalisation method of Blaizot et al. [J.-P. Blaizot, E. Iancu, U. Reinosa, Nucl. Phys. A 736 (2004) 149, hep ph/0312085]
Non-perturbative construction of counterterms for 2PI-approximation
A concise method is presented for the non-perturbative computation of the
counterterms renormalising 2PI-actions. The procedure is presented for a real
scalar field up to lambda^2 order in the skeleton truncation of Gamma_2PI with
respect to the self-coupling, and in a constant symmetry breaking background.
The method is easily generalizable to field theories with arbitrary global
symmetry.Comment: 4 pages, poster presented at Strong and Electroweak Matter
(SEWM2008), Amsterdam,August 25-29 200
Mesonic and nucleon fluctuation effects at finite baryon density
Mesonic and nucleon fluctuation effects are investigated in medium. We couple
the nucleon field to the flavor meson model and investigate the finite
temperature and density behavior of the system, in particular, the axial
anomaly function. Somewhat contrary to earlier expectations we find that it
tends to strengthen at finite density. At lower temperatures nucleon density
fluctuations can cause a relative difference in the axial anomaly of
about . This has important consequences on the mesonic spectra,
especially on the system, as we observe no drop in the
mass as a function of the baryochemical potential, irrespective of the
temperature. Based on the details of chiral symmetry restoration, it is argued
that there has to be a competition between underlying QCD effects of the
anomaly and fluctuations of the low energy hadronic degrees of freedom, and the
fate of the coefficient should be decided by taking into account both
effects simultaneously.Comment: 9 pages, 4 figures, matches published versio
The Impact of EU Norms and Policies on Consumer Protection Enforcement in Serbia
Pursuant to its 2008 Stabilization and Association Agreement governing the process of EU integration, Serbia is obliged to align its consumer protection standards (including those related to enforcement) with those of the EU. This article considers the overall approach to enforcement of consumer law in Serbia, focussing in particular on the extent to which EU enforcement principles have been successfully exported to Serbia and whether the goals of EU consumer policy have been achieved. It argues that the incorporation of EU norms has brought fundamental changes to Serbian enforcement mechanisms at a formal level, such as in relation to mediation processes as well as the introduction of injunctions for the protection of collective consumer interests. In practice, however, the impact of this incorporation is quite limited. A number of factors that restrict the practical effectiveness of the mediation processes and injunctions required by EU law are explored in the article, including weak sanctions, excessive reliance on poorly resourced consumer organizations, absence of a business culture of compliance or a sophisticated and determined consumer protection enforcement culture sufficiently grounded in expertise, as well as an overarching political, legislative, and institutional instability. These factors also undermine the general aim of EU policy to achieve effective consumer protection enforcement in the Serbian context
Achieving Safety and Affordability in the UK Payday Loans Market
In the aftermath of the global financial crisis, financial regulation and supervision has been significantly reformed in the UK. As an important part of this reform, consumer credit, including payday loans, has been transferred to the new conduct of business regulator and supervisor, the Financial Conduct Authority. This paper considers the key rules on responsible lending and product regulation, introduced to protect the payday loans consumers. It shows that the responsible lending regime now reduces the risk that payday loans will be given to those who cannot afford the high costs involved, although responsible lending will only be fully effective if credit reference agencies hold up-to-date and correct information. Product regulation, in the form of a rollover restriction and a price cap, should make payday loans cheaper and safer for those who do use them, although, for the price cap to be most effective, steps must be taken to enhance price competition in the space below the cap. Finally, it is shown that firms are now subject to interventionist, rigorous, and consumer-centric supervision, which seems to stand a good chance of securing compliance with the new rules