The strong coupling regime of twelve flavors QCD

We summarize the results recently reported in Ref.[1] [A. Deuzeman, M.P. Lombardo, T. Nunes da Silva and E. Pallante,"The bulk transition of QCD with twelve flavors and the role of improvement"] for the SU(3) gauge theory with Nf=12 fundamental flavors, and we add some numerical evidence and theoretical discussion. In particular, we study the nature of the bulk transition that separates a chirally broken phase at strong coupling from a chirally restored phase at weak coupling. When a non-improved action is used, a rapid crossover is observed at small bare quark masses. Our results confirm a first order nature for this transition, in agreement with previous results we obtained using an improved action. As shown in Ref.[1], when improvement of the action is used, the transition is preceded by a second rapid crossover at weaker coupling and an exotic phase emerges, where chiral symmetry is not yet broken. This can be explained [1] by the non hermiticity of the improved lattice Transfer matrix, arising from the competition of nearest-neighbor and non-nearest neighbor interactions, the latter introduced by improvement and becoming increasingly relevant at strong coupling and coarse lattices. We further comment on how improvement may generally affect any lattice system at strong coupling, be it graphene or non abelian gauge theories inside or slightly below the conformal window.Comment: 7 pages, 7 figures, Proceedings of the 30th International Symposium on Lattice Field Theory, June 24 - 29, 2012, Cairns, Australi

Conformal or Confining

We present a lattice study of the phase transitions at zero and nonzero temperature for the $SU(3)$ gauge theory with a varying number of flavours $N_f$ in the fundamental representation of the gauge group. We show that all results are consistent with a lower edge of the conformal window between $N_f=8$ and $N_f=6$. A lower edge in this interval is in remarkable agreement with perturbation theory and recent large-$N$ arguments. .Comment: 5 pages, 5 figures. New results added, conclusions strengthened. Scalar glueball now treated in a separate articl

The scalar glueball operator, the a-theorem, and the onset of conformality

We show that the anomalous dimension $\gamma_G$ of the scalar glueball operator contains information on the mechanism that leads to the onset of conformality at the lower edge of the conformal window in a non-Abelian gauge theory. In particular, it distinguishes whether the merging of an UV and an IR fixed point -- the simplest mechanism associated to a conformal phase transition and preconformal scaling -- does or does not occur. At the same time, we shed light on new analogies between QCD and its supersymmetric version. In SQCD, we derive an exact relation between $\gamma_G$ and the mass anomalous dimension $\gamma_m$, and we prove that the SQCD exact beta function is incompatible with merging as a consequence of the $a$-theorem; we also derive the general conditions that the latter imposes on the existence of fixed points, and prove the absence of an UV fixed point at nonzero coupling above the conformal window of SQCD. Perhaps not surprisingly, we then show that an exact relation between $\gamma_G$ and $\gamma_m$, fully analogous to SQCD, holds for the massless Veneziano limit of large-N QCD. We argue, based on the latter relation, the $a$-theorem, perturbation theory and physical arguments, that the incompatibility with merging may extend to QCD.Comment: 11 pages, 2 figures; some imprecisions in the notation fixed, version published in PL

Bulk transitions of twelve flavor QCD and UA(1)U_A(1) symmetry

We present an update on our ongoing study on the nature of the bulk transition observed at strong coupling in the SU(3) gauge theory with N_f = 12 flavors in the fundamental representation. We show evidence that there is a first order chiral symmetry breaking bulk transition separating a region at weak coupling where chiral symmetry is restored from a region at strong coupling where chiral symmetry is broken. We also discuss hints of a separate partial restoration of U_A(1) at weaker coupling. The results are in agreement with restoration of conformality in non abelian gauge theories as the number of flavors is increased.Comment: 7 pages, 10 figures, XXIX International Symposium on Lattice Field Theor

Avaliação in vitro da atividade leishmanicida de membranas de gelatina contendo ácido úsnico encapsulado em lipossomo

Localized Cutaneous Leishmaniasis is one of the most common clinical forms of Leishmaniasis, characterized by the presence of ulcer-crusted lesions well localized on the body surface. In Brazil, the main species associated with this form is Leishmania braziliensis. For its treatment, the Pentavalent Antimonials, which requires parenteral use and are associated with important systemic toxicity, are used as the first line drugs. In addition, in recent years there has been an increasing in parasites resistant to this class of drugs. Thus, there is a global stimulus for the development of a new form of localized treatment that has similar efficacy to the traditional one, but with fewer associated side effects. In this context, the Liposome-encapsulated Usnic Acid Gelatine Membrane System presents as a viable treatment proposal, due to the anti-inflammatory, anti-oxidant, healing and leishmanicidal abilities due to this composition combination. Because of what has been exposed, the present work aimed to evaluate the in vitro potential of this system as a new form of treatment for Localized Cutaneous Leishmaniasis caused by L. braziliensis isolates. For this, the parasite viability was evaluated by direct counting after the exposure of the parasites with the proposed treatment. A significant reduction in the parasite viability of those treated with the present system was observed according to a dose-dependent effect of the Usnic Acid concentration. In addition, it was found that this form of treatment showed an irreversible character, in which the cultures treated with this system, even after the suspension of the treatment, presented less parasitic viability. Based on the results of the in vitro experiments, it is possible to affirm that the Liposome-encapsulated Usnic Acid Gelatine Membrane System presents potential to serve as a therapeutic option for Localized Cutaneous Leishmaniasis caused by parasites of the species L. braziliensisA Leishmaniose Cutânea Localizada é uma das formas clínicas mais comuns de Leishmaniose, sendo caracterizada pela presença de lesões ulcero-crostosas bem localizadas e delimitadas na superfície corpórea. No Brasil, a principal espécie associada a esta forma é a Leishmania braziliensis. Para seu tratamento, utilizam-se como primeira linha os Antimoniais Pentavalentes, que são de uso parenteral e associados a importante toxicidade sistêmica. Além disso, destaca-se nos últimos anos, um aumento cada vez maior de parasitos resistentes a esta classe de drogas. Dessa forma, tem-se o estímulo para o desenvolvimento de uma nova forma de tratamento localizada que possua eficácia semelhante ao tradicional, mas com menos efeitos colaterais associados. Neste contexto, o Sistema de Membranas de Gelatina contendo Ácido Úsnico encapsulado em lipossomo apresenta-se como uma proposta viável de tratamento, em decorrência das capacidades anti-inflamatória, antioxidante, cicatrizante e leishmanicida associadas a essa combinação de composto. Diante do exposto, o presente trabalho teve como objetivo avaliar o potencial in vitro deste sistema como uma nova forma de tratamento para Leishmaniose Cutânea Localizada causadas por isolados de L. braziliensis. Para isso, foi avaliada a viabilidade parasitária através de contagem direta após a exposição dos parasitos com o tratamento proposto. Observou-se uma redução significativa da viabilidade parasitária daqueles tratados com o presente sistema de acordo com um efeito dose dependente da concentração do Ácido Úsnico. Ademais, constatou-se que esta forma de tratamento mostrou um caráter irreversível, em que as culturas tratadas com este sistema, mesmo após a suspensão do tratamento, apresentaram menor viabilidade parasitária. Frente os resultados dos experimentos in vitro realizados, é possível afirmar que o Sistema de Membranas de Gelatina contendo Ácido Úsnico encapsulado em lipossomo apresenta potencial de servir como uma opção terapêutica para Leishmaniose Cutânea Localizada causada por parasitos da espécie L. braziliensisAracaj