Unquenched Numerical Stochastic Perturbation Theory

The inclusion of fermionic loops contribution in Numerical Stochastic Perturbation Theory (NSPT) has a nice feature: it does not cost so much (provided only that an FFT can be implemented in a fairly efficient way). Focusing on Lattice SU(3), we report on the performance of the current implementation of the algorithm and the status of first computations undertaken.Comment: 3 pages, 3 figures, Lattice2002(algor

Two and three loops computations of renormalization constants for lattice QCD

Renormalization constants can be computed by means of Numerical Stochastic Perturbation Theory to two/three loops in lattice perturbation theory, both in the quenched approximation and in the full (unquenched) theory. As a case of study we report on the computation of renormalization constants of the propagator for Wilson fermions. We present our unquenched (N_f=2) computations and compare the results with non perturbative determinations.Comment: Lattice2004(improv), 3 pages, 4 figure

Associative responsibilities and political obligation

In this paper I criticise an influential version of associative theory of political obligation and I offer a reformulation of the theory in ‘quasi-voluntarist’ terms. I argue that although unable by itself to solve the problem of political obligation, my quasi-voluntarist associative model can play an important role in solving this problem. Moreover, the model teaches us an important methodological lesson about the way in which we should think about the question of political obligation. Finally, I suggest that the quasi-voluntarist associative model is particularly attractive because it manages to combine the main thrust of the traditional associative view with the most attractive feature of transactional theories, while avoiding at the same time the main problems that afflict each of these two approaches

A TQFT of Intersection Numbers on Moduli Spaces of Admissible Covers

We construct a two-level weighted TQFT whose structure coefficents are equivariant intersection numbers on moduli spaces of admissible covers. Such a structure is parallel (and strictly related) to the local Gromov-Witten theory of curves of Bryan-Pandharipande. We compute explicitly the theory using techniques of localization on moduli spaces of admissible covers of a parametrized projective line. The Frobenius Algebras we obtain are one parameter deformations of the class algebra of the symmetric group S_d. In certain special cases we are able to produce explicit closed formulas for such deformations in terms of the representation theory of S_d

State legitimacy and self-defence

In this paper I outline a theory of legitimacy that grounds the state’s right to rule on a natural duty not to harm others. I argue that by refusing to enter the state, anarchists expose those living next to them to the dangers of the state of nature, thereby posing an unjust threat. Since we have a duty not to pose unjust threats to others, anarchists have a duty to leave the state of nature and enter the state. This duty correlates to a claim-right possessed by those living next to them, who also have a right to act in self-defence to enforce this obligation. This argument, if successful, would be particularly attractive, as it provides an account of state legitimacy without importing any normative premises that libertarians would reject

Crimes against humanity and the limits of international criminal law

Crimes against humanity are supposed to have a collective dimension with respect both to their victims and their perpetrators. According to the orthodox view, these crimes can be committed by individuals against individuals, but only in the context of a widespread or systematic attack against the group to which the victims belong. In this paper I offer a new conception of crimes against humanity and a new justification for their international prosecution. This conception has important implications as to which crimes can be justifiably prosecuted and punished by the international community. I contend that the scope of the area of international criminal justice that deals with basic human rights violations should be wider than is currently acknowledged, in that it should include some individual violations of human rights, rather than only violations that have a collective dimension

Hodge-type integrals on moduli spaces of admissible covers

We study Hodge Integrals on Moduli Spaces of Admissible Covers. Motivation for this work comes from Bryan and Pandharipande's recent work on the local GW theory of curves, where analogouos intersection numbers, computed on Moduli Spaces of Relative Stable Maps, are the structure coefficients for a Topological Quantum Field Theory. Admissible Covers provide an alternative compactification of the Moduli Space of Maps, that is smooth and doesn't contain boundary components of excessive dimension. A parallel, yet different, TQFT, can then be constructed. In this paper we compute, using localization, the relevant Hodge integrals for admissible covers of a pointed sphere of degree 2 and 3, and formulate a conjecture for general degree. In genus 0, we recover the well-known Aspinwall Morrison formula in GW theory.Comment: This is the version published by Geometry & Topology Monographs on 21 September 200

Numerical Stochastic Perturbation Theory. Convergence and features of the stochastic process. Computations at fixed (Landau) Gauge

Concerning Numerical Stochastic Perturbation Theory, we discuss the convergence of the stochastic process (idea of the proof, features of the limit distribution, rate of convergence to equilibrium). Then we also discuss the expected fluctuations in the observables and give some idea to reduce them. In the end we show that also computation of quantities at fixed (Landau) Gauge is now possible.Comment: 3 pages. Contributed to 17th International Symposium on Lattice Field Theory (LATTICE 99), Pisa, Italy, 29 Jun - 3 Jul 199

3-d lattice SU(3) free energy to four loops

We report on the perturbative computation of the 3d lattice Yang-Mills free energy to four loops by means of Numerical Stochastic Perturbation Theory. The known first and second orders have been correctly reproduced; the third and fourth order coefficients are new results and the known logarithmic IR divergence in the fourth order has been correctly identified. Progress is being made in switching to the gluon mass IR regularization and the related inclusion of the Faddeev-Popov determinant.Comment: Lattice2004(non-zero), 3 pages, 2 figure