Higher derivative terms in the effective action of certain Yang-Mills theories can be severely co... more Higher derivative terms in the effective action of certain Yang-Mills theories can be severely constrained by supersymmetry. We show that requiring sixteen supersymmetries in quantum mechanical gauge theory determines the v 6 term in the effective action. Even the numerical coefficient of the v 6 term is fixed in terms of lower derivative terms in the effective action. 6/98 1 paban@sns.ias.edu
Acknowledgments I wish to thank the multitudes of people who helped me. Vadim Kaplunovsky was a s... more Acknowledgments I wish to thank the multitudes of people who helped me. Vadim Kaplunovsky was a superb advisor, paying attention at each step of my intel- lectual progress, with lot of patience. Sonia Paban, Willy Fischler and Steven Weinberg and Vadim taught me excellent classes, and Jacques Distler always brought clever insights in our group discussion and incentivated me to
We study the time evolution of unstable dS p × S q configurations with flux in theories of gravit... more We study the time evolution of unstable dS p × S q configurations with flux in theories of gravity with a cosmological constant. For certain values of the flux, we identify a stable configuration to which these unstable solutions flow. For other values of the flux the sphere wants to decompactify, regardless of the sign of the initial perturbation.
We study the extent to which the gauge symmetry of abelian Yang-Mills can be deformed under two c... more We study the extent to which the gauge symmetry of abelian Yang-Mills can be deformed under two conditions: first, that the deformation depend on a two-form scale. Second, that the deformation preserve supersymmetry. We show that (up to a single parameter) the only allowed deformation is the one determined by the star product. We then consider the supersymmetry algebra satisfied by NCYM expressed in commutative variables. The algebra is peculiar since the supercharges are not gauge-invariant. However, the action, expressed in commutative variables, appears to be quadratic in fermions to all orders in θ.
We study noncommutative field theories at finite temperature to learn more about the degrees of f... more We study noncommutative field theories at finite temperature to learn more about the degrees of freedom in the non-planar sector of these systems. We find evidence for winding states. At temperatures for which the thermal wavelength is smaller than the noncommutativity scale, there is a drastic reduction of the degrees of freedom in the non-planar sector. In this regime, the non-planar sector has thermodynamics resembling that of a 1 + 1 dimensional field theory.
Using a formalism developed to include collective coordinates, we calculate the contributions to ... more Using a formalism developed to include collective coordinates, we calculate the contributions to S-matrix elements due to off-shell D-branes in a string coupling expansion.
We derive several no-go theorems in the context of massive type IIA string theory compactified to... more We derive several no-go theorems in the context of massive type IIA string theory compactified to four dimensions in a way that, in the absence of fluxes, preserves N = 1 supersymmetry. Our derivation is based on the dilaton, Kähler and complex structure moduli dependence of the potential of the four-dimensional effective field theory, that is generated by the presence of D6-branes, O6-planes, RR fluxes, NSNS 3-form flux, and geometric fluxes. To demonstrate the usefulness of our theorems, we apply them to the most commonly studied class of toroidal orientifolds. We show that for all but two of the models in this class the slow-roll parameter ǫ is bounded from below by numbers of order unity as long as the fluxes satisfy the Bianchi identities, ruling out slow-roll inflation and even the existence of de Sitter extrema in these models. For the two cases that avoid the no-go theorems, we provide some details of our numerical studies, demonstrating that small ǫ can indeed be achieved. We stress that there seems to be an η-problem, suggesting that none of the models in this class are viable from a cosmological point of view at least at large volume, small string coupling, and leading order in the α ′ -expansion.
We consider quantum mechanical gauge theories with sixteen supersymmetries. The Hamiltonians or L... more We consider quantum mechanical gauge theories with sixteen supersymmetries. The Hamiltonians or Lagrangians characterizing these theories can contain higher derivative terms. In the operator approach, we show that the free theory is essentially the unique abelian theory with up to four derivatives in the following sense: any small deformation of the free theory, which preserves the supersymmetries, can be gauged away by a unitary conjugation. We also present a method for deriving constraints on terms appearing in an effective Lagrangian. We apply this method to the effective Lagrangian describing the dynamics of two well-separated clusters of D0-branes. As a result, we prove a nonrenormalization theorem for the v 4 interaction.
Journal of Cosmology and Astroparticle Physics, 2012
We investigate possible signatures of a pre-inflationary anisotropic phase in twopoint and three-... more We investigate possible signatures of a pre-inflationary anisotropic phase in twopoint and three-point correlation functions of the curvature perturbation for high-momentum modes which exit the horizon after isotropization. In this momentum regime, the early time dynamics admits a WKB description and the late time dynamics can be described in terms of a non-Bunch Davies vacuum state which encodes the information of initial anisotropy in the background spacetime. We compute the bi-spectrum for curvature perturbation in a canonical single-field action with and without higher derivative operators. We show that the bi-spectrum at late times, in either case, is enhanced for a flattened triangle configuration as well as a squeezed triangle configuration and compute the corresponding f N L parameters. The angular dependence and the particular momentum dependence of the f N L parameter appear as distinctive features of background anisotropy at early times.
Zeitschrift für Physik C Particles and Fields, 1987
We study the effective potential of three perturbatively nonrenormalizable scalar field theories,... more We study the effective potential of three perturbatively nonrenormalizable scalar field theories, (?f4+gf6)3+,?f4+14 and?f5+14, by nonperturbative methods. The requirements of existence, finiteness and interaction seem to demand such a weak nonrenormalizable interaction that no or little effects remain at the quantum level.
We show that the four derivative terms in the effective action of three-dimensional N=8 Yang-Mill... more We show that the four derivative terms in the effective action of three-dimensional N=8 Yang-Mills theory are determined by supersymmetry. These terms receive both perturbative and non-perturbative corrections. Using our technique for constraining the effective action, we are able to determine the exact form of the eight fermion terms in the supersymmetric completion of the F 4 term, including all instanton corrections. As a consequence, we argue that the integral of the Euler density over k monopole moduli space in SU (2) Yang-Mills is determined by our non-renormalization theorem for all values of k.
Higher derivative terms in the effective action of certain Yang-Mills theories can be severely co... more Higher derivative terms in the effective action of certain Yang-Mills theories can be severely constrained by supersymmetry. We show that requiring sixteen supersymmetries in quantum mechanical gauge theory determines the v 6 term in the effective action. Even the numerical coefficient of the v 6 term is fixed in terms of lower derivative terms in the effective action. 6/98 1 paban@sns.ias.edu
Acknowledgments I wish to thank the multitudes of people who helped me. Vadim Kaplunovsky was a s... more Acknowledgments I wish to thank the multitudes of people who helped me. Vadim Kaplunovsky was a superb advisor, paying attention at each step of my intel- lectual progress, with lot of patience. Sonia Paban, Willy Fischler and Steven Weinberg and Vadim taught me excellent classes, and Jacques Distler always brought clever insights in our group discussion and incentivated me to
We study the time evolution of unstable dS p × S q configurations with flux in theories of gravit... more We study the time evolution of unstable dS p × S q configurations with flux in theories of gravity with a cosmological constant. For certain values of the flux, we identify a stable configuration to which these unstable solutions flow. For other values of the flux the sphere wants to decompactify, regardless of the sign of the initial perturbation.
We study the extent to which the gauge symmetry of abelian Yang-Mills can be deformed under two c... more We study the extent to which the gauge symmetry of abelian Yang-Mills can be deformed under two conditions: first, that the deformation depend on a two-form scale. Second, that the deformation preserve supersymmetry. We show that (up to a single parameter) the only allowed deformation is the one determined by the star product. We then consider the supersymmetry algebra satisfied by NCYM expressed in commutative variables. The algebra is peculiar since the supercharges are not gauge-invariant. However, the action, expressed in commutative variables, appears to be quadratic in fermions to all orders in θ.
We study noncommutative field theories at finite temperature to learn more about the degrees of f... more We study noncommutative field theories at finite temperature to learn more about the degrees of freedom in the non-planar sector of these systems. We find evidence for winding states. At temperatures for which the thermal wavelength is smaller than the noncommutativity scale, there is a drastic reduction of the degrees of freedom in the non-planar sector. In this regime, the non-planar sector has thermodynamics resembling that of a 1 + 1 dimensional field theory.
Using a formalism developed to include collective coordinates, we calculate the contributions to ... more Using a formalism developed to include collective coordinates, we calculate the contributions to S-matrix elements due to off-shell D-branes in a string coupling expansion.
We derive several no-go theorems in the context of massive type IIA string theory compactified to... more We derive several no-go theorems in the context of massive type IIA string theory compactified to four dimensions in a way that, in the absence of fluxes, preserves N = 1 supersymmetry. Our derivation is based on the dilaton, Kähler and complex structure moduli dependence of the potential of the four-dimensional effective field theory, that is generated by the presence of D6-branes, O6-planes, RR fluxes, NSNS 3-form flux, and geometric fluxes. To demonstrate the usefulness of our theorems, we apply them to the most commonly studied class of toroidal orientifolds. We show that for all but two of the models in this class the slow-roll parameter ǫ is bounded from below by numbers of order unity as long as the fluxes satisfy the Bianchi identities, ruling out slow-roll inflation and even the existence of de Sitter extrema in these models. For the two cases that avoid the no-go theorems, we provide some details of our numerical studies, demonstrating that small ǫ can indeed be achieved. We stress that there seems to be an η-problem, suggesting that none of the models in this class are viable from a cosmological point of view at least at large volume, small string coupling, and leading order in the α ′ -expansion.
We consider quantum mechanical gauge theories with sixteen supersymmetries. The Hamiltonians or L... more We consider quantum mechanical gauge theories with sixteen supersymmetries. The Hamiltonians or Lagrangians characterizing these theories can contain higher derivative terms. In the operator approach, we show that the free theory is essentially the unique abelian theory with up to four derivatives in the following sense: any small deformation of the free theory, which preserves the supersymmetries, can be gauged away by a unitary conjugation. We also present a method for deriving constraints on terms appearing in an effective Lagrangian. We apply this method to the effective Lagrangian describing the dynamics of two well-separated clusters of D0-branes. As a result, we prove a nonrenormalization theorem for the v 4 interaction.
Journal of Cosmology and Astroparticle Physics, 2012
We investigate possible signatures of a pre-inflationary anisotropic phase in twopoint and three-... more We investigate possible signatures of a pre-inflationary anisotropic phase in twopoint and three-point correlation functions of the curvature perturbation for high-momentum modes which exit the horizon after isotropization. In this momentum regime, the early time dynamics admits a WKB description and the late time dynamics can be described in terms of a non-Bunch Davies vacuum state which encodes the information of initial anisotropy in the background spacetime. We compute the bi-spectrum for curvature perturbation in a canonical single-field action with and without higher derivative operators. We show that the bi-spectrum at late times, in either case, is enhanced for a flattened triangle configuration as well as a squeezed triangle configuration and compute the corresponding f N L parameters. The angular dependence and the particular momentum dependence of the f N L parameter appear as distinctive features of background anisotropy at early times.
Zeitschrift für Physik C Particles and Fields, 1987
We study the effective potential of three perturbatively nonrenormalizable scalar field theories,... more We study the effective potential of three perturbatively nonrenormalizable scalar field theories, (?f4+gf6)3+,?f4+14 and?f5+14, by nonperturbative methods. The requirements of existence, finiteness and interaction seem to demand such a weak nonrenormalizable interaction that no or little effects remain at the quantum level.
We show that the four derivative terms in the effective action of three-dimensional N=8 Yang-Mill... more We show that the four derivative terms in the effective action of three-dimensional N=8 Yang-Mills theory are determined by supersymmetry. These terms receive both perturbative and non-perturbative corrections. Using our technique for constraining the effective action, we are able to determine the exact form of the eight fermion terms in the supersymmetric completion of the F 4 term, including all instanton corrections. As a consequence, we argue that the integral of the Euler density over k monopole moduli space in SU (2) Yang-Mills is determined by our non-renormalization theorem for all values of k.
Uploads
Papers by Sonia Paban