Species doubling and effective Lagrangians

Coupling gauge fields to the chiral currents from an effective Lagrangian for pseudoscalar mesons naturally gives rise to a species doubling phenomenon similar to that seen with fermionic fields in lattice gauge theory.Comment: 4 pages, uses espcrc.sty. Talk presented at LATTICE96(poster

CPT and Other Symmetries in String/M Theory

We initiate a search for non-perturbative consistency conditions in M theory. Some non-perturbative conditions are already known in Type I theories; we review these and search for others. We focus principally on possible anomalies in discrete symmetries. It is generally believed that discrete symmetries in string theories are gauge symmetries, so anomalies would provide evidence for inconsistencies. Using the orbifold cosmic string construction, we give some evidence that the symmetries we study are gauged. We then search for anomalies in discrete symmetries in a variety of models, both with and without supersymmetry. In symmetric orbifold models we extend previous searches, and show in a variety of examples that all anomalies may be canceled by a Green-Schwarz mechanism. We explore some asymmetric orbifold constructions and again find that all anomalies may be canceled this way. Then we turn to Type IIB orientifold models where it is known that even perturbative anomalies are non-universal. In the examples we study, by combining geometric discrete symmetries with continuous gauge symmetries, one may define non-anomalous discrete symmetries already in perturbation theory; in other cases, the anomalies are universal. Finally, we turn to the question of CPT conservation in string/M theory. It is well known that CPT is conserved in all string perturbation expansions; here in a number of examples for which a non-perturbative formulation is available we provide evidence that it is conserved exactly.Comment: 52 pages.1 paragraph added in introduction to clarify assumption

Topology of SU(N) gauge theories at T=0 and T=Tc

We calculate the topological charge density of SU(N) lattice gauge fields for values of N up to N=8. Our T=0 topological susceptibility appears to approach a finite non-zero limit at N=infinity that is consistent with earlier extrapolations from smaller values of N. Near the deconfining temperature Tc we are able to investigate separately the confined and deconfined phases, since the transition is quite strongly first order. We find that the topological susceptibility of the confined phase is always very similar to that at T=0. By contrast, in the deconfined phase at larger N there are no topological fluctuations except for rare, isolated and small instantons. This shows that as N->infinity the large-T suppression of large instantons and the large-N suppression of small instantons overlap, even at T=Tc, so as to suppress all topological fluctuations in the deconfined phase. In the confined phase by contrast, the size distribution is much the same at all T, becoming more peaked as N grows, suggesting that D(rho) is proportional to a delta function at N=infinity, centered on rho close to 1/Tc.Comment: 31 page

On the Possibility of Large Axion Decay Constants

The decay constant of the QCD axion is required by observation to be small compared to the Planck scale. In theories of "natural inflation," and certain proposed anthropic solutions of the cosmological constant problem, it would be interesting to obtain a large decay constant for axion-like fields from microscopic physics. String theory is the only context in which one can sensibly address this question. Here we survey a number of periodic fields in string theory in a variety of string vacua. In some examples, the decay constant can be parameterically larger than the Planck scale but the effective action then contains appreciable harmonics of order $f_A/M_p$. As a result, these fields are no better inflaton candidates than Planck scale axions.Comment: 17 pages, no figures, minor change mad

Un estudio comparativo de las respuestas a cumplidos producidas por hablantes del español de México y del Inglés de Irlanda

The purpose of the present study is to compare the compliment responses (CRs) provided by 60 native Mexican Spanish speakers and 60 Irish English native speakers. Using a discourse completion task, 1080 responses were analyzed based on Herbert’s (1989) and Nelson, El Bakary and Al-Batal’s (1993) taxonomy. Findings suggest the existence of cross-cultural similarities in Irish and Mexican CRs in the frequency of deflecting comments and the mechanisms that are used to redirect the praise force. Second, the two languages differ in important ways. In responding to compliments, Irish recipients are much more likely than Mexican speakers to use a single strategy when formulating CRs. The findings further show that social factors (social distance, social power, gender, and the topic of the compliment) in both Mexican and Irish society seem to be crucial parameters in the formulation and acceptance or rejection of a compliment.El propósito del presente estudio fue comparar las respuestas a cumplidos (RC) producidas por 60 hablantes nativos de español de México y 60 hablantes nativos de inglés de Irlanda. La base de datos se recabó mediante un instrumento llamado discourse completion task, el cual permitió obtener 1080 respuestas, las cuales se analizaron usando la taxonomía propuesta por Herbert (1989) y Nelson, El Bakary y Al-Batal (1993). Los resultados muestran tres aspectos importantes. El primer resultado sugiere la existencia de similitudes entre las RCs irlandesas y mexicanas con respecto al empleo de estrategias de mitigación con el propósito de desviar los comentarios y redirigir el cumplido. En segundo lugar, los dos grupos difieren en aspectos importantes. Al responder a los cumplidos, los destinatarios irlandeses son mucho más propensos que los hablantes mexicanos a usar una sola estrategia, mientras que los mexicanos utilizan dos o más para formular las RCs. Los resultados muestran además que los factores sociales (distancia social, poder social, género y el tema del cumplido) en la sociedad mexicana y en la irlandesa parecen ser parámetros cruciales en la formulación y aceptación o rechazo de un cumplido

Some Explorations in Holomorphy

In supersymmetric theories, one can obtain striking results and insights by exploiting the fact that the superpotential and the gauge coupling function are holomorphic functions of the model parameters. The precise meaning of this holomorphy is subtle, and has been explained most clearly by Shifman and Vainshtein, who have stressed the role of the Wilsonian effective action. In this note, we elaborate on the Shifman-Vainshtein program, applying it to examples in grand unification, supersymmetric QCD and string theory. We stress that among the ``model parameters" are the cutoffs used to define the Wilsonian action itself, and that generically these must be defined in a field-dependent manner to obtain holomorphic results.Comment: (26 pages and 2 figures as one uuencoded PostScript file) SCIPP 94/11. Important references added; typos correcte

Effects of D-instantons

Scattering of fundamental states of type IIB supergravity and superstring theory is discussed at low orders in perturbation theory in the background of a D-instanton. The integration over fermionic zero modes in both the low energy supergravity and in the string theory leads to explicit nonperturbative terms in the effective action. These include a single instanton correction to the known tree-level and one-loop $R^4$ interactions. The `spectrum' of multiply-charged D-instantons is deduced by T-duality in nine dimensions from multiply-wound world-lines of marginally-bound D-particles. This, and other clues, lead to a conjectured SL(2,Z) completion of the $R^4$ terms which suggests that they are not renormalized by perturbative corrections in the zero-instanton sector beyond one loop. The string theory unit-charged D-instanton gives rise to point-like effects in fixed-angle scattering, raising unresolved issues concerning distance scales in superstring theory.Comment: 31 pages, 6 figures, Latex, Reference added, corrected coefficients in expansion of generalized Eisenstein series in equation 66 now agree with hep-th/970414

Modeling Time's Arrow

Quantum gravity, the initial low entropy state of the Universe, and the problem of time are interlocking puzzles. In this article, we address the origin of the arrow of time from a cosmological perspective motivated by a novel approach to quantum gravitation. Our proposal is based on a quantum counterpart of the equivalence principle, a general covariance of the dynamical phase space. We discuss how the nonlinear dynamics of such a system provides a natural description for cosmological evolution in the early Universe. We also underscore connections between the proposed non-perturbative quantum gravity model and fundamental questions in non-equilibrium statistical physics.Comment: 18 page

A Magnetic Monopole in Pure SU(2) Gauge Theory

The magnetic monopole in euclidean pure SU(2) gauge theory is investigated using a background field method on the lattice. With Monte Carlo methods we study the mass of the monopole in the full quantum theory. The monopole background under the quantum fluctuations is induced by imposing fixed monopole boundary conditions on the walls of a finite lattice volume. By varying the gauge coupling it is possible to study monopoles with scales from the hadronic scale up to high energies. The results for the monopole mass are consistent with a conjecture we made previously in a realization of the dual superconductor hypothesis of confinement.Comment: 33 pages uufiles-compressed PostScript including (all) 12 figures, preprint numbers ITFA-93-19 (Amsterdam), OUTP-93-21P (Oxford), DFTUZ/93/23 (Zaragoza

Note on Discrete Gauge Anomalies

We consider the probem of gauging discrete symmetries. All valid constraints on such symmetries can be understood in the low energy theory in terms of instantons. We note that string perturbation theory often exhibits global discrete symmetries, which are broken non-perturbatively.Comment: 9 page