Reducing full one-loop amplitudes to scalar integrals at the integrand level

Science.gov (United States)

Ossola, Giovanni; Papadopoulos, Costas G.; Pittau, Roberto

2007-02-01

We show how to extract the coefficients of the 4-, 3-, 2- and 1-point one-loop scalar integrals from the full one-loop amplitude of arbitrary scattering processes. In a similar fashion, also the rational terms can be derived. Basically no information on the analytical structure of the amplitude is required, making our method appealing for an efficient numerical implementation.

Reducing full one-loop amplitudes to scalar integrals at the integrand level

International Nuclear Information System (INIS)

Ossola, Giovanni; Papadopoulos, Costas G.; Pittau, Roberto

2007-01-01

We show how to extract the coefficients of the 4-, 3-, 2- and 1-point one-loop scalar integrals from the full one-loop amplitude of arbitrary scattering processes. In a similar fashion, also the rational terms can be derived. Basically no information on the analytical structure of the amplitude is required, making our method appealing for an efficient numerical implementation

The Nielsen identities for the two-point functions of QED and QCD

International Nuclear Information System (INIS)

Breckenridge, J.C.; Sasketchewan Univ., Saskatoon, SK; Lavelle, M.J.; Steele, T.G.; Sasketchewan Univ., Saskatoon, SK

1995-01-01

We consider the Nielsen identities for the two-point functions of full QCD and QED in the class of Lorentz gauges. For pedagogical reasons the identities are first derived in QED to demonstrate the gauge independence of the photon self-energy, and of the electron mass shell. In QCD we derive the general identity and hence the identities for the quark, gluon and ghost propagators. The explicit contributions to the gluon and ghost identities are calculated to one-loop order, and then we show that the quark identity requires that in on-shell schemes the quark mass renormalisation must be gauge independent. Furthermore, we obtain formal solutions for the gluon self-energy and ghost propagator in terms of the gauge dependence of other, independent Green functions. (orig.)

QED radiative corrections to the pionium life time

International Nuclear Information System (INIS)

Kuraev, Eh.A.

1997-01-01

The lowest order QED radiative corrections to the cross section of the recharged process of transition of two neutral ones and to the pionium lifetime are calculated in frame of scalar QED. It is argued that the ultraviolet cut-off of the loop momentum is to be chosen of order of ρ-meson mass. This fact permits to perform the calculation in frames of Effective Chiral Lagrangian theory with vector-meson dominance. The Coulomb factor corresponding to interaction in the initial state, shown, is to be removed to avoid the double counting. Resulting value of the radiative correction to the pionium lifetime is 0.25%

QED corrections to the Altarelli-Parisi splitting functions

Energy Technology Data Exchange (ETDEWEB)

Florian, Daniel de [Universidad de Buenos Aires, Departamento de Fisica and IFIBA, FCEyN, Capital Federal (Argentina); UNSAM, International Center for Advanced Studies (ICAS), Buenos Aires (Argentina); Sborlini, German F.R.; Rodrigo, German [Universitat de Valencia - Consejo Superior de Investigaciones Cientificas, Instituto de Fisica Corpuscular, Paterna, Valencia (Spain)

2016-05-15

We discuss the combined effect of QED and QCD corrections to the evolution of parton distributions. We extend the available knowledge of the Altarelli-Parisi splitting functions to one order higher in QED, and we provide explicit expressions for the splitting kernels up to O(α α{sub S}). The results presented in this article allow one to perform a parton distribution function analysis reaching full NLO QCD-QED combined precision. (orig.)

Noncommutative QED and anomalous dipole moments

International Nuclear Information System (INIS)

Riad, I.F.; Sheikh-Jabbari, M.M.

2000-09-01

We study QED on noncommutative spaces, NCQED. In particular we present the detailed calculation for the noncommutative electron-photon vertex and show that the Ward identity is satisfied. We discuss that in the noncommutative case moving electron will show electric dipole effects. In addition, we work out the electric and magnetic dipole moments up to one loop level. For the magnetic moment we show that noncommutative electron has an intrinsic (spin independent) magnetic moment. (author)

QED radiative corrections to impact factors

International Nuclear Information System (INIS)

Kuraev, E.A.; Lipatov, L.N.; Shishkina, T.V.

2001-01-01

We consider radiative corrections to the electron and photon impact factors. The generalized eikonal representation for the e + e - scattering amplitude at high energies and fixed momentum transfers is violated by nonplanar diagrams. An additional contribution to the two-loop approximation appears from the Bethe-Heitler mechanism of fermion pair production with the identity of the fermions in the final state taken into account. The violation of the generalized eikonal representation is also related to the charge parity conservation in QED. A one-loop correction to the photon impact factor for small virtualities of the exchanged photon is obtained using the known results for the cross section of the e + e - production during photon-nuclei interactions

Quantum Logic Network for Cloning a State Near a Given One Based on Cavity QED

International Nuclear Information System (INIS)

Da-Wei, Zhang; Xiao-Qiang, Shao; Ai-Dong, Zhu

2008-01-01

A quantum logic network is constructed to simulate a cloning machine which copies states near a given one. Meanwhile, a scheme for implementing this cloning network based on the technique of cavity quantum electrodynamics (QED) is presented. It is easy to implement this network of cloning machine in the framework of cavity QED and feasible in the experiment. (general)

QED contributions to electron g-2

Science.gov (United States)

Laporta, Stefano

2018-05-01

In this paper I briefly describe the results of the numerical evaluation of the mass-independent 4-loop contribution to the electron g-2 in QED with 1100 digits of precision. In particular I also show the semi-analytical fit to the numerical value, which contains harmonic polylogarithms of eiπ/3, e2iπ/3 and eiπ/2 one-dimensional integrals of products of complete elliptic integrals and six finite parts of master integrals, evaluated up to 4800 digits. I give also some information about the methods and the program used.

One-loop Higgs plus four gluon amplitudes. Full analytic results

International Nuclear Information System (INIS)

Badger, Simon; Nigel Glover, E.W.; Williams, Ciaran; Mastrolia, Pierpaolo

2009-10-01

We consider one-loop amplitudes of a Higgs boson coupled to gluons in the limit of a large top quark mass. We treat the Higgs as the real part of a complex field φ that couples to the self-dual field strengths and compute the one-loop corrections to the φ-NMHV amplitude, which contains one gluon of positive helicity whilst the remaining three have negative helicity. We use four-dimensional unitarity to construct the cut-containing contributions and a hybrid of Feynman diagram and recursive based techniques to determine the rational piece. Knowledge of the φ-NMHV contribution completes the analytic calculation of the Higgs plus four gluon amplitude. For completeness we also include expressions for the remaining helicity configurations which have been calculated elsewhere. These amplitudes are relevant for Higgs plus jet production via gluon fusion in the limit where the top quark is large compared to all other scales in the problem. (orig.)

Improved ring potential of QED at finite temperature and in the presence of weak and strong magnetic fields

International Nuclear Information System (INIS)

Sadooghi, N.; Anaraki, K. Sohrabi

2008-01-01

Using the general structure of the vacuum polarization tensor Π μν (k 0 ,k) in the infrared (IR) limit, k 0 →0, the ring contribution to the QED effective potential at finite temperature and the nonzero magnetic field is determined beyond the static limit, (k 0 →0, k→0). The resulting ring potential is then studied in weak and strong magnetic field limits. In the weak magnetic field limit, at high temperature and for α→0, the improved ring potential consists of a term proportional to T 4 α 5/2 , in addition to the expected T 4 α 3/2 term arising from the static limit. Here, α is the fine structure constant. In the limit of the strong magnetic field, where QED dynamics is dominated by the lowest Landau level, the ring potential includes a novel term consisting of dilogarithmic function (eB)Li 2 (-(2α/π)(eB/m 2 )). Using the ring improved (one-loop) effective potential including the one-loop effective potential and ring potential in the IR limit, the dynamical chiral symmetry breaking of QED is studied at finite temperature and in the presence of the strong magnetic field. The gap equation, the dynamical mass and the critical temperature of QED in the regime of the lowest Landau level dominance are determined in the improved IR as well as in the static limit. For a given value of the magnetic field, the improved ring potential is shown to be more efficient in decreasing the critical temperature arising from the one-loop effective potential.

Higher Order QED Contributions to the Atomic Structure at Strong Central Fields

International Nuclear Information System (INIS)

Mokler, P H

2007-01-01

An accurate determination of the precise structure of highly charged, very heavy ions is crucial for understanding QED at strong fields. The experimental advances in the spectroscopy of very heavy, highly charged ions-in particular H-, He- and Li-like species-are reviewed: Presently the ground state Lamb shift for H-like U ions is measured on a 1% level of accuracy; the screening terms in two-electron QED have just been touched by experiments for He-like U; and two-loop QED terms have been determined with ultimate accuracy for Li-like heavy species. The different approaches on QED measurements in strong fields will be discussed and the results compared to theory

Generic calculation of two-body partial decay widths at the full one-loop level

Science.gov (United States)

Goodsell, Mark D.; Liebler, Stefan; Staub, Florian

2017-11-01

We describe a fully generic implementation of two-body partial decay widths at the full one-loop level in the SARAH and SPheno framework compatible with most supported models. It incorporates fermionic decays to a fermion and a scalar or a gauge boson as well as scalar decays into two fermions, two gauge bosons, two scalars or a scalar and a gauge boson. We present the relevant generic expressions for virtual and real corrections. Whereas wave-function corrections are determined from on-shell conditions, the parameters of the underlying model are by default renormalised in a \\overline{ {DR}} (or \\overline{ {MS}}) scheme. However, the user can also define model-specific counter-terms. As an example we discuss the renormalisation of the electric charge in the Thomson limit for top-quark decays in the standard model. One-loop-induced decays are also supported. The framework additionally allows the addition of mass and mixing corrections induced at higher orders for the involved external states. We explain our procedure to cancel infrared divergences for such cases, which is achieved through an infrared counter-term taking into account corrected Goldstone boson vertices. We compare our results for sfermion, gluino and Higgs decays in the minimal supersymmetric standard model (MSSM) against the public codes SFOLD, FVSFOLD and HFOLD and explain observed differences. Radiatively induced gluino and neutralino decays are compared against the original implementation in SPheno in the MSSM. We exactly reproduce the results of the code CNNDecays for decays of neutralinos and charginos in R-parity violating models. The new version SARAH 4.11.0 by default includes the calculation of two-body decay widths at the full one-loop level. Current limitations for certain model classes are described.

Generic calculation of two-body partial decay widths at the full one-loop level

Energy Technology Data Exchange (ETDEWEB)

Goodsell, Mark D. [UPMC Univ. Paris 06 (France); Centre National de la Recherche Scientifique (CNRS), 75 - Paris (France); Sorbonne Univ., Paris (France); Liebler, Stefan [Deutsches Elektronen-Synchrotron (DESY), Hamburg (Germany); Staub, Florian [Karlsruhe Institute for Technology, Karlsruhe (Germany). Inst. for Theoretical Physics; Karlsruhe Institute for Technology, Eggenstein-Leopoldshafen (Germany). Inst. for Nuclear Physics

2017-04-15

We describe a fully generic implementation of two-body partial decay widths at the full one-loop level in the SARAH and SPheno framework compatible with most supported models. It incorporates fermionic decays to a fermion and a scalar or a gauge boson as well as scalar decays into two fermions, two gauge bosons, two scalars or a scalar and a gauge boson. We present the relevant generic expressions for virtual and real corrections. Whereas wavefunction corrections are determined from on-shell conditions, the parameters of the underlying model are by default renormalised in a DR (or MS) scheme. However, the user can also define model-specific counter-terms. As an example we discuss the renormalisation of the electric charge in the Thomson limit for top-quark decays in the standard model. One-loop induced decays are also supported. The framework additionally allows the addition of mass and mixing corrections induced at higher orders for the involved external states. We explain our procedure to cancel infra-red divergences for such cases, which is achieved through an infra-red counter-term taking into account corrected Goldstone boson vertices. We compare our results for sfermion, gluino and Higgs decays in the minimal supersymmetric standard model (MSSM) against the public codes SFOLD, FVSFOLD and HFOLD and explain observed differences. Radiative induced gluino and neutralino decays are compared against the original implementation in SPheno in the MSSM. We exactly reproduce the results of the code CNNDecays for decays of neutralinos and charginos in R-parity violating models. The new version SARAH 4.11.0 by default includes the calculation of two-body decay widths at the full one-loop level. Current limitations for certain model classes are described.

Generic calculation of two-body partial decay widths at the full one-loop level

Energy Technology Data Exchange (ETDEWEB)

Goodsell, Mark D. [Sorbonne Universites, UPMC Univ Paris 06, UMR 7589, LPTHE, Paris (France); CNRS, UMR 7589, LPTHE, Paris (France); Liebler, Stefan [DESY, Hamburg (Germany); Staub, Florian [Karlsruhe Institute of Technology, Institute for Theoretical Physics (ITP), Karlsruhe (Germany); Karlsruhe Institute of Technology, Institute for Nuclear Physics (IKP), Eggenstein-Leopoldshafen (Germany)

2017-11-15

We describe a fully generic implementation of two-body partial decay widths at the full one-loop level in the SARAH and SPheno framework compatible with most supported models. It incorporates fermionic decays to a fermion and a scalar or a gauge boson as well as scalar decays into two fermions, two gauge bosons, two scalars or a scalar and a gauge boson. We present the relevant generic expressions for virtual and real corrections. Whereas wave-function corrections are determined from on-shell conditions, the parameters of the underlying model are by default renormalised in a DR (or MS) scheme. However, the user can also define model-specific counter-terms. As an example we discuss the renormalisation of the electric charge in the Thomson limit for top-quark decays in the standard model. One-loop-induced decays are also supported. The framework additionally allows the addition of mass and mixing corrections induced at higher orders for the involved external states. We explain our procedure to cancel infrared divergences for such cases, which is achieved through an infrared counter-term taking into account corrected Goldstone boson vertices. We compare our results for sfermion, gluino and Higgs decays in the minimal supersymmetric standard model (MSSM) against the public codes SFOLD, FVSFOLD and HFOLD and explain observed differences. Radiatively induced gluino and neutralino decays are compared against the original implementation in SPheno in the MSSM. We exactly reproduce the results of the code CNNDecays for decays of neutralinos and charginos in R-parity violating models. The new version SARAH 4.11.0 by default includes the calculation of two-body decay widths at the full one-loop level. Current limitations for certain model classes are described. (orig.)

Generic calculation of two-body partial decay widths at the full one-loop level

International Nuclear Information System (INIS)

Goodsell, Mark D.; Liebler, Stefan; Staub, Florian; Karlsruhe Institute for Technology, Eggenstein-Leopoldshafen

2017-04-01

We describe a fully generic implementation of two-body partial decay widths at the full one-loop level in the SARAH and SPheno framework compatible with most supported models. It incorporates fermionic decays to a fermion and a scalar or a gauge boson as well as scalar decays into two fermions, two gauge bosons, two scalars or a scalar and a gauge boson. We present the relevant generic expressions for virtual and real corrections. Whereas wavefunction corrections are determined from on-shell conditions, the parameters of the underlying model are by default renormalised in a DR (or MS) scheme. However, the user can also define model-specific counter-terms. As an example we discuss the renormalisation of the electric charge in the Thomson limit for top-quark decays in the standard model. One-loop induced decays are also supported. The framework additionally allows the addition of mass and mixing corrections induced at higher orders for the involved external states. We explain our procedure to cancel infra-red divergences for such cases, which is achieved through an infra-red counter-term taking into account corrected Goldstone boson vertices. We compare our results for sfermion, gluino and Higgs decays in the minimal supersymmetric standard model (MSSM) against the public codes SFOLD, FVSFOLD and HFOLD and explain observed differences. Radiative induced gluino and neutralino decays are compared against the original implementation in SPheno in the MSSM. We exactly reproduce the results of the code CNNDecays for decays of neutralinos and charginos in R-parity violating models. The new version SARAH 4.11.0 by default includes the calculation of two-body decay widths at the full one-loop level. Current limitations for certain model classes are described.

Hammering towards QED

Directory of Open Access Journals (Sweden)

Jasmin C. Blanchette

2016-01-01

Full Text Available This paper surveys the emerging methods to automate reasoning over large libraries developed with formal proof assistants. We call these methods hammers. They give the authors of formal proofs a strong "one-stroke" tool for discharging difficult lemmas without the need for careful and detailed manual programming of proof search.The main ingredients underlying this approach are efficient automatic theorem provers that can cope with hundreds of axioms, suitable translations of richer logics to their formalisms, heuristic and learning methods that select relevant facts from large libraries, and methods that reconstruct the automatically found proofs inside the proof assistants.We outline the history of these methods, explain the main issues and techniques, and show their strength on several large benchmarks. We also discuss the relation of this technology to the QED Manifesto and consider its implications for QED-style efforts.

One-step generation of continuous-variable quadripartite cluster states in a circuit QED system

Science.gov (United States)

Yang, Zhi-peng; Li, Zhen; Ma, Sheng-li; Li, Fu-li

2017-07-01

We propose a dissipative scheme for one-step generation of continuous-variable quadripartite cluster states in a circuit QED setup consisting of four superconducting coplanar waveguide resonators and a gap-tunable superconducting flux qubit. With external driving fields to adjust the desired qubit-resonator and resonator-resonator interactions, we show that continuous-variable quadripartite cluster states of the four resonators can be generated with the assistance of energy relaxation of the qubit. By comparison with the previous proposals, the distinct advantage of our scheme is that only one step of quantum operation is needed to realize the quantum state engineering. This makes our scheme simpler and more feasible in experiment. Our result may have useful application for implementing quantum computation in solid-state circuit QED systems.

Precise predictions of higgs boson decays including the full one-loop corrections in supersymmetry

International Nuclear Information System (INIS)

Frisch, W.

2011-01-01

The Standard Model of elementary particle physics is a highly successful theory, describing the electromagnetic, strong and weak interaction of matter particles up to energy scales to a few hundred giga electronvolt. Despite its great success in explaining experimental results correctly, there is hardly no doubt that the SM is an effective theory, which means that the theory loses its predictability at higher energies. Therefore, the Standard Model has to be extended in a proper way to describe physics at higher energies. A most promising concept for the extension of the SM is those of Supersymmetry, where for each particle of the SM one or more superpartner particles are introduced. The simplest and most attractive extension of the SM is called Minimal Supersymmetric Standard Model (MSSM). Minimal refers to the additional field content, which is kept as low as possible. In fact the MSSM consists of the fields of the SM and their corresponding supersymmetric partner fields, as well as one additional Higgs doublet. The presence of this additional Higgs doublet leads to the existence of five physical Higgs bosons in the MSSM. The search for supersymmetric particles and Higgs bosons is one of the primary goals of the Large Hadron Collider (LHC) at the CERN laboratory, producing collisions at sufficiently high energies to detect these particles. For the discovery of these new particles, precise pre- dictions of the corresponding decay widths and branching rations are utmost mandatory. To contribute with the precision of the LHC and the future ILC, Feynman amplitudes should be calculated at least to one-loop order. Since these calculations lead to so called UV- and IR- divergences, it is essential to perform a renormalization procedure, where the divergences are subtracted by a proper definition of counterterms. The goal of this work was to develop a program package, which calculates all MSSM two- body Higgs decay widths and corresponding branching ratios at full one-loop

One-Step Generation of Multiqubit Greenberger-Horne-Zeilinger States in a Driven Circuit QED System

International Nuclear Information System (INIS)

Huang Jinsong; Nie Wei; Wei Lianfu

2011-01-01

We propose an efficient scheme to generate multiqubit Greenberger-Horne-Zeilinger (GHZ) states by one-step quantum operation in a driven circuit quantum electrodynamics (QED) system. Our proposal is based on a unitary evolution exp[-iλS 2 x ], with S x being the collective spin operator in x direction and λ a controllable parameter, induced by driving the resonator. The quantum operation avoids resonator-field decay and may achieve the GHZ states with ideal success probability. The feasibility with the experimentally-demonstrated circuit QED system is also discussed. (general)

Hopf-algebraic renormalization of QED in the linear covariant gauge

Energy Technology Data Exchange (ETDEWEB)

Kißler, Henry, E-mail: kissler@physik.hu-berlin.de

2016-09-15

In the context of massless quantum electrodynamics (QED) with a linear covariant gauge fixing, the connection between the counterterm and the Hopf-algebraic approach to renormalization is examined. The coproduct formula of Green’s functions contains two invariant charges, which give rise to different renormalization group functions. All formulas are tested by explicit computations to third loop order. The possibility of a finite electron self-energy by fixing a generalized linear covariant gauge is discussed. An analysis of subdivergences leads to the conclusion that such a gauge only exists in quenched QED.

Parton distributions with QED corrections

NARCIS (Netherlands)

Collaboration, The NNPDF; Ball, Richard D.; Bertone, Valerio; Carrazza, Stefano; Debbio, Luigi Del; Forte, Stefano; Guffanti, Alberto; Hartland, Nathan P.; Rojo, Juan

2013-01-01

We present a set of parton distribution functions (PDFs), based on the NNPDF2.3 set, which includes a photon PDF, and QED contributions to parton evolution. We describe the implementation of the combined QCD+QED evolution in the NNPDF framework. We then provide a first determination of the full set

Diagrammatic cancellations and the gauge dependence of QED

Energy Technology Data Exchange (ETDEWEB)

Kißler, Henry, E-mail: kissler@physik.hu-berlin.de [Department of Mathematical Sciences, University of Liverpool, L69 7ZL, Liverpool (United Kingdom); Department of Mathematics, Humboldt-Universität zu Berlin, Rudower Chaussee 25, D-12489 Berlin (Germany); Kreimer, Dirk, E-mail: kreimer@math.hu-berlin.de [Department of Mathematics, Humboldt-Universität zu Berlin, Rudower Chaussee 25, D-12489 Berlin (Germany)

2017-01-10

This letter examines diagrammatic cancellations for Quantum Electrodynamics (QED) in the general linear gauge. These cancellations combine Feynman graphs of various topologies and provide a method to reconstruct the gauge dependence of the electron propagator from the result of a particular gauge by means of a linear Dyson–Schwinger equation. We use this method in combination with dimensional regularization to demonstrate how the 3-loop ε-expansion in the Feynman gauge determines the ε-expansions for all gauge parameter dependent terms to 4 loops.

Two-body decays of gluino at full one-loop level in the quark-flavour violating MSSM.

Science.gov (United States)

Eberl, Helmut; Ginina, Elena; Hidaka, Keisho

2017-01-01

We study the two-body decays of the gluino at full one-loop level in the Minimal Supersymmetric Standard Model with quark-flavour violation (QFV) in the squark sector. The renormalisation is done in the [Formula: see text] scheme. The gluon and photon radiations are included by adding the corresponding three-body decay widths. We discuss the dependence of the gluino decay widths on the QFV parameters. The main dependence stems from the [Formula: see text]-[Formula: see text] mixing in the decays to up-type squarks, and from the [Formula: see text]-[Formula: see text] mixing in the decays to down-type squarks due to the strong constraints from B-physics on the other quark-flavour-mixing parameters. The full one-loop corrections to the gluino decay widths are mostly negative and of the order of about -10%. The QFV part stays small in the total width but can vary up to -8% for the decay width into the lightest [Formula: see text] squark. For the corresponding branching ratio the effect is somehow washed out by at least a factor of two. The electroweak corrections can be as large as 35% of the SUSY QCD corrections.

The QED Workshop

Energy Technology Data Exchange (ETDEWEB)

Pieper, G.W.

1994-07-01

On May 18--20, 1994, Argonne National Laboratory hosted the QED Workshop. The workshop was supported by special funding from the Office of Naval Research. The purpose of the workshop was to assemble of a group of researchers to consider whether it is desirable and feasible to build a proof-checked encyclopedia of mathematics, with an associated facility for theorem proving and proof checking. Among the projects represented were Coq, Eves, HOL, ILF, Imps, MathPert, Mizar, NQTHM, NuPrl, OTTER, Proof Pad, Qu-Prolog, and RRL. Although the content of the QED project is highly technical rigorously proof-checked mathematics of all sorts the discussions at the workshop were rarely technical. No prepared talks or papers were given. Instead, the discussions focused primarily on such political, sociological, practical, and aesthetic questions, such as Why do it? Who are the customers? How can one get mathematicians interested? What sort of interfaces are desirable? The most important conclusion of the workshop was that QED is an idea worthy pursuing, a statement with which virtually all the participants agreed. In this document, the authors capture some of the discussions and outline suggestions for the start of a QED scientific community.

Shear Viscosity of Hot QED at Finite Chemical Potential from Kubo Formula

International Nuclear Information System (INIS)

Liu Hui; Hou Defu; Li Jiarong

2008-01-01

Within the framework of finite temperature feld theory this paper discusses the shear viscosity of hot QED plasma through Kubo formula at one-loop skeleton diagram level with a finite chemical potential. The effective widths (damping rates) are introduced to regulate the pinch singularities and then gives a reliable estimation of the shear viscous coefficient. The finite chemical potential contributes positively compared to the pure temperature case. The result agrees with that from the kinetics theory qualitatively

Leading quantum gravitational corrections to QED

OpenAIRE

Butt, M. S.

2006-01-01

We consider the leading post-Newtonian and quantum corrections to the non-relativistic scattering amplitude of charged spin-1/2 fermions in the combined theory of general relativity and QED. The coupled Dirac-Einstein system is treated as an effective field theory. This allows for a consistent quantization of the gravitational field. The appropriate vertex rules are extracted from the action, and the non-analytic contributions to the 1-loop scattering matrix are calculated in the non-relativi...

Energy-momentum tensor in thermal strong-field QED with unstable vacuum

Energy Technology Data Exchange (ETDEWEB)

Gavrilov, S P [Department of General and Experimental Physics, Herzen State Pedagogical University of Russia, Moyka emb. 48, 191186 St Petersburg (Russian Federation); Gitman, D M [Instituto de Fisica, Universidade de Sao Paulo, CP 66318, CEP 05315-970 Sao Paulo, SP (Brazil)], E-mail: gavrilovsergeyp@yahoo.com, E-mail: gitman@dfn.if.usp.br

2008-04-25

The mean value of the one-loop energy-momentum tensor in thermal QED with an electric-like background that creates particles from vacuum is calculated. The problem is essentially different from calculations of effective actions (similar to the action of Heisenberg-Euler) in backgrounds that respect the stability of vacuum. The role of a constant electric background in the violation of both the stability of vacuum and the thermal character of particle distribution is investigated. Restrictions on the electric field and the duration over which one can neglect the back-reaction of created particles are established.

Energy-momentum tensor in thermal strong-field QED with unstable vacuum

International Nuclear Information System (INIS)

Gavrilov, S P; Gitman, D M

2008-01-01

The mean value of the one-loop energy-momentum tensor in thermal QED with an electric-like background that creates particles from vacuum is calculated. The problem is essentially different from calculations of effective actions (similar to the action of Heisenberg-Euler) in backgrounds that respect the stability of vacuum. The role of a constant electric background in the violation of both the stability of vacuum and the thermal character of particle distribution is investigated. Restrictions on the electric field and the duration over which one can neglect the back-reaction of created particles are established

QED revisited

International Nuclear Information System (INIS)

Hueffel, H.

2003-01-01

Full text: We perform the stochastic quantization of scalar as well as of fermionic QED based on a generalization of the stochastic gauge fixing scheme and its geometrical interpretation. It is shown that the stochastic quantization scheme agrees exactly with the usual path integral formulation. (author)

The refractive index of curved spacetime II: QED, Penrose limits and black holes

International Nuclear Information System (INIS)

Hollowood, Timothy J.; Shore, Graham M.; Stanley, Ross J.

2009-01-01

This work considers the way that quantum loop effects modify the propagation of light in curved space. The calculation of the refractive index for scalar QED is reviewed and then extended for the first time to QED with spinor particles in the loop. It is shown how, in both cases, the low frequency phase velocity can be greater than c, as found originally by Drummond and Hathrell, but causality is respected in the sense that retarded Green functions vanish outside the lightcone. A 'phenomenology' of the refractive index is then presented for black holes, FRW universes and gravitational waves. In some cases, some of the polarization states propagate with a refractive index having a negative imaginary part indicating a potential breakdown of the optical theorem in curved space and possible instabilities.

Quenched QED in the chiral limit

International Nuclear Information System (INIS)

Vandermark, S.W.

1993-01-01

The main goal in this project has been to understand, through analytical methods, whether there could be a continuum limit for QED. This possibility is motivated by recent lattice simulations on quenched QED which apparently exhibit a chiral phase transition at strong coupling in the chiral limit. Another goal is to develop a novel perturbation expansion which may also be usefully applied to other theories. The author begins with the general expression for the chiral order parameter, (bar ψψ), in the quenched limit of euclidean QED, where the number of fermion flavors goes to zero, using the path integral formulation. A cutoff scale, Λ, is introduced into the photon propagator and a new expansion, the open-quotes wormhole expansion,close quotes in powers of Λ 2 /m 2 , where m is the fermion mass, is derived. Graphical rules for the wormhole expansion of left-angle bar ψψ right-angle are described in detail. The author then devises algorithms to generate recursively the graphs at each successive order and to perform the loop momentum integral and γ matrix trace involved in the evaluation of each graph. These algorithms are implemented in Mathmatica and the left-angle bar ψψ right-angle expansion is carried out to order (Λ 2 / m 2 ) 6 . The author employs pade techniques to extrapolate this expansion to the chiral limit (Λ 2 /m 2 → ∞) and looks for a singularity at strong coupling to signal a phase transition. Indications have been found that there may be a phase transition but apparently there are not enough terms in the wormhole expansion to attain stability in our pade analysis. The author therefore cannot conclude that there is a chiral phase transition, although the results are consistent with the existence of one

Full One-loop Electro-Weak Corrections to Three-jet Observables at the Z pole and Beyond

CERN Document Server

Calame, C M Carloni; Piccinini, F; Ross, D A

2009-01-01

We describe the impact of the full one-loop EW terms of O(alpha_s alpha_EM^3) entering the electron-positron into three-jet cross-section from \\sqrt{s}=M_Z to TeV scale energies. We include both factorisable and non-factorisable virtual corrections, photon bremsstrahlung but not the real emission of W and Z bosons. Their importance for the measurement of alpha_S from jet rates and shape variables is explained qualitatively and illustrated quantitatively.

Quantum Private Comparison via Cavity QED

International Nuclear Information System (INIS)

Ye Tian-Yu

2017-01-01

The first quantum private comparison (QPC) protocol via cavity quantum electrodynamics (QED) is proposed in this paper by making full use of the evolution law of atom via cavity QED, where the third party (TP) is allowed to misbehave on his own but cannot conspire with either of the two users. The proposed protocol adopts two-atom product states rather than entangled states as the initial quantum resource, and only needs single-atom measurements for two users. Both the unitary operations and the quantum entanglement swapping operation are not necessary for the proposed protocol. The proposed protocol can compare the equality of one bit from each user in each round comparison with one two-atom product state. The proposed protocol can resist both the outside attack and the participant attack. Particularly, it can prevent TP from knowing two users’ secrets. Furthermore, the qubit efficiency of the proposed protocol is as high as 50%. (paper)

Leading quantum gravitational corrections to scalar QED

OpenAIRE

Bjerrum-Bohr, N. E. J.

2002-01-01

We consider the leading post-Newtonian and quantum corrections to the non-relativistic scattering amplitude of charged scalars in the combined theory of general relativity and scalar QED. The combined theory is treated as an effective field theory. This allows for a consistent quantization of the gravitational field. The appropriate vertex rules are extracted from the action, and the non-analytic contributions to the 1-loop scattering matrix are calculated in the non-relativistic limit. The n...

Effective Lagrangian of QED

International Nuclear Information System (INIS)

Kaminski, J.Z.

1981-01-01

A renormalization group equation for the effective Lagrangian of QED is obtained. Starting from this equation, perturbation theory for the renormalization group equation (PTRGE) is developed. The results are in full agreement with the standard perturbation theory. Conjecturing that the asymptotic effective coupling constant is finite, the effective Lagrangian for a strong magnetic field is obtained, which is proportional to the Maxwellian Lagrangian. For the asymptotically free theories the situation is diametrically opposed to QED. In these cases the effective Lagrangian of the Yang-Mills system tends to infinity for very strong external Yang-Mills fields. (Auth.)

The Asymptotic Expansion of Lattice Loop Integrals Around the Continuum Limit

International Nuclear Information System (INIS)

Becher, Thomas G

2002-01-01

We present a method of computing any one-loop integral in lattice perturbation theory by systematically expanding around its continuum limit. At any order in the expansion in the lattice spacing, the result can be written as a sum of continuum loop integrals in analytic regularization and a few genuine lattice integrals (''master integrals''). These lattice master integrals are independent of external momenta and masses and can be computed numerically. At the one-loop level, there are four master integrals in a theory with only bosonic fields, seven in HQET and sixteen in QED or QCD with Wilson fermions

Angular momentum in non-relativistic QED and photon contribution to spin of hydrogen atom

International Nuclear Information System (INIS)

Chen Panying; Ji Xiangdong; Xu Yang; Zhang Yue

2010-01-01

We study angular momentum in non-relativistic quantum electrodynamics (NRQED). We construct the effective total angular momentum operator by applying Noether's theorem to the NRQED lagrangian. We calculate the NRQED matching for the individual components of the QED angular momentum up to one loop. We illustrate an application of our results by the first calculation of the angular momentum of the ground state hydrogen atom carried in radiative photons, α em 3 /18π, which might be measurable in future atomic experiments.

Strong-field QED processes in short laser pulses. One- and two-photon Compton scattering

Energy Technology Data Exchange (ETDEWEB)

Seipt, Daniel

2012-12-20

The purpose of this thesis is to advance the understanding of strong-field QED processes in short laser pulses. The processes of non-linear one-photon and two-photon Compton scattering are studied, that is the scattering of photons in the interaction of relativistic electrons with ultra-short high-intensity laser pulses. These investigations are done in view of the present and next generation of ultra-high intensity optical lasers which are supposed to achieve unprecedented intensities of the order of 10{sup 24} W/cm{sup 2} and beyond, with pulse lengths in the order of some femtoseconds. The ultra-high laser intensity requires a non-perturbative description of the interaction of charged particles with the laser field to allow for multi-photon interactions, which is beyond the usual perturbative expansion of QED organized in powers of the fine structure constant. This is achieved in strong-field QED by employing the Furry picture and non-perturbative solutions of the Dirac equation in the presence of a background laser field as initial and final state wave functions, as well as the laser dressed Dirac-Volkov propagator. The primary objective is a realistic description of scattering processes with regard to the finite laser pulse duration beyond the common approximation of infinite plane waves, which is made necessary by the ultra-short pulse length of modern high-intensity lasers. Non-linear finite size effects are identified, which are a result of the interplay between the ultra-high intensity and the ultra-short pulse length. In particular, the frequency spectra and azimuthal photon emission spectra are studied emphasizing the differences between pulsed and infinite laser fields. The proper description of the finite temporal duration of the laser pulse leads to a regularization of unphysical infinities (due to the infinite plane-wave description) of the laser-dressed Dirac-Volkov propagator and in the second-order strong-field process of two-photon Compton

Multiloop stringlike formulas for QED

International Nuclear Information System (INIS)

Lam, C.S.

1993-01-01

Multiloop gauge-theory amplitudes written in the Feynman-parameter representation are poised to take advantage of two important developments of the past decade: the spinor-helicity technique and the superstring reorganization. The former has been considered in a previous paper; the latter will be elaborated in this paper. We show here how to write multiloop stringlike formulas in the Feynman-parameter representation for any diagram in QED, including those involving other nonelectromagnetic interactions, provided the internal photon lines are not adjacent to any external photon line. The general connection between the Feynman-parameter approach and the superstring and/or first-quantized approach is discussed. In the special case of a one-loop multiphoton amplitude, these formulas reduce to the ones obtained by the superstring and the first-quantized methods. The stringlike formulas exhibit a simple gauge structure which makes the Ward-Takahashi identity apparent, and enables the integration-by-parts technique of Bern and Kosower to be applied, so that gauge-invariant parts can be extracted diagram by diagram with the seagull vertex neglected

Power corrections to the HTL effective Lagrangian of QED

Science.gov (United States)

Carignano, Stefano; Manuel, Cristina; Soto, Joan

2018-05-01

We present compact expressions for the power corrections to the hard thermal loop (HTL) Lagrangian of QED in d space dimensions. These are corrections of order (L / T) 2, valid for momenta L ≪ T, where T is the temperature. In the limit d → 3 we achieve a consistent regularization of both infrared and ultraviolet divergences, which respects the gauge symmetry of the theory. Dimensional regularization also allows us to witness subtle cancellations of infrared divergences. We also discuss how to generalize our results in the presence of a chemical potential, so as to obtain the power corrections to the hard dense loop (HDL) Lagrangian.

Quasiparadoxes of massless QED

International Nuclear Information System (INIS)

Smilga, A.V.

1990-04-01

We show that the limit m e =0 in the conventional QED is not smooth. In contrast to the massless QED the massive QED, however small the mass is, involves finite probability chirality breaking processes. The chirality breaking effects may be observed provided the size of experimental installation is greater than the formation length ∼ E/m 2 . We discuss also the finite cross sections of virtual longitudinal photon production and scattering in massless QED recently found by Gorsky, Ioffe and Khodjamirian and argue that real longitudinal photons do not interact while the limit of zero virtuality is not smooth. (author). 23 refs, 4 figs

Strategies for real-time position control of a single atom in cavity QED

International Nuclear Information System (INIS)

Lynn, T W; Birnbaum, K; Kimble, H J

2005-01-01

Recent realizations of single-atom trapping and tracking in cavity QED open the door for feedback schemes which actively stabilize the motion of a single atom in real time. We present feedback algorithms for cooling the radial component of motion for a single atom trapped by strong coupling to single-photon fields in an optical cavity. Performance of various algorithms is studied through simulations of single-atom trajectories, with full dynamical and measurement noise included. Closed loop feedback algorithms compare favourably to open loop 'switching' analogues, demonstrating the importance of applying actual position information in real time. The high optical information rate in current experiments enables real-time tracking that approaches the standard quantum limit for broadband position measurements, suggesting that realistic active feedback schemes may reach a regime where measurement backaction appreciably alters the motional dynamics

Chargino and neutralino production at e{sup +}e{sup -} colliders in the complex MSSM. A full one-loop analysis

Energy Technology Data Exchange (ETDEWEB)

Heinemeyer, S. [Campus of International Excellence UAM+CSIC, Madrid (Spain); Universidad Autonoma de Madrid, Cantoblanco, Instituto de Fisica Teorica (UAM/CSIC), Madrid (Spain); Instituto de Fisica de Cantabria (CSIC-UC), Santander (Spain); Schappacher, C.

2017-09-15

For the search for charginos and neutralinos in the Minimal Supersymmetric Standard Model (MSSM) as well as for future precision analyses of these particles an accurate knowledge of their production and decay properties is mandatory. We evaluate the cross sections for the chargino and neutralino production at e{sup +}e{sup -} colliders in the MSSM with complex parameters (cMSSM). The evaluation is based on a full one-loop calculation of the production mechanisms e{sup +}e{sup -} → χ{sub c}{sup ±}χ{sub c}{sup {sub '}-+} and e{sup +}e{sup -} → χ{sub n}{sup 0}χ{sub n}{sup {sub '}0} including soft and hard photon radiation. We mostly restricted ourselves to a version of our renormalization scheme which is valid for vertical stroke M{sub 1} vertical stroke < vertical stroke M{sub 2} vertical stroke, vertical stroke μ vertical stroke and M{sub 2} ≠ μ to simplify the analysis, even though we are able to switch to other parameter regions and correspondingly different renormalization schemes. The dependence of the chargino/neutralino cross sections on the relevant cMSSM parameters is analyzed numerically. We find sizable contributions to many production cross sections. They amount to roughly ±15% of the tree-level results but can go up to ±40% or higher in extreme cases. Also the complex phase dependence of the one-loop corrections was found non-negligible. The full one-loop contributions are thus crucial for physics analyses at a future linear e{sup +}e{sup -} collider such as the ILC or CLIC. (orig.)

An introduction about precise measurements of QED γ structure functions

International Nuclear Information System (INIS)

Courau, A.

1989-11-01

Pure QED processes are theoretically exactly computable. However precise measurements and theoretical expectations of QED γ structure functions within a given experimental acceptance are not so trivial. Yet such a study is quite interesting. It supplies on the one hand a good QED test and, on the other hand, a good exercise for testing the procedure used for the determination of the hadronic γ structure functions

QED effects on individual atomic orbital energies

Science.gov (United States)

Kozioł, Karol; Aucar, Gustavo A.

2018-04-01

Several issues, concerning QED corrections, that are important in precise atomic calculations are presented. The leading QED corrections, self-energy and vacuum polarization, to the orbital energy for selected atoms with 30 ≤ Z ≤ 118 have been calculated. The sum of QED and Breit contributions to the orbital energy is analyzed. It has been found that for ns subshells the Breit and QED contributions are of comparative size, but for np and nd subshells the Breit contribution takes a major part of the QED+Breit sum. It has also, been found that the Breit to leading QED contributions ratio for ns subshells is almost independent of Z. The Z-dependence of QED and Breit+QED contributions per subshell is shown. The fitting coefficients may be used to estimate QED effects on inner molecular orbitals. We present results of our calculations for QED contributions to orbital energy of valence ns-subshell for group 1 and 11 atoms and discuss about the reliability of these numbers by comparing them with experimental first ionization potential data.

Measurement of the running of the QED coupling in small-angle Bhabha scattering at LEP

CERN Document Server

Abbiendi, G.; Akesson, P.F.; Alexander, G.; Anagnostou, G.; Anderson, K.J.; Asai, S.; Axen, D.; Bailey, I.; Barberio, E.; Barillari, T.; Barlow, R.J.; Batley, R.J.; Bechtle, P.; Behnke, T.; Bell, Kenneth Watson; Bell, P.J.; Bella, G.; Bellerive, A.; Benelli, G.; Bethke, S.; Biebel, O.; Boeriu, O.; Bock, P.; Boutemeur, M.; Braibant, S.; Brown, Robert M.; Burckhart, H.J.; Campana, S.; Capiluppi, P.; Carnegie, R.K.; Carter, A.A.; Carter, J.R.; Chang, C.Y.; Charlton, D.G.; Ciocca, C.; Csilling, A.; Cuffiani, M.; Dado, S.; Dallavalle, G.M.; De Roeck, A.; De Wolf, E.A.; Desch, K.; Dienes, B.; Dubbert, J.; Duchovni, E.; Duckeck, G.; Duerdoth, I.P.; Etzion, E.; Fabbri, F.; Ferrari, P.; Fiedler, F.; Fleck, I.; Ford, M.; Frey, A.; Gagnon, P.; Gary, John William; Geich-Gimbel, C.; Giacomelli, G.; Giacomelli, P.; Giacomelli, R.; Giunta, Marina; Goldberg, J.; Gross, E.; Grunhaus, J.; Gruwe, M.; Gunther, P.O.; Gupta, A.; Hajdu, C.; Hamann, M.; Hanson, G.G.; Harel, A.; Hauschild, M.; Hawkes, C.M.; Hawkings, R.; Hemingway, R.J.; Herten, G.; Heuer, R.D.; Hill, J.C.; Horvath, D.; Igo-Kemenes, P.; Ishii, K.; Jeremie, H.; Jovanovic, P.; Junk, T.R.; Kanzaki, J.; Karlen, D.; Kawagoe, K.; Kawamoto, T.; Keeler, R.K.; Kellogg, R.G.; Kennedy, B.W.; Kluth, S.; Kobayashi, T.; Kobel, M.; Komamiya, S.; Kramer, T.; Krieger, P.; von Krogh, J.; Kuhl, T.; Kupper, M.; Lafferty, G.D.; Landsman, H.; Lanske, D.; Lellouch, D.; Lettso, J.; Levinson, L.; Lillich, J.; Lloyd, S.L.; Loebinger, F.K.; Lu, J.; Ludwig, A.; Ludwig, J.; Mader, W.; Marcellini, S.; Martin, A.J.; Mashimo, T.; Mattig, Peter; McKenna, J.; McPherson, R.A.; Meijers, F.; Menges, W.; Merritt, F.S.; Mes, H.; Meyer, Niels T.; Michelini, A.; Mihara, S.; Mikenberg, G.; Miller, D.J.; Mohr, W.; Mori, T.; Mutter, A.; Nagai, K.; Nakamura, I.; Nanjo, H.; Neal, H.A.; Nisius, R.; ONeale, S.W.; Oh, A.; Oreglia, M.J.; Orito, S.; Pahl, C.; Pasztor, G.; Pater, J.R.; Pilcher, J.E.; Pinfold, J.; Plane, David E.; Pooth, O.; Przybycien, M.; Quadt, A.; Rabbertz, K.; Rembser, C.; Renkel, P.; Roney, J.M.; Runge, K.; Sachs, K.; Saeki, T.; Sarkisyan, E.K.G.; Schaile, A.D.; Schaile, O.; Scharff-Hansen, P.; Schieck, J.; Schorner-Sadenius, T.; Schroder, Matthias; Schumacher, M.; Seuster, R.; Shears, T.G.; Shen, B.C.; Sherwood, P.; Skuja, A.; Smith, A.M.; Sobie, R.; Soldner-Rembold, S.; Spano, F.; Stahl, A.; Strom, David M.; Strohmer, R.; Tarem, S.; Tasevsky, M.; Teuscher, R.; Thomson, M.A.; Torrence, E.; Toya, D.; Tran, P.; Trigger, I.; Trocsanyi, Z.; Tsur, E.; Turner-Watson, M.F.; Ueda, I.; Ujvari, B.; Vollmer, C.F.; Vannerem, P.; Vertesi, R.; Verzocchi, M.; Voss, H.; Vossebeld, J.; Ward, C.P.; Ward, D.R.; Watkins, P.M.; Watson, A.T.; Watson, N.K.; Wells, P.S.; Wengler, T.; Wermes, N.; Wilson, G.W.; Wilson, J.A.; Wolf, G.; Wyatt, T.R.; Yamashita, S.; Zer-Zion, D.; Zivkovic, Lidija

2006-01-01

Using the OPAL detector at LEP, the running of the effective QED coupling alpha(t) is measured for space-like momentum transfer through its effect on the angular spectrum of small-angle Bhabha scattering. In an almost ideal QED framework, with very favourable experimental conditions, we obtain: Delta alpha(-6.07GeV^2) - Delta alpha(-1.81GeV^2) = (440 pm 58 pm 43 pm 30) X 10^-5, where the first error is statistical, the second is the experimental systematic and the third is the theoretical uncertainty. This is the strongest direct evidence ever presented that the running of alpha is consistent with Standard Model expectations. The null hypothesis that alpha remains constant within the above interval of -t is excluded with a significance above 5sigma. Similarly, our results are inconsistent at the level of 3sigma with the hypothesis that only leptonic loops contribute to the running, and therefore provide the first clear experimental evidence that hadronic loops also contribute.

Improved hard-thermal-loop effective action for hot QED and QCD

International Nuclear Information System (INIS)

Flechsig, F.; Rebhan, A.K.

1995-01-01

The conventional results for hard thermal loops, which are the building blocks of resummed perturbation theory in thermal field theories, have collinear singularities when external momenta are light-like. It is shown that by taking into account asymptotic thermal masses these singularities are removed. The thus improved hard thermal loops can be summarized by compact gauge-invariant effective actions, generalizing the ones found by Taylor and Wong, and by Braaten and Pisarski. (orig.)

One-loop renormalization of Resonance Chiral Theory: scalar and pseudoscalar resonances

International Nuclear Information System (INIS)

Rosell, Ignasi; Ruiz-FemenIa, Pedro; Portoles, Jorge

2005-01-01

We consider the Resonance Chiral Theory with one multiplet of scalar and pseudoscalar resonances, up to bilinear couplings in the resonance fields, and evaluate its β-function at one-loop with the use of the background field method. Thus we also provide the full set of operators that renormalize the theory at one loop and render it finite

Numerical evaluation of one-loop QCD amplitudes

DEFF Research Database (Denmark)

Badger, Simon David; Biedermann, Benedikt; Uwer, Peter

2012-01-01

We present the publicly available program NGluon allowing the numerical evaluation of primitive amplitudes at one-loop order in massless QCD. The program allows the computation of one-loop amplitudes for an arbitrary number of gluons. The focus of the present article is the extension to one-loop ...

Full O(α) electroweak radiative corrections to e+e- → t anti t γ with GRACE-Loop

International Nuclear Information System (INIS)

Khiem, P.H.; Fujimoto, J.; Ishikawa, T.; Kaneko, T.; Kurihara, Y.; Shimizu, Y.; Kato, K.; Ueda, T.; Vermaseren, J.A.M.; Yasui, Y.

2013-01-01

We present the full O(α) electroweak radiative corrections to the process e + e - → t anti t γ at the International Linear Collider (ILC). The computation is performed with the help of the GRACE-Loop system. We present the total cross-section and the top quark forward-backward asymmetry (A FB ) as a function of the center-of-mass energy and compare them with the process e + e - → t anti t γ. We find that the value of A FB in t anti t γ production is larger than A FB in t anti t production. It is an important result for the measurement of the top quark forward-backward asymmetry at the ILC. Applying a structure function method, we also subtract the QED correction to gain the genuine weak correction in both the α scheme and the G μ scheme (δ W G μ ). We obtain numerical values for δ W G μ which are changing from 2 % to -24 % when we vary the center-of-mass energy from 360 GeV to 1 TeV. (orig.)

One-particle reducible contribution to the one-loop spinor propagator in a constant field

Directory of Open Access Journals (Sweden)

N. Ahmadiniaz

2017-11-01

Full Text Available Extending work by Gies and Karbstein on the Euler–Heisenberg Lagrangian, it has recently been shown that the one-loop propagator of a charged scalar particle in a constant electromagnetic field has a one-particle reducible contribution in addition to the well-studied irreducible one. Here we further generalize this result to the spinor case, and find the same relation between the reducible term, the tree-level propagator and the one-loop Euler–Heisenberg Lagrangian as in the scalar case. Our demonstration uses a novel worldline path integral representation of the photon-dressed spinor propagator in a constant electromagnetic field background.

Numerical approach to one-loop integrals

International Nuclear Information System (INIS)

Fujimoto, Junpei; Shimizu, Yoshimitsu; Kato, Kiyoshi; Oyanagi, Yoshio.

1992-01-01

Two numerical methods are proposed for the calculation of one-loop scalar integrals. In the first method, the singularity is cancelled by the symmetrization of the integrand and the integration is done by a Monte-Carlo method. In the second one, after the transform of the integrand into a standard form, the integral is reduced into a regular numerical integral. These methods provide us practical tools to evaluate one-loop Feynman diagrams with desired numerical accuracy. They are extended to the integral with numerator and the treatment of the one-loop virtual correction to the cross section is also presented. (author)

Constructing QCD one-loop amplitudes

International Nuclear Information System (INIS)

Forde, D

2008-01-01

In the context of constructing one-loop amplitudes using a unitarity bootstrap approach we discuss a general systematic procedure for obtaining the coefficients of the scalar bubble and triangle integral functions of one-loop amplitudes. Coefficients are extracted after examining the behavior of the cut integrand as the unconstrained parameters of a specifically chosen parameterization of the cut loop momentum approach infinity. Measurements of new physics at the forthcoming experimental program at CERN's Large Hadron Collider (LHC) will require a precise understanding of processes at next-to-leading order (NLO). This places increased demands for the computation of new one-loop amplitudes. This in turn has spurred recent developments towards improved calculational techniques. Direct calculations using Feynman diagrams are in general inefficient. Developments of more efficient techniques have usually centered around unitarity techniques [1], where tree amplitudes are effectively 'glued' together to form loops. The most straightforward application of this method, in which the cut loop momentum is in D = 4, allows for the computation of 'cut-constructible' terms only, i.e. (poly)logarithmic containing terms and any related constants. QCD amplitudes contain, in addition to such terms, rational pieces which cannot be derived using such cuts. These 'missing' rational parts can be extracted using cut loop momenta in D = 4-2 (var e psilon). The greater difficulty of such calculations has restricted the application of this approach, although recent developments [3, 4] have provided new promise for this technique. Recently the application of on-shell recursion relations [5] to obtaining the 'missing' rational parts of one-loop processes [6] has provided an alternative very promising solution to this problem. In combination with unitarity methods an 'on-shell bootstrap' approach provides an efficient technique for computing complete one-loop QCD amplitudes [7]. Additionally

Large orders in strong-field QED

Energy Technology Data Exchange (ETDEWEB)

Heinzl, Thomas [School of Mathematics and Statistics, University of Plymouth, Drake Circus, Plymouth PL4 8AA (United Kingdom); Schroeder, Oliver [Science-Computing ag, Hagellocher Weg 73, D-72070 Tuebingen (Germany)

2006-09-15

We address the issue of large-order expansions in strong-field QED. Our approach is based on the one-loop effective action encoded in the associated photon polarization tensor. We concentrate on the simple case of crossed fields aiming at possible applications of high-power lasers to measure vacuum birefringence. A simple next-to-leading order derivative expansion reveals that the indices of refraction increase with frequency. This signals normal dispersion in the small-frequency regime where the derivative expansion makes sense. To gain information beyond that regime we determine the factorial growth of the derivative expansion coefficients evaluating the first 82 orders by means of computer algebra. From this we can infer a nonperturbative imaginary part for the indices of refraction indicating absorption (pair production) as soon as energy and intensity become (super)critical. These results compare favourably with an analytic evaluation of the polarization tensor asymptotics. Kramers-Kronig relations finally allow for a nonperturbative definition of the real parts as well and show that absorption goes hand in hand with anomalous dispersion for sufficiently large frequencies and fields.

One-loop Yukawa Couplings in Local Models

CERN Document Server

Conlon, Joseph P; Palti, Eran; 10.1007

2010-01-01

We calculate the one-loop Yukawa couplings and threshold corrections for supersymmetric local models of branes at singularities in type IIB string theory. We compute the corrections coming both from wavefunction and vertex renormalisation. The former comes in the IR from conventional field theory running and in the UV from threshold corrections that cause it to run from the winding scale associated to the full Calabi-Yau volume. The vertex correction is naively absent as it appears to correspond to superpotential renormalisation. However, we find that while the Wilsonian superpotential is not renormalised there is a physical vertex correction in the 1PI action associated to light particle loops.

One-loop Yukawa couplings in local models

International Nuclear Information System (INIS)

Conlon, Joseph P.; Goodsell, Mark; Palti, Eran

2010-07-01

We calculate the one-loop Yukawa couplings and threshold corrections for supersymmetric local models of branes at singularities in type IIB string theory. We compute the corrections coming both from wavefunction and vertex renormalisation. The former comes in the IR from conventional field theory running and in the UV from threshold corrections that cause it to run from the winding scale associated to the full Calabi-Yau volume. The vertex correction is naively absent as it appears to correspond to superpotential renormalisation. However, we find that while the Wilsonian superpotential is not renormalised there is a physical vertex correction in the 1PI action associated to light particle loops. (orig.)

One-loop Yukawa couplings in local models

Energy Technology Data Exchange (ETDEWEB)

Conlon, Joseph P. [Rudolf Peierls Center for Theoretical Physics, Oxford (United Kingdom); Balliol College, Oxford (United Kingdom); Goodsell, Mark [Deutsches Elektronen-Synchrotron (DESY), Hamburg (Germany); Palti, Eran [Centre de Physique Theorique, Ecole Polytechnique, CNRS, Palaiseau (France)

2010-07-15

We calculate the one-loop Yukawa couplings and threshold corrections for supersymmetric local models of branes at singularities in type IIB string theory. We compute the corrections coming both from wavefunction and vertex renormalisation. The former comes in the IR from conventional field theory running and in the UV from threshold corrections that cause it to run from the winding scale associated to the full Calabi-Yau volume. The vertex correction is naively absent as it appears to correspond to superpotential renormalisation. However, we find that while the Wilsonian superpotential is not renormalised there is a physical vertex correction in the 1PI action associated to light particle loops. (orig.)

The Hamiltonian of QED. Zero mode

International Nuclear Information System (INIS)

Zastavenko, L.G.

1990-01-01

We start with the standard QED Lagrangian. New derivation of the spinor QED Hamiltonian is given. We have taken into account the zero mode. Our derivation is faultless from the point of view of gauge invariance. It gives important corrections to the standard QED Hamiltonian. Our derivation of the Hamiltonian can be generalized to the case of QCD. 5 refs

Full one-loop QCD and electroweak corrections to sfermion pair production in γγ collisions

International Nuclear Information System (INIS)

Xing Lirong; Zhang Renyou; Jiang Yi; Han Liang; Li Gang; Ma Wengan

2005-01-01

We have calculated the full one-loop electroweak (EW) and QCD corrections to the third generation scalar-fermion pair production processes e + e - →γγ→f i -tildef i -tilde(f=t,b,τ) at an electron-positron linear collider(LC) in the minimal supersymmetric standard model (MSSM). We analyze the dependence of the radiative corrections on the parameters such as the colliding energy √(s-circumflex) and the SUSY fundamental parameters A f , tanβ, μ, M SUSY and so forth. The numerical results show that the EW corrections to the squark-, stau-pair production processes and QCD corrections to the squark-pair production processes give substantial contributions in some parameter space. The EW relative corrections to squark-pair production processes can be comparable with QCD corrections at high energies. Therefore, these EW and QCD corrections cannot be neglected in precise measurement of sfermion pair productions via γγ collision at future linear colliders

Polarizability sum rules in QED

International Nuclear Information System (INIS)

Llanta, E.; Tarrach, R.

1978-01-01

The well founded total photoproduction and the, assumed subtraction free, longitudinal photoproduction polarizability sum rules are checked in QED at the lowest non-trivial order. The first one is shown to hold, whereas the second one turns out to need a subtraction, which makes its usefulness for determining the electromagnetic polarizabilities of the nucleons quite doubtful. (Auth.)

One-loop calculations with massive particles

International Nuclear Information System (INIS)

Oldenborgh, G.J. van.

1990-01-01

In this thesis some techniques for performing one-loop calculations with massive particles are presented. Numerical techniques are presented necessary for evaluating one-loop integrals which occur in one-loop calculations of photon-photon scattering. The algorithms have been coded in FORTRAN (to evaluate the scalar integrals) and the algebraic language FORM (to reduce the tensor integrals to scalar integrals). Applications are made in the theory of the strong interaction, QCD, i.e. in handling one-loop integrals with massive particles, in order to regulate the infinities by mass parameters encountered in this theory. However this simplifies the computation considerably, the description of the proton structure functions have to be renormalized in order to obtain physical results. This renormalization is different from the published results for the gluon and thus has to be redone. The first physics results that have been obtained with these new methods are presented. These concern heavy quark production in semi-leptonic interactions, for instance neutrino charm production and top production at the electron-proton (ep) collider HERA and the proposed LEP/LHC combination. Total and differential cross-sections for one-loop corrections to top production at the HERA and proposed LEP/HLC ep colliders are given and structure functions for charmed quark production are compared with previously published results. (author). 58 refs.; 18 figs.; 5 tabs

The Universal One-Loop Effective Action

CERN Document Server

Drozd, Aleksandra; Quevillon, Jérémie; You, Tevong

2016-01-01

We present the universal one-loop effective action for all operators of dimension up to six obtained by integrating out massive, non-degenerate multiplets. Our general expression may be applied to loops of heavy fermions or bosons, and has been checked against partial results available in the literature. The broad applicability of this approach simplifies one-loop matching from an ultraviolet model to a lower-energy effective field theory (EFT), a procedure which is now reduced to the evaluation of a combination of matrices in our universal expression, without any loop integrals to evaluate. We illustrate the relationship of our results to the Standard Model (SM) EFT, using as an example the supersymmetric stop and sbottom squark Lagrangian and extracting from our universal expression the Wilson coefficients of dimension-six operators composed of SM fields.

The universal one-loop effective action

International Nuclear Information System (INIS)

Drozd, Aleksandra; Ellis, John; Quevillon, Jérémie; You, Tevong

2016-01-01

We present the universal one-loop effective action for all operators of dimension up to six obtained by integrating out massive, non-degenerate multiplets. Our general expression may be applied to loops of heavy fermions or bosons, and has been checked against partial results available in the literature. The broad applicability of this approach simplifies one-loop matching from an ultraviolet model to a lower-energy effective field theory (EFT), a procedure which is now reduced to the evaluation of a combination of matrices in our universal expression, without any loop integrals to evaluate. We illustrate the relationship of our results to the Standard Model (SM) EFT, using as an example the supersymmetric stop and sbottom squark Lagrangian and extracting from our universal expression the Wilson coefficients of dimension-six operators composed of SM fields.

Results from GRACE/SUSY at one-loop

International Nuclear Information System (INIS)

Fujimoto, J.; Ishikawa, T.; Kurihara, Y.; Jimbo, M.; Yasui, Y.; Kaneko, T.; Kon, T.; Kuroda, M.; Shimizu, Y.

2007-01-01

We report the recent development on the SUSY calculations with the help of GRACE system. GRACE/SUSY/1LOOP is the computer code which can generate Feynman diagrams in the MSSM automatically and compute one-loop amplitudes in the numerical way. We present new results of various two-body widths and chargino pair production at ILC (international linear collider) at one-loop level. (author)

Ultrafast quantum computation in ultrastrongly coupled circuit QED systems

Science.gov (United States)

Wang, Yimin; Guo, Chu; Zhang, Guo-Qiang; Wang, Gangcheng; Wu, Chunfeng

2017-01-01

The latest technological progress of achieving the ultrastrong-coupling regime in circuit quantum electrodynamics (QED) systems has greatly promoted the developments of quantum physics, where novel quantum optics phenomena and potential computational benefits have been predicted. Here, we propose a scheme to accelerate the nontrivial two-qubit phase gate in a circuit QED system, where superconducting flux qubits are ultrastrongly coupled to a transmission line resonator (TLR), and two more TLRs are coupled to the ultrastrongly-coupled system for assistant. The nontrivial unconventional geometric phase gate between the two flux qubits is achieved based on close-loop displacements of the three-mode intracavity fields. Moreover, as there are three resonators contributing to the phase accumulation, the requirement of the coupling strength to realize the two-qubit gate can be reduced. Further reduction in the coupling strength to achieve a specific controlled-phase gate can be realized by adding more auxiliary resonators to the ultrastrongly-coupled system through superconducting quantum interference devices. We also present a study of our scheme with realistic parameters considering imperfect controls and noisy environment. Our scheme possesses the merits of ultrafastness and noise-tolerance due to the advantages of geometric phases. PMID:28281654

No parity anomaly in massless QED3: A BPHZL approach

International Nuclear Information System (INIS)

Del Cima, O.M.; Franco, D.H.T.; Piguet, O.; Schweda, M.

2009-01-01

In this Letter we call into question the perturbatively parity breakdown at 1-loop for the massless QED 3 frequently claimed in the literature. As long as perturbative quantum field theory is concerned, whether a parity anomaly owing to radiative corrections exists or not shall be definitely proved by using a renormalization method independent of any regularization scheme. Such a problem has been investigated in the framework of BPHZL renormalization method, by adopting the Lowenstein-Zimmermann subtraction scheme. The 1-loop parity-odd contribution to the vacuum-polarization tensor is explicitly computed in the framework of the BPHZL renormalization method. It is shown that a Chern-Simons term is generated at that order induced through the infrared subtractions - which violate parity. We show then that, what is called 'parity anomaly', is in fact a parity-odd counterterm needed for restauring parity.

The five-gluon amplitude and one-loop integrals

International Nuclear Information System (INIS)

Bern, Z.; Dixon, L.; Kosower, D.A.

1992-12-01

We review the conventional field theory description of the string motivated technique. This technique is applied to the one-loop five-gluon amplitude. To evaluate the amplitude a general method for computing dimensionally regulated one-loop integrals is outlined including results for one-loop integrals required for the pentagon diagram and beyond. Finally, two five-gluon helicity amplitudes are given

Automated one-loop calculations with GOSAM

International Nuclear Information System (INIS)

Cullen, Gavin; Greiner, Nicolas; Heinrich, Gudrun; Reiter, Thomas; Luisoni, Gionata

2011-11-01

We present the program package GoSam which is designed for the automated calculation of one-loop amplitudes for multi-particle processes in renormalisable quantum field theories. The amplitudes, which are generated in terms of Feynman diagrams, can be reduced using either D-dimensional integrand-level decomposition or tensor reduction. GoSam can be used to calculate one-loop QCD and/or electroweak corrections to Standard Model processes and offers the flexibility to link model files for theories Beyond the Standard Model. A standard interface to programs calculating real radiation is also implemented. We demonstrate the flexibility of the program by presenting examples of processes with up to six external legs attached to the loop. (orig.)

Automated one-loop calculations with GOSAM

Energy Technology Data Exchange (ETDEWEB)

Cullen, Gavin [Edinburgh Univ. (United Kingdom). School of Physics and Astronomy; Deutsches Elektronen-Synchrotron, Zeuthen [DESY; Germany; Greiner, Nicolas [Illinois Univ., Urbana-Champaign, IL (United States). Dept. of Physics; Max-Planck-Institut fuer Physik, Muenchen (Germany); Heinrich, Gudrun; Reiter, Thomas [Max-Planck-Institut fuer Physik, Muenchen (Germany); Luisoni, Gionata [Durham Univ. (United Kingdom). Inst. for Particle Physics Phenomenology; Mastrolia, Pierpaolo [Max-Planck-Institut fuer Physik, Muenchen (Germany); Padua Univ. (Italy). Dipt. di Fisica; Ossola, Giovanni [New York City Univ., NY (United States). New York City College of Technology; New York City Univ., NY (United States). The Graduate School and University Center; Tramontano, Francesco [European Organization for Nuclear Research (CERN), Geneva (Switzerland)

2011-11-15

We present the program package GoSam which is designed for the automated calculation of one-loop amplitudes for multi-particle processes in renormalisable quantum field theories. The amplitudes, which are generated in terms of Feynman diagrams, can be reduced using either D-dimensional integrand-level decomposition or tensor reduction. GoSam can be used to calculate one-loop QCD and/or electroweak corrections to Standard Model processes and offers the flexibility to link model files for theories Beyond the Standard Model. A standard interface to programs calculating real radiation is also implemented. We demonstrate the flexibility of the program by presenting examples of processes with up to six external legs attached to the loop. (orig.)

Strong coupling phase in QED

International Nuclear Information System (INIS)

Aoki, Ken-ichi

1988-01-01

Existence of a strong coupling phase in QED has been suggested in solutions of the Schwinger-Dyson equation and in Monte Carlo simulation of lattice QED. In this article we recapitulate the previous arguments, and formulate the problem in the modern framework of the renormalization theory, Wilsonian renormalization. This scheme of renormalization gives the best understanding of the basic structure of a field theory especially when it has a multi-phase structure. We resolve some misleading arguments in the previous literature. Then we set up a strategy to attack the strong phase, if any. We describe a trial; a coupled Schwinger-Dyson equation. Possible picture of the strong coupling phase QED is presented. (author)

Full colour for loop amplitudes in Yang-Mills theory

Energy Technology Data Exchange (ETDEWEB)

Ochirov, Alexander [Higgs Centre for Theoretical Physics, School of Physics and Astronomy,The University of Edinburgh,Edinburgh EH9 3JZ, Scotland (United Kingdom); Page, Ben [Albert-Ludwigs-Universität Freiburg, Physikalisches Institut,D-79104 Freiburg (Germany)

2017-02-20

We present a general method to account for full colour dependence Yang-Mills amplitudes at loop level. The method fits most naturally into the framework of multi-loop integrand reduction and in a nutshell amounts to consistently retaining the colour structures of the unitarity cuts from which the integrand is gradually constructed. This technique has already been used in the recent calculation of the two-loop five-gluon amplitude in pure Yang-Mills theory with all positive helicities, (DOI: 10.1007/JHEP10(2015)064). In this note, we give a careful exposition of the method and discuss its connection to loop-level Kleiss-Kuijf relations. We also explore its implications for cancellation of nontrivial symmetry factors at two loops. As an example of its generality, we show how it applies to the three-loop case in supersymmetric Yang-Mills case.

A few more comments on secularly growing loop corrections in strong electric fields

International Nuclear Information System (INIS)

Akhmedov, E.T.; Popov, F.K.

2015-01-01

We extend the observations of our previous paper http://dx.doi.org/10.1007/JHEP09(2014)071 [http://arxiv.org/abs/1405.5285]. particular, we show that the secular growth of the loop corrections to the two-point correlation functions is gauge independent: we observe the same growth in the case of the static gauge for the constant background electric field. Furthermore we solve the kinetic equation describing photon production from the background fields, which was derived in our previous paper and allows one to sum up leading secularly growing corrections from all loops. Finally, we show that in the constant electric field background the one-loop correction to the current of the produced pairs is not zero: it also grows with time and violates time translational and reversal invariance of QED on the constant electric field background.

From strong to ultrastrong coupling in circuit QED architectures

Energy Technology Data Exchange (ETDEWEB)

Niemczyk, Thomas

2011-08-10

The field of cavity quantum electrodynamics (cavity QED) studies the interaction between light and matter on a fundamental level: a single atom interacts with a single photon. If the atom-photon coupling is larger than any dissipative effects, the system enters the strong-coupling limit. A peculiarity of this regime is the possibility to form coherent superpositions of light and matter excitations - a kind of 'molecule' consisting of an atomic and a photonic contribution. The novel research field of circuit QED extends cavity QED concepts to solid-state based system. Here, a superconducting quantum bit is coupled to an on-chip superconducting one-dimensional waveguide resonator. Owing to the small mode-volume of the resonant cavity, the large dipole moment of the 'artificial atom' and the enormous engineering potential inherent to superconducting quantum circuits, remarkable atom-photon coupling strengths can be realized. This thesis describes the theoretical framework, the development of fabrication techniques and the implementation of experimental characterization techniques for superconducting quantum circuits for circuit QED applications. In particular, we study the interaction between superconducting flux quantum bits and high-quality coplanar waveguide resonators in the strong-coupling limit. Furthermore, we report on the first experimental realization of a circuit QED system operating in the ultrastrong-coupling regime, where the atom-photon coupling rate reaches a considerable fraction of the relevant system frequencies. In these experiments we could observe phenomena that can not be explained within the renowned Jaynes-Cummings model. (orig.)

From strong to ultrastrong coupling in circuit QED architectures

International Nuclear Information System (INIS)

Niemczyk, Thomas

2011-01-01

The field of cavity quantum electrodynamics (cavity QED) studies the interaction between light and matter on a fundamental level: a single atom interacts with a single photon. If the atom-photon coupling is larger than any dissipative effects, the system enters the strong-coupling limit. A peculiarity of this regime is the possibility to form coherent superpositions of light and matter excitations - a kind of 'molecule' consisting of an atomic and a photonic contribution. The novel research field of circuit QED extends cavity QED concepts to solid-state based system. Here, a superconducting quantum bit is coupled to an on-chip superconducting one-dimensional waveguide resonator. Owing to the small mode-volume of the resonant cavity, the large dipole moment of the 'artificial atom' and the enormous engineering potential inherent to superconducting quantum circuits, remarkable atom-photon coupling strengths can be realized. This thesis describes the theoretical framework, the development of fabrication techniques and the implementation of experimental characterization techniques for superconducting quantum circuits for circuit QED applications. In particular, we study the interaction between superconducting flux quantum bits and high-quality coplanar waveguide resonators in the strong-coupling limit. Furthermore, we report on the first experimental realization of a circuit QED system operating in the ultrastrong-coupling regime, where the atom-photon coupling rate reaches a considerable fraction of the relevant system frequencies. In these experiments we could observe phenomena that can not be explained within the renowned Jaynes-Cummings model. (orig.)

One-loop Wilson loops and the particle-interface potential in AdS/dCFT

Directory of Open Access Journals (Sweden)

Marius de Leeuw

2017-05-01

Full Text Available We initiate the calculation of quantum corrections to Wilson loops in a class of four-dimensional defect conformal field theories with vacuum expectation values based on N=4 super Yang–Mills theory. Concretely, we consider an infinite straight Wilson line, obtaining explicit results for the one-loop correction to its expectation value in the large-N limit. This allows us to extract the particle-interface potential of the theory. In a further double-scaling limit, we compare our results to those of a previous calculation in the dual string-theory set-up consisting of a D5-D3 probe-brane system with flux, and we find perfect agreement.

Recoil effects in the hyperfine structure of QED bound states

International Nuclear Information System (INIS)

Bodwin, G.T.; Yennie, D.R.; Gregorio, M.A.

1985-01-01

The authors give a general discussion of the derivation from field theory of a formalism for the perturbative solution of the relativistic two-body problem. The lowest-order expression for the four-point function is given in terms of a two-particle three-dimensional propagator in a static potential. It is obtained by fixing the loop energy in the four-dimensional formalism at a point which is independent of the loop momentum and is symmetric in the two particle variables. This method avoids awkward positive- and negative-energy projectors, with their attendant energy square roots, and allows one to recover the Dirac equation straightforwardly in the nonrecoil limit. The perturbations appear as a variety of four-dimensional kernels which are rearranged and regrouped into convenient sets. In particular, they are transformed from the Coulomb to the Feynman gauge, which greatly simplifies the expressions that must be evaluated. Although the approach is particularly convenient for the precision analysis of QED bound states, it is not limited to such applications. The authors use it to give the first unified treatment of all presently known recoil corrections to the muonium hyperfine structure and also to verify the corresponding contributions through order α 2 lnαE/sub F/ in positronium. The required integrals are evaluated analytically

High order QED corrections in Z physics

International Nuclear Information System (INIS)

Marck, S.C. van der.

1991-01-01

In this thesis a number of calculations of higher order QED corrections are presented, all applying to the standard LEP/SLC processes e + e - → f-bar f, where f stands for any fermion. In cases where f≠ e - , ν e , the above process is only possible via annihilation of the incoming electron positron pair. At LEP/SLC this mainly occurs via the production and the subsequent decay of a Z boson, i.e. the cross section is heavily dominated by the Z resonance. These processes and the corrections to them, treated in a semi-analytical way, are discussed (ch. 2). In the case f = e - (Bhabha scattering) the process can also occur via the exchange of a virtual photon in the t-channel. Since the latter contribution is dominant at small scattering angles one has to exclude these angles if one is interested in Z physics. Having excluded that region one has to recalculate all QED corrections (ch. 3). The techniques introduced there enables for the calculation the difference between forward and backward scattering, the forward backward symmetry, for the cases f ≠ e - , ν e (ch. 4). At small scattering angles, where Bhabha scattering is dominated by photon exchange in the t-channel, this process is used in experiments to determine the luminosity of the e + e - accelerator. hence an accurate theoretical description of this process at small angles is of vital interest to the overall normalization of all measurements at LEP/SLC. Ch. 5 gives such a description in a semi-analytical way. The last two chapters discuss Monte Carlo techniques that are used for the cases f≠ e - , ν e . Ch. 6 describes the simulation of two photon bremsstrahlung, which is a second order QED correction effect. The results are compared with results of the semi-analytical treatment in ch. 2. Finally ch. 7 reviews several techniques that have been used to simulate higher order QED corrections for the cases f≠ e - , ν e . (author). 132 refs.; 10 figs.; 16 tabs

The lattice spinor QED Hamiltonian critique of the continuous space approach

International Nuclear Information System (INIS)

Sidorov, A.V.; Zastavenko, L.G.

1993-01-01

We give the irreproachable, from the point of view of gauge invariance, derivation of the lattice spinor QED Hamiltonian. Our QED Hamiltonian is manifestly gauge invariant. We point out important defects of the continuous space formulation of the QED that make, in our opinion, the lattice QED obviously preferable to the continuous space QED. We state that it is impossible to give a continuous space QED formulation which is compatible with the condition of gauge invariance. 17 refs

QED at high energies

International Nuclear Information System (INIS)

Gastmans, R.

1980-01-01

This chapter demonstrates that to establish the validity of QED at the level of a few percent requires knowledge of the cross sections of the QED processes to the same accuracy. Discusses the virtual radiative corrections to the processes. Calculates the vertex correction effect to illustrate the technique. Examines the hadronic vacuum polarization because of its numerical significance. Calculates the effects of soft real photon bremsstrahlung, and shows that they cancel infrared divergences introduced by the virtual corrections. Outlines the analytical work and introduces the dimensional regularization of the infrared divergences as for the virtual photon case. Describes the calculation of the cross section for the bremsstrahlung processes in the ultra-relativistic limit. Shows the surprising simplicity of these cross sections. Discusses the phase space and the choice of integration variables in which the selection criteria must be expressed. Concludes with a comparison of some of the latest experiments on these QED reactions

Compact lattice QED with Wilson fermions

International Nuclear Information System (INIS)

Hoferichter, A.

1994-08-01

We study the phase structure and the chiral limit of 4d compact lattice QED with Wilson fermions (both dynamical and quenched). We use the standard Wilson gauge action and also a modified one suppressing lattice artifacts. Different techniques and observables to locate the chiral limit are discussed. (orig.)

Leading quantum gravitational corrections to scalar QED

International Nuclear Information System (INIS)

Bjerrum-Bohr, N.E.J.

2002-01-01

We consider the leading post-Newtonian and quantum corrections to the non-relativistic scattering amplitude of charged scalars in the combined theory of general relativity and scalar QED. The combined theory is treated as an effective field theory. This allows for a consistent quantization of the gravitational field. The appropriate vertex rules are extracted from the action, and the non-analytic contributions to the 1-loop scattering matrix are calculated in the non-relativistic limit. The non-analytical parts of the scattering amplitude, which are known to give the long range, low energy, leading quantum corrections, are used to construct the leading post-Newtonian and quantum corrections to the two-particle non-relativistic scattering matrix potential for two charged scalars. The result is discussed in relation to experimental verifications

Measurement of the running of the QED coupling in small angle Bhabha scattering with the OPAL detector

Energy Technology Data Exchange (ETDEWEB)

Guenther, P.

2005-06-01

Using the high precision OPAL Silicon-Tungsten luminometer at LEP, the running of the effective QED coupling {alpha}(t) is measured for space-like momentum transfer 1.81 {<=} -t {<=} 6.07 GeV{sup 2} through its effect on the angular spectrum of small angle Bhabha scattering. In an almost ideal QED framework, with very favourable experimental conditions, we obtain a strong direct evidence that the running of {alpha}(t) is consistent with standard model expectations. The null hypothesis that {alpha} remains constant within the above interval of -t is excluded with a significance above 5{sigma}: {delta}{alpha}(-6.07 GeV{sup 2}) - {delta}{alpha}(-1.81 GeV{sup 2}) = 0.00450 {+-} 0.00079 The hadronic contribution to the running of the coupling has been estimated to be: {delta}{alpha}{sub had}(-6.07 GeV{sup 2}) - {delta}{alpha}{sub had}(-1.81 GeV{sup 2}) = 0.00248 {+-} 0.00079. This result is inconsistent at the level of more than 3{sigma} with the hypothesis that only leptonic loops contribute to the running, and therefore provide the first clear space-like experimental evidence that hadronic loops also contribute. (orig.)

QED as the tensionless limit of the spinning string with contact interaction

Energy Technology Data Exchange (ETDEWEB)

Edwards, James P., E-mail: J.P.Edwards@durham.ac.uk; Mansfield, Paul, E-mail: P.R.W.Mansfield@durham.ac.uk

2015-06-30

QED with spinor matter is argued to correspond to the tensionless limit of spinning strings with contact interactions. The strings represent electric lines of force with charges at their ends. The interaction is constructed from a delta-function on the world-sheet which, although off-shell, decouples from the world-sheet metric. Integrating out the string degrees of freedom with fixed boundary generates the super-Wilson loop that couples spinor matter to electromagnetism in the world-line formalism. World-sheet and world-line, but not spacetime, supersymmetry underpin the model.

Theory of superfluorescence-laser crossover in a cavity QED system

Energy Technology Data Exchange (ETDEWEB)

Sezaki, Riku; Ishikawa, Akira; Kobayashi, Kiyoshi [University of Yamanashi, Department of Science for Advanced Materials, Kofu, Yamanashi (Japan); Miyajima, Kensuke [Tokyo University of Science, Department of Applied Physics, Tokyo (Japan)

2017-11-15

Coherent emissions of photons, originating from coherently-coupled polarizations, are created by laser and superfluorescence, but the mechanisms remain obscure to be fully explored in nanophotonics from the application viewpoint to coherent-light sources. In this paper, we present a comprehensive full quantum theory to clarify the crossover between laser and superfluorescence caused by the competition between stimulated and spontaneous emissions in a cavity QED system. As a result, in case of steady-state emission, we show the feasibility of coherent-light emission by superfluorescence different from laser, depending on the quality factor of a cavity QED system. In particular, the coherence generation due to superfluorescence occurs in a shorter timescale in a cavity QED systems with a lower Q factor than laser due to stimulated emission. This result suggests that superfluorescence can be applied to a novel coherent-light source by a mechanism greatly different from laser. (orig.)

XLOOPS - a package calculating one- and two-loop diagrams

International Nuclear Information System (INIS)

Bruecher, L.

1997-01-01

A program package for calculating massive one- and two-loop diagrams is introduced. It consists of five parts: - a graphical user interface, - routines for generating diagrams from particle input, - procedures for calculating one-loop integrals both analytically and numerically, - routines for massive two-loop integrals, - programs for numerical integration of two-loop diagrams. Here the graphical user interface and the text interface to Maple are presented. (orig.)

QED3 formulation of vortices in boson condensates and metafluid

International Nuclear Information System (INIS)

Soares, Thales Costa; Spalenza, Wesley; Helayel Neto, Jose Abdalla

2002-01-01

Full text: One consider a system of many non-relativistic particles as a fluid, going from the discrete set of space-time coordinates of each particle to a continuous field. With an interparticle potential that satisfies a number of physically reasonable assumptions, one shows how the Lagrangian describing the motion of the fluid displays an exact local gauge invariance governed by a scalar parameter. The conserved quantity associated to this local symmetry is derived and discussed in the light of planar Electrodynamics, with photons identified as sound waves in the fluid and point-like charges corresponding to vortices with azimuthal circulation. On the other hand, exploiting further the field configurations of planar Electrodynamics, one finds a peculiar source for the electrostatic sector with azimuthal electric field and a string-like scalar potential. This work sets out to attempt at establishing a parallel between this vortex-like electric field configurations in fluid dynamics. Vortices in boson condensates and the fluid dynamics of the condensates are reassessed and translated into electromagnetic fields of planar (Chern-Simons massive) QED. On The other hand, the metafluid equations, once suitable reduced from 3 to 2 space dimensions, are also seen to match field configurations of Maxwell (massless photons) planar QED. (author)

Results and techniques of multi-loop calculations

International Nuclear Information System (INIS)

Steinhauser, M.

2002-01-01

In this review some recent multi-loop results obtained in the framework of perturbative quantum chromodynamics (QCD) and quantum electrodynamics (QED) are discussed. After reviewing the most advanced techniques used for the computation of renormalization group functions, we consider the decoupling of heavy quarks. In particular, an effective method for the evaluation of the decoupling constants is presented and explicit results are given. Furthermore the connection to observables involving a scalar Higgs boson is worked out in detail. An all-order low energy v theorem is derived which establishes a relation between the coefficient functions in the hadronic Higgs decay and the decoupling constants. We review the radiative corrections of a Higgs boson into gluons and quarks and present explicit results up to order α s 4 and α s 3 , respectively. In this review special emphasis is put on the applications of asymptotic expansions. A method is described which combines expansion terms of different kinematical regions with the help of conformal mapping and Pade approximation. This method allows us to proceed beyond the present scope of exact multi-loop calculations. As far as physical processes are concerned, we review the computation of three-loop current correlators in QCD taking into account the full mass-dependence. In particular, we concentrate on the evaluation of the total cross section for the production of hadrons in e + e - annihilation. The knowledge of the complete mass dependence at order α s 2 has triggered a bunch of theory-driven analyses of the hadronic contribution to the electromagnetic coupling evaluated at high energy scales. The status is summarized in this review. In a further application four-loop diagrams are considered which contribute to the order α 2 QED corrections to the μ decay. Its relevance for the determination of the Fermi constant G F is discussed. Finally the calculation of the three-loop relation between the anti M anti S and on

Pair production by a constant external field in noncommutative QED

International Nuclear Information System (INIS)

Chair, N.; Sheikh-Jabbari, M.M.

2000-09-01

In this paper we study QED on the noncommutative space in the constant electro-magnetic field background. Using the explicit solutions of the noncommutative version of Dirac equation in such background, we show that there are well-defined in and out-going asymptotic states and also there is a causal Green's function. We calculate the pair production rate in this case. We show that at tree level noncommutativity will not change the pair production and the threshold electric field. We also calculate the pair production rate considering the first loop corrections. In this case we show that the threshold electric field is decreased by the noncommutativity effects. (author)

One-loop effective lagrangians after matching

Energy Technology Data Exchange (ETDEWEB)

Aguila, F. del; Santiago, J. [Universidad de Granada, Departamento de Fisica Teorica y del Cosmos and CAFPE, Granada (Spain); Kunszt, Z. [ETH Zuerich, Institute for Theoretical Physics, Zuerich (Switzerland)

2016-05-15

We discuss the limitations of the covariant derivative expansion prescription advocated to compute the one-loop Standard Model (SM) effective lagrangian when the heavy fields couple linearly to the SM. In particular, one-loop contributions resulting from the exchange of both heavy and light fields must be explicitly taken into account through matching because the proposed functional approach alone does not account for them. We review a simple case with a heavy scalar singlet of charge -1 to illustrate the argument. As two other examples where this matching is needed and this functional method gives a vanishing result, up to renormalization of the heavy sector parameters, we re-evaluate the one-loop corrections to the T-parameter due to a heavy scalar triplet with vanishing hypercharge coupling to the Brout-Englert-Higgs boson and to a heavy vector-like quark singlet of charged 2/3 mixing with the top quark, respectively. In all cases we make use of a new code for matching fundamental and effective theories in models with arbitrary heavy field additions. (orig.)

Gluon quasidistribution function at one loop

Energy Technology Data Exchange (ETDEWEB)

Wang, Wei; Zhao, Shuai [Shanghai Jiao Tong University, INPAC, Shanghai Key Laboratory for Particle Physics and Cosmology, School of Physics and Astronomy, Shanghai (China); Zhu, Ruilin [Shanghai Jiao Tong University, INPAC, Shanghai Key Laboratory for Particle Physics and Cosmology, School of Physics and Astronomy, Shanghai (China); Nanjing Normal University, Department of Physics and Institute of Theoretical Physics, Nanjing, Jiangsu (China)

2018-02-15

We study the unpolarized gluon quasidistribution function in the nucleon at one loop level in the large momentum effective theory. For the quark quasidistribution, power law ultraviolet divergences arise in the cut-off scheme and an important observation is that they all are subjected to Wilson lines. However for the gluon quasidistribution function, we first point out that the linear ultraviolet divergences also exist in the real diagram which is not connected to any Wilson line. We then study the one loop corrections to parton distribution functions in both cut-off scheme and dimensional regularization to deal with the ultraviolet divergences. In addition to the ordinary quark and gluon distributions, we also include the quark to gluon and gluon to quark splitting diagrams. The complete one-loop matching factors between the quasi and light cone parton distribution functions are presented in the cut-off scheme. We derive the P{sup z} evolution equation for quasi parton distribution functions, and find that the P{sup z} evolution kernels are identical to the DGLAP evolution kernels. (orig.)

Covariant diagrams for one-loop matching

International Nuclear Information System (INIS)

Zhang, Zhengkang

2016-10-01

We present a diagrammatic formulation of recently-revived covariant functional approaches to one-loop matching from an ultraviolet (UV) theory to a low-energy effective field theory. Various terms following from a covariant derivative expansion (CDE) are represented by diagrams which, unlike conventional Feynman diagrams, involve gaugecovariant quantities and are thus dubbed ''covariant diagrams.'' The use of covariant diagrams helps organize and simplify one-loop matching calculations, which we illustrate with examples. Of particular interest is the derivation of UV model-independent universal results, which reduce matching calculations of specific UV models to applications of master formulas. We show how such derivation can be done in a more concise manner than the previous literature, and discuss how additional structures that are not directly captured by existing universal results, including mixed heavy-light loops, open covariant derivatives, and mixed statistics, can be easily accounted for.

Covariant diagrams for one-loop matching

Energy Technology Data Exchange (ETDEWEB)

Zhang, Zhengkang [Michigan Center for Theoretical Physics (MCTP), University of Michigan,450 Church Street, Ann Arbor, MI 48109 (United States); Deutsches Elektronen-Synchrotron (DESY),Notkestraße 85, 22607 Hamburg (Germany)

2017-05-30

We present a diagrammatic formulation of recently-revived covariant functional approaches to one-loop matching from an ultraviolet (UV) theory to a low-energy effective field theory. Various terms following from a covariant derivative expansion (CDE) are represented by diagrams which, unlike conventional Feynman diagrams, involve gauge-covariant quantities and are thus dubbed “covariant diagrams.” The use of covariant diagrams helps organize and simplify one-loop matching calculations, which we illustrate with examples. Of particular interest is the derivation of UV model-independent universal results, which reduce matching calculations of specific UV models to applications of master formulas. We show how such derivation can be done in a more concise manner than the previous literature, and discuss how additional structures that are not directly captured by existing universal results, including mixed heavy-light loops, open covariant derivatives, and mixed statistics, can be easily accounted for.

Covariant diagrams for one-loop matching

Energy Technology Data Exchange (ETDEWEB)

Zhang, Zhengkang [Michigan Univ., Ann Arbor, MI (United States). Michigan Center for Theoretical Physics; Deutsches Elektronen-Synchrotron (DESY), Hamburg (Germany)

2016-10-15

We present a diagrammatic formulation of recently-revived covariant functional approaches to one-loop matching from an ultraviolet (UV) theory to a low-energy effective field theory. Various terms following from a covariant derivative expansion (CDE) are represented by diagrams which, unlike conventional Feynman diagrams, involve gaugecovariant quantities and are thus dubbed ''covariant diagrams.'' The use of covariant diagrams helps organize and simplify one-loop matching calculations, which we illustrate with examples. Of particular interest is the derivation of UV model-independent universal results, which reduce matching calculations of specific UV models to applications of master formulas. We show how such derivation can be done in a more concise manner than the previous literature, and discuss how additional structures that are not directly captured by existing universal results, including mixed heavy-light loops, open covariant derivatives, and mixed statistics, can be easily accounted for.

Covariant diagrams for one-loop matching

International Nuclear Information System (INIS)

Zhang, Zhengkang

2017-01-01

We present a diagrammatic formulation of recently-revived covariant functional approaches to one-loop matching from an ultraviolet (UV) theory to a low-energy effective field theory. Various terms following from a covariant derivative expansion (CDE) are represented by diagrams which, unlike conventional Feynman diagrams, involve gauge-covariant quantities and are thus dubbed “covariant diagrams.” The use of covariant diagrams helps organize and simplify one-loop matching calculations, which we illustrate with examples. Of particular interest is the derivation of UV model-independent universal results, which reduce matching calculations of specific UV models to applications of master formulas. We show how such derivation can be done in a more concise manner than the previous literature, and discuss how additional structures that are not directly captured by existing universal results, including mixed heavy-light loops, open covariant derivatives, and mixed statistics, can be easily accounted for.

QED coherence in matter

CERN Document Server

Preparata, Giuliano

1995-01-01

Up until now the dominant view of condensed matter physics has been that of an "electrostatic MECCANO" (erector set, for Americans). This book is the first systematic attempt to consider the full quantum-electrodynamical interaction (QED), thus greatly enriching the possible dynamical mechanisms that operate in the construction of the wonderful variety of condensed matter systems, including life itself.A new paradigm is emerging, replacing the "electrostatic MECCANO" with an "electrodynamic NETWORK," which builds condensed matter through the long range (as opposed to the "short range" nature o

One-loop effective potential on hyperbolic manifolds

International Nuclear Information System (INIS)

Cognola, G.; Kirsten, K.; Zerbini, S.

1993-01-01

The one-loop effective potential for a scalar field defined on an ultrastatic space-time whose spatial part is a compact hyperbolic manifold is studied using ζ-function regularization for the one-loop effective action. Other possible regularizations are discussed in detail. The renormalization group equations are derived, and their connection with the conformal anomaly is pointed out. The symmetry breaking and the topological mass generation are also discussed

One-loop partition functions of 3D gravity

International Nuclear Information System (INIS)

Giombi, Simone; Yin Xi; Maloney, Alexander

2008-01-01

We consider the one-loop partition function of free quantum field theory in locally Anti-de Sitter space-times. In three dimensions, the one loop determinants for scalar, gauge and graviton excitations are computed explicitly using heat kernel techniques. We obtain precisely the result anticipated by Brown and Henneaux: the partition function includes a sum over 'boundary excitations' of AdS 3 , which are the Virasoro descendants of empty Anti-de Sitter space. This result also allows us to compute the one-loop corrections to the Euclidean action of the BTZ black hole as well its higher genus generalizations.

One-loop triple collinear splitting amplitudes in QCD

Energy Technology Data Exchange (ETDEWEB)

Badger, Simon; Buciuni, Francesco; Peraro, Tiziano [Higgs Centre for Theoretical Physics, School of Physics and Astronomy, University of Edinburgh,Edinburgh EH9 3JZ, Scotland (United Kingdom)

2015-09-28

We study the factorisation properties of one-loop scattering amplitudes in the triple collinear limit and extract the universal splitting amplitudes for processes initiated by a gluon. The splitting amplitudes are derived from the analytic Higgs plus four partons amplitudes. We present compact results for primitive helicity splitting amplitudes making use of super-symmetric decompositions. The universality of the collinear factorisation is checked numerically against the full colour six parton squared matrix elements.

No parity anomaly in massless QED{sub 3}: A BPHZL approach

Energy Technology Data Exchange (ETDEWEB)

Del Cima, O.M. [Universidade Federal Fluminense (UFF), Polo Universitario de Rio das Ostras (PURO), Departamento de Ciencia e Tecnologia, Rua Recife s/n, 28890-000, Rio das Ostras, RJ (Brazil)], E-mail: wadodelcima@if.uff.br; Franco, D.H.T. [Universidade Federal de Vicosa (UFV), Departamento de Fisica - Campus Universitario, Avenida Peter Henry Rolfs s/n, 36570-000, Vicosa, MG (Brazil)], E-mail: dhtfranco@gmail.com; Piguet, O. [Universidade Federal do Espirito Santo (UFES), CCE, Departamento de Fisica, Campus Universitario de Goiabeiras, 29060-900, Vitoria, ES (Brazil)], E-mail: opiguet@pq.cnpq.br; Schweda, M. [Institut fuer Theoretische Physik, Technische Universitaet Wien (TU-Wien), Wiedner Hauptstrasse 8-10, A-1040, Vienna (Austria)], E-mail: mschweda@tph.tuwien.ac.at

2009-09-14

In this Letter we call into question the perturbatively parity breakdown at 1-loop for the massless QED{sub 3} frequently claimed in the literature. As long as perturbative quantum field theory is concerned, whether a parity anomaly owing to radiative corrections exists or not shall be definitely proved by using a renormalization method independent of any regularization scheme. Such a problem has been investigated in the framework of BPHZL renormalization method, by adopting the Lowenstein-Zimmermann subtraction scheme. The 1-loop parity-odd contribution to the vacuum-polarization tensor is explicitly computed in the framework of the BPHZL renormalization method. It is shown that a Chern-Simons term is generated at that order induced through the infrared subtractions - which violate parity. We show then that, what is called 'parity anomaly', is in fact a parity-odd counterterm needed for restauring parity.

Automated one-loop calculations with GoSam

International Nuclear Information System (INIS)

Cullen, Gavin; Greiner, Nicolas; Heinrich, Gudrun; Reiter, Thomas; Luisoni, Gionata; Mastrolia, Pierpaolo; Ossola, Giovanni; Tramontano, Francesco

2012-01-01

We present the program package GoSam which is designed for the automated calculation of one-loop amplitudes for multi-particle processes in renormalisable quantum field theories. The amplitudes, which are generated in terms of Feynman diagrams, can be reduced using either D-dimensional integrand-level decomposition or tensor reduction. GoSam can be used to calculate one-loop QCD and/or electroweak corrections to Standard Model processes and offers the flexibility to link model files for theories Beyond the Standard Model. A standard interface to programs calculating real radiation is also implemented. We demonstrate the flexibility of the program by presenting examples of processes with up to six external legs attached to the loop. (orig.)

Automated One-Loop Calculations with GoSam

CERN Document Server

Cullen, Gavin; Heinrich, Gudrun; Luisoni, Gionata; Mastrolia, Pierpaolo; Ossola, Giovanni; Reiter, Thomas; Tramontano, Francesco

2012-01-01

We present the program package GoSam which is designed for the automated calculation of one-loop amplitudes for multi-particle processes in renormalisable quantum field theories. The amplitudes, which are generated in terms of Feynman diagrams, can be reduced using either D-dimensional integrand-level decomposition or tensor reduction. GoSam can be used to calculate one-loop QCD and/or electroweak corrections to Standard Model processes and offers the flexibility to link model files for theories Beyond the Standard Model. A standard interface to programs calculating real radiation is also implemented. We demonstrate the flexibility of the program by presenting examples of processes with up to six external legs attached to the loop.

Relativistic and QED corrections to the g factor of Li-like ions

International Nuclear Information System (INIS)

Glazov, D.A.; Shabaev, V.M.; Volotka, A.V.; Tupitsyn, I.I.; Yerokhin, V.A.; Plunien, G.; Soff, G.

2004-01-01

Calculations of various corrections to the g factor of Li-like ions are presented, which result in a significant improvement of the theoretical accuracy in the region Z=6-92. The configuration-interaction Dirac-Fock method is employed for the evaluation of the interelectronic-interaction correction of order 1/Z 2 and higher. This correction is combined with the 1/Z interelectronic-interaction term derived within a rigorous QED approach. The one-electron QED correction of first order in α is obtained by employing our recent results for the self-energy term and by evaluating the vacuum-polarization contribution. The screening of QED corrections is taken into account to the leading orders in αZ and 1/Z

Automated computation of one-loop integrals in massless theories

International Nuclear Information System (INIS)

Hameren, A. van; Vollinga, J.; Weinzierl, S.

2005-01-01

We consider one-loop tensor and scalar integrals, which occur in a massless quantum field theory, and we report on the implementation into a numerical program of an algorithm for the automated computation of these one-loop integrals. The number of external legs of the loop integrals is not restricted. All calculations are done within dimensional regularization. (orig.)

Parton distribution functions with QED corrections in the valon model

Science.gov (United States)

Mottaghizadeh, Marzieh; Taghavi Shahri, Fatemeh; Eslami, Parvin

2017-10-01

The parton distribution functions (PDFs) with QED corrections are obtained by solving the QCD ⊗QED DGLAP evolution equations in the framework of the "valon" model at the next-to-leading-order QCD and the leading-order QED approximations. Our results for the PDFs with QED corrections in this phenomenological model are in good agreement with the newly related CT14QED global fits code [Phys. Rev. D 93, 114015 (2016), 10.1103/PhysRevD.93.114015] and APFEL (NNPDF2.3QED) program [Comput. Phys. Commun. 185, 1647 (2014), 10.1016/j.cpc.2014.03.007] in a wide range of x =[10-5,1 ] and Q2=[0.283 ,108] GeV2 . The model calculations agree rather well with those codes. In the latter, we proposed a new method for studying the symmetry breaking of the sea quark distribution functions inside the proton.

On the One Loop Corrections to Inflation II

DEFF Research Database (Denmark)

Sloth, Martin Snoager

2006-01-01

In this paper we extend our previous treatment of the one-loop corrections to inflation. Previously we calculated the one-loop corrections to the background and the two-point correlation function of inflaton fluctuations in a specific model of chaotic inflation. We showed that the loop correction...... model of chaotic inflation with a quadratic inflationary potential. We discuss the physical interpretation of the effect in terms of the tensor-to-scalar consistency relation. Finally, we discuss the relation to the work of Weinberg on quantum contributions to cosmological correlators....

Results from GRACE/SUSY at one-loop

Indian Academy of Sciences (India)

We report the recent development on the SUSY calculations with the help of GRACE system. GRACE/SUSY/1LOOP is the computer code which can generate Feynman diagrams in the MSSM automatically and compute one-loop amplitudes in the numerical way. We present new results of various two-body decay widths ...

Finite field-energy of a point charge in QED

International Nuclear Information System (INIS)

Costa, Caio V; Gitman, Dmitry M; Shabad, Anatoly E

2015-01-01

We consider a simple nonlinear (quartic in the fields) gauge-invariant modification of classical electrodynamics, to show that it possesses a regularizing ability sufficient to make the field energy of a point charge finite. The model is exactly solved in the class of static central-symmetric electric fields. Collation with quantum electrodynamics (QED) results in the total field energy of a point elementary charge about twice the electron mass. The proof of the finiteness of the field energy is extended to include any polynomial selfinteraction, thereby the one that stems from the truncated expansion of the Euler–Heisenberg local Lagrangian in QED in powers of the field strength. (paper)

Checking the transverse Ward-Takahashi relation at one-loop order in four dimensions

International Nuclear Information System (INIS)

Pennington, M R; Williams, R

2006-01-01

Some time ago Takahashi derived the so-called transverse relations relating Green's functions of different orders to complement the well-known Ward-Green-Takahashi identities of gauge theories by considering wedge rather than inner products. These transverse relations have the potential to determine the full fermion-boson vertex in terms of the renormalization functions of the fermion propagator. He and Yu have given an indicative proof at one-loop level in four dimensions. However, their construct involves the fourth-rank Levi-Civita tensor defined only unambiguously in four dimensions exactly where the loop integrals diverge. Consequently, here we explicitly check the proposed transverse Ward-Takahashi relation holds at one-loop order in d-dimensions, with d = 4 + ε

Perturbative renormalization of QED via flow equations

International Nuclear Information System (INIS)

Keller, G.; Kopper, C.

1991-01-01

We prove the perturbative renormalizability of euclidean QED 4 with a small photon mass in the framework of effective lagrangians due to Wilson and Polchinski. In particular we show that the QED identities, which become violated by our momentum space regularization at intermediate stages, are restored in the renormalized theory. (orig.)

Infrared singularities of fermion propagator and their connection with the Wilson loop

International Nuclear Information System (INIS)

Sissakyan, A.N.; Skachkov, N.B.; Shevchenko, O.Yu.

1987-01-01

The factorization of infrared singularities of gauge-invariant spinor propagator is proved in the framework of QED. It turns out that this infrared factor coincides with the Wilson loop and accumulates all the dependence on the form of the path of the initial Green function

Universality hypothesis breakdown at one-loop order

Science.gov (United States)

Carvalho, P. R. S.

2018-05-01

We probe the universality hypothesis by analytically computing the at least two-loop corrections to the critical exponents for q -deformed O (N ) self-interacting λ ϕ4 scalar field theories through six distinct and independent field-theoretic renormalization group methods and ɛ -expansion techniques. We show that the effect of q deformation on the one-loop corrections to the q -deformed critical exponents is null, so the universality hypothesis is broken down at this loop order. Such an effect emerges only at the two-loop and higher levels, and the validity of the universality hypothesis is restored. The q -deformed critical exponents obtained through the six methods are the same and, furthermore, reduce to their nondeformed values in the appropriated limit.

On the loop-loop scattering amplitudes in Abelian and non-Abelian gauge theories

International Nuclear Information System (INIS)

Meggiolaro, Enrico

2005-01-01

The high-energy elastic scattering amplitude of two colour-singlet qq-bar pairs is governed by the correlation function of two Wilson loops, which follow the classical straight lines for quark (antiquark) trajectories. This quantity is expected to be free of IR divergences, differently from what happens for the parton-parton elastic scattering amplitude, described, in the high-energy limit, by the expectation value of two Wilson lines. We shall explicitly test this IR finiteness by a direct non-perturbative computation of the loop-loop scattering amplitudes in the (pedagogic, but surely physically interesting) case of quenched QED. The results obtained for the Abelian case will be generalized to the case of a non-Abelian gauge theory with Nc colours, but stopping to the order O(g4) in perturbation theory. In connection with the above-mentioned IR finiteness, we shall also discuss some analytic properties of the loop-loop scattering amplitudes in both Abelian and non-Abelian gauge theories, when going from Minkowskian to Euclidean theory, which can be relevant to the still unsolved problem of the s-dependence of hadron-hadron total cross-sections

Gravitational interaction to one loop in effective quantum gravity

International Nuclear Information System (INIS)

Akhundov, A.

1996-10-01

The authors carry out the first step of a program conceived, in order to build a realistic model, having the particle spectrum of the standard model and renormalized masses, interaction terms and coupling, etc. which include the class of quantum gravity corrections, obtained by handling gravity as an effective theory. This provides an adequate picture at low energies, i.e. much less than the scale of strong gravity (the Planck mass). Hence the results are valid, irrespectively of any proposal for the full quantum gravity as a fundamental theory. The authors consider only non-analytic contributions to the one-loop scattering matrix elements, which provide the dominant quantum effect at long distance. These contributions are finite and independent from the finite value of the renormalization counter terms of the effective Lagrangian. The authors calculate the interaction of two heavy scalar particles, i.e. close to rest, due to the effective quantum gravity to the one loop order and compare with similar results in the literature

Gravitational interaction to one loop in effective quantum gravity

Energy Technology Data Exchange (ETDEWEB)

Akhundov, A. [Universitaet-gesamthochschule Siegen (Germany)]|[Azerbaijan Academy of Sciences, Baku (Azerbaijan). Institute of Physics; Bellucci, S. [INFN, Laboratori Nazionali di Frascati, Rome (Italy); Shiekh, A. [International Centre for Theoretical Physics, Trieste (Italy)

1996-10-01

The authors carry out the first step of a program conceived, in order to build a realistic model, having the particle spectrum of the standard model and renormalized masses, interaction terms and coupling, etc. which include the class of quantum gravity corrections, obtained by handling gravity as an effective theory. This provides an adequate picture at low energies, i.e. much less than the scale of strong gravity (the Planck mass). Hence the results are valid, irrespectively of any proposal for the full quantum gravity as a fundamental theory. The authors consider only non-analytic contributions to the one-loop scattering matrix elements, which provide the dominant quantum effect at long distance. These contributions are finite and independent from the finite value of the renormalization counter terms of the effective Lagrangian. The authors calculate the interaction of two heavy scalar particles, i.e. close to rest, due to the effective quantum gravity to the one loop order and compare with similar results in the literature.

Perturbative renormalization of QED via flow equations

Energy Technology Data Exchange (ETDEWEB)

Keller, G. (Max-Planck-Inst. fuer Physik, Werner-Heisenberg-Inst., Munich (Germany)); Kopper, C. (Max-Planck-Inst. fuer Physik, Werner-Heisenberg-Inst., Munich (Germany) Inst. fuer Theoretische Physik, Univ. Goettingen (Germany))

1991-12-19

We prove the perturbative renormalizability of euclidean QED{sub 4} with a small photon mass in the framework of effective lagrangians due to Wilson and Polchinski. In particular we show that the QED identities, which become violated by our momentum space regularization at intermediate stages, are restored in the renormalized theory. (orig.).

Automated one-loop calculations with GoSam

International Nuclear Information System (INIS)

Cullen, G.; Greiner, N.; Heinrich, G.; Reiter, T.; Luisoni, G.; Mastrolia, P.; Padua Univ.; Ossola, G.; Tramontano, F.

2012-01-01

In this talk, the program package GOSAM is presented which can be used for the automated calculation of one-loop amplitudes for multi-particle processes. The integrands are generated in terms of Feynman diagrams and can be reduced by d-dimensional integrand-level decomposition, or tensor reduction, or a combination of both. Through various examples we show that GOSAM can produce one-loop amplitudes for both QCD and electroweak theory; model files for theories Beyond the Standard Model can be linked as well. (orig.)

Automated one-loop calculations with GoSam

Energy Technology Data Exchange (ETDEWEB)

Cullen, G. [Deutsches Elektronen-Synchrotron (DESY), Zeuthen (Germany); Greiner, N.; Heinrich, G.; Reiter, T. [Max-Planck-Institut fuer Physik, Muenchen (Germany); Luisoni, G. [Durham Univ. (United Kingdom). Inst. for Particle Physics Phenomenology; Mastrolia, P. [Max-Planck-Institut fuer Physik, Muenchen (Germany); Padua Univ. (Italy). Dipt. di Fisica; Ossola, G. [City Univ. of New York, NY (United States). New York City College of Technology; Tramontano, F. [CERN, Geneva (Switzerland). AS Div.

2012-01-15

In this talk, the program package GOSAM is presented which can be used for the automated calculation of one-loop amplitudes for multi-particle processes. The integrands are generated in terms of Feynman diagrams and can be reduced by d-dimensional integrand-level decomposition, or tensor reduction, or a combination of both. Through various examples we show that GOSAM can produce one-loop amplitudes for both QCD and electroweak theory; model files for theories Beyond the Standard Model can be linked as well. (orig.)

One-loop infinities in dimensionally reduced supergravities

International Nuclear Information System (INIS)

Fradkin, E.S.; Tseytlin, A.A.

1983-11-01

It is proved explicitly in the paper that d=4 theory following via reduction from N=1, d=10 supergravities is not finite at one loop while the version of N=8 supergravity directly following from N=1, d=11 theory is one-loop finite. The method used is based on quantization of initial higher dimensional theory as a first step. The results also suggest possible existence of non-standard (higher N) d>4 supergravities which reduce to d=4 theories with finite N=8 supergravity sector. (author)

Chiral symmetry breaking is permitted in supersymmetric QED

International Nuclear Information System (INIS)

Walker, M.

2000-01-01

Full text: A chirally symmetric theory will generally have a chirally symmetric and a chirally asymmetric solution for the dressed fermionic propagator. It has been claimed that no chirally asymmetric solution for the fermionic propagator exists in supersymmetric QED. This result in the superfield formalism uses a gauge dependent argument whose validity has since been questioned. We present an analogous analysis using the component formalism which demonstrates that chiral symmetry breaking is permitted in this theory. We open the presentation with a brief introduction to supersymmetry, supersymmetric QED, and the superfield formalism. We describe chiral symmetry breaking and the Dyson-Schwinger equation used to analyse it. The derivation of the erroneous theorem claiming the lack of an a chiral propagator is outlined and its flaws discussed. We finish with the equivalent derivation in component fields and our contradictory result

On-shell recurrence relations for one-loop QCD amplitudes

International Nuclear Information System (INIS)

Bern, Zvi; Dixon, Lance J.; Kosower, David A.

2005-01-01

We present examples of on-shell recurrence relations for determining rational functions appearing in one-loop QCD amplitudes. In particular, we give relations for one-loop QCD amplitudes with all legs of positive helicity, or with one leg of negative helicity and the rest of positive helicity. Our recurrence relations are similar to the tree-level ones described by Britto, Cachazo, Feng, and Witten. A number of new features arise for loop amplitudes in nonsupersymmetric theories like QCD, including boundary terms and double poles. We show how to eliminate the boundary terms, which would interfere with obtaining useful relations. Using the relations we give compact explicit expressions for the n-gluon amplitudes with one negative-helicity gluon, up through n=7

The parity-preserving massive QED3: Vanishing β-function and no parity anomaly

Directory of Open Access Journals (Sweden)

O.M. Del Cima

2015-11-01

Full Text Available The parity-preserving massive QED3 exhibits vanishing gauge coupling β-function and is parity and infrared anomaly free at all orders in perturbation theory. Parity is not an anomalous symmetry, even for the parity-preserving massive QED3, in spite of some claims about the possibility of a perturbative parity breakdown, called parity anomaly. The proof is done by using the algebraic renormalization method, which is independent of any regularization scheme, based on general theorems of perturbative quantum field theory.

Combining NNPDF3.0 and NNPDF2.3QED through the APFEL evolution code

CERN Document Server

Bertone, Valerio

2016-01-01

We present sets of parton distribution functions (PDFs), based on the NNPDF3.0 family, which include the photon PDF from the NNPDF2.3QED sets, and leading-order QED contributions to the DGLAP evolution as implemented in the public code APFEL. The aim is to combine our state-of-the-art determination of quark and gluon PDFs with the so far only direct determination of the photon PDF from LHC data. In addition, the use of APFEL allowed us to employ a solution of the DGLAP equation that, differently from that used for the NNPDF2.3QED sets, includes QED corrections in a more accurate way. We briefly discuss how these sets are constructed and investigate the effect of the inclusion of the QED corrections on PDFs and parton luminosities. Finally, we compare the resulting sets, which we dubbed NNPDF3.0QED, to the older NNPDF2.3QED sets and to all presently available PDF sets that include QED corrections, namely CT14QED and MRST2004QED.

FF. A package to evaluate one-loop Feynman diagrams

International Nuclear Information System (INIS)

Oldenborgh, G.J. van

1990-09-01

A short description and a user's guide of the FF package are given. This package contains routines to evaluate numerically the scalar one-loop integrals occurring in the evaluation in one-loop Feynman diagrams. The algorithms chosen are numerically stable over most parameter space. (author). 5 refs.; 1 tab

Extending two Higgs doublet models for two-loop neutrino mass generation and one-loop neutrinoless double beta decay

Directory of Open Access Journals (Sweden)

Zhen Liu

2017-02-01

Full Text Available We extend some two Higgs doublet models, where the Yukawa couplings for the charged fermion mass generation only involve one Higgs doublet, by two singlet scalars respectively carrying a singly electric charge and a doubly electric charge. The doublet and singlet scalars together can mediate a two-loop diagram to generate a tiny Majorana mass matrix of the standard model neutrinos. Remarkably, the structure of the neutrino mass matrix is fully determined by the symmetric Yukawa couplings of the doubly charged scalar to the right-handed leptons. Meanwhile, a one-loop induced neutrinoless double beta decay can arrive at a testable level even if the electron neutrino has an extremely small Majorana mass. We also study other experimental constraints and implications including some rare processes and Higgs phenomenology.

Optical Search for QED vacuum magnetic birefringence, Axions and photon Regeneration

CERN Multimedia

Pugnat, P; Hryczuk, A; Finger, M; Finger, M; Kral, M

2007-01-01

Since its prediction in 1936 by Euler, Heisenberg and Weisskopf in the earlier development of the Quantum Electrodynamic (QED) theory, the Vacuum Magnetic Birefringence (VMB) is still a challenge for optical metrology techniques. According to QED, the vacuum behaves as an optically active medium in the presence of an external magnetic field. It can be experimentally probed with a linearly polarized laser beam. After propagating through the vacuum submitted to a transverse magnetic field, the polarization of the laser beam will change to elliptical and the parameters of the polarization are directly related to fundamental constants such as the fine structure constant and the electron Compton wavelength. Contributions to the VMB could also arise from the existence of light scalar or pseudo-scalar particles like axions that couple to two photons and this would manifest itself as a sizeable deviation from the initial QED prediction. On one side, the interest in axion search, providing an answer to the strong-CP p...

The two-photon self-energy and other QED radiative corrections

International Nuclear Information System (INIS)

Zschocke, S.

2001-07-01

One of the main issues in current nuclear physics is the precise measurement of the Lamb shift of strongly bound electrons in quantum electrodynamic (QED) tests in strong fields in highly charged ions. The currently performed high-precision measurements require extreme accuracy in the theoretical calculation of Lamb shift. This requires consideration of all α and α 2 order QED corrections as well as of precisely all orders in Zα. In the past years most of these QED corrections have been calculated both in 1st order and in 2nd order interference theory. As yet however, it has not been possible to assess the contribution of the two-photon self-energy, which has therefore been the greatest uncertainty factor in predicting Lamb shift in hydrogen-like systems. This study examines the contribution of these processes to Lamb shift. It also provides the first ever derivation of renormalized terms of two-photon vacuum polarisation and self-energy vacuum polarisation. Until now it has only been possible to evaluate these contributions by way of an Uehling approximation [de

Nonperturbative infrared dynamics in three dimensional QED

International Nuclear Information System (INIS)

Gusynin, V.P.

2000-01-01

A non-linear Schwinger-Dyson (SD) equation for the gauge boson propagator of massless QED in 2 + 1 dimensions is studied. It is shown that the nonperturbative solution leads to a non-trivial renormalization-group infrared fixed point quantitatively close to the one found in the leading order of the 1/N expansion, with N the number of fermion flavors

Chiral symmetry breaking and confinement in Minkowski space QED2+1

International Nuclear Information System (INIS)

Sauli, V.; Batiz, Z.

2010-01-01

Without any analytical assumption we solve the ladder QED2+1 in Minkowski space. Obtained complex fermion propagator exhibits confinement in the sense that it has no pole. Further, we transform Greens functions to the Temporal Euclidean space, wherein we show that in the special case of ladder QED2+1 the solution is fully equivalent to the Minkowski one. Obvious invalidity of Wick rotation is briefly discussed. The infrared value of the dynamical mass is compared with other known approaches, e. g. with the standard Euclidean calculation. We have presented for the first analysis of the electron gap equation in Minkowski and Temporal Euclidean space. The dynamical generation of imaginary part of the fermion mass leads to the absence of Khallen-Lehmann representation, providing thus confining solution for all value of m. Apart very small κ the real pole in the propagator is absent as well. Similarly to Euclidean QED3 Minkowski QED2+1 exhibits spontaneous chiral symmetry breaking the mass function has nontrivial solution in the limit m = 0, however the mass is complex function. Furthermore, we compare with QED solved in similar approximation in spacelike Euclidean and Temporal Euclidean space. As a interesting results, although based on the simple ladder approximation, is the proof of the exact equivalence between the theories defined in Minkowski 2+1 and 3D Temporal Euclidean space. We expect large quantitative changes when the polarization effect is taken account, especially the existence of critical number of flavors can be different when compared to the known Euclidean space estimates. Opposite to naive belief we showed and explained that the Wick rotation -the well known calculational trick in quantum theory- provides continuation of Schwinger function of the Euclidean theory which do not correspond with the Greens function calculated directly in the original Minkowski space. We can note our finding has a little to do with the know usefulness of various

An introduction to QED

International Nuclear Information System (INIS)

Martin, A.D.

1984-01-01

The lecture concerns quantum electrodynamics (QED), the relativistic quantum theory of electromagnetic interactions. Antiparticles, electrodynamics of spinless particles, the dirac equation and electrodynamics of spin 1/2 particles are discussed in detail. (U.K.)

Cavity QED experiments with ion Coulomb crystals

DEFF Research Database (Denmark)

Herskind, Peter Fønss; Dantan, Aurélien; Marler, Joan

2009-01-01

Cavity QED experimental results demonstrating collective strong coupling between ensembles of atomic ions cooled into Coulomb crystals and optical cavity fields have been achieved. Collective Zeeman coherence times of milliseconds have furthermore been obtained.......Cavity QED experimental results demonstrating collective strong coupling between ensembles of atomic ions cooled into Coulomb crystals and optical cavity fields have been achieved. Collective Zeeman coherence times of milliseconds have furthermore been obtained....

Invariant measure of the one-loop quantum gravitational backreaction on inflation

Science.gov (United States)

Miao, S. P.; Tsamis, N. C.; Woodard, R. P.

2017-06-01

We use dimensional regularization in pure quantum gravity on a de Sitter background to evaluate the one-loop expectation value of an invariant operator which gives the local expansion rate. We show that the renormalization of this nonlocal composite operator can be accomplished using the counterterms of a simple local theory of gravity plus matter, at least at one-loop order. This renormalization completely absorbs the one-loop correction, which accords with the prediction that the lowest secular backreaction should be a two-loop effect.

High-precision QED calculations of the hyperfine structure in hydrogen and transition rates in multicharged ions

Energy Technology Data Exchange (ETDEWEB)

Volotka, A.V.

2006-07-01

accounted for preserving gauge invariance. One-loop QED corrections to the magnetic-dipole transition amplitude between the fine-structure levels 2p{sub 3/2} and 2p{sub 1/2} are calculated to all orders in {alpha}Z. Taking into account consistently relativistic, interelectronic-interaction, and QED corrections to the magnetic-dipole transition amplitude allows for predictions of the lifetimes of the states (1s{sup 2}2s{sup 2}2p) {sup 2}P{sub 3/2} in B-like ions and (1s{sup 2}2s2p) {sup 3}P{sub 2} in Be-like ions with utmost precision. The results of corresponding calculations are compared with experimental data obtained in recent measurements at the Heidelberg EBIT. Finally, for He-like ions with nonzero-spin nuclei the effect of hyperfine quenching on the lifetimes of the 2{sup 3}P{sub 0,2} states is investigated and again compared available experimental data. (orig.)

High-precision QED calculations of the hyperfine structure in hydrogen and transition rates in multicharged ions

International Nuclear Information System (INIS)

Volotka, A.V.

2006-01-01

accounted for preserving gauge invariance. One-loop QED corrections to the magnetic-dipole transition amplitude between the fine-structure levels 2p 3/2 and 2p 1/2 are calculated to all orders in αZ. Taking into account consistently relativistic, interelectronic-interaction, and QED corrections to the magnetic-dipole transition amplitude allows for predictions of the lifetimes of the states (1s 2 2s 2 2p) 2 P 3/2 in B-like ions and (1s 2 2s2p) 3 P 2 in Be-like ions with utmost precision. The results of corresponding calculations are compared with experimental data obtained in recent measurements at the Heidelberg EBIT. Finally, for He-like ions with nonzero-spin nuclei the effect of hyperfine quenching on the lifetimes of the 2 3 P 0,2 states is investigated and again compared available experimental data. (orig.)

Automation of one-loop QCD corrections

CERN Document Server

Hirschi, Valentin; Frixione, Stefano; Garzelli, Maria Vittoria; Maltoni, Fabio; Pittau, Roberto

2011-01-01

We present the complete automation of the computation of one-loop QCD corrections, including UV renormalization, to an arbitrary scattering process in the Standard Model. This is achieved by embedding the OPP integrand reduction technique, as implemented in CutTools, into the MadGraph framework. By interfacing the tool so constructed, which we dub MadLoop, with MadFKS, the fully automatic computation of any infrared-safe observable at the next-to-leading order in QCD is attained. We demonstrate the flexibility and the reach of our method by calculating the production rates for a variety of processes at the 7 TeV LHC.

Simulations of relativistic quantum plasmas using real-time lattice scalar QED

Science.gov (United States)

Shi, Yuan; Xiao, Jianyuan; Qin, Hong; Fisch, Nathaniel J.

2018-05-01

Real-time lattice quantum electrodynamics (QED) provides a unique tool for simulating plasmas in the strong-field regime, where collective plasma scales are not well separated from relativistic-quantum scales. As a toy model, we study scalar QED, which describes self-consistent interactions between charged bosons and electromagnetic fields. To solve this model on a computer, we first discretize the scalar-QED action on a lattice, in a way that respects geometric structures of exterior calculus and U(1)-gauge symmetry. The lattice scalar QED can then be solved, in the classical-statistics regime, by advancing an ensemble of statistically equivalent initial conditions in time, using classical field equations obtained by extremizing the discrete action. To demonstrate the capability of our numerical scheme, we apply it to two example problems. The first example is the propagation of linear waves, where we recover analytic wave dispersion relations using numerical spectrum. The second example is an intense laser interacting with a one-dimensional plasma slab, where we demonstrate natural transition from wakefield acceleration to pair production when the wave amplitude exceeds the Schwinger threshold. Our real-time lattice scheme is fully explicit and respects local conservation laws, making it reliable for long-time dynamics. The algorithm is readily parallelized using domain decomposition, and the ensemble may be computed using quantum parallelism in the future.

Effective photon mass from black-hole formation

Directory of Open Access Journals (Sweden)

Slava Emelyanov

2017-06-01

Full Text Available We compute the value of effective photon mass mγ at one-loop level in QED in the background of small (1010 g≲M≪1016 g spherically symmetric black hole in asymptotically flat spacetime. This effect is associated with the modification of electron/positron propagator in presence of event horizon. Physical manifestations of black-hole environment are compared with those of hot neutral plasma. We estimate the distance to the nearest black hole from the upper bound on mγ obtained in the Coulomb-law test. We also find that corrections to electron mass me and fine structure constant α at one-loop level in QED are negligible in the weak gravity regime.

Scalar one-loop integrals for QCD

International Nuclear Information System (INIS)

Ellis, R. Keith; Zanderighi, Giulia

2008-01-01

We construct a basis set of infra-red and/or collinearly divergent scalar one-loop integrals and give analytic formulas, for tadpole, bubble, triangle and box integrals, regulating the divergences (ultra-violet, infra-red or collinear) by regularization in D = 4-2ε dimensions. For scalar triangle integrals we give results for our basis set containing 6 divergent integrals. For scalar box integrals we give results for our basis set containing 16 divergent integrals. We provide analytic results for the 5 divergent box integrals in the basis set which are missing in the literature. Building on the work of van Oldenborgh, a general, publicly available code has been constructed, which calculates both finite and divergent one-loop integrals. The code returns the coefficients of 1/ε 2 ,1/ε 1 and 1/ε 0 as complex numbers for an arbitrary tadpole, bubble, triangle or box integral

Light-by-light-type corrections to the muon anomalous magnetic moment at four-loop order

International Nuclear Information System (INIS)

Kurz, Alexander; Smirnov, Alexander V.; Smirnov, Vladimir A.

2015-08-01

The numerically dominant QED contributions to the anomalous magnetic moment of the muon stem from Feynman diagrams with internal electron loops. We consider such corrections and present a calculation of the four-loop light-by-light-type corrections where the external photon couples to a closed electron or muon loop. We perform an asymptotic expansion in the ratio of electron and muon mass and reduce the resulting integrals to master integrals which we evaluate using analytical and numerical methods. We confirm the results present in the literature which are based on different computational methods.

One-loop matching and running with covariant derivative expansion

Science.gov (United States)

Henning, Brian; Lu, Xiaochuan; Murayama, Hitoshi

2018-01-01

We develop tools for performing effective field theory (EFT) calculations in a manifestly gauge-covariant fashion. We clarify how functional methods account for one-loop diagrams resulting from the exchange of both heavy and light fields, as some confusion has recently arisen in the literature. To efficiently evaluate functional traces containing these "mixed" one-loop terms, we develop a new covariant derivative expansion (CDE) technique that is capable of evaluating a much wider class of traces than previous methods. The technique is detailed in an appendix, so that it can be read independently from the rest of this work. We review the well-known matching procedure to one-loop order with functional methods. What we add to this story is showing how to isolate one-loop terms coming from diagrams involving only heavy propagators from diagrams with mixed heavy and light propagators. This is done using a non-local effective action, which physically connects to the notion of "integrating out" heavy fields. Lastly, we show how to use a CDE to do running analyses in EFTs, i.e. to obtain the anomalous dimension matrix. We demonstrate the methodologies by several explicit example calculations.

Nonlinear QED effects in X-ray emission of pulsars

Energy Technology Data Exchange (ETDEWEB)

Shakeri, Soroush [Department of Physics, Isfahan University of Technology, Isfahan 84156-83111 (Iran, Islamic Republic of); Haghighat, Mansour [Department of Physics, Shiraz University, Shiraz 71946-84795 (Iran, Islamic Republic of); Xue, She-Sheng, E-mail: Soroush.Shakeri@ph.iut.ac.ir, E-mail: m.haghighat@shirazu.ac.ir, E-mail: xue@icra.it [ICRANet, Piazzale della Repubblica 10, 65122, Pescara (Italy)

2017-10-01

In the presence of strong magnetic fields near pulsars, the QED vacuum becomes a birefringent medium due to nonlinear QED interactions. Here, we explore the impact of the effective photon-photon interaction on the polarization evolution of photons propagating through the magnetized QED vacuum of a pulsar. We solve the quantum Boltzmann equation within the framework of the Euler-Heisenberg Lagrangian to find the evolution of the Stokes parameters. We find that linearly polarized X-ray photons propagating outward in the magnetosphere of a rotating neutron star can acquire high values for the circular polarization parameter. Meanwhile, it is shown that the polarization characteristics of photons besides photon energy depend strongly on parameters of the pulsars such as magnetic field strength, inclination angle and rotational period. Our results are clear predictions of QED vacuum polarization effects in the near vicinity of magnetic stars which can be tested with the upcoming X-ray polarimetric observations.

Quantum Bayesian rule for weak measurements of qubits in superconducting circuit QED

International Nuclear Information System (INIS)

Wang, Peiyue; Qin, Lupei; Li, Xin-Qi

2014-01-01

Compared with the quantum trajectory equation (QTE), the quantum Bayesian approach has the advantage of being more efficient to infer a quantum state under monitoring, based on the integrated output of measurements. For weak measurement of qubits in circuit quantum electrodynamics (cQED), properly accounting for the measurement backaction effects within the Bayesian framework is an important problem of current interest. Elegant work towards this task was carried out by Korotkov in ‘bad-cavity’ and weak-response limits (Korotkov 2011 Quantum Bayesian approach to circuit QED measurement (arXiv:1111.4016)). In the present work, based on insights from the cavity-field states (dynamics) and the help of an effective QTE, we generalize the results of Korotkov to more general system parameters. The obtained Bayesian rule is in full agreement with Korotkov's result in limiting cases and as well holds satisfactory accuracy in non-limiting cases in comparison with the QTE simulations. We expect the proposed Bayesian rule to be useful for future cQED measurement and control experiments. (paper)

QED radiative corrections under the SANC project

International Nuclear Information System (INIS)

Christova, P.

2003-01-01

Automatic calculations of the QED radiative corrections in the framework of the SANC computer system is described. A collection of the computer programs written in FORM3 language is aimed at compiling a database of analytic results to be used to theoretically support the experiments on high-energy accelerators. Presented here is the scheme of automatic analytical calculations of the QED radiative corrections to the fermionic decays of the Z, H and W boson in the framework of the SANC system

Local expressions for one-loop calculations

International Nuclear Information System (INIS)

Wasson, D.A.; Koonin, S.E.

1991-01-01

We develop local expressions for the contributions of the short-wavelength vacuum modes to the one-loop vacuum energy. These expressions significantly improve the convergence properties of various ''brute-force'' calculational methods. They also provide a continuous series of approximations that interpolate between the brute-force calculations and the derivative expansion

One-loop soft theorems via dual superconformal symmetry

Energy Technology Data Exchange (ETDEWEB)

Brandhuber, Andreas; Hughes, Edward; Spence, Bill; Travaglini, Gabriele [Centre for Research in String Theory, School of Physics and Astronomy,Queen Mary University of London,Mile End Road, London E1 4NS (United Kingdom)

2016-03-14

We study soft theorems at one loop in planar N = 4 super Yang-Mills theory through finite order in the infrared regulator and to subleading order in the soft parameter δ. In particular, we derive a universal constraint from dual superconformal symmetry, which we use to bootstrap subleading log δ behaviour. Moreover, we determine the complete infrared-finite subleading soft contribution of n-point MHV amplitudes using momentum twistors. Finally, we compute the subleading log δ behaviour of one-loop NMHV ratio functions at six and seven points, finding that universality holds within but not between helicity sectors.

Complete one-loop renormalization of the Higgs-electroweak chiral Lagrangian

Science.gov (United States)

Buchalla, G.; Catà, O.; Celis, A.; Knecht, M.; Krause, C.

2018-03-01

Employing background-field method and super-heat-kernel expansion, we compute the complete one-loop renormalization of the electroweak chiral Lagrangian with a light Higgs boson. Earlier results from purely scalar fluctuations are confirmed as a special case. We also recover the one-loop renormalization of the conventional Standard Model in the appropriate limit.

Exploring high-intensity QED at ELI

Energy Technology Data Exchange (ETDEWEB)

Heinzl, T. [Plymouth Univ., School of Mathematics and Statistics, Drake Circus, PL4 8AA (United Kingdom); Ilderton, A. [School of Mathematics, Hamilton Building, Trinity College, Dublin (Ireland)

2009-11-15

We give a non-technical overview of quantum electrodynamics (QED) effects arising in the presence of ultra-strong electromagnetic fields highlighting the new prospects provided by a realisation of the ELI laser facility. Vacuum polarization is a genuine QED process describing the probability amplitude of a propagating photon fluctuating into a virtual electron-positron pair. It has measurable effects such as the Lamb shift and charge screening at short distances. Nonlinear Compton scattering that consists of processes of the type: e + ngamma{sub L} -> e' + gamma (where n counting the number of laser photons involved) is an intensity dependent effect that is accessible to experimental observation

Local and non-local Schroedinger cat states in cavity QED

International Nuclear Information System (INIS)

Haroche, S.

2005-01-01

Full text: I will review recent experiments performed on mesoscopic state superpositions of field states in cavity QED. Proposals to extend these studies to Schroedinger cat states delocalized in two cavities will be discussed. New versions of Bell's inequality tests will probe the non-local behavior of these cats and study their sensitivity to decoherence. (author)

Electron contribution to the muon anomalous magnetic moment at four loops

International Nuclear Information System (INIS)

Kurz, Alexander; Liu, Tao; Smirnov, Alexander V.; Smirnov, Vladimir A.; Humboldt-Universitaet, Berlin; Humboldt-Universitaet, Berlin; Steinhauser, Matthias

2016-02-01

We present results for the QED contributions to the anomalous magnetic moment of the muon containing closed electron loops. The main focus is on perturbative corrections at four-loop order where the external photon couples to the external muon. Furthermore, all four-loop contributions involving simultaneously a closed electron and tau loop are computed. In combination with our recent results on the light-by-light-type corrections the complete four-loop electron-loop contribution to the anomalous magnetic moment of the muon has been obtained with an independent calculation. Our calculation is based on an asymptotic expansion in the ratio of the electron and the muon mass and shows the importance of higher order terms in this ratio. We perform a detailed comparison with results available in the literature and find good numerical agreement. As a by-product we present analytic results for the on-shell muon mass and wave function renormalization constants at three-loop order including massive closed electron and tau loops, which we also calculated using the method of asymptotic expansion.

Gluons and gravitons at one loop from ambitwistor strings

Science.gov (United States)

Geyer, Yvonne; Monteiro, Ricardo

2018-03-01

We present new and explicit formulae for the one-loop integrands of scattering amplitudes in non-supersymmetric gauge theory and gravity, valid for any number of particles. The results exhibit the colour-kinematics duality in gauge theory and the double-copy relation to gravity, in a form that was recently observed in supersymmetric theories. The new formulae are expressed in a particular representation of the loop integrand, with only one quadratic propagator, which arises naturally from the framework of the loop-level scattering equations. The starting point in our work are the expressions based on the scattering equations that were recently derived from ambitwistor string theory. We turn these expressions into explicit formulae depending only on the loop momentum, the external momenta and the external polarisations. These formulae are valid in any number of spacetime dimensions for pure Yang-Mills theory (gluon) and its natural double copy, NS-NS gravity (graviton, dilaton, B-field), and we also present formulae in four spacetime dimensions for pure gravity (graviton). We perform several tests of our results, such as checking gauge invariance and directly matching our four-particle formulae to previously known expressions. While these tests would be elaborate in a Feynman-type representation of the loop integrand, they become straightforward in the representation we use.

Existence of Green's functions in perturbative Q.E.D

International Nuclear Information System (INIS)

Seneor, R.

1976-01-01

A report is made on some work done in collaboration with P. Blanchard which shows how, in the framework developped by H.Epstein and V.Glaser, one can prove the existence of Green's functions in quantum electrodynamics (Q.E.D.). The proof can be extended, in principle, to any theory involving massive and non massive particles. (Auth.)

One-loop corrections to classical masses of kink families

International Nuclear Information System (INIS)

Alonso Izquierdo, A.; Garcia Fuertes, W.; Gonzalez Leon, M.A.; Mateos Guilarte, J.

2004-01-01

One-loop corrections to kink masses in a family of (1+1)-dimensional field theoretical models with two real scalar fields are computed. A generalized DHN formula applicable to potentials with and without reflection is obtained. It is shown how half-bound states arising in the spectrum of the second-order fluctuation operator for one-component topological kinks and the vacuum play a central role in the computation of the kink Casimir energy. The issue of whether or not the kink degeneracy exhibited by this family of models at the classical level survives one-loop quantum fluctuations is addressed

One-loop contributions to neutral minima in the inert doublet model

Energy Technology Data Exchange (ETDEWEB)

Ferreira, P.M. [Instituto Superior de Engenharia de Lisboa - ISEL,1959-007 Lisboa (Portugal); Centro de Física Teórica e Computacional - FCUL,Universidade de Lisboa, R. Ernesto de Vasconcelos, 1749-016 Lisboa (Portugal); Świeżewska, Bogumiła [Faculty of Physics, University of Warsaw,Pasteura 5, 02-093 Warsaw (Poland)

2016-04-15

The vacuum structure of the inert doublet model is analysed at the one-loop level using the effective potential formalism, to verify the validity of tree-level predictions for the properties of the global minimum. An inert minimum (with massive fermions) and an inert-like minimum (with massless fermions) can coexist at tree level. But the one-loop analysis reveals that the allowed parameter space for the coexistence of more than one minimum is larger than the tree-level expected one. It is also shown that for some choices of parameters, the global minimum found at the one-loop level may be inert (or inert-like), contrary to what the tree-level analysis indicates.

Quantum revolution. [Vol.] 2: QED: the jewel of physics

International Nuclear Information System (INIS)

Venkataraman, G.

1994-01-01

Events leading to the plague or crisis of infinities in the field of quantum mechanics are surveyed in brief. How that crisis was contained by formulation of quantum electrodynamics (QED) theory is narrated in this volume. Contributions of Tomanoga, Schwinger and Feynman to the QED theory are discussed. The story of quantum mechanics is brought up to fifties. (M.G.B.)

Atom-field dressed states in slow-light waveguide QED

Science.gov (United States)

Calajó, Giuseppe; Ciccarello, Francesco; Chang, Darrick; Rabl, Peter

2016-03-01

We discuss the properties of atom-photon bound states in waveguide QED systems consisting of single or multiple atoms coupled strongly to a finite-bandwidth photonic channel. Such bound states are formed by an atom and a localized photonic excitation and represent the continuum analog of the familiar dressed states in single-mode cavity QED. Here we present a detailed analysis of the linear and nonlinear spectral features associated with single- and multiphoton dressed states and show how the formation of bound states affects the waveguide-mediated dipole-dipole interactions between separated atoms. Our results provide both a qualitative and quantitative description of the essential strong-coupling processes in waveguide QED systems, which are currently being developed in the optical and microwave regimes.

A gauge/gravity relation in the one-loop effective action

International Nuclear Information System (INIS)

Basar, Goekce; Dunne, Gerald V

2010-01-01

We identify an unusual new gauge/gravity relation: the one-loop effective action for a massive spinor in 2n-dimensional AdS space is expressed in terms of precisely the same function (a certain multiple gamma function) as the one-loop effective action for a massive charged scalar in 4n dimensions in a maximally symmetric background electromagnetic field (one for which the eigenvalues of F μν are maximally degenerate, corresponding in four dimensions to a self-dual field, equivalently to a field of definite helicity), subject to the identification F 2 ↔Λ, where Λ is the gravitational curvature. Since these effective actions generate the low energy limit of all one-loop multi-leg graviton or gauge amplitudes, this implies a nontrivial gauge/gravity relation at the non-perturbative level and at the amplitude level. (fast track communication)

Quark loops and spin-flip effects in pomeron exchange

International Nuclear Information System (INIS)

Goloskokov, S.V.

1991-01-01

On the basis of QCD at large distances with taking account of some nonperturbative properties of the theory, the possibility of spin-flip effects in high energy hadron processes at fixed momenta transfer is investigated. It is shown that the diagrams with the quark loops in QCD at large distances may lead to the spin-flip amplitude growing as s for s→∞, t-fixed. The confirmation of this result is obtained by calculations of the nonleading contributions from quark loops in t-channel exchange in QED up to the end. Physical mechanisms leading to that behaviour of the spin-flip amplitude is discussed. So we conclude that the pomeron has a complicated spin structure. (orig.)

One loop integration with hypergeometric series by using recursion relations

International Nuclear Information System (INIS)

Watanabe, Norihisa; Kaneko, Toshiaki

2014-01-01

General one-loop integrals with arbitrary mass and kinematical parameters in d-dimensional space-time are studied. By using Bernstein theorem, a recursion relation is obtained which connects (n + 1)-point to n-point functions. In solving this recursion relation, we have shown that one-loop integrals are expressed by a newly defined hypergeometric function, which is a special case of Aomoto-Gelfand hypergeometric functions. We have also obtained coefficients of power series expansion around 4-dimensional space-time for two-, three- and four-point functions. The numerical results are compared with ''LoopTools'' for the case of two- and three-point functions as examples

One-loop divergences in 6D, N=(1,0) SYM theory

Energy Technology Data Exchange (ETDEWEB)

Buchbinder, I.L. [Department of Theoretical Physics, Tomsk State Pedagogical University,634061, Tomsk (Russian Federation); National Research Tomsk State University,634050, Tomsk (Russian Federation); Ivanov, E.A. [Bogoliubov Laboratory of Theoretical Physics,JINR, 141980 Dubna, Moscow region (Russian Federation); Merzlikin, B.S. [Department of Theoretical Physics, Tomsk State Pedagogical University,634061, Tomsk (Russian Federation); Department of Higher Mathematics and Mathematical Physics,Tomsk Polytechnic University,634050, Tomsk (Russian Federation); Stepanyantz, K.V. [Department of Theoretical Physics, Moscow State University,119991, Moscow (Russian Federation)

2017-01-30

We consider, in the harmonic superspace approach, the six-dimensional N=(1,0) supersymmetric Yang-Mills gauge multiplet minimally coupled to a hypermultiplet in an arbitrary representation of the gauge group. Using the superfield proper-time and background-field techniques, we compute the divergent part of the one-loop effective action depending on both the gauge multiplet and the hypermultiplet. We demonstrate that in the particular case of N=(1,1) SYM theory, which corresponds to the hypermultiplet in the adjoint representation, all one-loop divergencies vanish, so that N=(1,1) SYM theory is one-loop finite off shell.

A one-loop test of string duality

International Nuclear Information System (INIS)

Vafa, C.

1995-01-01

We test Type IIA-heterotic string duality in six dimensions by showing that the sigma model anomaly of the heterotic string is generated by a combination of a tree level and a string one-loop correction on the Type IIA side. (orig.)

A Coherence Preservation Control Strategy in Cavity QED Based on Classical Quantum Feedback

Directory of Open Access Journals (Sweden)

Ming Li

2013-01-01

Full Text Available For eliminating the unexpected decoherence effect in cavity quantum electrodynamics (cavity QED, the transfer function of Rabi oscillation is derived theoretically using optical Bloch equations. In particular, the decoherence in cavity QED from the atomic spontaneous emission is especially considered. A feedback control strategy is proposed to preserve the coherence through Rabi oscillation stabilization. In the scheme, a classical quantum feedback channel for the quantum information acquisition is constructed via the quantum tomography technology, and a compensation system based on the root locus theory is put forward to suppress the atomic spontaneous emission and the associated decoherence. The simulation results have proved its effectiveness and superiority for the coherence preservation.

3D full-loop simulation of an industrial-scale circulating fluidized boiler

Energy Technology Data Exchange (ETDEWEB)

Lu, Bona; Zhang, Nan; Wang, Wei; Li, Jinghai [Chinese Academy of Sciences, Beijing (China). State Key Lab. of Multi-phase Complex Systems

2013-07-01

In this study, 3D full-loop simulations of a CFB boiler are carried out. FLUENT {sup registered} 6.3 is used as the solver, where an Eulerian multiphase model with EMMS-based drag model is employed. The wide particle size distribution are considered and divided into several groups to better represent the polydisperse behavior of ash particles. The simulation shows that, compared to the conventional drag model, EMMS-based model predicts more reasonable pressure drop of furnace and larger slip velocity at the lower elevations of the furnace. Further work is under way to improve the full-loop simulation.

The Color Antisymmetric Ghost Propagator and One-Loop Vertex Renormalization

OpenAIRE

Furui, Sadataka

2007-01-01

The color matrix elements of the ghost triangle diagram that appears in the triple gluon vertex and the ghost-ghost-gluon triangle diagram that appears in the ghost-gluon-ghost vertex are calculated. The ghost-ghost-gluon triangle contains a loop consisting of two color diagonal ghosts and one gluon and a loop consisting of two color antisymmetric ghosts and one gluon. Consequently, the pQCD argument in the infrared region based on the one particle irreducible diagram should be modified. Impl...

The one-loop Green's functions of dimensionally reduced gauge theories

International Nuclear Information System (INIS)

Ketov, S.V.; Prager, Y.S.

1988-01-01

The dimensional regularization technique as well as that by dimensional reduction is applied to the calculation of the regularized one-loop Green's functions in dsub(o)-dimensional Yang-Mills theory with real massless scalars and spinors in arbitrary (real) representations of a gauge group G. As a particular example, the super-symmetrically regularized one-loop Green's functions of the N=4 supersymmetric Yang-Mills model are derived. (author). 17 refs

Supergraph analysis of the one-loop divergences in 6D, N=(1,0 and N=(1,1 gauge theories

Directory of Open Access Journals (Sweden)

I.L. Buchbinder

2017-08-01

Full Text Available We study the one-loop effective action for 6D, N=(1,0 supersymmetric Yang–Mills (SYM theory with hypermultiplets and 6D, N=(1,1 SYM theory as a subclass of the former, using the off-shell formulation of these theories in 6D, N=(1,0 harmonic superspace. We develop the corresponding supergraph technique and apply it to compute the one-loop divergences in the background field method ensuring the manifest gauge invariance. We calculate the two-point Green functions of the gauge superfield and the hypermultiplet, as well as the three-point gauge-hypermultipet Green function. Using these Green functions and exploiting gauge invariance of the theory, we find the full set of the off-shell one-loop divergent contributions, including the logarithmic and power ones. Our results precisely match with those obtained earlier in [1,2] within the proper time superfield method.

One-loop contributions to neutral Higgs decay h→μτ

International Nuclear Information System (INIS)

Phan, K. H.; Hung, H.T.; Hue, L.T.

2016-01-01

In calculating one-loop contributions to amplitudes of the lepton-flavor violating decays of the neutral Higgses (LFVHD) to different flavor charged leptons, the analytic expressions can be written in term of Passarino–Veltman functions. Then, they can be computed numerically by LoopTools [1]. Another approach is using suitable analytic expressions established for just this particular case. We compare numerical results obtained from LoopTools and those computed by different expressions that have been applied recently. Then we derive the preferable ones that are applicable for large ranges of free parameters introduced in extensions of the standard model. For illustration, the LFVHD in a simple model, which has been discussed recently, will be investigated more precisely.

Full cyclic coordinate descent: solving the protein loop closure problem in Cα space

Directory of Open Access Journals (Sweden)

Hamelryck Thomas

2005-06-01

Full Text Available Abstract Background Various forms of the so-called loop closure problem are crucial to protein structure prediction methods. Given an N- and a C-terminal end, the problem consists of finding a suitable segment of a certain length that bridges the ends seamlessly. In homology modelling, the problem arises in predicting loop regions. In de novo protein structure prediction, the problem is encountered when implementing local moves for Markov Chain Monte Carlo simulations. Most loop closure algorithms keep the bond angles fixed or semi-fixed, and only vary the dihedral angles. This is appropriate for a full-atom protein backbone, since the bond angles can be considered as fixed, while the (φ, ψ dihedral angles are variable. However, many de novo structure prediction methods use protein models that only consist of Cα atoms, or otherwise do not make use of all backbone atoms. These methods require a method that alters both bond and dihedral angles, since the pseudo bond angle between three consecutive Cα atoms also varies considerably. Results Here we present a method that solves the loop closure problem for Cα only protein models. We developed a variant of Cyclic Coordinate Descent (CCD, an inverse kinematics method from the field of robotics, which was recently applied to the loop closure problem. Since the method alters both bond and dihedral angles, which is equivalent to applying a full rotation matrix, we call our method Full CCD (FCDD. FCCD replaces CCD's vector-based optimization of a rotation around an axis with a singular value decomposition-based optimization of a general rotation matrix. The method is easy to implement and numerically stable. Conclusion We tested the method's performance on sets of random protein Cα segments between 5 and 30 amino acids long, and a number of loops of length 4, 8 and 12. FCCD is fast, has a high success rate and readily generates conformations close to those of real loops. The presence of constraints

Unimodular gravity and the lepton anomalous magnetic moment at one-loop

Energy Technology Data Exchange (ETDEWEB)

Martín, Carmelo P., E-mail: carmelop@fis.ucm.es [Departamento de Física Teórica I, Facultad de Ciencias Físicas, Universidad Complutense de Madrid, 28040 Madrid (Spain)

2017-07-01

We work out the one-loop contribution to the lepton anomalous magnetic moment coming from Unimodular Gravity. We use Dimensional Regularization and Dimensional Reduction to carry out the computations. In either case, we find that Unimodular Gravity gives rise to the same one-loop correction as that of General Relativity.

QED effects induced harmonics generation in extreme intense laser foil interaction

Science.gov (United States)

Yu, J. Y.; Yuan, T.; Liu, W. Y.; Chen, M.; Luo, W.; Weng, S. M.; Sheng, Z. M.

2018-04-01

A new mechanism of harmonics generation (HG) induced by quantum electrodynamics (QED) effects in extreme intense laser foil interaction is found and investigated by particle-in-cell (PIC) simulations. When two laser pulses with identical intensities of 1.6× {10}24 {{W}} {{{cm}}}-2 are counter-incident on a thin foil target, harmonics emission is observed in their reflected electromagnetic waves. Such harmonics radiation is excited due to transversely oscillating electric currents coming from the vibration of QED effect generated {e}-{e}+ pairs. The effects of laser intensity and polarization were studied. By distinguishing the cascade depth of generated photons and pairs, the influence of QED cascades on HG was analyzed. Although the current HG is not an efficient way for radiation source applications, it may provide a unique way to detect the QED processes in the near future ultra-relativistic laser solid interactions.

Probing Black Hole Magnetic Fields with QED

Directory of Open Access Journals (Sweden)

Ilaria Caiazzo

2018-05-01

Full Text Available The effect of vacuum birefringence is one of the first predictions of quantum electrodynamics (QED: the presence of a charged Dirac field makes the vacuum birefringent when threaded by magnetic fields. This effect, extremely weak for terrestrial magnetic fields, becomes important for highly magnetized astrophysical objects, such as accreting black holes. In the X-ray regime, the polarization of photons traveling in the magnetosphere of a black hole is not frozen at emission but is changed by the local magnetic field. We show that, for photons traveling along the plane of the disk, where the field is expected to be partially organized, this results in a depolarization of the X-ray radiation. Because the amount of depolarization depends on the strength of the magnetic field, this effect can provide a way to probe the magnetic field in black-hole accretion disks and to study the role of magnetic fields in astrophysical accretion in general.

New BCJ representations for one-loop amplitudes in gauge theories and gravity

Science.gov (United States)

He, Song; Schlotterer, Oliver; Zhang, Yong

2018-05-01

We explain a procedure to manifest the Bern-Carrasco-Johansson duality between color and kinematics in n-point one-loop amplitudes of a variety of supersymmetric gauge theories. Explicit amplitude representations are constructed through a systematic reorganization of the integrands in the Cachazo-He-Yuan formalism. Our construction holds for any nonzero number of supersymmetries and does not depend on the number of spacetime dimensions. The cancellations from supersymmetry multiplets in the loop as well as the resulting power counting of loop momenta is manifested along the lines of the corresponding superstring computations. The setup is used to derive the one-loop version of the Kawai-Lewellen-Tye formula for the loop integrands of gravitational amplitudes.

Chiral current generation in QED by longitudinal photons

Directory of Open Access Journals (Sweden)

J.L. Acosta Avalo

2016-08-01

Full Text Available We report the generation of a pseudovector electric current having imbalanced chirality in an electron–positron strongly magnetized gas in QED. It propagates along the external applied magnetic field B as a chiral magnetic effect in QED. It is triggered by a perturbative electric field parallel to B, associated to a pseudovector longitudinal mode propagating along B. An electromagnetic chemical potential was introduced, but our results remain valid even when it vanishes. A nonzero fermion mass was assumed, which is usually considered vanishing in the literature. In the quantum field theory formalism at finite temperature and density, an anomaly relation for the axial current was found for a medium of massive fermions. It bears some analogy to the Adler–Bell–Jackiw anomaly. From the expression for the chiral current in terms of the photon self-energy tensor in a medium, it is obtained that electrons and positrons scattered by longitudinal photons (inside the light cone contribute to the chiral current, as well as the to pair creation due to longitudinal photons (out of light cone. In the static limit, an electric pseudovector current is obtained in the lowest Landau level.

Quenched Chiral Perturbation Theory to one loop

NARCIS (Netherlands)

Colangelo, G.; Pallante, E.

The divergences of the generating functional of quenched Chiral Perturbation theory (qCHPT) to one loop are computed in closed form. We show how the quenched chiral logarithms can be reabsorbed in the renormalization of the B0 parameter of the leading order Lagrangian. Finally, we do the chiral

Algebraic evaluation of rational polynomials in one-loop amplitudes

International Nuclear Information System (INIS)

Binoth, Thomas; Guillet, Jean-Philippe; Heinrich, Gudrun

2007-01-01

One-loop amplitudes are to a large extent determined by their unitarity cuts in four dimensions. We show that the remaining rational terms can be obtained from the ultraviolet behaviour of the amplitude, and determine universal form factors for these rational parts by applying reduction techniques to the Feynman diagrammatic representation of the amplitude. The method is valid for massless and massive internal particles. We illustrate this method by evaluating the rational terms of the one-loop amplitudes for gg→H, γγ→γγ, gg→gg,γγ→ggg and γγ→γγγγ

GoSam. A program for automated one-loop calculations

Energy Technology Data Exchange (ETDEWEB)

Cullen, G. [Deutsches Elektronen-Synchrotron (DESY), Zeuthen (Germany); Greiner, N.; Heinrich, G.; Reiter, T. [Max-Planck-Institut fuer Physik, Muenchen (Germany); Luisoni, G. [Durham Univ. (United Kingdom). Inst. for Particle Physics Phenomenology; Mastrolia, P. [Max-Planck-Institut fuer Physik, Muenchen (Germany); Padua Univ. (Italy). Dipt. di Fisica; Ossola, G. [City Univ. of New York, NY (United States). New York City College of Technology; Tramontano, F. [European Organization for Nuclear Research (CERN), Geneva (Switzerland)

2011-11-15

The program package GoSam is presented which aims at the automated calculation of one-loop amplitudes for multi-particle processes. The amplitudes are generated in terms of Feynman diagrams and can be reduced using either D-dimensional integrand-level decomposition or tensor reduction, or a combination of both. GoSam can be used to calculate one-loop corrections to both QCD and electroweak theory, and model files for theories Beyond the Standard Model can be linked as well. A standard interface to programs calculating real radiation is also included. The flexibility of the program is demonstrated by various examples. (orig.)

GoSam. A program for automated one-loop calculations

International Nuclear Information System (INIS)

Cullen, G.; Greiner, N.; Heinrich, G.; Reiter, T.; Luisoni, G.

2011-11-01

The program package GoSam is presented which aims at the automated calculation of one-loop amplitudes for multi-particle processes. The amplitudes are generated in terms of Feynman diagrams and can be reduced using either D-dimensional integrand-level decomposition or tensor reduction, or a combination of both. GoSam can be used to calculate one-loop corrections to both QCD and electroweak theory, and model files for theories Beyond the Standard Model can be linked as well. A standard interface to programs calculating real radiation is also included. The flexibility of the program is demonstrated by various examples. (orig.)

GoSam: A program for automated one-loop calculations

International Nuclear Information System (INIS)

Cullen, G; Greiner, N; Heinrich, G; Mastrolia, P; Reiter, T; Luisoni, G; Ossola, G; Tramontano, F

2012-01-01

The program package GoSam is presented which aims at the automated calculation of one-loop amplitudes for multi-particle processes. The amplitudes are generated in terms of Feynman diagrams and can be reduced using either D-dimensional integrand-level decomposition or tensor reduction, or a combination of both. GoSam can be used to calculate one-loop corrections to both QCD and electroweak theory, and model files for theories Beyond the Standard Model can be linked as well. A standard interface to programs calculating real radiation is also included. The flexibility of the program is demonstrated by various examples.

The covariant-evolution-operator method in bound-state QED

International Nuclear Information System (INIS)

Lindgren, Ingvar; Salomonson, Sten; Aasen, Bjoern

2004-01-01

The methods of quantum-electrodynamical (QED) calculations on bound atomic systems are reviewed with emphasis on the newly developed covariant-evolution-operator method. The aim is to compare that method with other available methods and also to point out possibilities to combine that with standard many-body perturbation theory (MBPT) in order to perform accurate numerical QED calculations, including quasi-degeneracy, also for light elements, where the electron correlation is relatively strong. As a background, the time-independent many-body perturbation theory (MBPT) is briefly reviewed, particularly the method with extended model space. Time-dependent perturbation theory is discussed in some detail, introducing the time-evolution operator and the Gell-Mann-Low relation, generalized to an arbitrary model space. Three methods of treating the bound-state QED problem are discussed. The standard S-matrix formulation, which is restricted to a degenerate model space, is discussed only briefly. Two methods applicable also to the quasi-degenerate problem are treated in more detail, the two-times Green's-function and the covariant-evolution-operator techniques. The treatment is concentrated on the latter technique, which has been developed more recently and which has not been discussed in more detail before. A comparison of the two-times Green's-function and the covariant-evolution-operator techniques, which have great similarities, is performed. In the appendix a simple procedure is derived for expressing the evolution-operator diagrams of arbitrary order. The possibilities of merging QED in the covariant evolution-operator formulation with MBPT in a systematic way is indicated. With such a technique it might be feasible to perform accurate QED calculations also on light elements, which is presently not possible with the techniques available

Full parabolic trough qualification from prototype to demonstration loop

Science.gov (United States)

Janotte, Nicole; Lüpfert, Eckhard; Pottler, Klaus; Schmitz, Mark

2017-06-01

On the example of the HelioTrough® collector development the full accompanying and supporting qualification program for large-scale parabolic trough collectors for solar thermal power plants is described from prototype to demonstration loop scale. In the evaluation process the actual state and the optimization potential are assessed. This includes the optical and geometrical performance determined by concentrator shape, deformation, assembly quality and local intercept factor values. Furthermore, its mechanical performance in terms of tracking accuracy and torsional stiffness and its thermal system performance on the basis of the overall thermal output and heat loss are evaluated. Demonstration loop tests deliver results of collector modules statistical slope deviation of 1.9 to 2.6 mrad, intercept factor above 98%, peak optical performance of 81.6% and heat loss coefficients from field tests. The benefit of such a closely monitored development lies in prompt feedback on strengths, weaknesses and potential improvements on the new product at any development stage from first module tests until demonstration loop evaluation. The product developer takes advantage of the achieved technical maturity, already before the implementation in a commercial power plant. The well-understood performance characteristics allow the reduction of safety margins making the new HelioTrough collector competitive from the start.

Reduction schemes for one-loop tensor integrals

International Nuclear Information System (INIS)

Denner, A.; Dittmaier, S.

2006-01-01

We present new methods for the evaluation of one-loop tensor integrals which have been used in the calculation of the complete electroweak one-loop corrections to e + e - ->4 fermions. The described methods for 3-point and 4-point integrals are, in particular, applicable in the case where the conventional Passarino-Veltman reduction breaks down owing to the appearance of Gram determinants in the denominator. One method consists of different variants for expanding tensor coefficients about limits of vanishing Gram determinants or other kinematical determinants, thereby reducing all tensor coefficients to the usual scalar integrals. In a second method a specific tensor coefficient with a logarithmic integrand is evaluated numerically, and the remaining coefficients as well as the standard scalar integral are algebraically derived from this coefficient. For 5-point tensor integrals, we give explicit formulas that reduce the corresponding tensor coefficients to coefficients of 4-point integrals with tensor rank reduced by one. Similar formulas are provided for 6-point functions, and the generalization to functions with more internal propagators is straightforward. All the presented methods are also applicable if infrared (soft or collinear) divergences are treated in dimensional regularization or if mass parameters (for unstable particles) become complex

Implementation of Traveling Odd Schrödinger Cat States in Circuit-QED

Directory of Open Access Journals (Sweden)

Jaewoo Joo

2016-10-01

Full Text Available We propose a realistic scheme of generating a traveling odd Schrödinger cat state and a generalized entangled coherent state in circuit quantum electrodynamics (circuit-QED. A squeezed vacuum state is used as the initial resource of nonclassical states, which can be created through a Josephson traveling-wave parametric amplifier, and travels through a transmission line. Because a single-photon subtraction from the squeezed vacuum gives an odd Schrödinger cat state with very high fidelity, we consider a specific circuit-QED setup consisting of the Josephson amplifier creating the traveling resource in a line, a beam-splitter coupling two transmission lines, and a single photon detector located at the end of the other line. When a single microwave photon is detected by measuring the excited state of a superconducting qubit in the detector, a heralded cat state is generated with high fidelity in the opposite line. For example, we show that the high fidelity of the outcome with the ideal cat state can be achieved with appropriate squeezing parameters theoretically. As its extended setup, we suggest that generalized entangled coherent states can be also built probabilistically and that they are useful for microwave quantum information processing for error-correctable qudits in circuit-QED.

One-loop Pfaffians and large-field inflation in string theory

Energy Technology Data Exchange (ETDEWEB)

Ruehle, Fabian, E-mail: fabian.ruehle@physics.ox.ac.uk [Rudolf Peierls Centre for Theoretical Physics, Oxford University, 1 Keble Road, Oxford, OX1 3NP (United Kingdom); Wieck, Clemens, E-mail: clemens.wieck@uam.es [Departamento de Física Teórica and Instituto de Física Teórica UAM/CSIC, Universidad Autónoma de Madrid, Cantoblanco, 28049 Madrid (Spain)

2017-06-10

We study the consistency of large-field inflation in low-energy effective field theories of string theory. In particular, we focus on the stability of Kähler moduli in the particularly interesting case where the non-perturbative superpotential of the Kähler sector explicitly depends on the inflaton field. This situation arises generically due to one-loop corrections to the instanton action. The field dependence of the modulus potential feeds back into the inflationary dynamics, potentially impairing slow roll. We distinguish between world-sheet instantons from Euclidean D-branes, which typically yield polynomial one-loop Pfaffians, and gaugino condensates, which can yield exponential or periodic corrections. In all scenarios successful slow-roll inflation imposes bounds on the magnitude of the one-loop correction, corresponding to constraints on possible compactifications. While we put a certain emphasis on Type IIB constructions with mobile D7-branes, our results seem to apply more generally.

Resonator QED experiments with single {sup 40}Ca{sup +} ions; Resonator-QED-Experimente mit einzelnen {sup 40}Ca{sup +}-Ionen

Energy Technology Data Exchange (ETDEWEB)

Lange, B.

2006-12-20

Combining an optical resonator with an ion trap provides the possibility for QED experiments with single or few particles interacting with a single mode of the electro-magnetic field (Cavity-QED). In the present setup, fluctuations in the count rate on a time scale below 30 seconds were purely determined by the photon statistics due to finite emission and detection efficiency, whereas a marginal drift of the system was noticeable above 200 seconds. To find methods to increase the efficiency of the photon source, investigations were conducted and experimental improvements of the setup implemented in the frame of this thesis. Damping of the resonator field and coupling of ion and field were considered as the most important factors. To reduce the damping of the resonator field, a resonator with a smaller transmissivity of the output mirror was set up. The linear trap used in the experiment allows for the interaction of multiple ions with the resonator field, so that more than one photon may be emitted per pump pulse. This was investigated in this thesis with two ions coupled to the resonator. The cross correlation of the emitted photons was measured with the Hanbury Brown-Twiss method. (orig.)

One-loop renormalization of a gravity-scalar system

Energy Technology Data Exchange (ETDEWEB)

Park, I.Y. [Philander Smith College, Department of Applied Mathematics, Little Rock, AR (United States)

2017-05-15

Extending the renormalizability proposal of the physical sector of 4D Einstein gravity, we have recently proposed renormalizability of the 3D physical sector of gravity-matter systems. The main goal of the present work is to conduct systematic one-loop renormalization of a gravity-matter system by applying our foliation-based quantization scheme. In this work we explicitly carry out renormalization of a gravity-scalar system with a Higgs-type potential. With the fluctuation part of the scalar field gauged away, the system becomes renormalizable through a metric field redefinition. We use dimensional regularization throughout. One of the salient aspects of our analysis is how the graviton propagator acquires the ''mass'' term. One-loop calculations lead to renormalization of the cosmological and Newton constants. We discuss other implications of our results as well: time-varying vacuum energy density and masses of the elementary particles as well as the potential relevance of Neumann boundary condition for black hole information. (orig.)

One-loop renormalization of a gravity-scalar system

International Nuclear Information System (INIS)

Park, I.Y.

2017-01-01

Extending the renormalizability proposal of the physical sector of 4D Einstein gravity, we have recently proposed renormalizability of the 3D physical sector of gravity-matter systems. The main goal of the present work is to conduct systematic one-loop renormalization of a gravity-matter system by applying our foliation-based quantization scheme. In this work we explicitly carry out renormalization of a gravity-scalar system with a Higgs-type potential. With the fluctuation part of the scalar field gauged away, the system becomes renormalizable through a metric field redefinition. We use dimensional regularization throughout. One of the salient aspects of our analysis is how the graviton propagator acquires the ''mass'' term. One-loop calculations lead to renormalization of the cosmological and Newton constants. We discuss other implications of our results as well: time-varying vacuum energy density and masses of the elementary particles as well as the potential relevance of Neumann boundary condition for black hole information. (orig.)

One-loop renormalization of a gravity-scalar system

Science.gov (United States)

Park, I. Y.

2017-05-01

Extending the renormalizability proposal of the physical sector of 4D Einstein gravity, we have recently proposed renormalizability of the 3D physical sector of gravity-matter systems. The main goal of the present work is to conduct systematic one-loop renormalization of a gravity-matter system by applying our foliation-based quantization scheme. In this work we explicitly carry out renormalization of a gravity-scalar system with a Higgs-type potential. With the fluctuation part of the scalar field gauged away, the system becomes renormalizable through a metric field redefinition. We use dimensional regularization throughout. One of the salient aspects of our analysis is how the graviton propagator acquires the "mass" term. One-loop calculations lead to renormalization of the cosmological and Newton constants. We discuss other implications of our results as well: time-varying vacuum energy density and masses of the elementary particles as well as the potential relevance of Neumann boundary condition for black hole information.

On the problem of unboundedness from below of the spinor QED Hamiltonian

International Nuclear Information System (INIS)

Zastavenko, L.G.

1993-01-01

It is show that the Hamiltonian H QED + H 2 , where H QED is the spinor QED Hamiltonian and H 2 is the positive transversal photon mass term, is unbounded from below if the electromagnetic coupling constant e 2 is small enough, e 2 0 2 , and the transversal photon squared mass parameter M 2 is not large: 0 2 2 (1 - e 2 /e 0 2 )l 2 , here, l is the cut-off parameter; and c and e 0 2 , positive constants which do not depend on any parameters. 7 refs

The color antisymmetric ghost propagator and one-loop vertex renormalization

International Nuclear Information System (INIS)

Furui, Sadataka

2008-01-01

The color matrix elements of the ghost triangle diagram that appears in the triple gluon vertex and the ghost-ghost-gluon triangle diagram that appears in the ghost-gluon-ghost vertex are calculated. The ghost-ghost-gluon triangle contains a loop consisting of two color diagonal ghosts and one gluon and a loop consisting of two color antisymmetric ghosts and one gluon. Consequently, the pQCD argument in the infrared region based on the one particle irreducible diagram should be modified. Implications for the Kugo-Ojima color confinement and the QCD running coupling are discussed. (author)

Exact one-fermion-loop contributions in (1+1)-dimensional solitons

International Nuclear Information System (INIS)

Shepard, J.R.; Price, C.E.; Ferree, T.C.

1993-01-01

We find solutions to the (1+1)-dimensional scalar-only linear σ model. A new method is used to compute one-fermion-loop contributions exactly, and agreemment with published results employing other methods is excellent. A renormalization scheme which differs from that commonly used in such calculations but is similar to that required in 1+3 dimensions is also presented. We compare ''kink'' versus ''shallow bag'' solutions, paying careful attention to the implications of the one-fermion-loop contributions for the stability of the former. We find that, for small fermion multiplicities, self-consistent shallow bag solutions are always more bound than their metastable kink counterparts. However, as the fermion multiplicity increases, shallow bags evolve into kinks which eventually are the only self-consistent configurations. This situation is qualitatively the same for the two renormalization schemes considered. When we construct ''baryons,'' each containing three fermions, the kink configuration is typically more bound than the shallow bag when one-fermion-loop contributions are included

One-Loop BPS amplitudes as BPS-state sums

CERN Document Server

Angelantonj, Carlo; Pioline, Boris

2012-01-01

Recently, we introduced a new procedure for computing a class of one-loop BPS-saturated amplitudes in String Theory, which expresses them as a sum of one-loop contributions of all perturbative BPS states in a manifestly T-duality invariant fashion. In this paper, we extend this procedure to all BPS-saturated amplitudes of the form \\int_F \\Gamma_{d+k,d} {\\Phi}, with {\\Phi} being a weak (almost) holomorphic modular form of weight -k/2. We use the fact that any such {\\Phi} can be expressed as a linear combination of certain absolutely convergent Poincar\\'e series, against which the fundamental domain F can be unfolded. The resulting BPS-state sum neatly exhibits the singularities of the amplitude at points of gauge symmetry enhancement, in a chamber-independent fashion. We illustrate our method with concrete examples of interest in heterotic string compactifications.

CERN LEP2 constraint on 4D QED having a dynamically generated spatial dimension

International Nuclear Information System (INIS)

Cho, G.-C.; Izumi, Etsuko; Sugamoto, Akio

2002-01-01

We study 4D QED in which one spatial dimension is dynamically generated from the 3D action, following the mechanism proposed by Arkani-Hamed, Cohen, and Georgi. In this model, the generated fourth dimension is discretized by an interval parameter a. We examine the phenomenological constraint on the parameter a coming from collider experiments on the QED process e + e - →γγ. It is found that the CERN e + e - collider LEP2 experiments give the constraint of 1/a > or approx. 461 GeV. The expected bound on the same parameter a at a future e + e - linear collider is briefly discussed

The QED contribution to J/{psi} plus light hadrons production at B-factories

Energy Technology Data Exchange (ETDEWEB)

He, Zhi-Guo [Hamburg Univ. (Germany). 2. Inst. fuer Theoretische Physik; Wang, Jian-Xiong [Chinese Academy of Science, Beijing (China). Inst. of High Energy Physics; Chinese Academy of Science, Beijing (China). Theoretical Physics Center for Science Facilities

2013-01-15

To understand the direct J/{psi}+X{sub non-c} {sub anti} {sub c} production mechanism in e{sup +}e{sup -} annihilation, in this work, we propose to measure the inclusive J/{psi} plus light hadrons (LH) production at B-factories and present a detailed study on its QED production due to {psi}(2S) feed-down, where the {psi}(2S) are produced in e{sup +}e{sup -}{yields}{psi}(2S)+{gamma} and e{sup +}e{sup -}{yields}{psi}(2S) +f anti f, f = lepton, lightquark, and QED contribution to direct J/{psi}+q anti q production with q = u, d, s quark. We find that the QED contribution is huge in the whole phase space region, but can be reduced largely and is in the same order as the QCD contribution when a suitable cut on the angel {theta}{sub J/{psi}} between J/{psi} and the e{sup +}e{sup -} beam is made. In this way, the cross section of J/{psi} + LH QCD production % which was predicted theoretical at next-to-leading order QCD together with relativistic correction, can be obtained by subtracting the QED contribution from the experimental measurement on inclusive J/{psi} plus light hadrons. To help to remove the QED background, we also calculate the angular and momentum distribution of J/{psi} in the QED contribution.

Electric fields and monopole currents in compact QED

International Nuclear Information System (INIS)

Zach, M.; Faber, M.; Kainz, W.; Skala, P.

1995-01-01

The confinement in compact QED is known to be related to magnetic monopoles. Magnetic currents form a solenoid around electric flux lines between a pair of electric charges. This behaviour can be described by the dual version of Maxwell-London equations including a fluctuating string. We use a definition of magnetic monopole currents adjusted to the definition of the electric field strength on a lattice and get good agreement for field and current distributions between compact QED and the predictions of dual Maxwell-London equations. Further we show that the monopole fluctuations in the vacuum are suppressed by the flux tube. ((orig.))

Resonator QED experiments with single 40Ca+ ions

International Nuclear Information System (INIS)

Lange, B.

2006-01-01

Combining an optical resonator with an ion trap provides the possibility for QED experiments with single or few particles interacting with a single mode of the electro-magnetic field (Cavity-QED). In the present setup, fluctuations in the count rate on a time scale below 30 seconds were purely determined by the photon statistics due to finite emission and detection efficiency, whereas a marginal drift of the system was noticeable above 200 seconds. To find methods to increase the efficiency of the photon source, investigations were conducted and experimental improvements of the setup implemented in the frame of this thesis. Damping of the resonator field and coupling of ion and field were considered as the most important factors. To reduce the damping of the resonator field, a resonator with a smaller transmissivity of the output mirror was set up. The linear trap used in the experiment allows for the interaction of multiple ions with the resonator field, so that more than one photon may be emitted per pump pulse. This was investigated in this thesis with two ions coupled to the resonator. The cross correlation of the emitted photons was measured with the Hanbury Brown-Twiss method. (orig.)

On the screening of static electromagnetic fields in hot QED plasmas

International Nuclear Information System (INIS)

Blaizot, J.P.

1995-01-01

The screening of static magnetic and electric fields was studied in massless quantum electrodynamics (QED) and massless scalar electrodynamics (SQED) at temperature T. Various exact relations for the static polarization tensor are first reviewed, and then verified perturbatively to fifth order (in the coupling) in QED and fourth order in SQED, using different resummation techniques. The magnetic and electric screening masses squared, as defined through the pole of the static propagators, are also calculated to fifth order in QED and fourth order in SQED, and their gauge-independence and renormalisation-group invariance is checked. Finally, arguments are provided for the vanishing of the magnetic mass to all orders in perturbation theory. (author) 26 refs

Symplectic matrix, gauge invariance and Dirac brackets for super-QED

Energy Technology Data Exchange (ETDEWEB)

Alves, D.T. [Centro Brasileiro de Pesquisas Fisicas (CBPF), Rio de Janeiro, RJ (Brazil); Cheb-Terrab, E.S. [British Columbia Univ., Vancouver, BC (Canada). Dept. of Mathematics

1999-08-01

The calculation of Dirac brackets (DB) using a symplectic matrix approach but in a Hamiltonian framework is discussed, and the calculation of the DB for the supersymmetric extension of QED (super-QED) is shown. The relation between the zero-mode of the pre-symplectic matrix and the gauge transformations admitted by the model is verified. A general description to construct Lagrangians linear in the velocities is also presented. (author)

Low-mass Higgs decays to four leptons at one loop and beyond

Energy Technology Data Exchange (ETDEWEB)

Kniehl, Bernd A.; Veretin, Oleg L. [Hamburg Univ. (Germany). II. Inst. fuer Theoretische Physik

2012-06-15

The ongoing searches for Higgs-boson signals in data taken at the CERN LHC and the Fermilab Tevatron crucially rely on the decay channels H{yields}Zll and H{yields}Wl{nu}{sub l}. We present a precision study of the partial widths of these decay channels including the full one-loop electroweak corrections and the dominant contributions at two and three loops, of O(G{sub F}{sup 2}m{sub t}{sup 4}), O(G{sub F}m{sub t}{sup 2}{alpha}{sub s}), and O(G{sub F}m{sub t}{sup 2}{alpha}{sub s}{sup 2}). Since the invariant mass of the off-shell intermediate boson is relatively low in the mass window 115 GeV< m{sub H}<129 GeV of current interest, lepton mass effects are relevant, especially for the {tau} lepton. (orig.)

Tunable-Range, Photon-Mediated Atomic Interactions in Multimode Cavity QED

Directory of Open Access Journals (Sweden)

Varun D. Vaidya

2018-01-01

Full Text Available Optical cavity QED provides a platform with which to explore quantum many-body physics in driven-dissipative systems. Single-mode cavities provide strong, infinite-range photon-mediated interactions among intracavity atoms. However, these global all-to-all couplings are limiting from the perspective of exploring quantum many-body physics beyond the mean-field approximation. The present work demonstrates that local couplings can be created using multimode cavity QED. This is established through measurements of the threshold of a superradiant, self-organization phase transition versus atomic position. Specifically, we experimentally show that the interference of near-degenerate cavity modes leads to both a strong and tunable-range interaction between Bose-Einstein condensates (BECs trapped within the cavity. We exploit the symmetry of a confocal cavity to measure the interaction between real BECs and their virtual images without unwanted contributions arising from the merger of real BECs. Atom-atom coupling may be tuned from short range to long range. This capability paves the way toward future explorations of exotic, strongly correlated systems such as quantum liquid crystals and driven-dissipative spin glasses.

The Gribov problem in noncommutative QED

Energy Technology Data Exchange (ETDEWEB)

Canfora, Fabrizio [Centro de Estudios Científicos (CECS),Casilla 1469, Valdivia (Chile); Kurkov, Maxim A. [Dipartimento di Matematica, Università di Napoli Federico II,Monte S. Angelo, Via Cintia, 80126 Napoli (Italy); CMCC-Universidade Federal do ABC,Santo André, S.P. (Brazil); INFN, Sezione di Napoli,Monte S. Angelo, Via Cintia, 80126 Napoli (Italy); Rosa, Luigi; Vitale, Patrizia [Dipartimento di Fisica, Università di Napoli Federico II,Monte S. Angelo, Via Cintia, 80126 Napoli (Italy); INFN, Sezione di Napoli,Monte S. Angelo, Via Cintia, 80126 Napoli (Italy)

2016-01-04

It is shown that in the noncommutative version of QED (NCQED) Gribov copies induced by the noncommutativity of space-time appear in the Landau gauge. This is a genuine effect of noncommutative geometry which disappears when the noncommutative parameter vanishes.

String-inspired BCJ numerators for one-loop MHV amplitudes

International Nuclear Information System (INIS)

He, Song; Monteiro, Ricardo; Schlotterer, Oliver

2016-01-01

We find simple expressions for the kinematic numerators of one-loop MHV amplitudes in maximally supersymmetric Yang-Mills theory and supergravity, at any multiplicity. The gauge-theory numerators satisfy the Bern-Carrasco-Johansson (BCJ) duality between color and kinematics, so that the gravity numerators are simply the square of the gauge-theory ones. The duality holds because the numerators can be written in terms of structure constants of a kinematic algebra, which is familiar from the BCJ organization of self-dual gauge theory and gravity. The close connection that we find between one-loop amplitudes in the self-dual case and in the maximally supersymmetric case is reminiscent of the dimension-shifting formula. The starting point for arriving at our expressions is the dimensional reduction of ten-dimensional amplitudes obtained in the field-theory limit of open superstrings.

Does the Higgs mechanism favour electron-electron bound states in Maxwell-Chern-Simons QED3?

International Nuclear Information System (INIS)

Belich, Humberto; Helayeel-Neto, Jose Abdalla; Ferreira Junior, Manoel Messias

2000-01-01

Full text follows: We show that low-energy electron-electron bound states appear in the Maxwell-Chern-Simons (MCS) planar QED. In spite of the repulsive interaction mediated by the MCS gauge field, a net attractive interaction stems due to the Higgs mechanism through an Yukawa-type interaction. The spontaneous breaking of a local U(1)-symmetry is realized by a γ 6 -type potential. We conclude, by using the Schroedinger equation associated to the net attractive scattering potential, that electron-electron bound states arise in the model. Therefore, the Higgs mechanism overcomes the difficulties found out by Girotti et al. (Phys. Rev. Lett. 69 (1992) 2623) in searching for bound states in the MCS planar QED. (author)

QED polarization asymmetries for e+e- scattering due to helicity flips

International Nuclear Information System (INIS)

Anders, T.B.; Sell, E.W.

1992-01-01

The polarization asymmetries for the e + e - scattering with polarized incoming of outgoing beams, which are proportional to the amplitudes φ 5 describing one helicity flip and φ 2 describing two helicity flips, have been calculated including their pure QED radiative corrections. These asymmetries are partly large and can be observed well at low energies. (orig.)

A semi perturbative method for QED

OpenAIRE

Jora, Renata; Schechter, Joseph

2014-01-01

We compute the QED beta function using a new method of functional integration. It turns out that in this procedure the beta function contains only the first two orders coefficients and thus corresponds to a new renormalization scheme, long time supposed to exist.

Master formulas for the dressed scalar propagator in a constant field

Directory of Open Access Journals (Sweden)

Aftab Ahmad

2017-06-01

Full Text Available The worldline formalism has previously been used for deriving compact master formulas for the one-loop N-photon amplitudes in both scalar and spinor QED, and in the vacuum as well as in a constant external field. For scalar QED, there is also an analogous master formula for the propagator dressed with N photons in the vacuum. Here, we extend this master formula to include a constant field. The two-photon case is worked out explicitly, yielding an integral representation for the Compton scattering cross section in the field suitable for numerical integration in the full range of electric and magnetic field strengths.

Nonlinear optics quantum computing with circuit QED.

Science.gov (United States)

Adhikari, Prabin; Hafezi, Mohammad; Taylor, J M

2013-02-08

One approach to quantum information processing is to use photons as quantum bits and rely on linear optical elements for most operations. However, some optical nonlinearity is necessary to enable universal quantum computing. Here, we suggest a circuit-QED approach to nonlinear optics quantum computing in the microwave regime, including a deterministic two-photon phase gate. Our specific example uses a hybrid quantum system comprising a LC resonator coupled to a superconducting flux qubit to implement a nonlinear coupling. Compared to the self-Kerr nonlinearity, we find that our approach has improved tolerance to noise in the qubit while maintaining fast operation.

Recursive relations for processes with n photons of noncommutative QED

International Nuclear Information System (INIS)

Jafari, Abolfazl

2007-01-01

Recursion relations are derived in the sense of Berends-Giele for the multi-photon processes of noncommutative QED. The relations concern purely photonic processes as well as the processes with two fermions involved, both for arbitrary number of photons at tree level. It is shown that despite of the dependence of noncommutative vertices on momentum, in contrast to momentum-independent color factors of QCD, the recursion relation method can be employed for multi-photon processes of noncommutative QED

QED Theory of the Nuclear Magnetic Shielding in Hydrogenlike Ions

International Nuclear Information System (INIS)

Yerokhin, V. A.; Pachucki, K.; Harman, Z.; Keitel, C. H.

2011-01-01

The shielding of the nuclear magnetic moment by the bound electron in hydrogenlike ions is calculated ab initio with inclusion of relativistic, nuclear, and quantum electrodynamics (QED) effects. The QED correction is evaluated to all orders in the nuclear binding strength parameter and, independently, to the first order in the expansion in this parameter. The results obtained lay the basis for the high-precision determination of nuclear magnetic dipole moments from measurements of the g factor of hydrogenlike ions.

Landau singularities and symbology: one- and two-loop MHV amplitudes in SYM theory

Energy Technology Data Exchange (ETDEWEB)

Dennen, Tristan; Spradlin, Marcus; Volovich, Anastasia [Department of Physics, Brown University,Providence RI 02912 (United States)

2016-03-14

We apply the Landau equations, whose solutions parameterize the locus of possible branch points, to the one- and two-loop Feynman integrals relevant to MHV amplitudes in planar N=4 super-Yang-Mills theory. We then identify which of the Landau singularities appear in the symbols of the amplitudes, and which do not. We observe that all of the symbol entries in the two-loop MHV amplitudes are already present as Landau singularities of one-loop pentagon integrals.

Landau singularities and symbology: one- and two-loop MHV amplitudes in SYM theory

International Nuclear Information System (INIS)

Dennen, Tristan; Spradlin, Marcus; Volovich, Anastasia

2016-01-01

We apply the Landau equations, whose solutions parameterize the locus of possible branch points, to the one- and two-loop Feynman integrals relevant to MHV amplitudes in planar N=4 super-Yang-Mills theory. We then identify which of the Landau singularities appear in the symbols of the amplitudes, and which do not. We observe that all of the symbol entries in the two-loop MHV amplitudes are already present as Landau singularities of one-loop pentagon integrals.

Partially massless higher-spin theory II: one-loop effective actions

Energy Technology Data Exchange (ETDEWEB)

Brust, Christopher [Perimeter Institute for Theoretical Physics,31 Caroline St. N, Waterloo, Ontario, N2L 2Y5 (Canada); Hinterbichler, Kurt [CERCA, Department of Physics, Case Western Reserve University,10900 Euclid Ave, Cleveland, OH, 44106 (United States)

2017-01-30

We continue our study of a generalization of the D-dimensional linearized Vasiliev higher-spin equations to include a tower of partially massless (PM) fields. We compute one-loop effective actions by evaluating zeta functions for both the “minimal” and “non-minimal” parity-even versions of the theory. Specifically, we compute the log-divergent part of the effective action in odd-dimensional Euclidean AdS spaces for D=7 through 19 (dual to the a-type conformal anomaly of the dual boundary theory), and the finite part of the effective action in even-dimensional Euclidean AdS spaces for D=4 through 8 (dual to the free energy on a sphere of the dual boundary theory). We pay special attention to the case D=4, where module mixings occur in the dual field theory and subtlety arises in the one-loop computation. The results provide evidence that the theory is UV complete and one-loop exact, and we conjecture and provide evidence for a map between the inverse Newton’s constant of the partially massless higher-spin theory and the number of colors in the dual CFT.

Partially massless higher-spin theory II: one-loop effective actions

International Nuclear Information System (INIS)

Brust, Christopher; Hinterbichler, Kurt

2017-01-01

We continue our study of a generalization of the D-dimensional linearized Vasiliev higher-spin equations to include a tower of partially massless (PM) fields. We compute one-loop effective actions by evaluating zeta functions for both the “minimal” and “non-minimal” parity-even versions of the theory. Specifically, we compute the log-divergent part of the effective action in odd-dimensional Euclidean AdS spaces for D=7 through 19 (dual to the a-type conformal anomaly of the dual boundary theory), and the finite part of the effective action in even-dimensional Euclidean AdS spaces for D=4 through 8 (dual to the free energy on a sphere of the dual boundary theory). We pay special attention to the case D=4, where module mixings occur in the dual field theory and subtlety arises in the one-loop computation. The results provide evidence that the theory is UV complete and one-loop exact, and we conjecture and provide evidence for a map between the inverse Newton’s constant of the partially massless higher-spin theory and the number of colors in the dual CFT.

Comparing EFT and Exact One-Loop Analyses of Non-Degenerate Stops

CERN Document Server

Drozd, Aleksandra; Quevillon, Jeremie; You, Tevong

2015-01-01

We develop a universal approach to the one-loop effective field theory (EFT) using the Covariant Derivative Expansion (CDE) method. We generalise previous results to include broader classes of UV models, showing how expressions previously obtained assuming degenerate heavy-particle masses can be extended to non-degenerate cases. We apply our method to the general MSSM with non-degenerate stop squarks, illustrating our approach with calculations of the coefficients of dimension-6 operators contributing to the $hgg$ and $h\\gamma\\gamma$ couplings, and comparing with exact calculations of one-loop Feynman diagrams. We then use present and projected future sensitivities to these operator coefficients to obtain present and possible future indirect constraints on stop masses. The current sensitivity is already comparable to that of direct LHC searches, and future FCC-ee measurements could be sensitive to stop masses above a TeV. The universality of our one-loop EFT approach facilitates extending these constraints to...

Engineering non-linear resonator mode interactions in circuit QED by continuous driving: Introduction

Science.gov (United States)

Pfaff, Wolfgang; Reagor, Matthew; Heeres, Reinier; Ofek, Nissim; Chou, Kevin; Blumoff, Jacob; Leghtas, Zaki; Touzard, Steven; Sliwa, Katrina; Holland, Eric; Krastanov, Stefan; Frunzio, Luigi; Devoret, Michel; Jiang, Liang; Schoelkopf, Robert

2015-03-01

High-Q microwave resonators show great promise for storing and manipulating quantum states in circuit QED. Using resonator modes as such a resource in quantum information processing applications requires the ability to manipulate the state of a resonator efficiently. Further, one must engineer appropriate coupling channels without spoiling the coherence properties of the resonator. We present an architecture that combines millisecond lifetimes for photonic quantum states stored in a linear resonator with fast measurement provided by a low-Q readout resonator. We demonstrate experimentally how a continuous drive on a transmon can be utilized to generate highly non-classical photonic states inside the high-Q resonator via effective nonlinear resonator mode interactions. Our approach opens new avenues for using modes of long-lived linear resonators in the circuit QED platform for quantum information processing tasks.

Exact solutions for fermionic Green's functions in the Bloch-Nordsieck approximation of QED

International Nuclear Information System (INIS)

Kernemann, A.; Stefanis, N.G.

1989-01-01

A set of new closed-form solutions for fermionic Green's functions in the Bloch-Nordsieck approximation of QED is presented. A manifestly covariant phase-space path-integral method is applied for calculating the n-fermion Green's function in a classical external field. In the case of one and two fermions, explicit expressions for the full Green's functions are analytically obtained, with renormalization carried out in the modified minimal subtraction scheme. The renormalization constants and the corresponding anomalous dimensions are determined. The mass-shell behavior of the two-fermion Green's function is investigated in detail. No assumptions are made concerning the structure of asymptotic states and no IR cutoff is used in the calculations

Discussion on some one-loop induced flavour-changing decays

International Nuclear Information System (INIS)

Wang Jianxiong; Chang Chaohsi

1990-08-01

We calculate the one-loop flavour-changing processes Z 0 → bs-bar, B s(d) → X + γγ, B s → γγ and B s → gg in the Standard Model, provided t quark mass is very heavy, and obtain Br(B s (d) → X + γγ) ∼ 10 -5 , Br(B s → γγ) ∼ 10 -6 and Br(B s → gg) ∼ 10 -5 . The branching ratios increase 2-4 times as m t from 80 to 240 GeV. The results show that the contribution from t quark-loop is dominant. (author). 4 refs

arXiv Diagrammatic Hopf algebra of cut Feynman integrals: the one-loop case

CERN Document Server

Abreu, Samuel; Duhr, Claude; Gardi, Einan

2017-12-15

We construct a diagrammatic coaction acting on one-loop Feynman graphs and their cuts. The graphs are naturally identified with the corresponding (cut) Feynman integrals in dimensional regularization, whose coefficients of the Laurent expansion in the dimensional regulator are multiple polylogarithms (MPLs). Our main result is the conjecture that this diagrammatic coaction reproduces the combinatorics of the coaction on MPLs order by order in the Laurent expansion. We show that our conjecture holds in a broad range of nontrivial one-loop integrals. We then explore its consequences for the study of discontinuities of Feynman integrals, and the differential equations that they satisfy. In particular, using the diagrammatic coaction along with information from cuts, we explicitly derive differential equations for any one-loop Feynman integral. We also explain how to construct the symbol of any one-loop Feynman integral recursively. Finally, we show that our diagrammatic coaction follows, in the special case of o...

The stimulated Breit–Wheeler process as a source of background e+ ...

Indian Academy of Sciences (India)

... at the international linear collider. A Hartin. Machine Detector Interface Volume 69 Issue 6 December 2007 pp 1159-1164 ... A full QED calculation of this stimulated Breit-Wheeler process reveals cross-section resonances due to the virtual particle reaching the mass shell. The one-loop electron self-energy in the bunch ...

Full instantaneous traversal rupture of the primary loop pipeline

International Nuclear Information System (INIS)

Baytelesov, S.A.; Kungurov, F.R.

2010-01-01

Accident, reflecting full immediate cross rupture of primary loop pipe of WWR-SM research reactor of INP AS RUz is observed in this paper. Calculations for accident situation and analysis for different reactor cores, formed from fully IRT-3M type high enriched fuel (36% enrichment on 235 U), first mixed core, compiled from 16 IRT-3M fuel assemblies and 4 IRT-4M type fuel assemblies with low enriched fuel (19,7% enrichment on 235 U) and the core fully formed from low enriched fuel are carried out

An ambiguity in one-loop quantum gravity

International Nuclear Information System (INIS)

Capper, D.M.; Kimber, D.P.

1980-01-01

It is argued that the application of the dimensional regularisation technique to one-loop quantum gravity calculations is ambiguous. However, for the calculation of on-mass-shell S-matrix elements, this ambiguity can be resolved by requiring consistency with results obtained from other regularisation schemes. Some discussion is also given of the implications of this work for recent attempts to use higher derivative Lagrangians to solve the renormalisability problem in quantum gravity. (author)

One loop back reaction on power law inflation

International Nuclear Information System (INIS)

Abramo, L.R.; Woodard, R.P.

1999-01-01

We consider quantum-mechanical corrections to a homogeneous, isotropic, and spatially flat geometry whose scale factor expands classically as a general power of the comoving time. The effects of both gravitons and the scalar inflaton are computed at one loop using the manifestly causal formalism of Schwinger [J. Math. Phys. 2, 407 (1961); Particles, Sources and Fields (Addison, Wesley, Reading, MA, 1970)] with the Feynman rules recently developed by Iliopoulos et al. [Nucl. Phys. B 534, 419 (1998)]. We find no significant effect, in marked contrast to the result obtained by Mukhanov and co-workers [Phys. Rev. Lett. 78, 1624 (1998); Phys. Rev. D 56, 3248 (1997)] for chaotic inflation based on a quadratic potential. By applying the canonical technique of Mukhanov and co-workers to the exponential potentials of power law inflation, we show that the two methods produce the same results, within the approximations employed, for these backgrounds. We therefore conclude that the shape of the inflaton potential can have an enormous impact on the one loop back reaction. copyright 1999 The American Physical Society

Mixed heavy–light matching in the Universal One-Loop Effective Action

International Nuclear Information System (INIS)

Ellis, Sebastian A.R.; Quevillon, Jérémie; You, Tevong; Zhang, Zhengkang

2016-01-01

Recently, a general result for evaluating the path integral at one loop was obtained in the form of the Universal One-Loop Effective Action. It may be used to derive effective field theory operators of dimensions up to six, by evaluating the traces of matrices in this expression, with the mass dependence encapsulated in the universal coefficients. Here we show that it can account for loops of mixed heavy–light particles in the matching procedure. Our prescription for computing these mixed contributions to the Wilson coefficients is conceptually simple. Moreover it has the advantage of maintaining the universal structure of the effective action, which we illustrate using the example of integrating out a heavy electroweak triplet scalar coupling to a light Higgs doublet. Finally we also identify new structures that were previously neglected in the universal results.

Preparation of genuine Yeo-Chua entangled state and teleportation of two-atom state via cavity QED

Institute of Scientific and Technical Information of China (English)

无

2010-01-01

We first propose a scheme for preparing the genuine Yeo-Chua 4-qubit entangled state via cavity QED. Using the genuine Yeo-Chua atomic state, we further propose a cavity QED scheme for teleporting an arbitrary two-atom state. In two schemes the large-detuning is chosen and the necessary time is designed to be much shorter than Rydberg-atom’s lifespan. Both schemes share the distinct advantage that cavity decay and atom decay can be neglected. As for the interaction manipulation, our preparation scheme is more feasible than a recent similar one. Compared with the Yeo and Chua’s scheme, our teleportation scheme has significantly reduced the measuring difficulty.

Analytic results for the one loop NMHV H anti qqgg amplitude

International Nuclear Information System (INIS)

Badger, Simon; Campbell, John M.; Williams, Ciaran

2009-01-01

We compute the one-loop amplitude for a Higgs boson, a quark-antiquark pair and a pair of gluons of negative helicity, i.e. for the next-to-maximally helicity violating (NMHV) case, A(H, 1 - anti q , 2 + q , 3 - g , 4 - g ). The calculation is performed using an effective Lagrangian which is valid in the limit of very large top quark mass. As a result of this paper all amplitudes for the transition of a Higgs boson into 4 partons are now known analytically at one-loop order. (orig.)

{Delta}r in the Two-Higgs-Doublet Model at full one loop level - and beyond

Energy Technology Data Exchange (ETDEWEB)

Lopez-Val, David [Universitaet Heidelberg, Institut fuer Theoretische Physik, Heidelberg (Germany); Sola, Joan [Universitat de Barcelona, Dept. Estructura i Constituents de la Materia, Barcelona, Catalonia (Spain); Institut de Ciencies del Cosmos, Barcelona, Catalonia (Spain)

2013-04-15

After the recent discovery of a Higgs-like boson particle at the CERN LHC-collider, it becomes more necessary than ever to prepare ourselves for identifying its standard or non-standard nature. The fundamental parameter {Delta}r, relating the values of the electroweak gauge boson masses and the Fermi constant, is the traditional observable encoding high precision information of the quantum effects. In this work we present a complete quantitative study of {Delta}r in the framework of the general Two-Higgs-Doublet Model (2HDM). While the one-loop analysis of {Delta}r in this model was carried out long ago, in the first part of our work we consistently incorporate the higher order effects that have been computed since then for the SM part of {Delta}r. Within the on-shell scheme, we find typical corrections leading to shifts of {proportional_to}20-40 MeV on the W mass, resulting in a better agreement with its experimentally measured value and in a degree no less significant than in the MSSM case. In the second part of our study we devise a set of effective couplings that capture the dominant higher order genuine 2HDM quantum effects on the {delta}{rho} part of {Delta}r in the limit of large Higgs boson self-interactions. This limit constitutes a telltale property of the general 2HDM which is unmatched by e.g. the MSSM. (orig.)

Δr in the Two-Higgs-Doublet Model at full one loop level - and beyond

International Nuclear Information System (INIS)

Lopez-Val, David; Sola, Joan

2013-01-01

After the recent discovery of a Higgs-like boson particle at the CERN LHC-collider, it becomes more necessary than ever to prepare ourselves for identifying its standard or non-standard nature. The fundamental parameter Δr, relating the values of the electroweak gauge boson masses and the Fermi constant, is the traditional observable encoding high precision information of the quantum effects. In this work we present a complete quantitative study of Δr in the framework of the general Two-Higgs-Doublet Model (2HDM). While the one-loop analysis of Δr in this model was carried out long ago, in the first part of our work we consistently incorporate the higher order effects that have been computed since then for the SM part of Δr. Within the on-shell scheme, we find typical corrections leading to shifts of ∝20-40 MeV on the W mass, resulting in a better agreement with its experimentally measured value and in a degree no less significant than in the MSSM case. In the second part of our study we devise a set of effective couplings that capture the dominant higher order genuine 2HDM quantum effects on the δρ part of Δr in the limit of large Higgs boson self-interactions. This limit constitutes a telltale property of the general 2HDM which is unmatched by e.g. the MSSM. (orig.)

One-loop masses of open-string scalar fields in string theory

International Nuclear Information System (INIS)

Kitazawa, Noriaki

2008-01-01

In phenomenological models with D-branes, there are in general open-string massless scalar fields, in addition to closed-string massless moduli fields corresponding to the compactification. It is interesting to focus on the fate of such scalar fields in models with broken supersymmetry, because no symmetry forbids their masses. The one-loop effect may give non-zero masses to them, and in some cases mass squared may become negative, which means the radiative gauge symmetry breaking. In this article we investigate and propose a simple method for calculating the one-loop corrections using the boundary state formalism. There are two categories of massless open-string scalar fields. One consists the gauge potential fields corresponding to compactified directions, which can be understood as scalar fields in uncompactified space-time (related with Wilson line degrees of freedom). The other consists 'gauge potential fields' corresponding to transverse directions of D-brane, which emerge as scalar fields in D-brane world-volume (related with brane moduli fields). The D-brane boundary states with constant backgrounds of these scalar fields are constructed, and one-loop scalar masses are calculated in the closed string picture. Explicit calculations are given in the following four concrete models: one D25-brane with a circle compactification in bosonic string theory, one D9-brane with a circle compactification in superstring theory, D3-branes at a supersymmetric C 3 /Z 3 orbifold singularity, and a model of brane supersymmetry breaking with D3-branes and anti-D7-branes at a supersymmetric C 3 /Z 3 orbifold singularity. We show that the sign of the mass squared has a strong correlation with the sign of the related open-string one-loop vacuum amplitude.

The full spectrum of AdS5/CFT4 I: representation theory and one-loop Q-system

Science.gov (United States)

Marboe, Christian; Volin, Dmytro

2018-04-01

With the formulation of the quantum spectral curve for the AdS5/CFT4 integrable system, it became potentially possible to compute its full spectrum with high efficiency. This is the first paper in a series devoted to the explicit design of such computations, with no restrictions to particular subsectors being imposed. We revisit the representation theoretical classification of possible states in the spectrum and map the symmetry multiplets to solutions of the quantum spectral curve at zero coupling. To this end it is practical to introduce a generalisation of Young diagrams to the case of non-compact representations and define algebraic Q-systems directly on these diagrams. Furthermore, we propose an algorithm to explicitly solve such Q-systems that circumvents the traditional usage of Bethe equations and simplifies the computation effort. For example, our algorithm quickly obtains explicit analytic results for all 495 multiplets that accommodate single-trace operators in N=4 SYM with classical conformal dimension up to \\frac{13}{2} . We plan to use these results as the seed for solving the quantum spectral curve perturbatively to high loop orders in the next paper of the series.

Perturbative formulation of pure space-like axial gauge QED with infrared divergences regularized by residual gauge fields

International Nuclear Information System (INIS)

Nakawaki, Yuji; McCartor, Gary

2006-01-01

We construct a new perturbative formulation of pure space-like axial gauge QED in which the inherent infrared divergences are regularized by residual gauge fields. For this purpose, we carry out our calculations in the coordinates x μ =(x + , x - , x 1 , x 2 ), where x + =x 0 sinθ + x 3 cosθ and x - = x 0 cosθ - x 3 sinθ. Here, A=A 0 cosθ + A 3 sinθ = n·A=0 is taken as the gauge fixing condition. We show in detail that, in perturbation theory, infrared divergences resulting from the residual gauge fields cancel infrared divergences resulting from the physical parts of the gauge field. As a result, we obtain the gauge field propagator proposed by Mandelstam and Leibbrandt. By taking the limit θ→π/4, we are able to construct a light-cone formulation that is free from infrared divergences. With that analysis complete, we next calculate the one-loop electron self-energy, something not previously done in the light-cone quantization and light-cone gauge. (author)

Master formulas for the dressed scalar propagator in a constant field

Energy Technology Data Exchange (ETDEWEB)

Ahmad, Aftab [Department of Physics, Gomal University, 29220 D.I. Khan, K.P.K (Pakistan); Instituto de Física y Matemáticas, Universidad Michoacana de San Nicolás de Hidalgo, Edificio C-3, Ciudad Universitaria, Morelia 58040, Michoacán (Mexico); Ahmadiniaz, Naser, E-mail: Ahmadiniaz@ibs.re.kr [Center for Relativistic Laser Science, Institute for Basic Science, Gwangju 61005 (Korea, Republic of); Department of Physics, Kunsan National University, Kunsan 54150 (Korea, Republic of); Corradini, Olindo [Dipartimento di Scienze Fisiche, Informatiche e Matematiche, Università di Modena e Reggio Emilia, Via Campi 213/A, I-41125 Modena (Italy); INFN, Sezione di Bologna, Via Irnerio 46, I-40126 Bologna (Italy); Kim, Sang Pyo [Center for Relativistic Laser Science, Institute for Basic Science, Gwangju 61005 (Korea, Republic of); Department of Physics, Kunsan National University, Kunsan 54150 (Korea, Republic of); Schubert, Christian [Instituto de Física y Matemáticas, Universidad Michoacana de San Nicolás de Hidalgo, Edificio C-3, Ciudad Universitaria, Morelia 58040, Michoacán (Mexico)

2017-06-15

The worldline formalism has previously been used for deriving compact master formulas for the one-loop N-photon amplitudes in both scalar and spinor QED, and in the vacuum as well as in a constant external field. For scalar QED, there is also an analogous master formula for the propagator dressed with N photons in the vacuum. Here, we extend this master formula to include a constant field. The two-photon case is worked out explicitly, yielding an integral representation for the Compton scattering cross section in the field suitable for numerical integration in the full range of electric and magnetic field strengths.

One-loop mass shifts in O(32) open superstring theory

International Nuclear Information System (INIS)

Yamamoto, Hisashi.

1987-08-01

One-loop amplitudes of O(N) open superstring with emission of massive bosons are studied. Divergences appearing at λ = 0 (λ: the over-all Teichmueller parameter) are shown to be canceled if N = 32 just as in the massless case. We explicitly evaluate the two-point on-shell amplitudes for all the levels of bosons lying on the leading (m 2 = 2 l, J = l + 1, m:mass J:spin l:level number of an excited state) and the next-to-leading (m 2 = 2 l, J = l) Regge trajectories and observe that they are nonvanishing even at N = 32. This implies that O(32) open super-string one-loop amplitudes with massive bosons generally suffer from external-line divergences. Further the obtained expressions of on-shell self energies (mass shifts δm 2 (l)) seem to have nontrivial dependences on l (being not proportional to l), although mass degeneracies remain. This strongly suggests that the Regge trajectories form a set of parallel polygonal lines at one-loop level so that the mass shifts cannot be absorbed by the shift of the slope parameter. The divergences would have to be cured by the vertex operator renormalizations at every excited level. (author)

A differential operator for integrating one-loop scattering equations

Energy Technology Data Exchange (ETDEWEB)

Wang, Tianheng [Department of Physics, Nanjing University,Nanjing, Jiangsu Province (China); Chen, Gang [Department of Physics, Zhejiang Normal University,Jinhua, Zhejiang Province (China); Department of Physics and Astronomy, Uppsala University,Uppsala (Sweden); Department of Physics, Nanjing University,Nanjing, Jiangsu Province (China); Cheung, Yeuk-Kwan E. [Department of Physics, Nanjing University,Nanjing, Jiangsu Province (China); Xu, Feng [Weavi Corporation Limited, Nanjing,Jiangsu Province (China)

2017-01-09

We propose a differential operator for computing the residues associated with a class of meromorphic n-forms that frequently appear in the Cachazo-He-Yuan form of the scattering amplitudes. This differential operator is conjectured to be uniquely determined by the local duality theorem and the intersection number of the divisors in the n-form. We use the operator to evaluate the one-loop integrand of Yang-Mills theory from their generalized CHY formulae. The method can reduce the complexity of the calculation. In addition, the expression for the 1-loop four-point Yang-Mills integrand obtained in our approach has a clear correspondence with the Q-cut results.

Circuit QED lattices: Towards quantum simulation with superconducting circuits

Energy Technology Data Exchange (ETDEWEB)

Schmidt, Sebastian [Institute for Theoretical Physics, ETH Zurich, 8093, Zurich (Switzerland); Koch, Jens [Department of Physics and Astronomy, Northwestern University, Evanston, IL, 60208 (United States)

2013-06-15

The Jaynes-Cummings model describes the coupling between photons and a single two-level atom in a simplified representation of light-matter interactions. In circuit QED, this model is implemented by combining microwave resonators and superconducting qubits on a microchip with unprecedented experimental control. Arranging qubits and resonators in the form of a lattice realizes a new kind of Hubbard model, the Jaynes-Cummings-Hubbard model, in which the elementary excitations are polariton quasi-particles. Due to the genuine openness of photonic systems, circuit QED lattices offer the possibility to study the intricate interplay of collective behavior, strong correlations and non-equilibrium physics. Thus, turning circuit QED into an architecture for quantum simulation, i.e., using a well-controlled system to mimic the intricate quantum behavior of another system too daunting for a theorist to tackle head-on, is an exciting idea which has served as theorists' playground for a while and is now also starting to catch on in experiments. This review gives a summary of the most recent theoretical proposals and experimental efforts. (copyright 2013 by WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

arXiv Cuts from residues: the one-loop case

CERN Document Server

Abreu, Samuel; Duhr, Claude; Gardi, Einan

2017-06-14

Using the multivariate residue calculus of Leray, we give a precise definition of the notion of a cut Feynman integral in dimensional regularization, as a residue evaluated on the variety where some of the propagators are put on shell. These are naturally associated to Landau singularities of the first type. Focusing on the one-loop case, we give an explicit parametrization to compute such cut integrals, with which we study some of their properties and list explicit results for maximal and next-to-maximal cuts. By analyzing homology groups, we show that cut integrals associated to Landau singularities of the second type are specific combinations of the usual cut integrals, and we obtain linear relations among different cuts of the same integral. We also show that all one-loop Feynman integrals and their cuts belong to the same class of functions, which can be written as parametric integrals.

Boundary string field theory and an open string one-loop

International Nuclear Information System (INIS)

Lee, Tae Jin; Viswanathan, K. S.; Yang, Yi

2003-01-01

We discuss the open string one-loop partition function in the tachyon condensation background of an unstable D-brane system. We evaluate the partition function by using the boundary-state formulation and find that it is in complete agreement with the result obtained in the boundary string field theory. This suggests that the open string higher loop diagrams may be produced consistently by using a closed string field theory, where the D-brane plays the role of a source for the closed string field

Controlled teleportation of a multipartite quantum state via driven QED cavity

International Nuclear Information System (INIS)

Cao Haijing; Song Heshan

2007-01-01

We propose a scheme for teleporting a multipartite quantum state via driven QED cavity technologies. The combined state of Bell states is employed as a quantum channel. By adopting QED cavity technologies, our scheme does not involve the Bell-state measurements and can be perfectly realized by communicators' single particle measurements, possible C-not transformation and classical communication. The probability of successful teleportation can reach 1.0. The theoretical scheme is experimentally feasible via current technologies

Ambitwistor strings and the scattering equations at one loop

Energy Technology Data Exchange (ETDEWEB)

Adamo, Tim; Casali, Eduardo; Skinner, David [Department of Applied Mathematics & Theoretical Physics, University of Cambridge, Wilberforce Road, Cambridge CB3 0WA (United Kingdom)

2014-04-15

Ambitwistor strings are chiral, infinite tension analogues of conventional string theory whose target space is the space of complex null geodesics and whose spectrum consists exclusively of massless states. At genus zero, these strings underpin the Cachazo-He-Yuan formulæ for tree level scattering of gravitons, gluons and scalars. In this paper we extend these formulæ in a number of directions. Firstly, we consider Ramond sector vertex operators and construct simple amplitudes involving space-time fermions. These agree with tree amplitudes in ten dimensional supergravity and super Yang-Mills. We then show that, after the usual GSO projections, the ambitwistor string partition function is modular invariant. We consider the scattering equations at genus one, and calculate one loop scattering amplitudes for NS-NS external states in the Type II ambitwistor string. We conjecture that these give new representations of (the integrand of) one loop supergravity amplitudes and we show that they have the expected behaviour under factorization of the worldsheet in both non-separating and separating degenerations.

Analytic results for the one loop NMHV H anti qqgg amplitude

Energy Technology Data Exchange (ETDEWEB)

Badger, Simon [Deutsches Elektronen-Synchrotron (DESY), Zeuthen (Germany); Campbell, John M. [Glasgow Univ. (United Kingdom). Dept. of Physics and Astronomy; Ellis, R. Keith [Fermilab, Batavia, IL (United States); Williams, Ciaran [Durham Univ. (United Kingdom). Dept. of Physics

2009-10-23

We compute the one-loop amplitude for a Higgs boson, a quark-antiquark pair and a pair of gluons of negative helicity, i.e. for the next-to-maximally helicity violating (NMHV) case, A(H, 1{sup -} {sub anti} {sub q}, 2{sup +}{sub q}, 3{sup -}{sub g}, 4{sup -}{sub g}). The calculation is performed using an effective Lagrangian which is valid in the limit of very large top quark mass. As a result of this paper all amplitudes for the transition of a Higgs boson into 4 partons are now known analytically at one-loop order. (orig.)

One-loop calculation in time-dependent non-equilibrium thermo field dynamics

International Nuclear Information System (INIS)

Umezawa, H.; Yamanaka, Y.

1989-01-01

This paper is a review on the structure of thermo field dynamics (TFD) in which the basic concepts such as the thermal doublets, the quasi-particles and the self-consistent renormalization are presented in detail. A strong emphasis is put on the computational scheme. A detailed structure of this scheme is illustrated by the one-loop calculation in a non-equilibrium time-dependent process. A detailed account of the one-loop calculation has never been reported anywhere. The role of the self-consistent renormalization is explained. The equilibrium TFD is obtained as the long-time limit of non-equilibrium TFD. (author)

Nonsequential multiphoton double ionization of He in intense laser - a QED approach

International Nuclear Information System (INIS)

Bhattacharyya, S.; Mazumder, Mina; Chakrabarti, J.; Faisal, F.H.M.

2010-01-01

The non-sequential muItiphoton double ionization (NSDI) of He in intense laser field is not yet completely understood, more so for spin resolved currents. We are tempted to use QED and Feynman diagram to obtain spin polarized currents. Hartree-Fock (HF) ground-state correlated wave function of He atom is considered in circularly polarized laser. In QED approach one of the electrons is directly ionized by photon absorption while the second electron is shaken off due to the change in the internal potential of the atom. In He-atom the two ionized electrons can only be in the singlet spin state. Spin-symmetric and spin-flip transitions are eventually possible for the direct and the shake-off electrons. In an ensemble of (HF type) He-atoms the ionized Volkov electrons may acquire 4 pairs of momenta indicating e-e correlation in the final state. Coulomb correction is taken care off through the Sommerfeld factor

A Cavity QED Implementation of Deutsch-Jozsa Algorithm

OpenAIRE

Guerra, E. S.

2004-01-01

The Deutsch-Jozsa algorithm is a generalization of the Deutsch algorithm which was the first algorithm written. We present schemes to implement the Deutsch algorithm and the Deutsch-Jozsa algorithm via cavity QED.

QED corrections to the 4p-4d transition energies of copperlike heavy ions

International Nuclear Information System (INIS)

Chen, M. H.; Cheng, K. T.; Johnson, W. R.; Sapirstein, J.

2006-01-01

Quantum electrodynamic (QED) corrections to 4p-4d transition energies of several copperlike ions with Z=70-92 are calculated nonperturbatively in strong external fields to all orders in binding corrections. Dirac-Kohn-Sham potentials are used to account for screening and core-relaxation effects. For the 4p 1/2 -4d 3/2 transition in copperlike bismuth, thorium, and uranium, results are in good agreement with empirical QED corrections deduced from differences between transition energies obtained from recent high-precision electron-beam ion-trap measurements and those calculated with the relativistic many-body perturbation theory (RMBPT). These comparisons provide sensitive tests of QED corrections for high-angular-momentum states in many-electron heavy ions and illustrate the importance of core-relaxation corrections. Comparisons are also made with other theories and with experiments on the 4s-4p transition energies of high-Z Cu-like ions as accuracy checks of the present RMBPT and QED calculations

The renormalization group study of the effective theory of lattice QED

International Nuclear Information System (INIS)

Sugiyama, Y.

1988-01-01

The compact U(1) lattice gauge theory with massless fermions (Lattice QED) is studied through the effective model analytically, using the renormalization group method. The obtained effective model is the local boson field system with non-local interactions. The authors study the existence of non-trivial fixed point and its scaling behavior. This fixed point seems to be tri-critical. Such fixed point is interpreted in terms of the original Lattice QED model, and the results are consistent with the Monte Calro study

Secular effects on inflation from one-loop quantum gravity

International Nuclear Information System (INIS)

Cabrer, J.A.; Espriu, D.

2008-01-01

In this Letter we revisit and extend a previous analysis where the possible relevance of quantum gravity effects in a cosmological setup was studied. The object of interest are non-local (logarithmic) terms generated in the effective action of gravity due to the exchange in loops of massless modes (such as photons or the gravitons themselves). We correct one mistake existing in the previous work and discuss the issue in a more general setting in different cosmological scenarios. We obtain the one-loop quantum-corrected evolution equations for the cosmological scale factor up to a given order in a derivative expansion in two particular cases: a matter dominated universe with vanishing cosmological constant, and in a de Sitter universe. We show that the quantum corrections, albeit tiny, may have a secular effect that eventually modifies the expansion rate. For a de Sitter universe they tend to slow down the rate of the expansion, while the effect may be the opposite in a matter dominated universe

One-loop potential with scale invariance and effective operators

CERN Document Server

Ghilencea, D M

2016-01-01

We study quantum corrections to the scalar potential in classically scale invariant theories, using a manifestly scale invariant regularization. To this purpose, the subtraction scale $\\mu$ of the dimensional regularization is generated after spontaneous scale symmetry breaking, from a subtraction function of the fields, $\\mu(\\phi,\\sigma)$. This function is then uniquely determined from general principles showing that it depends on the dilaton only, with $\\mu(\\sigma)\\sim \\sigma$. The result is a scale invariant one-loop potential $U$ for a higgs field $\\phi$ and dilaton $\\sigma$ that contains an additional {\\it finite} quantum correction $\\Delta U(\\phi,\\sigma)$, beyond the Coleman Weinberg term. $\\Delta U$ contains new, non-polynomial effective operators like $\\phi^6/\\sigma^2$ whose quantum origin is explained. A flat direction is maintained at the quantum level, the model has vanishing vacuum energy and the one-loop correction to the mass of $\\phi$ remains small without tuning (of its self-coupling, etc) bey...

Numerical evaluation of one-loop diagrams near exceptional momentum configurations

International Nuclear Information System (INIS)

Giele, Walter T.; Zanderighi, Giulia; Glover, E.W.N.

2004-01-01

One problem which plagues the numerical evaluation of one-loop Feynman diagrams using recursive integration by part relations is a numerical instability near exceptional momentum configurations. In this contribution we will discuss a generic solution to this problem. As an example we consider the case of forward light-by-light scattering

One-loop corrections for e+e- annihilation into μ+μ- in the Weinberg model

NARCIS (Netherlands)

Veltman, M.J.G.; Passarino, G.

1979-01-01

Analytical expressions for the cross section including all the one-loop radiative corrections in the context of the Weinberg model are presented. The systematic calculation of one-loop diagrams has been carried out using a recently proposed scheme. Numerical results are shown in a region from

Automated evaluation of one-loop scattering amplitudes

International Nuclear Information System (INIS)

Deurzen, Hans van

2015-01-01

In this dissertation the developments toward fully automated evaluation of one-loop scattering amplitudes will be presented, as implemented in the GoSam framework. The code Xsamurai, part of GoSam, is described, which implements the integrand reduction algorithm including an extension to higher-rank capability. GoSam was used to compute several Higgs boson production channels at NLO QCD. An interface between GoSam and a Monte Carlo program was constructed, which enables computing any process at NLO precision needed in the LHC era.

Scaling laws, renormalization group flow and the continuum limit in non-compact lattice QED

International Nuclear Information System (INIS)

Goeckeler, M.; Horsley, R.; Rakow, P.; Schierholz, G.; Sommer, R.

1992-01-01

We investigate the ultra-violet behavior of non-compact lattice QED with light staggered fermions. The main question is whether QED is a non-trivial theory in the continuum limit, and if not, what is its range of validity as a low-energy theory. Perhaps the limited range of validity could offer an explanation of why the fine-structure constant is so small. Non-compact QED undergoes a second-order chiral phase transition at strong coupling, at which the continuum limit can be taken. We examine the phase diagram and the critical behavior of the theory in detail. Moreover, we address the question as to whether QED confines in the chirally broken phase. This is done by investigating the potential between static external charges. We then compute the renormalized charge and derive the Callan-Symanzik β-function in the critical region. No ultra-violet stable zero is found. Instead, we find that the evolution of charge is well described by renormalized perturbation theory, and that the renormalized charge vanishes at the critical point. The consequence is that QED can only be regarded as a cut-off theory. We evaluate the maximum value of the cut-off as a function of the renormalized charge. Next, we compute the masses of fermion-antifermion composite states. The scaling behavior of these masses is well described by an effective action with mean-field critical exponents plus logarithmic corrections. This indicates that also the matter sector of the theory is non-interacting. Finally, we investigate and compare the renormalization group flow of different quantities. Altogether, we find that QED is a valid theory only for samll renormalized charges. (orig.)

Scalar one-loop vertex integrals as meromorphic functions of space-time dimension d

International Nuclear Information System (INIS)

Bluemlein, Johannes; Phan, Khiem Hong; Vietnam National Univ., Ho Chi Minh City; Riemann, Tord; Silesia Univ., Chorzow

2017-11-01

Representations are derived for the basic scalar one-loop vertex Feynman integrals as meromorphic functions of the space-time dimension d in terms of (generalized) hypergeometric functions 2 F 1 and F 1 . Values at asymptotic or exceptional kinematic points as well as expansions around the singular points at d=4+2n, n non-negative integers, may be derived from the representations easily. The Feynman integrals studied here may be used as building blocks for the calculation of one-loop and higher-loop scalar and tensor amplitudes. From the recursion relation presented, higher n-point functions may be obtained in a straightforward manner.

Scalar one-loop vertex integrals as meromorphic functions of space-time dimension d

Energy Technology Data Exchange (ETDEWEB)

Bluemlein, Johannes [Deutsches Elektronen-Synchrotron (DESY), Zeuthen (Germany); Phan, Khiem Hong [Deutsches Elektronen-Synchrotron (DESY), Zeuthen (Germany); Vietnam National Univ., Ho Chi Minh City (Viet Nam). Univ. of Science; Riemann, Tord [Deutsches Elektronen-Synchrotron (DESY), Zeuthen (Germany); Silesia Univ., Chorzow (Poland). Inst. of Physics

2017-11-15

Representations are derived for the basic scalar one-loop vertex Feynman integrals as meromorphic functions of the space-time dimension d in terms of (generalized) hypergeometric functions {sub 2}F{sub 1} and F{sub 1}. Values at asymptotic or exceptional kinematic points as well as expansions around the singular points at d=4+2n, n non-negative integers, may be derived from the representations easily. The Feynman integrals studied here may be used as building blocks for the calculation of one-loop and higher-loop scalar and tensor amplitudes. From the recursion relation presented, higher n-point functions may be obtained in a straightforward manner.

Monopoles and chiral symmetry breaking in compact and noncompact QED3

International Nuclear Information System (INIS)

Fiebig, H.R.

1990-11-01

A comparison of the compact and the noncompact lattice action for 2+1 dimensional QED is made. In particular, the chiral order parameter and the monopole density ρ m are computed as functions of β for N f = 0.2 fermion flavours. The results reveal a strong correlation between and ρ m . Moreover, this correlation is identical for the compact and noncompact theories. This is interpreted as evidence that monopole condensation drives chiral symmetry breaking in lattice QED 3 . (Author) (6 refs., 5 figs.)

LOOP CALCULUS AND BELIEF PROPAGATION FOR Q-ARY ALPHABET: LOOP TOWER

Energy Technology Data Exchange (ETDEWEB)

CHERTKOV, MICHAEL [Los Alamos National Laboratory; CHERNYAK, VLADIMIR [Los Alamos National Laboratory

2007-01-10

Loop calculus introduced in [1], [2] constitutes a new theoretical tool that explicitly expresses symbol Maximum-A-Posteriori (MAP) solution of a general statistical inference problem via a solution of the Belief Propagation (BP) equations. This finding brought a new significance to the BP concept, which in the past was thought of as just a loop-free approximation. In this paper they continue a discussion of the Loop Calculus, partitioning the results into three Sections. In Section 1 they introduce a new formulation of the Loop Calculus in terms of a set of transformations (gauges) that keeping the partition function of the problem invariant. The full expression contains two terms referred to as the 'ground state' and 'excited states' contributions. The BP equations are interpreted as a special (BP) gauge fixing condition that emerges as a special orthogonality constraint between the ground state and excited states, which also selects loop contributions as the only surviving ones among the excited states. In Section 2 they demonstrate how the invariant interpretation of the Loop Calculus, introduced in Section 1, allows a natural extension to the case of a general q-ary alphabet, this is achieved via a loop tower sequential construction. The ground level in the tower is exactly equivalent to assigning one color (out of q available) to the 'ground state' and considering all 'excited' states colored in the remaining (q-1) colors, according to the loop calculus rule. Sequentially, the second level in the tower corresponds to selecting a loop from the previous step, colored in (q-1) colors, and repeating the same ground vs excited states splitting procedure into one and (q-2) colors respectively. The construction proceeds till the full (q-1)-levels deep loop tower (and the corresponding contributions to the partition function) are established. In Section 3 they discuss an ultimate relation between the loop calculus and the Bethe

QED blue-sheet effects inside black holes

International Nuclear Information System (INIS)

Burko, L.M.

1997-01-01

The interaction of the unboundedly blueshifted photons of the cosmic microwave background radiation with a physical object falling towards the inner horizon of a Reissner-Nordstroem black hole is analyzed. To evaluate this interaction we consider the QED effects up to the second order in the perturbation expansion. We then extrapolate the QED effects up to a cutoff, which we introduce at the Planckian level. (Our results are not sensitive to the cutoff energy.) We find that the energy absorbed by an infalling observer is finite, and for typical parameters would not lead to a catastrophic heating. However, this interaction would almost certainly be fatal for a human being, or other living organisms of similar size. On the other hand, we find that smaller objects may survive the interaction. Our results do not provide support for the idea that the Cauchy horizon is to be regarded as the boundary of spacetime. copyright 1997 The American Physical Society

One-loop quantum gravity repulsion in the early Universe.

Science.gov (United States)

Broda, Bogusław

2011-03-11

Perturbative quantum gravity formalism is applied to compute the lowest order corrections to the classical spatially flat cosmological Friedmann-Lemaître-Robertson-Walker solution (for the radiation). The presented approach is analogous to the approach applied to compute quantum corrections to the Coulomb potential in electrodynamics, or rather to the approach applied to compute quantum corrections to the Schwarzschild solution in gravity. In the framework of the standard perturbative quantum gravity, it is shown that the corrections to the classical deceleration, coming from the one-loop graviton vacuum polarization (self-energy), have (UV cutoff free) opposite to the classical repulsive properties which are not negligible in the very early Universe. The repulsive "quantum forces" resemble those known from loop quantum cosmology.

One-Loop Effective Action in Orbifold Compactifications

CERN Document Server

Von Gersdorff, Gero

2008-01-01

We employ the covariant background formalism to derive generic expressions for the one-loop effective action in field theoretic orbifold compactifications. The contribution of each orbifold sector is given by the effective action of its fixed torus with a shifted mass matrix. We thus study in detail the computation of the heat kernel on tori. Our formalism manifestly separates UV sensitive (local) from UV-insensitive (nonlocal) renormalization. To exemplify our methods, we study the effective potential of 6d gauge theory as well as kinetic terms for gravitational moduli in 11d supergravity.

Numerical simulation of a full-loop circulating fluidized bed under different operating conditions

Energy Technology Data Exchange (ETDEWEB)

Xu, Yupeng [National Energy Technology Lab. (NETL), Morgantown, WV (United States); Musser, Jordan M. [National Energy Technology Lab. (NETL), Morgantown, WV (United States); Li, Tingwen [National Energy Technology Lab. (NETL), Morgantown, WV (United States); AECOM, Morgantown, WV (United States); Rogers, William A. [National Energy Technology Lab. (NETL), Morgantown, WV (United States)

2017-10-17

Both experimental and computational studies of the fluidization of high-density polyethylene (HDPE) particles in a small-scale full-loop circulating fluidized bed are conducted. Experimental measurements of pressure drop are taken at different locations along the bed. The solids circulation rate is measured with an advanced Particle Image Velocimetry (PIV) technique. The bed height of the quasi-static region in the standpipe is also measured. Comparative numerical simulations are performed with a Computational Fluid Dynamics solver utilizing a Discrete Element Method (CFD-DEM). This paper reports a detailed and direct comparison between CFD-DEM results and experimental data for realistic gas-solid fluidization in a full-loop circulating fluidized bed system. The comparison reveals good agreement with respect to system component pressure drop and inventory height in the standpipe. In addition, the effect of different drag laws applied within the CFD simulation is examined and compared with experimental results.

Three-point Green's function of massless QED in position space to lowest order

International Nuclear Information System (INIS)

Mitra, Indrajit

2009-01-01

The transverse part of the three-point Green's function of massless QED is determined to the lowest order in position space. Taken together with the evaluation of the longitudinal part in Mitra (2008) (J. Phys. A: Math. Theor. 41 315401), this gives a relation for QED which is analogous to the star-triangle relation. We relate our result to conformal-invariant three-point functions

Simulations of QCD and QED with C* boundary conditions

Science.gov (United States)

Hansen, Martin; Lucini, Biagio; Patella, Agostino; Tantalo, Nazario

2018-03-01

We present exploratory results from dynamical simulations of QCD in isolation, as well as QCD coupled to QED, with C* boundary conditions. In finite volume, the use of C* boundary conditions allows for a gauge invariant and local formulation of QED without zero modes. In particular we show that the simulations reproduce known results and that masses of charged mesons can be extracted in a completely gauge invariant way. For the simulations we use a modified version of the HiRep code. The primary features of the simulation code are presented and we discuss some details regarding the implementation of C* boundary conditions and the simulated lattice action. Preprint: CP3-Origins-2017-046 DNRF90, CERN-TH-2017-214

QED fermi fields as operator-valued distributions and anomalies

International Nuclear Information System (INIS)

Grange, P.; Werner, E.

2005-01-01

The treatment of fields as operator-valued distributions (OPVD) is recalled with the emphasis on the importance of causality following the work of Epstein and Glaser. Gauge-invariant theories demand the extension of the usual translation operation on OPVD, thereby leading to a generalized QED formulation. At D = 2 the solvability of the Schwinger model is totally preserved. At D = 4 the paracompactness property of the Euclidean manifold permits the use of test functions which are a decomposition of unity and thereby provides a natural justification and extension of the non-perturbative heat kernel method (Fujikawa) for Abelian anomalies. On the Minkowski manifold the specific role of causality in the restauration of gauge invariance (and mass generation for QED 2 is exemplified in a simple way. (author)

Explicit evaluation of covariant one-loop four-point amplitude for open fermionic string

International Nuclear Information System (INIS)

Yamamoto, Hisashi; Nakazawa, Naohito.

1986-11-01

We carry out the explicit evaluation of the covariant one-loop amplitude with four massless external bosons for open fermionic string by the operator formalism. The resulting expression of the amplitude completely coincides with that of the light-cone new formalism for type-I superstring theory, providing the explicit demonstration for the one-loop equivalence of the old and new formalisms for the open superstring theory at the four-point interacting level. (author)

Minding one's P's and Q's: From the one loop effective action in quantum field theory to classical transport theory

International Nuclear Information System (INIS)

Jalilian-Marian, Jamal; Jeon, Sangyong; Venugopalan, Raju; Wirstam, Jens

2000-01-01

The one loop effective action in quantum field theory can be expressed as a quantum mechanical path integral over world lines, with internal symmetries represented by Grassmanian variables. In this paper, we develop a real time, many body, world line formalism for the one loop effective action. In particular, we study hot QCD and obtain the classical transport equations which, as Litim and Manuel have shown, reduce in the appropriate limit to the non-Abelian Boltzmann-Langevin equation first obtained by Boedeker. In the Vlasov limit, the classical kinetic equations are those that correspond to the hard thermal loop effective action. We also discuss the imaginary time world line formalism for a hot φ 4 theory, and elucidate its relation to classical transport theory. (c) 2000 The American Physical Society

The Performance Characteristics of a Closed Loop, One Axis ...

African Journals Online (AJOL)

This paper presents a closed loop one axis solar tracking device of the polar axis type, which achieves an accurate tracking of the sun with a steady state error of less, than 2%. This prototype uses a photo-sensing system to generate an error signal. This error signal switches on a relay, which actuates an electromechanical ...

An addendum to the Heisenberg-Euler effective action beyond one loop

Energy Technology Data Exchange (ETDEWEB)

Gies, Holger; Karbstein, Felix [Helmholtz-Institut Jena,Fröbelstieg 3, 07743 Jena (Germany); Theoretisch-Physikalisches Institut, Abbe Center of Photonics,Friedrich-Schiller-Universität Jena, Max-Wien-Platz 1, 07743 Jena (Germany)

2017-03-21

We study the effective interactions of external electromagnetic fields induced by fluctuations of virtual particles in the vacuum of quantum electrodynamics. Our main focus is on these interactions at two-loop order. We discuss in detail the emergence of the renowned Heisenberg-Euler effective action from the underlying microscopic theory of quantum electrodynamics, emphasizing its distinction from a standard one-particle irreducible effective action. In our explicit calculations we limit ourselves to constant and slowly varying external fields, allowing us to adopt a locally constant field approximation. One of our main findings is that at two-loop order there is a finite one-particle reducible contribution to the Heisenberg-Euler effective action in constant fields, which was previously assumed to vanish. In addition to their conceptual significance, our results are relevant for high-precision probes of quantum vacuum nonlinearity in strong electromagnetic fields.

One-loop calculations in quantum field theory: from Feynman diagrams to unitarity cuts

Energy Technology Data Exchange (ETDEWEB)

Ellis, R. Keith [Fermi National Accelerator Laboratory (FNAL), Batavia, IL (United States); Kunszt, Zoltan [Institute for Theoretical Physics (Switzerland); Melnikov, Kirill [Johns Hopkins Univ., Baltimore, MD (United States); Zanderighi, Giulia [Rudolf Peierls Centre for Theoretical Physics (United Kingdom)

2012-09-01

The success of the experimental program at the Tevatron re-inforced the idea that precision physics at hadron colliders is desirable and, indeed, possible. The Tevatron data strongly suggests that one-loop computations in QCD describe hard scattering well. Extrapolating this observation to the LHC, we conclude that knowledge of many short-distance processes at next-to-leading order may be required to describe the physics of hard scattering. While the field of one-loop computations is quite mature, parton multiplicities in hard LHC events are so high that traditional computational techniques become inefficient. Recently new approaches based on unitarity have been developed for calculating one-loop scattering amplitudes in quantum field theory. These methods are especially suitable for the description of multi-particle processes in QCD and are amenable to numerical implementations. We present a systematic pedagogical description of both conceptual and technical aspects of the new methods.

One-loop calculations in quantum field theory: From Feynman diagrams to unitarity cuts

International Nuclear Information System (INIS)

Ellis, R. Keith; Kunszt, Zoltan; Melnikov, Kirill; Zanderighi, Giulia

2012-01-01

The success of the experimental program at the Tevatron re-inforced the idea that precision physics at hadron colliders is desirable and, indeed, possible. The Tevatron data strongly suggests that one-loop computations in QCD describe hard scattering well. Extrapolating this observation to the LHC, we conclude that knowledge of many short-distance processes at next-to-leading order may be required to describe the physics of hard scattering. While the field of one-loop computations is quite mature, parton multiplicities in hard LHC events are so high that traditional computational techniques become inefficient. Recently, new approaches based on unitarity have been developed for calculating one-loop scattering amplitudes in quantum field theory. These methods are especially suitable for the description of multi-particle processes in QCD and are amenable to numerical implementations. We present a systematic pedagogical description of both conceptual and technical aspects of the new methods.

The rational parts of one-loop QCD amplitudes I: The general formalism

International Nuclear Information System (INIS)

Xiao Zhiguang; Yang Gang; Zhu Chuanjie

2006-01-01

A general formalism for computing only the rational parts of one-loop QCD amplitudes is developed. Starting from the Feynman integral representation of the one-loop amplitude, we use tensor reduction and recursive relations to compute the rational parts directly. Explicit formulas for the rational parts are given for all bubble and triangle integrals. Formulas are also given for box integrals up to two-mass-hard boxes which are the needed ingredients to compute up to 6-gluon QCD amplitudes. We use this method to compute explicitly the rational parts of the 5- and 6-gluon QCD amplitudes in two accompanying papers

QED, QCD en pratique

OpenAIRE

Aurenche , P; Guillet , J.-Ph; Pilon , E

2016-01-01

3rd cycle; Ces notes sont une introduction à l'application de l'électrodynamique quantique (QED) et de la chromodynamiques quantique (QCD) aux réactions de diffusion à hautes énergies. Le premier thème abordé est celui des divergences ultraviolettes et de la renormalisation à une boucle, avec comme conséquence pour QCD la liberté asymptotique. Le deuxième thème est celui des divergences infrarouges et colinéaires qui dans QCD sont traitées dans le cadre du modèle des partons avec l'introducti...

High precision hyperfine measurements in Bismuth challenge bound-state strong-field QED.

Science.gov (United States)

Ullmann, Johannes; Andelkovic, Zoran; Brandau, Carsten; Dax, Andreas; Geithner, Wolfgang; Geppert, Christopher; Gorges, Christian; Hammen, Michael; Hannen, Volker; Kaufmann, Simon; König, Kristian; Litvinov, Yuri A; Lochmann, Matthias; Maaß, Bernhard; Meisner, Johann; Murböck, Tobias; Sánchez, Rodolfo; Schmidt, Matthias; Schmidt, Stefan; Steck, Markus; Stöhlker, Thomas; Thompson, Richard C; Trageser, Christian; Vollbrecht, Jonas; Weinheimer, Christian; Nörtershäuser, Wilfried

2017-05-16

Electrons bound in highly charged heavy ions such as hydrogen-like bismuth 209 Bi 82+ experience electromagnetic fields that are a million times stronger than in light atoms. Measuring the wavelength of light emitted and absorbed by these ions is therefore a sensitive testing ground for quantum electrodynamical (QED) effects and especially the electron-nucleus interaction under such extreme conditions. However, insufficient knowledge of the nuclear structure has prevented a rigorous test of strong-field QED. Here we present a measurement of the so-called specific difference between the hyperfine splittings in hydrogen-like and lithium-like bismuth 209 Bi 82+,80+ with a precision that is improved by more than an order of magnitude. Even though this quantity is believed to be largely insensitive to nuclear structure and therefore the most decisive test of QED in the strong magnetic field regime, we find a 7-σ discrepancy compared with the theoretical prediction.

Charged hadrons in local finite-volume QED+QCD with C* boundary conditions

CERN Document Server

Lucini, Biagio; Ramos, Alberto; Tantalo, Nazario

2016-01-01

In order to calculate QED corrections to hadronic physical quantities by means of lattice simulations, a coherent description of electrically-charged states in finite volume is needed. In the usual periodic setup, Gauss's law and large gauge transformations forbid the propagation of electrically-charged states. A possible solution to this problem, which does not violate the axioms of local quantum field theory, has been proposed by Wiese and Polley, and is based on the use of C* boundary conditions. We present a thorough analysis of the properties and symmetries of QED in isolation and QED coupled to QCD, with C* boundary conditions. In particular we learn that a certain class of electrically-charged states can be constructed in this setup in a fully consistent fashion, without relying on gauge fixing. We argue that this class of states covers most of the interesting phenomenological applications in the framework of numerical simulations. We also calculate finite-volume corrections to the mass of stable charg...

QED effects in the pseudoscalar meson sector

Energy Technology Data Exchange (ETDEWEB)

Horsley, R. [School of Physics and Astronomy, University of Edinburgh, Peter Guthrie Tait Road, Edinburgh, EH9 3FD (United Kingdom); Nakamura, Y. [RIKEN Advanced Institute for Computational Science, Kobe, Hyogo, 650-0047 (Japan); Perlt, H. [Institut für Theoretische Physik, Universität Leipzig, Brüderstrasse 16, Leipzig, 04109 (Germany); Pleiter, D. [Jülich Supercomputer Centre, Forschungszentrum Jülich, Jülich, 52425 (Germany); Institut für Theoretische Physik, Universität Regensburg, Regensburg, 93040 (Germany); Rakow, P.E.L. [Theoretical Physics Division, Department of Mathematical Sciences, University of Liverpool, Peach Street , Liverpool, L69 3BX (United Kingdom); Schierholz, G. [Deutsches Elektronen-Synchrotron DESY, Hamburg, 22603 (Germany); Schiller, A. [Institut für Theoretische Physik, Universität Leipzig, Brüderstrasse 16, Leipzig, 04109 (Germany); Stokes, R. [CSSM, Department of Physics, University of Adelaide, Adelaide, SA, 5005 (Australia); Stüben, H. [Regionales Rechenzentrum, Universität Hamburg, Hamburg, 20146 (Germany); Young, R.D.; Zanotti, J.M. [CSSM, Department of Physics, University of Adelaide, Adelaide, SA, 5005 (Australia); Collaboration: the QCDSF and UKQCD collaboration

2016-04-15

In this paper we present results on the pseudoscalar meson masses from a fully dynamical simulation of QCD+QED, concentrating particularly on violations of isospin symmetry. We calculate the π{sup +}–π{sup 0} splitting and also look at other isospin violating mass differences. We have presented results for these isospin splittings in http://arxiv.org/abs/1508.06401. In this paper we give more details of the techniques employed, discussing in particular the question of how much of the symmetry violation is due to QCD, arising from the different masses of the u and d quarks, and how much is due to QED, arising from the different charges of the quarks. This decomposition is not unique, it depends on the renormalisation scheme and scale. We suggest a renormalisation scheme in which Dashen’s theorem for neutral mesons holds, so that the electromagnetic self-energies of the neutral mesons are zero, and discuss how the self-energies change when we transform to a scheme such as (MS)-bar , in which Dashen’s theorem for neutral mesons is violated.

Endemic infrared divergences in QED3 at finite temperature

International Nuclear Information System (INIS)

Lo, Pok Man; Swanson, Eric S.

2011-01-01

We demonstrate that massless QED in three dimensions contains endemic infrared divergences. It is argued that these divergences do not affect observables; furthermore, it is possible to choose a gauge that renders the theory finite.

Extending two Higgs doublet models for two-loop neutrino mass generation and one-loop neutrinoless double beta decay

Energy Technology Data Exchange (ETDEWEB)

Liu, Zhen, E-mail: liu-zhen@sjtu.edu.cn; Gu, Pei-Hong, E-mail: peihong.gu@sjtu.edu.cn

2017-02-15

We extend some two Higgs doublet models, where the Yukawa couplings for the charged fermion mass generation only involve one Higgs doublet, by two singlet scalars respectively carrying a singly electric charge and a doubly electric charge. The doublet and singlet scalars together can mediate a two-loop diagram to generate a tiny Majorana mass matrix of the standard model neutrinos. Remarkably, the structure of the neutrino mass matrix is fully determined by the symmetric Yukawa couplings of the doubly charged scalar to the right-handed leptons. Meanwhile, a one-loop induced neutrinoless double beta decay can arrive at a testable level even if the electron neutrino has an extremely small Majorana mass. We also study other experimental constraints and implications including some rare processes and Higgs phenomenology.

Effective potential in Lorentz-breaking field theory models

Energy Technology Data Exchange (ETDEWEB)

Baeta Scarpelli, A.P. [Centro Federal de Educacao Tecnologica, Nova Gameleira Belo Horizonte, MG (Brazil); Setor Tecnico-Cientifico, Departamento de Policia Federal, Belo Horizonte, MG (Brazil); Brito, L.C.T. [Universidade Federal de Lavras, Departamento de Fisica, Lavras, MG (Brazil); Felipe, J.C.C. [Universidade Federal de Lavras, Departamento de Fisica, Lavras, MG (Brazil); Universidade Federal dos Vales do Jequitinhonha e Mucuri, Instituto de Engenharia, Ciencia e Tecnologia, Veredas, Janauba, MG (Brazil); Nascimento, J.R.; Petrov, A.Yu. [Universidade Federal da Paraiba, Departamento de Fisica, Joao Pessoa, Paraiba (Brazil)

2017-12-15

We calculate explicitly the one-loop effective potential in different Lorentz-breaking field theory models. First, we consider a Yukawa-like theory and some examples of Lorentz-violating extensions of scalar QED. We observe, for the extended QED models, that the resulting effective potential converges to the known result in the limit in which Lorentz symmetry is restored. Besides, the one-loop corrections to the effective potential in all the cases we study depend on the background tensors responsible for the Lorentz-symmetry violation. This has consequences for physical quantities like, for example, in the induced mass due to the Coleman-Weinberg mechanism. (orig.)

Effective potential in Lorentz-breaking field theory models

International Nuclear Information System (INIS)

Baeta Scarpelli, A.P.; Brito, L.C.T.; Felipe, J.C.C.; Nascimento, J.R.; Petrov, A.Yu.

2017-01-01

We calculate explicitly the one-loop effective potential in different Lorentz-breaking field theory models. First, we consider a Yukawa-like theory and some examples of Lorentz-violating extensions of scalar QED. We observe, for the extended QED models, that the resulting effective potential converges to the known result in the limit in which Lorentz symmetry is restored. Besides, the one-loop corrections to the effective potential in all the cases we study depend on the background tensors responsible for the Lorentz-symmetry violation. This has consequences for physical quantities like, for example, in the induced mass due to the Coleman-Weinberg mechanism. (orig.)

DsixTools: the standard model effective field theory toolkit

Energy Technology Data Exchange (ETDEWEB)

Celis, Alejandro [Ludwig-Maximilians-Universitaet Muenchen, Fakultaet fuer Physik, Arnold Sommerfeld Center for Theoretical Physics, Munich (Germany); Fuentes-Martin, Javier; Vicente, Avelino [Universitat de Valencia-CSIC, Instituto de Fisica Corpuscular, Valencia (Spain); Virto, Javier [University of Bern, Albert Einstein Center for Fundamental Physics, Institute for Theoretical Physics, Bern (Switzerland)

2017-06-15

We present DsixTools, a Mathematica package for the handling of the dimension-six standard model effective field theory. Among other features, DsixTools allows the user to perform the full one-loop renormalization group evolution of the Wilson coefficients in the Warsaw basis. This is achieved thanks to the SMEFTrunner module, which implements the full one-loop anomalous dimension matrix previously derived in the literature. In addition, DsixTools also contains modules devoted to the matching to the ΔB = ΔS = 1, 2 and ΔB = ΔC = 1 operators of the Weak Effective Theory at the electroweak scale, and their QCD and QED Renormalization group evolution below the electroweak scale. (orig.)

Hamiltonian formulation of QED in the superaxial gauge

International Nuclear Information System (INIS)

Girotti, H.O.; Rothe, H.J.

A Hamiltonian formulation of QED in a fully fixed axial gauge is presented. The equal-time commutators for all field variables are computed and are shown to lead to the correct equations of motion. The constraints and gauge conditions hold as strong operator relations. (Author) [pt

APFEL : A PDF Evolution Library with QED corrections

NARCIS (Netherlands)

Bertone, Valerio; Carrazza, Stefano; Rojo, Juan

Quantum electrodynamics and electroweak corrections are important ingredients for many theoretical predictions at the LHC. This paper documents APFEL, a new PDF evolution package that allows for the first time to perform DGLAP evolution up to NNLO in QCD and to LO in QED, in the

The one-loop effects in the electroweak Glashow-Weinberg-Salam theory

International Nuclear Information System (INIS)

Christova Christova, P.

1987-01-01

In the near future the experiment will reach a great precision and will be able to test the standard electroweak theory. It is important now to put in order calculations of radiative corrections in this theory and to make correct and exact present theoretical predictions for the measured quantities. The survey of some results of group working in the JINR, Dubna, may serve this aim. We discuss here on-mass-shell renormalization scheme in the unitary gauge; the one-loop amplitudes of both charge and neutral currents-induced fermion scatterings; the large constant effects; the dynamical behaviour of the one-loop neutral-current corrections; the calculation of the W-and Z-boson masses; the difference between the various Weinberg parameters sin 2 Θ W . 44 refs., 10 figs., 1 tab. (author)

Large gauge symmetries and asymptotic states in QED

Energy Technology Data Exchange (ETDEWEB)

Gabai, Barak; Sever, Amit [School of Physics and Astronomy, Tel Aviv University,Ramat Aviv 69978 (Israel)

2016-12-19

Large Gauge Transformations (LGT) are gauge transformations that do not vanish at infinity. Instead, they asymptotically approach arbitrary functions on the conformal sphere at infinity. Recently, it was argued that the LGT should be treated as an infinite set of global symmetries which are spontaneously broken by the vacuum. It was established that in QED, the Ward identities of their induced symmetries are equivalent to the Soft Photon Theorem. In this paper we study the implications of LGT on the S-matrix between physical asymptotic states in massive QED. In appose to the naively free scattering states, physical asymptotic states incorporate the long range electric field between asymptotic charged particles and were already constructed in 1970 by Kulish and Faddeev. We find that the LGT charge is independent of the particles’ momenta and may be associated to the vacuum. The soft theorem’s manifestation as a Ward identity turns out to be an outcome of not working with the physical asymptotic states.

Measurements of the QED Structure of the Photon

CERN Document Server

Abbiendi, G.; Alexander, G.; Allison, John; Altekamp, N.; Anderson, K.J.; Anderson, S.; Arcelli, S.; Asai, S.; Ashby, S.F.; Axen, D.; Azuelos, G.; Ball, A.H.; Barberio, E.; Barlow, Roger J.; Batley, J.R.; Baumann, S.; Bechtluft, J.; Behnke, T.; Bell, Kenneth Watson; Bella, G.; Bellerive, A.; Bentvelsen, S.; Bethke, S.; Betts, S.; Biebel, O.; Biguzzi, A.; Blobel, V.; Bloodworth, I.J.; Bock, P.; Bohme, J.; Bonacorsi, D.; Boutemeur, M.; Braibant, S.; Bright-Thomas, P.; Brigliadori, L.; Brown, Robert M.; Burckhart, H.J.; Capiluppi, P.; Carnegie, R.K.; Carter, A.A.; Carter, J.R.; Chang, C.Y.; Charlton, David G.; Chrisman, D.; Ciocca, C.; Clarke, P.E.L.; Clay, E.; Cohen, I.; Conboy, J.E.; Cooke, O.C.; Couyoumtzelis, C.; Coxe, R.L.; Cuffiani, M.; Dado, S.; Dallavalle, G.Marco; Davis, R.; De Jong, S.; de Roeck, A.; Dervan, P.; Desch, K.; Dienes, B.; Dixit, M.S.; Doucet, M.; Dubbert, J.; Duchovni, E.; Duckeck, G.; Duerdoth, I.P.; Estabrooks, P.G.; Etzion, E.; Fabbri, F.; Fanfani, A.; Fanti, M.; Faust, A.A.; Fiedler, F.; Fierro, M.; Fleck, I.; Folman, R.; Frey, A.; Furtjes, A.; Futyan, D.I.; Gagnon, P.; Gary, J.W.; Gascon, J.; Gascon-Shotkin, S.M.; Gaycken, G.; Geich-Gimbel, C.; Giacomelli, G.; Giacomelli, P.; Gibson, V.; Gibson, W.R.; Gingrich, D.M.; Glenzinski, D.; Goldberg, J.; Gorn, W.; Grandi, C.; Graham, K.; Gross, E.; Grunhaus, J.; Gruwe, M.; Hanson, G.G.; Hansroul, M.; Hapke, M.; Harder, K.; Harel, A.; Hargrove, C.K.; Hauschild, M.; Hawkes, C.M.; Hawkings, R.; Hemingway, R.J.; Herndon, M.; Herten, G.; Heuer, R.D.; Hildreth, M.D.; Hill, J.C.; Hobson, P.R.; Hoch, M.; Hocker, James Andrew; Hoffman, Kara Dion; Homer, R.J.; Honma, A.K.; Horvath, D.; Hossain, K.R.; Howard, R.; Huntemeyer, P.; Igo-Kemenes, P.; Imrie, D.C.; Ishii, K.; Jacob, F.R.; Jawahery, A.; Jeremie, H.; Jimack, M.; Jones, C.R.; Jovanovic, P.; Junk, T.R.; Kanzaki, J.; Karlen, D.; Kartvelishvili, V.; Kawagoe, K.; Kawamoto, T.; Kayal, P.I.; Keeler, R.K.; Kellogg, R.G.; Kennedy, B.W.; Kim, D.H.; Klier, A.; Kobayashi, T.; Kobel, M.; Kokott, T.P.; Kolrep, M.; Komamiya, S.; Kowalewski, Robert V.; Kress, T.; Krieger, P.; von Krogh, J.; Kuhl, T.; Kyberd, P.; Lafferty, G.D.; Landsman, H.; Lanske, D.; Lauber, J.; Lautenschlager, S.R.; Lawson, I.; Layter, J.G.; Lazic, D.; Lee, A.M.; Lellouch, D.; Letts, J.; Levinson, L.; Liebisch, R.; List, B.; Littlewood, C.; Lloyd, A.W.; Lloyd, S.L.; Loebinger, F.K.; Long, G.D.; Losty, M.J.; Lu, J.; Ludwig, J.; Lui, D.; Macchiolo, A.; Macpherson, A.; Mader, W.; Mannelli, M.; Marcellini, S.; Markopoulos, C.; Martin, A.J.; Martin, J.P.; Martinez, G.; Mashimo, T.; Mattig, Peter; McDonald, W.John; McKenna, J.; Mckigney, E.A.; McMahon, T.J.; McPherson, R.A.; Meijers, F.; Menke, S.; Merritt, F.S.; Mes, H.; Meyer, J.; Michelini, A.; Mihara, S.; Mikenberg, G.; Miller, D.J.; Mir, R.; Mohr, W.; Montanari, A.; Mori, T.; Nagai, K.; Nakamura, I.; Neal, H.A.; Nisius, R.; O'Neale, S.W.; Oakham, F.G.; Odorici, F.; Ogren, H.O.; Oreglia, M.J.; Orito, S.; Palinkas, J.; Pasztor, G.; Pater, J.R.; Patrick, G.N.; Patt, J.; Perez-Ochoa, R.; Petzold, S.; Pfeifenschneider, P.; Pilcher, J.E.; Pinfold, J.; Plane, David E.; Poffenberger, P.; Poli, B.; Polok, J.; Przybycien, M.; Rembser, C.; Rick, H.; Robertson, S.; Robins, S.A.; Rodning, N.; Roney, J.M.; Rosati, S.; Roscoe, K.; Rossi, A.M.; Rozen, Y.; Runge, K.; Runolfsson, O.; Rust, D.R.; Sachs, K.; Saeki, T.; Sahr, O.; Sang, W.M.; Sarkisian, E.K.G.; Sbarra, C.; Schaile, A.D.; Schaile, O.; Scharff-Hansen, P.; Schieck, J.; Schmitt, S.; Schoning, A.; Schroder, Matthias; Schumacher, M.; Schwick, C.; Scott, W.G.; Seuster, R.; Shears, T.G.; Shen, B.C.; Shepherd-Themistocleous, C.H.; Sherwood, P.; Siroli, G.P.; Sittler, A.; Skuja, A.; Smith, A.M.; Snow, G.A.; Sobie, R.; Soldner-Rembold, S.; Spagnolo, S.; Sproston, M.; Stahl, A.; Stephens, K.; Steuerer, J.; Stoll, K.; Strom, David M.; Strohmer, R.; Surrow, B.; Talbot, S.D.; Taras, P.; Tarem, S.; Teuscher, R.; Thiergen, M.; Thomas, J.; Thomson, M.A.; Torrence, E.; Towers, S.; Trigger, I.; Trocsanyi, Z.; Tsur, E.; Turcot, A.S.; Turner-Watson, M.F.; Ueda, I.; Van Kooten, Rick J.; Vannerem, P.; Verzocchi, M.; Voss, H.; Wackerle, F.; Wagner, A.; Ward, C.P.; Ward, D.R.; Watkins, P.M.; Watson, A.T.; Watson, N.K.; Wells, P.S.; Wermes, N.; White, J.S.; Wilson, G.W.; Wilson, J.A.; Wyatt, T.R.; Yamashita, S.; Yekutieli, G.; Zacek, V.; Zer-Zion, D.

1999-01-01

The structure of both quasi-real and highly virtual photons is investigated using the reaction e+e- -> e+e-mu+mu-, proceeding via the exchange of two photons. The results are based on the complete OPAL dataset taken at e+e- centre-of-mass energies close to the mass of the Z boson. The QED structure function F_2^gamma and the differential cross-section dsigdx for quasi-real photons are obtained as functions of the fractional momentum x from the muon momentum which is carried by the struck muon in the quasi-real photon for values of Q**2 ranging from 1.5 to 400 GeV**2. The differential cross-section dsigdx for highly virtual photons is measured for 1.5 P**2. Based on azimuthal correlations the QED structure functions F_A^gamma and F_B^gamma for quasi-real photons are determined for an average Q**2 of 5.4 GeV**2.

Heat transfer in a one-dimensional mixed convection loop

International Nuclear Information System (INIS)

Kim, Min Joon; Lee, Yong Bum; Kim, Yong Kyun; Kim, Jong Man; Nam, Ho Yun

1999-01-01

Effects of non-uniform heating in the core and additional forced circulation during decay heat removal operation are studied with a simplified mixed convection loop. The heat transfer coefficient is calculated analytically and measured experimentally. The analytic solution obtained from a one-dimensional heat equation is found to agree well with the experimental results. The effects of the non-uniform heating and the forced circulation are discussed

One-loop tensor Feynman integral reduction with signed minors

DEFF Research Database (Denmark)

Fleischer, Jochem; Riemann, Tord; Yundin, Valery

2012-01-01

of the formalism is the immediate evaluation of complete contractions of the tensor integrals with external momenta. This leads to the problem of evaluating sums over products of signed minors with scalar products of chords. Chords are differences of external momenta. These sums may be evaluated analytically......We present an algebraic approach to one-loop tensor integral reduction. The integrals are presented in terms of scalar one- to four-point functions. The reduction is worked out explicitly until five-point functions of rank five. The numerical C++ package PJFry evaluates tensor coefficients in terms...

Scalar one-loop integrals using the negative-dimension approach

International Nuclear Information System (INIS)

Anastasiou, C.; Glover, E.W.N.; Oleari, C.

2000-01-01

We study massive one-loop integrals by analytically continuing the Feynman integral to negative dimensions as advocated by Halliday and Ricotta and developed by Suzuki and Schmidt. We consider n-point one-loop integrals with arbitrary powers of propagators in general dimension D. For integrals with m mass scales and q external momentum scales, we construct a template solution valid for all n which allows us to obtain a representation of the graph in terms of a finite sum of generalised hypergeometric functions with m+q-1 variables. All solutions for all possible kinematic regions are given simultaneously, allowing the investigation of different ranges of variation of mass and momentum scales. As a first step, we develop the general framework and apply it to massive bubble and vertex integrals. Of course many of these integrals are well known and we show that the known results are recovered. To give a concrete new result, we present expressions for the general vertex integral with one off-shell leg and two internal masses in terms of hypergeometric functions of two variables that converge in the appropriate kinematic regions. The kinematic singularity structure of this graph is sufficiently complex to give insight into how the negative-dimension method operates and gives some hope that more complicated graphs can also be evaluated

On C{sub J} and C{sub T} in conformal QED

Energy Technology Data Exchange (ETDEWEB)

Giombi, Simone; Tarnopolsky, Grigory [Princeton University, Department of Physics,Jadwin Hall, Washington Road, Princeton NJ 08544 (United States); Klebanov, Igor R. [Princeton University, Department of Physics,Jadwin Hall, Washington Road, Princeton NJ 08544 (United States); Princeton Center for Theoretical Science, Princeton University,Jadwin Hall, Washington Road, Princeton NJ 08544 (United States)

2016-08-26

QED with a large number N of massless fermionic degrees of freedom has a conformal phase in a range of space-time dimensions. We use a large N diagrammatic approach to calculate the leading corrections to C{sub T}, the coefficient of the two-point function of the stress-energy tensor, and C{sub J}, the coefficient of the two-point function of the global symmetry current. We present explicit formulae as a function of d and check them versus the expectations in 2 and 4−ϵ dimensions. Using our results in higher even dimensions we find a concise formula for C{sub T} of the conformal Maxwell theory with higher derivative action F{sub μν}(−∇{sup 2}){sup (d/2)−2}F{sup μν}. In d=3, QED has a topological symmetry current, and we calculate the correction to its two-point function coefficient, C{sub J}{sup top}. We also show that some RG flows involving QED in d=3 obey C{sub T}{sup UV}>C{sub T}{sup IR} and discuss possible implications of this inequality for the symmetry breaking at small values of N.

Direct measurement of alpha_QED(mZ)at the FCC-ee

CERN Document Server

Janot, Patrick

2016-02-08

When the measurements from the FCC-ee become available, an improved determination of the standard-model "input" parameters will be needed to fully exploit the new precision data towards either constraining or fitting the parameters of beyond-the-standard-model theories. Among these input parameters is the electromagnetic coupling constant estimated at the Z mass scale, alpha_QED(mZ). The measurement of the muon forward- backward asymmetry at the FCC-ee, just below and just above the Z pole, can be used to make a direct determination of alpha_QED(mZ) with an accuracy deemed adequate for an optimal use of the FCC-ee precision data.

Quantum master equation for QED in exact renormalization group

International Nuclear Information System (INIS)

Igarashi, Yuji; Itoh, Katsumi; Sonoda, Hidenori

2007-01-01

Recently, one of us (H. S.) gave an explicit form of the Ward-Takahashi identity for the Wilson action of QED. We first rederive the identity using a functional method. The identity makes it possible to realize the gauge symmetry even in the presence of a momentum cutoff. In the cutoff dependent realization, the nilpotency of the BRS transformation is lost. Using the Batalin-Vilkovisky formalism, we extend the Wilson action by including the antifield contributions. Then, the Ward-Takahashi identity for the Wilson action is lifted to a quantum master equation, and the modified BRS transformation regains nilpotency. We also obtain a flow equation for the extended Wilson action. (author)

Gauge covariance of the fermion Schwinger–Dyson equation in QED

Energy Technology Data Exchange (ETDEWEB)

Jia, Shaoyang, E-mail: sjia@email.wm.edu [Physics Department, College of William & Mary, Williamsburg, VA 23187 (United States); Pennington, M.R., E-mail: michaelp@jlab.org [Physics Department, College of William & Mary, Williamsburg, VA 23187 (United States); Theory Center, Thomas Jefferson National Accelerator Facility, Newport News, VA 23606 (United States)

2017-06-10

Any practical application of the Schwinger–Dyson equations to the study of n-point Green's functions in a strong coupling field theory requires truncations. In the case of QED, the gauge covariance, governed by the Landau–Khalatnikov–Fradkin transformations (LKFT), provides a unique constraint on such truncation. By using a spectral representation for the massive fermion propagator in QED, we are able to show that the constraints imposed by the LKFT are linear operations on the spectral densities. We formally define these group operations and show with a couple of examples how in practice they provide a straightforward way to test the gauge covariance of any viable truncation of the Schwinger–Dyson equation for the fermion 2-point function.

Gauge fixing problem in the conformal QED

International Nuclear Information System (INIS)

Ichinose, Shoichi

1986-01-01

The gauge fixing problem in the conformal (spinor and scalar) QED is examined. For the analysis, we generalize Dirac's manifestly conformal-covariant formalism. It is shown that the (vector and matter) fields must obey a certain mixed (conformal and gauge) type of transformation law in order to fix the local gauge symmetry preserving the conformal invariance in the Lagrangian. (orig.)

QED contribution to the color-singlet J/ψ production in Υ decay near the endpoint

International Nuclear Information System (INIS)

Liu Xiaohui

2010-01-01

A recent study indicates that the α 2 α s 2 order QED processes of Υ→J/ψ+X decay are compatible with those of QCD processes. However, in the endpoint region, the nonrelativistic QED calculation breaks down since the collinear degrees of freedom are missing under the framework of this effective theory. In this paper we apply the soft-collinear effective theory (SCET) to study the color-singlet QED process at the kinematic limit. Within this approach we are able to sum the kinematic logarithms by running operators using the renormalization group equations of soft-collinear effective theory, which will lead to a dramatic change in the momentum distribution near the endpoint and the spectrum shape consistent with the experimental results.

Spoiling of radiation zeros at the one-loop level and infrared finiteness

International Nuclear Information System (INIS)

Laursen, M.L.; Samuel, M.A.; Sen, A.

1983-01-01

We consider the amplitude for the radiative decay W - →phi 1 phi 2 #betta# (scalar quarks) including one-loop gluon corrections. We study this process to see if the amplitude (radiation) zeros found in lowest order survive at the one-loop level. The subset of diagrams containing self-mass insertions preserves the zero. Seagull types are shown to have a violation which is similar to kappanot =1. Triangle and box diagrams spoil the zeros as they do in the case of a scalar W. However, the amplitude is completely free of any mass singularities in the classical null zone. We conjecture that this will remain true for spin-(1/2) quarks

One-loop regularization of the Polyakov string functional

International Nuclear Information System (INIS)

Cohen, E.; Kluberg-Stern, H.; Peschanski, R.

1989-01-01

The divergences of the vacuum amplitude for the bosonic Polyakov string are studied at the one-loop level in a modular invariant regularization scheme, characterized by a dimensional cutoff analogous to proper time. As a result, the singular behaviour in the cutoff is not uniform in the range of the modulus variable and this yields a control on the singularities induced by the tachyon and the dilaton. The divergences are those of a sigma model, but the coefficients of the sigma-model counter-terms are different for the sphere and the flat torus. (orig.)

Non-markovian effects in semiconductor cavity QED: Role of phonon-mediated processes

DEFF Research Database (Denmark)

Nielsen, Per Kær; Nielsen, Torben Roland; Lodahl, Peter

We show theoretically that the non-Markovian nature of the carrier-phonon interaction influences the dynamical properties of a semiconductor cavity QED system considerably, leading to asymmetries with respect to detuning in carrier lifetimes. This pronounced phonon effect originates from the pola......We show theoretically that the non-Markovian nature of the carrier-phonon interaction influences the dynamical properties of a semiconductor cavity QED system considerably, leading to asymmetries with respect to detuning in carrier lifetimes. This pronounced phonon effect originates from...... the polaritonic quasi-particle nature of the carrier-photon system interacting with the phonon reservoir....

QED Effects in Molecules: Test on Rotational Quantum States of H2

Science.gov (United States)

Salumbides, E. J.; Dickenson, G. D.; Ivanov, T. I.; Ubachs, W.

2011-07-01

Quantum electrodynamic effects have been systematically tested in the progression of rotational quantum states in the XΣg+1, v=0 vibronic ground state of molecular hydrogen. High-precision Doppler-free spectroscopy of the EFΣg+1-XΣg+1 (0,0) band was performed with 0.005cm-1 accuracy on rotationally hot H2 (with rotational quantum states J up to 16). QED and relativistic contributions to rotational level energies as high as 0.13cm-1 are extracted, and are in perfect agreement with recent calculations of QED and high-order relativistic effects for the H2 ground state.

Electron-electron attractive interaction in Maxwell-Chern-Simons QED3 at zero temperature

International Nuclear Information System (INIS)

Belich, H.; Ferreira Junior, M.M.; Helayel-Neto, J.A.; Ferreira Junior, M.M.

2001-04-01

One discusses the issue of low-energy electron-electron bound states in the Maxwell-Chern-Simons model coupled to QED 3 with spontaneous breaking of a local U(1)-symmetry. The scattering potential, in the non-relativistic limit, steaming from the electron-electron Moeller scattering, mediated by the Maxwell-Chern-Simons-Proca gauge field and the Higgs scalar, might be attractive by fine-tuning properly the physical parameters of the model. (author)

Classical Electron Model with QED Corrections

OpenAIRE

Lenk, Ron

2010-01-01

In this article we build a metric for a classical general relativistic electron model with QED corrections. We calculate the stress-energy tensor for the radiative corrections to the Coulomb potential in both the near-field and far-field approximations. We solve the three field equations in both cases by using a perturbative expansion to first order in alpha (the fine-structure constant) while insisting that the usual (+, +, -, -) structure of the stress-energy tensor is maintained. The resul...

Polynomial structures in one-loop amplitudes

International Nuclear Information System (INIS)

Britto, Ruth; Feng Bo; Yang Gang

2008-01-01

A general one-loop scattering amplitude may be expanded in terms of master integrals. The coefficients of the master integrals can be obtained from tree-level input in a two-step process. First, use known formulas to write the coefficients of (4-2ε)-dimensional master integrals; these formulas depend on an additional variable, u, which encodes the dimensional shift. Second, convert the u-dependent coefficients of (4-2ε)-dimensional master integrals to explicit coefficients of dimensionally shifted master integrals. This procedure requires the initial formulas for coefficients to have polynomial dependence on u. Here, we give a proof of this property in the case of massless propagators. The proof is constructive. Thus, as a byproduct, we produce different algebraic expressions for the scalar integral coefficients, in which the polynomial property is apparent. In these formulas, the box and pentagon contributions are separated explicitly.

One-loop dimensional reduction of the linear σ model

International Nuclear Information System (INIS)

Malbouisson, A.P.C.; Silva-Neto, M.B.; Svaiter, N.F.

1997-05-01

We perform the dimensional reduction of the linear σ model at one-loop level. The effective of the reduced theory obtained from the integration over the nonzero Matsubara frequencies is exhibited. Thermal mass and coupling constant renormalization constants are given, as well as the thermal renormalization group which controls the dependence of the counterterms on the temperature. We also recover, for the reduced theory, the vacuum instability of the model for large N. (author)

Test of QED in e+e- → γγ at LEP

International Nuclear Information System (INIS)

Adeva, B.; Adriani, O.; Aguilar-Benitez, M.; Akbari, H.; Alcaraz, J.; Aloisio, A.; Alverson, G.; Alviggi, M.G.; An, Q.; Anderhub, H.; Anderson, A.L.; Andreev, V.P.; Angelov, T.; Antonov, L.; Antreasyan, D.; Arce, P.; Arefiev, A.; Azemoon, T.; Aziz, T.; Baba, P.V.K.S.; Bagnaia, P.; Bakken, J.A.; Baksay, L.; Ball, R.C.; Banerjee, S.; Bao, J.; Barone, L.; Bay, A.; Becker, U.; Behrens, J.; Beingessner, S.; Bencze, G.L.; Berdugo, J.; Berges, P.; Bertucci, B.; Betev, B.L.; Biland, A.; Bizzarri, R.; Blaising, J.J.; Bloemeke, P.; Blumenfeld, B.; Bobbink, G.J.; Bocciolini, M.; Boehlen, W.; Boehm, A.; Boehringer, T.; Borgia, B.; Borilkov, D.; Bourquin, M.; Boutigny, D.; Branson, J.G.; Brock, I.C.; Bryant, F.; Buisson, C.; Bujak, A.; Burger, J.D.; Burq, J.P.; Busenitz, J.; Cai, X.D.; Camps, C.; Capell, M.; Carbonara, F.; Carmianti, F.; Cartacci, A.M.; Cerrada, M.; Cesaroni, F.; Chang, Y.H.; Chaturvedi, U.K.; Chemarin, M.; Chen, A.; Chen, C.; Chen, G.M.; Chen, H.F.; Chen, H.S.; Chen, M.; Chen, M.L.; Chiefari, G.; Chien, C.Y.; Civinini, C.; Clare, I.; Clare, R.; Coignet, G.; Colino, N.; Commichau, V.; Conforto, G.; Contin, A.; Crijns, F.; Cui, X.Y.; Dai, T.S.; D'Alessandro, R.; De Asmudis, R.; Degre, A.; Deiters, K.; Denes, E.; Denes, P.; De Notaristefani, F.; Dhina, M.; DiBitonto, D.; Diemoz, M.; Diez-Hedo, F.; Dimitrov, H.R.; Dionisi, C.; Dittus, F.; Dolin, R.; Drago, E.; Driever, T.; Duchesneau, D.; Duinker, P.; Duran, I.; El Mamouni, H.; Engler, A.; Eppling, F.J.; Erne, F.C.; Extermann, P.; Fabretti, R.; Faber, G.; Falciano, S.; Fan, Q.; Fan, S.J.; Fabre, M.; Fay, J.; Fehlmann, J.; Fenker, H.; Ferguson, T.; Fernandez, G.; Ferroni, F.; Fesefeldt, H.; Field, J.; Finocchiaro, G.; Fisher, P.H.; Forconi, G.; Foreman, T.; Freudenreich, K.; Friebel, W.; Fukushima, M.; Gailloud, M.; Galaktionov, Yu.; Gallo, E.; Ganguli, S.N.; Garcia-Abia, P.; Gau, S.S.; Gentile, S.; Glaubman, M.; Goldfarb, S.; Gong, Z.F.; Gonzalez, E.; Gordeev, A.; Goettlicher, P.; Goujon, D.; Gratta, G.; Grinnell, C.; Gruenewald, M.; Guanziroli, M.; Gurtu, A.; Gustafson, H.R.; Gutay, L.J.; Haan, H.; Hancke, S.; Hangarter, K.; Harris, M.; Hasan, A.; He, C.F.; Hebbeker, T.; Herbert, M.; Herten, G.; Herten, U.; Herve, A.; Hilgers, K.; Hofer, H.; Hoorani, H.; Hsu, L.S.; Hu, G.; Hu, G.Q.; Ille, B.; Ilyas, M.M.; Innocente, V.; Isiksal, E.; Jagel, E.; Jin, B.N.; Jones, L.W.; Khan, R.A.; Kamyshkov, Yu.; Karyotakis, Y.; Kaur, M.; Khokhar, S.; Khoze, V.; Kirkby, D.; Kittel, W.; Klimentov, A.; Koenig, A.C.; Kornadt, O.; Koutsenko, V.; Kraemer, R.W.; Kramer, T.; Kratsev, V.R.; Krenz, W.; Krizmanic, J.; Kuhn, A.; Kumar, K.S.; Kumar, V.; Kunin, A.; Laak, A. van; Lalieu, V.; Landi, G.; Lanius, K.; Lange, W.; Lanske, D.; Lanzano, S.; Lebrun, P.

1990-01-01

We have measured the cross-section of the reaction e + e - →γγ at center of mass energies around the Z 0 mass. The results are in good agreement with QED predictions. For the QED cutoff parameters the limit of Λ + >103 GeV and Λ - >118 GeV are found. For the decays Z 0 →γγ, Z 0 →π 0 γ, Z 0 →ηγ and Z 0 →γγγ we find upper limits of 2.9x10 -4 , 2.9x10 -4 , 4.1x10 -4 and 1.2x10 -4 , respectively. All limits are at 95% CL. (orig.)

One-loop tensor integrals in dimensional regularisation

International Nuclear Information System (INIS)

Campbell, J.M.; Glover, E.W.N.; Miller, D.J.

1997-01-01

We show how to evaluate tensor one-loop integrals in momentum space avoiding the usual plague of Gram determinants. We do this by constructing combinations of n- and (n-1)-point scalar integrals that are finite in the limit of vanishing Gram determinant. These non-trivial combinations of dilogarithms, logarithms and constants are systematically obtained by either differentiating with respect to the external parameters - essentially yielding scalar integrals with Feynman parameters in the numerator - or by developing the scalar integral in D=6-2ε or higher dimensions. An additional advantage is that other spurious kinematic singularities are also controlled. As an explicit example, we develop the tensor integrals and associated scalar integral combinations for processes where the internal particles are massless and where up to five (four massless and one massive) external particles are involved. For more general processes, we present the equations needed for deriving the relevant combinations of scalar integrals. (orig.)

The one-loop partition function of N=4 super-Yang-Mills theory on RxS3

International Nuclear Information System (INIS)

Spradlin, Marcus; Volovich, Anastasia

2005-01-01

We study weakly coupled SU(N)N=4 super-Yang-Mills theory on RxS 3 at infinite N, which has interesting thermodynamics, including a Hagedorn transition, even at zero Yang-Mills coupling. We calculate the exact one-loop partition function below the Hagedorn temperature. Our calculation employs the representation of the one-loop dilatation operator as a spin chain Hamiltonian acting on neighboring sites and a generalization of Polya's counting of necklaces (gauge-invariant operators) to include necklaces with a 'pendant' (an operator which acts on neighboring beads). We find that the one-loop correction to the Hagedorn temperature is δlnT H =+λ/8π 2

Complete one-loop electroweak corrections to ZZZ production at the ILC

International Nuclear Information System (INIS)

Su Jijuan; Ma Wengan; Zhang Renyou; Wang Shaoming; Guo Lei

2008-01-01

We study the complete O(α ew ) electroweak (EW) corrections to the production of three Z 0 bosons in the framework of the standard model (SM) at the ILC. The leading-order and the EW next-to-leading-order corrected cross sections are presented, and their dependence on the colliding energy √(s) and Higgs-boson mass m H is analyzed. We investigate also the LO and one-loop EW corrected distributions of the transverse momentum of the final Z 0 boson, and the invariant mass of the Z 0 Z 0 pair. Our numerical results show that the EW one-loop correction generally suppresses the tree-level cross section, and the relative correction with m H =120 GeV(150 GeV) varies between -15.8%(-13.9%) and -7.5%(-6.2%) when √(s) goes up from 350 GeV to 1 TeV.

Non-Gaussianity at tree and one-loop levels from vector field perturbations

International Nuclear Information System (INIS)

Valenzuela-Toledo, Cesar A.; Rodriguez, Yeinzon; Lyth, David H.

2009-01-01

We study the spectrum P ζ and bispectrum B ζ of the primordial curvature perturbation ζ when the latter is generated by scalar and vector field perturbations. The tree-level and one-loop contributions from vector field perturbations are worked out considering the possibility that the one-loop contributions may be dominant over the tree-level terms [both (either) in P ζ and (or) in B ζ ] and vice versa. The level of non-Gaussianity in the bispectrum, f NL , is calculated and related to the level of statistical anisotropy in the power spectrum, g ζ . For very small amounts of statistical anisotropy in the power spectrum, the level of non-Gaussianity may be very high, in some cases exceeding the current observational limit.

One-loop correlation functions in the model of noncritical fermionic strings

International Nuclear Information System (INIS)

Belokurov, V.V.; Iofa, M.Z.

1996-01-01

In the model of noncritical fermionic strings, the David-Distler-Kawai ansatz is used to study one-loop n-point (n≤4) correlation functions for the vertex operators of massless bosonic states. The action functional of the model is the sum of super-Liouville action functional for the conformal mode and the action functional of d scalar supermultiplets. It is assumed that the total cosmological term is equal to zero. The amplitudes are calculated as the residues at the pole of the correlation function that corresponds to the conservation of Liouville momentum in the form Σβi=Q(1-h), where Q=√(9-d)/2 and h is the genus of the work sheet. In the one-loop approximation, the amplitudes can be obtained in the modular-invariant form, provided that the coefficients appearing in the sum over spin structures depend on moduli. In this case, the modular measure is defined up to a modular-invariant factor. This arbitrariness can be used to represent one-point correlation functions in the same functional form as for strings of critical dimension

Implementing quantum information splitting using a five-partite cluster state in cavity QED

International Nuclear Information System (INIS)

Ye Liu; Song Qingmin; Li Aixia

2010-01-01

We propose an explicit scheme for splitting up quantum information into parts using five-atom cluster states in cavity quantum electrodynamics (QED). It is found that the quantum information splitting of an arbitrary two-atomic state can be realized by using the five-atom cluster state. During the process, the cavity fields are excited only virtually. The scheme is insensitive to cavity decay. Therefore, the scheme can be experimentally realized using a range of current cavity QED techniques. The schemes considered here are also secure against certain eavesdropping attacks.

New uncertainties in QCD–QED rescaling factors using quadrature ...

Indian Academy of Sciences (India)

mf ). This is true for heavier quarks ... mass scale down to the physical quark mass scale is parametrised by the QCD–. QED rescaling factors ηf ... It will be an important numerical exercise to estimate the uncertainties in ηf using the quadrature ...

Multipartite quantum correlations among atoms in QED cavities

Science.gov (United States)

Batle, J.; Farouk, A.; Tarawneh, O.; Abdalla, S.

2018-02-01

We study the nonlocality dynamics for two models of atoms in cavity quantum electrodynamics (QED); the first model contains atoms in a single cavity undergoing nearest-neighbor interactions with no initial correlation, and the second contains atoms confined in n different and noninteracting cavities, all of which were initially prepared in a maximally correlated state of n qubits corresponding to the atomic degrees of freedom. The nonlocality evolution of the states in the second model shows that the corresponding maximal violation of a multipartite Bell inequality exhibits revivals at precise times, defining, nonlocality sudden deaths and nonlocality sudden rebirths, in analogy with entanglement. These quantum correlations are provided analytically for the second model to make the study more thorough. Differences in the first model regarding whether the array of atoms inside the cavity is arranged in a periodic or open fashion are crucial to the generation or redistribution of quantum correlations. This contribution paves the way to using the nonlocality multipartite correlation measure for describing the collective complex behavior displayed by slightly interacting cavity QED arrays.

Loop Quantum Cosmology

Directory of Open Access Journals (Sweden)

Bojowald Martin

2008-07-01

Full Text Available Quantum gravity is expected to be necessary in order to understand situations in which classical general relativity breaks down. In particular in cosmology one has to deal with initial singularities, i.e., the fact that the backward evolution of a classical spacetime inevitably comes to an end after a finite amount of proper time. This presents a breakdown of the classical picture and requires an extended theory for a meaningful description. Since small length scales and high curvatures are involved, quantum effects must play a role. Not only the singularity itself but also the surrounding spacetime is then modified. One particular theory is loop quantum cosmology, an application of loop quantum gravity to homogeneous systems, which removes classical singularities. Its implications can be studied at different levels. The main effects are introduced into effective classical equations, which allow one to avoid the interpretational problems of quantum theory. They give rise to new kinds of early-universe phenomenology with applications to inflation and cyclic models. To resolve classical singularities and to understand the structure of geometry around them, the quantum description is necessary. Classical evolution is then replaced by a difference equation for a wave function, which allows an extension of quantum spacetime beyond classical singularities. One main question is how these homogeneous scenarios are related to full loop quantum gravity, which can be dealt with at the level of distributional symmetric states. Finally, the new structure of spacetime arising in loop quantum gravity and its application to cosmology sheds light on more general issues, such as the nature of time.

One-loop fluctuation-dissipation formula for bubble-wall velocity

International Nuclear Information System (INIS)

Arnold, P.

1993-01-01

The limiting bubble wall velocity during a first-order electroweak phase transition is of interest in scenarios for electroweak baryogenesis. Khlebnikov has recently proposed an interesting method for computing this velocity based on the fluctuation-dissipation theorem. It is demonstrated that at one-loop order this method is identical to simple, earlier techniques for computing the wall velocity based on computing the friction from particles reflecting off or transmitting through the wall in the ideal gas limit

One-loop fluctuation-dissipation formula for bubble-wall velocity

International Nuclear Information System (INIS)

Arnold, P.

1993-01-01

The limiting bubble-wall velocity during a first-order electroweak phase transition is of interest in scenarios for electroweak baryogenesis. Khlebnikov has recently proposed an interesting method for computing this velocity based on the fluctuation-dissipation theorem. I demonstrate that at one-loop order this method is identical to simple, earlier techniques for computing the wall velocity based on computing the friction from particles reflecting off or transmitting through the wall in the ideal gas (''thin-wall'') limit

Chiral symmetry breaking in QED for weak coupling

Energy Technology Data Exchange (ETDEWEB)

Huang, J.C. (Missouri Univ., Columbia, MO (USA). Dept. of Physics and Astronomy); Shen, T.C. (Illinois Univ., Urbana, IL (USA). Beckman Inst.)

1991-05-01

We examine the procedure for studying chiral symmetry breaking for weak coupling in QED. We note that while the lowest non-trivial order calculations using numerical solutions to the Schwinger-Dyson equation indicate a breaking of chiral symmetry, the neglected higher-order contributions to the effective potential have imaginary values which can indicate possible instabilities in the theory. (author).

Chiral symmetry breaking in QED for weak coupling

International Nuclear Information System (INIS)

Huang, J.C.; Shen, T.C.

1991-01-01

We examine the procedure for studying chiral symmetry breaking for weak coupling in QED. We note that while the lowest non-trivial order calculations using numerical solutions to the Schwinger-Dyson equation indicate a breaking of chiral symmetry, the neglected higher-order contributions to the effective potential have imaginary values which can indicate possible instabilities in the theory. (author)

Causal theory in (2+1)-dimensional Qed

International Nuclear Information System (INIS)

Scharf, G.; Wreszinski, W.F.

1994-01-01

The program of constructing the S-matrix by means of causality in quantum field theory goes back to Stueckelberg and Bogoliubov. Epstein and Glaser proposed an axiomatic construct where ultraviolet divergences do not appear, leading directly to the renormalized perturbation series. They have shown that in the causal theory the UV problem is a consequence of incorrect distribution splitting. This paper studies the causal theory in (2+1)D Qed

On Resumming Inflationary Perturbations beyond One-loop

DEFF Research Database (Denmark)

Riotto, Antonio; Sloth, Martin Snoager

2008-01-01

It is well known that the correlation functions of a scalar field in a quasi-de Sitter space exhibit at the loop level cumulative infra-red effects proportional to the total number of e-foldings of inflation. Using the in-in formalism, we explore the behavior of these infra-red effects in the large...... N limit of an O(N) invariant scalar field theory with quartic self-interactions. By resumming all higher-order loop diagrams non-perturbatively, we show that the connected four-point correlation function, which is a signal of non-Gaussianity, is non-perturbatively enhanced with respect to its tree-level...

Four-loop vacuum energy density of the SU(Nc) + adjoint Higgs theory

International Nuclear Information System (INIS)

Kajantie, K.; Rummukainen, K.; Schroder, Y.; Laine, M.

2003-01-01

We compute the dimensionally regularised four-loop vacuum energy density of the SU(N c ) gauge + adjoint Higgs theory, in the disordered phase. 'Scalarisation', or reduction to a small set of master integrals of the type appearing in scalar field theories, is carried out in d dimensions, employing general partial integration identities through an algorithm developed by Laporta, while the remaining scalar integrals are evaluated in d=3-2ε dimensions, by expanding in ε 6 ln(1/g)), O(g 6 ) to the pressure, while the general methods are applicable also to studies of critical phenomena in QED-like statistical physics systems. (author)

Bern-Kosower rule for scalar QED

International Nuclear Information System (INIS)

Daikouji, K.; Shino, M.; Sumino, Y.

1996-01-01

We derive a full Bern-Kosower-type rule for scalar QED starting from quantum field theory: we derive a set of rules for calculating S-matrix elements for any processes at any order of the coupling constant. A gauge-invariant set of diagrams in general is first written in the world line path-integral expression. Then we integrate over x(τ), and the resulting expression is given in terms of a correlation function on the world line left-angle x(τ)x(τ ' )right-angle. Simple rules to decompose the correlation function into basic elements are obtained. A gauge transformation known as the integration by parts technique can be used to reduce the number of independent terms before integration over proper-time variables. The surface terms can be omitted provided the external scalars are on shell. Also, we clarify correspondence to the conventional Feynman rule, which enabled us to avoid any ambiguity coming from the infinite dimensionality of the path-integral approach. copyright 1996 The American Physical Society

Full one-loop electroweak corrections to h0(H0,A0)H±W± associated productions at e+e- linear colliders

International Nuclear Information System (INIS)

Liu Jing; Ma Wengan; Zhang Renyu; Guo Lei; Jiang Yi; Han Liang

2007-01-01

We study the complete one-loop electroweak (EW) corrections to the processes of single charged Higgs boson production associated with a neutral Higgs boson (h 0 ,H 0 ,A 0 ) and a gauge boson W ± in the framework of the minimal supersymmetric standard model (MSSM). Numerical results at the SPS1a ' benchmark point as proposed in the SPA project, are presented for demonstration. We find that for the process e + e - →h 0 H ± W ± the EW relative correction can be either positive or negative and in the range of -15%∼20% in our chosen parameter space. While for the processes e + e - →H 0 (A 0 )H ± W ± the corrections generally reduce the Born cross sections and the EW relative corrections are typically of order -10%∼-20%

The scalar-photon 3-point vertex in massless quenched scalar QED

International Nuclear Information System (INIS)

Concha-Sánchez, Y; Gutiérrez-Guerrero, L X; Fernández-Rangel, L A

2016-01-01

Non perturbative studies of Schwinger-Dyson equations (SDEs) require their infinite, coupled tower to be truncated in order to reduce them to a practically solvable set. In this connection, a physically acceptable ansatz for the three point vertex is the most favorite choice. Scalar quantum electrodynamics (sQED) provides a simple and neat platform to address this problem. The most general form of the scalar-photon three point vertex can be expressed in terms of only two independent form factors, longitudinal and transverse. Ball and Chiu have demonstrated that the longitudinal vertex is fixed by requiring the Ward-Fradkin-Green- Takahashi identity (WFGTI), while the transverse vertex remains undetermined. In massless quenched sQED, we propose the transverse part of the non perturbative scalar-photon vertex. (paper)

One-Loop Operation of Primary Heat Transport System in MONJU During Heat Transport System Modifications

International Nuclear Information System (INIS)

Goto, T.; Tsushima, H.; Sakurai, N.; Jo, T.

2006-01-01

MONJU is a prototype fast breeder reactor (FBR). Modification work commenced in March 2005. Since June 2004, MONJU has changed to one-loop operation of the primary heat transport system (PHTS) with all of the secondary heat transport systems (SHTS) drained of sodium. The purposes of this change are to shorten the modification period and to reduce the cost incurred for circuit trace heating electrical consumption. Before changing condition, the following issues were investigated to show that this mode of operation was possible. The heat loss from the reactor vessel and the single primary loop must exceed the decay heat by an acceptable margin but the capacity of pre-heaters to keep the sodium within the primary vessel at about 200 deg. C must be maintained. With regard to the heat loss and the decay heat, the estimated heat loss in the primary system was in the range of 90-170 kW in one-loop operation, and the calculated decay heat was 21.2 kW. Although the heat input of the primary pump was considered, it was clear that circuit heat loss greatly exceeded the decay heat. As for pre-heaters, effective capacity was less than the heat loss. Therefore, the temperature of the reactor vessel room was raised to reduce the heat loss. One-loop operation of the PHTS was able to be executed by means of these measures. The cost of electrical consumption in the power plant has been reduced by one-loop operation of the PHTS and the modification period was shortened. (authors)

The effective χ parameter in polarizable polymeric systems: One-loop perturbation theory and field-theoretic simulations.

Science.gov (United States)

Grzetic, Douglas J; Delaney, Kris T; Fredrickson, Glenn H

2018-05-28

We derive the effective Flory-Huggins parameter in polarizable polymeric systems, within a recently introduced polarizable field theory framework. The incorporation of bead polarizabilities in the model self-consistently embeds dielectric response, as well as van der Waals interactions. The latter generate a χ parameter (denoted χ̃) between any two species with polarizability contrast. Using one-loop perturbation theory, we compute corrections to the structure factor Sk and the dielectric function ϵ^(k) for a polarizable binary homopolymer blend in the one-phase region of the phase diagram. The electrostatic corrections to S(k) can be entirely accounted for by a renormalization of the excluded volume parameter B into three van der Waals-corrected parameters B AA , B AB , and B BB , which then determine χ̃. The one-loop theory not only enables the quantitative prediction of χ̃ but also provides useful insight into the dependence of χ̃ on the electrostatic environment (for example, its sensitivity to electrostatic screening). The unapproximated polarizable field theory is amenable to direct simulation via complex Langevin sampling, which we employ here to test the validity of the one-loop results. From simulations of S(k) and ϵ^(k) for a system of polarizable homopolymers, we find that the one-loop theory is best suited to high concentrations, where it performs very well. Finally, we measure χ̃N in simulations of a polarizable diblock copolymer melt and obtain excellent agreement with the one-loop theory. These constitute the first fully fluctuating simulations conducted within the polarizable field theory framework.

Quantum Simulation with Circuit-QED Lattices: from Elementary Building Blocks to Many-Body Theory

Science.gov (United States)

Zhu, Guanyu

Recent experimental and theoretical progress in superconducting circuits and circuit QED (quantum electrodynamics) has helped to develop high-precision techniques to control, manipulate, and detect individual mesoscopic quantum systems. A promising direction is hence to scale up from individual building blocks to form larger-scale quantum many-body systems. Although realizing a scalable fault-tolerant quantum computer still faces major barriers of decoherence and quantum error correction, it is feasible to realize scalable quantum simulators with state-of-the-art technology. From the technological point of view, this could serve as an intermediate stage towards the final goal of a large-scale quantum computer, and could help accumulating experience with the control of quantum systems with a large number of degrees of freedom. From the physical point of view, this opens up a new regime where condensed matter systems can be simulated and studied, here in the context of strongly correlated photons and two-level systems. In this thesis, we mainly focus on two aspects of circuit-QED based quantum simulation. First, we discuss the elementary building blocks of the quantum simulator, in particular a fluxonium circuit coupled to a superconducting resonator. We show the interesting properties of the fluxonium circuit as a qubit, including the unusual structure of its charge matrix elements. We also employ perturbation theory to derive the effective Hamiltonian of the coupled system in the dispersive regime, where qubit and the photon frequencies are detuned. The observables predicted with our theory, including dispersive shifts and Kerr nonlinearity, are compared with data from experiments, such as homodyne transmission and two-tone spectroscopy. These studies also relate to the problem of detection in a circuit-QED quantum simulator. Second, we study many-body physics of circuit-QED lattices, serving as quantum simulators. In particular, we focus on two different

Electron-electron attractive interaction in Maxwell-Chern-Simons QED{sub 3} at zero temperature

Energy Technology Data Exchange (ETDEWEB)

Belich, H.; Ferreira Junior, M.M.; Helayel-Neto, J.A. [Centro Brasileiro de Pesquisas Fisicas (CBPF), Rio de Janeiro, RJ (Brazil). E-mail: belich@cbpf.br; manojr@cbpf.br; helayel@gft.ucp.br; Ferreira Junior, M.M. [Universidade Catolica de Petropolis, RJ (Brazil). Grupo de Fisica Teorica. E-mail: delcima@gft.ucp.br

2001-04-01

One discusses the issue of low-energy electron-electron bound states in the Maxwell-Chern-Simons model coupled to QED{sub 3} with spontaneous breaking of a local U(1)-symmetry. The scattering potential, in the non-relativistic limit, steaming from the electron-electron Moeller scattering, mediated by the Maxwell-Chern-Simons-Proca gauge field and the Higgs scalar, might be attractive by fine-tuning properly the physical parameters of the model. (author)

On the tensor reduction of one-loop pentagons and hexagons

International Nuclear Information System (INIS)

Diakonidis, T.; Riemann, T.; Tausk, J.B.; Fleischer, J.; Bielefeld Univ.; Gluza, J.; Kajda, K.

2008-07-01

We perform analytical reductions of one-loop tensor integrals with 5 and 6 legs to scalar master integrals. They are based on the use of recurrence relations connecting integrals in different space-time dimensions. The reductions are expressed in a compact form in terms of signed minors, and have been implemented in a mathematica package called hexagon.m. We present several numerical examples. (orig.)

IR finite one-loop box scalar integral with massless internal lines

International Nuclear Information System (INIS)

Duplancic, G.; Nizic, B.

2002-01-01

The IR finite one-loop box scalar integral with massless internal lines has been recalculated. The result is very compact, simple and valid for arbitrary values of the relevant kinematic variables. It is given in terms of only two dilogarithms and a few logarithms, all of very simple arguments. (orig.)

Dynamics of symmetry breaking in strongly coupled QED

International Nuclear Information System (INIS)

Bardeen, W.A.

1988-10-01

I review the dynamical structure of strong coupled QED in the quenched planar limit. The symmetry structure of this theory is examined with reference to the nature of both chiral and scale symmetry breaking. The renormalization structure of the strong coupled phase is analysed. The compatibility of spontaneous scale and chiral symmetry breaking is studied using effective lagrangian methods. 14 refs., 3 figs

Iterative structure within the five-particle two-loop amplitude

International Nuclear Information System (INIS)

Cachazo, Freddy; Spradlin, Marcus; Volovich, Anastasia

2006-01-01

We find an unexpected iterative structure within the two-loop five-gluon amplitude in N=4 supersymmetric Yang-Mills theory. Specifically, we show that a subset of diagrams contributing to the full amplitude, including a two-loop pentagon-box integral with nontrivial dependence on five kinematical variables, satisfies an iterative relation in terms of one-loop scalar box diagrams. The implications of this result for the possible iterative structure of the full two-loop amplitude are discussed

The Z decay width in the SMEFT: y{sub t} and λ corrections at one loop

Energy Technology Data Exchange (ETDEWEB)

Hartmann, Christine [Niels Bohr International Academy, University of Copenhagen,Blegdamsvej 17, DK-2100 Copenhagen (Denmark); Shepherd, William [Niels Bohr International Academy, University of Copenhagen,Blegdamsvej 17, DK-2100 Copenhagen (Denmark); Institut für Physik, Johannes-Gutenberg-Universität Mainz,Staudingerweg 7, D-55128 Mainz (Germany); Trott, Michael [Niels Bohr International Academy, University of Copenhagen,Blegdamsvej 17, DK-2100 Copenhagen (Denmark)

2017-03-10

We calculate one loop y{sub t} and λ dependent corrections to Γ̄{sub Z},R̄{sub f}{sup 0} and the partial Z widths due to dimension six operators in the Standard Model Effective Field Theory (SMEFT), including finite terms. We assume CP symmetry and a U(3){sup 5} symmetry in the UV matching onto the dimension six operators, dominantly broken by the Standard Model Yukawa matrices. Corrections to these observables are predicted using the input parameters {α̂_e_w,M̂_Z,Ĝ_F,m̂_t,m̂_h} extracted with one loop corrections in the same limit. We show that at one loop the number of SMEFT parameters contributing to the precise LEPI pseudo-observables exceeds the number of measurements. As a result the SMEFT parameters contributing to LEP data are formally unbounded when the size of loop corrections are reached until other data is considered in a global analysis. The size of these loop effects is generically a correction of order ∼% to leading effects in the SMEFT, but we find multiple large numerical coefficients in our calculation at this order. We use a (MS)-bar scheme, modified for the SMEFT, for renormalization. Some subtleties involving novel evanescent scheme dependence present in this result are explained.

On the low-energy limit of one-loop photon-graviton amplitudes

International Nuclear Information System (INIS)

Bastianelli, F.; Corradini, O.; Dávila, J.M.; Schubert, C.

2012-01-01

We present first results of a systematic study of the structure of the low-energy limit of the one-loop photon-graviton amplitudes induced by massive scalars and spinors. Our main objective is the search of KLT-type relations where effectively two photons merge into a graviton. We find such a relation at the graviton-photon-photon level. We also derive the diffeomorphism Ward identity for the 1PI one-graviton-N-photon amplitudes.

One-loop lattice artifacts of a dynamical charm quark

Energy Technology Data Exchange (ETDEWEB)

Athenodorou, Andreas; Sommer, Rainer [Deutsches Elektronen-Synchrotron (DESY), Zeuthen (Germany). John von Neumann-Inst. fuer Computing NIC

2011-10-15

For a few observables in O(a) improved lattice QCD, we compute discretization effects arising from the vacuum polarization of a heavy quark at one-loop order. In particular, the force between static quarks, the running coupling in the Schroedinger functional and a related quantity, anti {upsilon}, are considered. Results show that the cutoff effects of a dynamical charm quark are typically smaller than those present in the pure gauge theory. This perturbative result is a good indication that dynamical charm quarks are feasible already now. (orig.)

One-loop lattice artifacts of a dynamical charm quark

International Nuclear Information System (INIS)

Athenodorou, Andreas; Sommer, Rainer

2011-10-01

For a few observables in O(a) improved lattice QCD, we compute discretization effects arising from the vacuum polarization of a heavy quark at one-loop order. In particular, the force between static quarks, the running coupling in the Schroedinger functional and a related quantity, anti υ, are considered. Results show that the cutoff effects of a dynamical charm quark are typically smaller than those present in the pure gauge theory. This perturbative result is a good indication that dynamical charm quarks are feasible already now. (orig.)

Circuit QED with transmon qubits

Energy Technology Data Exchange (ETDEWEB)

Wulschner, Karl Friedrich; Puertas, Javier; Baust, Alexander; Eder, Peter; Fischer, Michael; Goetz, Jan; Haeberlein, Max; Schwarz, Manuel; Xie, Edwar; Zhong, Ling; Deppe, Frank; Fedorov, Kirill; Marx, Achim; Menzel, Edwin; Gross, Rudolf [Walther-Meissner-Institut, Bayerische Akademie der Wissenschaften, Garching (Germany); Physik-Department, TU Muenchen, Garching (Germany); Nanosystems Initiative Munich (NIM), Muenchen (Germany); Huebl, Hans [Walther-Meissner-Institut, Bayerische Akademie der Wissenschaften, Garching (Germany); Nanosystems Initiative Munich (NIM), Muenchen (Germany); Weides, Martin [Karlsruhe Institute of Technology (KIT), Karlsruhe (Germany)

2015-07-01

Superconducting quantum bits are basic building blocks for circuit QED systems. Applications in the fields of quantum computation and quantum simulation require long coherence times. We have fabricated and characterized superconducting transmon qubits which are designed to operate at a high ratio of Josephson energy and charging energy. Due to their low sensitivity to charge noise transmon qubits show good coherence properties. We couple transmon qubits to coplanar waveguide resonators and coplanar slotline resonators and characterize the devices at mK-temperatures. From the experimental data we derive the qubit-resonator coupling strength, the qubit relaxation time and calibrate the photon number in the resonator via Stark shifts.

Towards bootstrapping QED{sub 3}

Energy Technology Data Exchange (ETDEWEB)

Chester, Shai M.; Pufu, Silviu S. [Joseph Henry Laboratories, Princeton University,Princeton, NJ 08544 (United States)

2016-08-02

We initiate the conformal bootstrap study of Quantum Electrodynamics in 2+1 space-time dimensions (QED{sub 3}) with N flavors of charged fermions by focusing on the 4-point function of four monopole operators with the lowest unit of topological charge. We obtain upper bounds on the scaling dimension of the doubly-charged monopole operator, with and without assuming other gaps in the operator spectrum. Intriguingly, we find a (gap-dependent) kink in these bounds that comes reasonably close to the large N extrapolation of the scaling dimensions of the singly-charged and doubly-charged monopole operators down to N=4 and N=6.

Decoherence in semiconductor cavity QED systems due to phonon couplings

DEFF Research Database (Denmark)

Nielsen, Per Kær; Mørk, Jesper

2014-01-01

We investigate the effect of electron-phonon interactions on the coherence properties of single photons emitted from a semiconductor cavity QED (quantum electrodynamics) system, i.e., a quantum dot embedded in an optical cavity. The degree of indistinguishability, governing the quantum mechanical...

Loop Quantum Cosmology

Directory of Open Access Journals (Sweden)

Bojowald Martin

2005-12-01

Full Text Available Quantum gravity is expected to be necessary in order to understand situations where classical general relativity breaks down. In particular in cosmology one has to deal with initial singularities, i.e., the fact that the backward evolution of a classical space-time inevitably comes to an end after a finite amount of proper time. This presents a breakdown of the classical picture and requires an extended theory for a meaningful description. Since small length scales and high curvatures are involved, quantum effects must play a role. Not only the singularity itself but also the surrounding space-time is then modified. One particular realization is loop quantum cosmology, an application of loop quantum gravity to homogeneous systems, which removes classical singularities. Its implications can be studied at different levels. Main effects are introduced into effective classical equations which allow to avoid interpretational problems of quantum theory. They give rise to new kinds of early universe phenomenology with applications to inflation and cyclic models. To resolve classical singularities and to understand the structure of geometry around them, the quantum description is necessary. Classical evolution is then replaced by a difference equation for a wave function which allows to extend space-time beyond classical singularities. One main question is how these homogeneous scenarios are related to full loop quantum gravity, which can be dealt with at the level of distributional symmetric states. Finally, the new structure of space-time arising in loop quantum gravity and its application to cosmology sheds new light on more general issues such as time.

On the equivalence of massive qed with renormalizable and in unitary gauge

International Nuclear Information System (INIS)

Abdalla, E.

1978-03-01

In the framework of BPHZ renormalization procedure, we discuss the equivalence between 4-dimensional renormalizable massive quantum electrodynamics (Stueckelberg lagrangian), and massive QED in the unitary gauge

An architecture for integrating planar and 3D cQED devices

Energy Technology Data Exchange (ETDEWEB)

Axline, C.; Reagor, M.; Heeres, R.; Reinhold, P.; Wang, C.; Shain, K.; Pfaff, W.; Chu, Y.; Frunzio, L.; Schoelkopf, R. J. [Department of Applied Physics, Yale University, New Haven, Connecticut 06511 (United States)

2016-07-25

Numerous loss mechanisms can limit coherence and scalability of planar and 3D-based circuit quantum electrodynamics (cQED) devices, particularly due to their packaging. The low loss and natural isolation of 3D enclosures make them good candidates for coherent scaling. We introduce a coaxial transmission line device architecture with coherence similar to traditional 3D cQED systems. Measurements demonstrate well-controlled external and on-chip couplings, a spectrum absent of cross-talk or spurious modes, and excellent resonator and qubit lifetimes. We integrate a resonator-qubit system in this architecture with a seamless 3D cavity, and separately pattern a qubit, readout resonator, Purcell filter, and high-Q stripline resonator on a single chip. Device coherence and its ease of integration make this a promising tool for complex experiments.

One-loop helicity amplitudes for t anti t production at hadron colliders

International Nuclear Information System (INIS)

Badger, Simon; Yundin, Valery

2011-01-01

We present compact analytic expressions for all one-loop helicity amplitudes contributing to t anti t production at hadron colliders. Using recently developed generalised unitarity methods and a traditional Feynman based approach we produce a fast and flexible implementation. (ORIG.)

One-loop helicity amplitudes for t anti t production at hadron colliders

Energy Technology Data Exchange (ETDEWEB)

Badger, Simon [The Niels Bohr International Academy and Discovery Center, Copenhagen (Denmark). Niels Bohr Inst.; Sattler, Ralf [Humboldt Univ. Berlin (Germany). Inst. fuer Physik; Deutsches Elektronen-Synchrotron (DESY), Zeuthen (Germany); Yundin, Valery [Silesia Univ., Katowice (Poland). Inst. of Physics; Deutsches Elektronen-Synchrotron (DESY), Zeuthen (Germany)

2011-01-15

We present compact analytic expressions for all one-loop helicity amplitudes contributing to t anti t production at hadron colliders. Using recently developed generalised unitarity methods and a traditional Feynman based approach we produce a fast and flexible implementation. (ORIG.)

Chiral current generation in QED by longitudinal photons

Energy Technology Data Exchange (ETDEWEB)

Acosta Avalo, J.L., E-mail: jlacosta@instec.cu [Instituto Superior de Tecnologías y Ciencias Aplicadas (INSTEC), Ave Salvador Allende, No. 1110, Vedado, La Habana 10400 (Cuba); Pérez Rojas, H., E-mail: hugo@icimaf.cu [Instituto de Cibernética, Matemática y Física (ICIMAF), Calle E esq 15, No. 309, Vedado, La Habana 10400 (Cuba)

2016-08-15

We report the generation of a pseudovector electric current having imbalanced chirality in an electron–positron strongly magnetized gas in QED. It propagates along the external applied magnetic field B as a chiral magnetic effect in QED. It is triggered by a perturbative electric field parallel to B, associated to a pseudovector longitudinal mode propagating along B. An electromagnetic chemical potential was introduced, but our results remain valid even when it vanishes. A nonzero fermion mass was assumed, which is usually considered vanishing in the literature. In the quantum field theory formalism at finite temperature and density, an anomaly relation for the axial current was found for a medium of massive fermions. It bears some analogy to the Adler–Bell–Jackiw anomaly. From the expression for the chiral current in terms of the photon self-energy tensor in a medium, it is obtained that electrons and positrons scattered by longitudinal photons (inside the light cone) contribute to the chiral current, as well as the to pair creation due to longitudinal photons (out of light cone). In the static limit, an electric pseudovector current is obtained in the lowest Landau level.

One-loop analysis of the electroweak breaking in supersymmetric models and the fine-tuning problem

CERN Document Server

De Carlos, B

1993-01-01

We examine the electroweak breaking mechanism in the minimal supersymmetric standard model (MSSM) using the {\\em complete} one-loop effective potential $V_1$. First, we study what is the region of the whole MSSM parameter space (i.e. $M_{1/2},m_o,\\mu,...$) that leads to a succesful $SU(2)\\times U(1)$ breaking with an acceptable top quark mass. In doing this it is observed that all the one-loop corrections to $V_1$ (even the apparently small ones) must be taken into account in order to get reliable results. We find that the allowed region of parameters is considerably enhanced with respect to former "improved" tree level results. Next, we study the fine-tuning problem associated with the high sensitivity of $M_Z$ to $h_t$ (the top Yukawa coupling). Again, we find that this fine-tuning is appreciably smaller once the one-loop effects are considered than in previous tree level calculations. Finally, we explore the ambiguities and limitations of the ordinary criterion to estimate the degree of fine-tuning. As a r...

Strong Coupling Cavity QED with Gate-Defined Double Quantum Dots Enabled by a High Impedance Resonator

Directory of Open Access Journals (Sweden)

A. Stockklauser

2017-03-01

Full Text Available The strong coupling limit of cavity quantum electrodynamics (QED implies the capability of a matterlike quantum system to coherently transform an individual excitation into a single photon within a resonant structure. This not only enables essential processes required for quantum information processing but also allows for fundamental studies of matter-light interaction. In this work, we demonstrate strong coupling between the charge degree of freedom in a gate-defined GaAs double quantum dot (DQD and a frequency-tunable high impedance resonator realized using an array of superconducting quantum interference devices. In the resonant regime, we resolve the vacuum Rabi mode splitting of size 2g/2π=238  MHz at a resonator linewidth κ/2π=12  MHz and a DQD charge qubit decoherence rate of γ_{2}/2π=40  MHz extracted independently from microwave spectroscopy in the dispersive regime. Our measurements indicate a viable path towards using circuit-based cavity QED for quantum information processing in semiconductor nanostructures.

Realization of Arbitrary Positive-Operator-Value Measurement of Single Atomic Qubit via Cavity QED

International Nuclear Information System (INIS)

Yang, Han; Wei, Wu; Chun-Wang, Wu; Hong-Yi, Dai; Cheng-Zu, Li

2008-01-01

Positive-operator-value measurement (POVM) is the most general class of quantum measurement. We propose a scheme to deterministically implement arbitrary POVMs of single atomic qubit via cavity QED catalysed by only one ancilla atomic qubit. By appropriately entangling two atomic qubits and sequentially measuring the ancilla qubit, any POVM can be implemented step by step. As an application of our scheme, the realization of a specific POVM for optimal unambiguous discrimination (OUD) between two nonorthogonal states is given

Realization of Arbitrary Positive-Operator-Value Measurement of Single Atomic Qubit via Cavity QED

Science.gov (United States)

Han, Yang; Wu, Wei; Wu, Chun-Wang; Dai, Hong-Yi; Li, Cheng-Zu

2008-12-01

Positive-operator-value measurement (POVM) is the most general class of quantum measurement. We propose a scheme to deterministically implement arbitrary POVMs of single atomic qubit via cavity QED catalysed by only one ancilla atomic qubit. By appropriately entangling two atomic qubits and sequentially measuring the ancilla qubit, any POVM can be implemented step by step. As an application of our scheme, the realization of a specific POVM for optimal unambiguous discrimination (OUD) between two nonorthogonal states is given.

Supergravity one-loop corrections on AdS7 and AdS3, higher spins and AdS/CFT

Directory of Open Access Journals (Sweden)

Matteo Beccaria

2015-03-01

Full Text Available As was shown earlier, the one-loop correction in 10d supergravity on AdS5×S5 corresponds to the contributions to the vacuum energy and 4d boundary conformal anomaly which are minus the values for one N=4 Maxwell supermultiplet, thus reproducing the subleading term in the N2−1 coefficient in the dual SU(N SYM theory. We perform similar one-loop computations in 11d supergravity on AdS7×S4 and 10d supergravity on AdS3×S3×T4. In the AdS7 case we find that the corrections to the 6d conformal anomaly a-coefficient and the vacuum energy are again minus the ones for one (2,0 tensor multiplet, suggesting that the total a-anomaly coefficient for the dual (2,0 theory is 4N3−9/4N−7/4 and thus vanishes for N=1. In the AdS3 case the one-loop correction to the vacuum energy or 2d central charge turns out to be equal to that of one free (4,4 scalar multiplet, i.e. is c=+6. This reproduces the subleading term in the central charge c=6(Q1Q5+1 of the dual 2d CFT describing decoupling limit of D5–D1 system. We also present the expressions for the 6d a-anomaly coefficient and vacuum energy contributions of general-symmetry higher spin field in AdS7 and consider their application to tests of vectorial AdS/CFT with the boundary conformal 6d theory represented by free scalars, spinors or rank-2 antisymmetric tensors.

Colour decompositions of multi-quark one-loop QCD amplitudes

DEFF Research Database (Denmark)

Ita, Harald; Ozeren, Kemal

2012-01-01

We describe the decomposition of one-loop QCD amplitudes in terms of colour-ordered building blocks. We give new expressions for the coefficients of QCD colour structures in terms of ordered objects called primitive amplitudes, for processes with up to seven partons. These results are needed in c...... to the cross section for W+4-jet production at the Large Hadron Collider, and verify that it is very well approximated by keeping only the leading terms in an expansion around the formal limit of a large number of colours....

Azimuthal asymmetry in processes of nonlinear QED for linearly polarized photon

International Nuclear Information System (INIS)

Bajer, V.N.; Mil'shtejn, A.I.

1994-01-01

Cross sections of nonlinear QED processes (photon-photon scattering, photon splitting in a Coulomb field, and Delbrueck scattering) are considered for linearly polarized initial photon. The cross sections have sizeable azimuthal asymmetry. 15 refs.; 3 figs

A general reduction method for one-loop N-point integrals

International Nuclear Information System (INIS)

Heinrich, G.; Binoth, T.

2000-01-01

In order to calculate cross sections with a large number of particles/jets in the final state at next-to-leading order, one has to reduce the occurring scalar and tensor one-loop integrals to a small set of known integrals. In massless theories, this reduction procedure is complicated by the presence of infrared divergences. Working in n = 4 - 2ε dimensions, it will be outlined how to achieve such a reduction for diagrams with an arbitrary number of external legs. As a result, any integral with more than four propagators and generic 4-dimensional external momenta can be reduced to box integrals

Numerical evaluation of Feynman loop integrals by reduction to tree graphs

International Nuclear Information System (INIS)

Kleinschmidt, T.

2007-12-01

We present a method for the numerical evaluation of loop integrals, based on the Feynman Tree Theorem. This states that loop graphs can be expressed as a sum of tree graphs with additional external on-shell particles. The original loop integral is replaced by a phase space integration over the additional particles. In cross section calculations and for event generation, this phase space can be sampled simultaneously with the phase space of the original external particles. Since very sophisticated matrix element generators for tree graph amplitudes exist and phase space integrations are generically well understood, this method is suited for a future implementation in a fully automated Monte Carlo event generator. A scheme for renormalization and regularization is presented. We show the construction of subtraction graphs which cancel ultraviolet divergences and present a method to cancel internal on-shell singularities. Real emission graphs can be naturally included in the phase space integral of the additional on-shell particles to cancel infrared divergences. As a proof of concept, we apply this method to NLO Bhabha scattering in QED. Cross sections are calculated and are in agreement with results from conventional methods. We also construct a Monte Carlo event generator and present results. (orig.)

Numerical evaluation of Feynman loop integrals by reduction to tree graphs

Energy Technology Data Exchange (ETDEWEB)

Kleinschmidt, T.

2007-12-15

We present a method for the numerical evaluation of loop integrals, based on the Feynman Tree Theorem. This states that loop graphs can be expressed as a sum of tree graphs with additional external on-shell particles. The original loop integral is replaced by a phase space integration over the additional particles. In cross section calculations and for event generation, this phase space can be sampled simultaneously with the phase space of the original external particles. Since very sophisticated matrix element generators for tree graph amplitudes exist and phase space integrations are generically well understood, this method is suited for a future implementation in a fully automated Monte Carlo event generator. A scheme for renormalization and regularization is presented. We show the construction of subtraction graphs which cancel ultraviolet divergences and present a method to cancel internal on-shell singularities. Real emission graphs can be naturally included in the phase space integral of the additional on-shell particles to cancel infrared divergences. As a proof of concept, we apply this method to NLO Bhabha scattering in QED. Cross sections are calculated and are in agreement with results from conventional methods. We also construct a Monte Carlo event generator and present results. (orig.)

Deconstructing scalar QED at zero and finite temperature

International Nuclear Information System (INIS)

Kan, N.; Sakamoto, K.; Shiraishi, K.

2003-01-01

We calculate the effective potential for the WLPNGB in a world with a circular latticized extra dimension. The mass of the Wilson line pseudo-Nambu-Goldstone boson (WLPNGB) is calculated from the one-loop quantum effect of scalar fields at zero and finite temperature. We show that a series expansion by the modified Bessel functions is useful to calculate the one-loop effective potentials. (orig.)

Alternative Scheme for Teleportation of Two-Atom Entangled State in Cavity QED

Institute of Scientific and Technical Information of China (English)

YANG Zhen-Biao

2006-01-01

We have proposed an alternative scheme for teleportation of two-atom entangled state in cavity QED. It is based on the degenerate Raman interaction of a single-mode cavity field with a ∧-type three-level atom. The prominent feature of the scheme is that only one cavity is required, which is prior to the previous one. Moreover, the atoms need to be detected are reduced compared with the previous scheme. The experimental feasibility of the scheme is discussed.The scheme can easily be generalized for teleportation of N-atom GHZ entangled states. The number of the atoms needed to be detected does not increase as the number of the atoms in GHZ state increases.

One-loop Renormalization of Resonance Chiral Theory with Scalar and Pseudoscalar Resonances

International Nuclear Information System (INIS)

Rosell, I.

2007-01-01

The divergent part of the generating functional of the Resonance Chiral Theory is evaluated up to one loop when one multiplet of scalar and pseudoscalar resonances are included and interaction terms which couple up to two resonances are considered. Hence we obtain the renormalization of the couplings of the initial Lagrangian and, moreover, the complete list of operators that make this theory finite, at this order

New Circuit QED system based on Triple-leg Stripline Resonator.

Science.gov (United States)

Kim, Dongmin; Moon, Kyungsun

Conventional circuit QED system consists of a qubit located inside a linear stripline resonator, which has successfully demonstrated a strong coupling between a single photon and a qubit. Here we present a new circuit QED system, where the qubit is coupled to triple-leg stripline resonator (TSR). We have shown that TSR supports two-fold degenerate photon modes among others. By coupling them to a single qubit, we have obtained the dressed states of a coupled system of a single qubit and two-fold degenerate photon modes. By locating two qubits at two legs of TSR, we have studied a potential two-bit gate operation (e.g., CNOT gate) of the system. We will discuss the main advantage of utilizing two-fold degenerate photon modes This work is partially supported by Basic Science Research Program through the National Research Foundation of Korea (NRF) funded by the Ministry of Education, Science and Technology (NRF-2016R1D1A1B01013756).

Physical pictures of symmetry breaking in quenched QED4

International Nuclear Information System (INIS)

Kogut, J.B.; Argonne National Lab., IL

1989-01-01

We discuss 'collapse of the wavefunction' as the phenomenon underlying chiral symmetry breaking in quenched QED4. The 1/r singularity in the 'collapsed' qanti q wavefunction causes 'catalyzed symmetry breaking' which is the field theoretic analog of 'monopole induced proton decay'. The evasion of mean field exponents by the quenched theory's chiral phase transition is emphasized. (orig.)

Four-dimensional aether-like Lorentz-breaking QED revisited and problem of ambiguities

Energy Technology Data Exchange (ETDEWEB)

Baeta Scarpelli, A.P. [Setor Tecnico-Cientifico, Departamento de Policia Federal, Rua Hugo D' Antola, 95, Lapa, Sao Paulo (Brazil); Mariz, T. [Universidade Federal de Alagoas, Instituto de Fisica, Maceio, Alagoas (Brazil); Nascimento, J.R.; Petrov, A.Yu. [Universidade Federal da Paraiba, Departamento de Fisica, Caixa Postal 5008, Joao Pessoa, Paraiba (Brazil)

2013-08-15

In this paper, we consider the perturbative generation of the CPT-even aether-like Lorentz-breaking term in the extended Lorentz-breaking QED within different approaches and discuss its ambiguities. (orig.)

Four-dimensional aether-like Lorentz-breaking QED revisited and problem of ambiguities

International Nuclear Information System (INIS)

Baeta Scarpelli, A.P.; Mariz, T.; Nascimento, J.R.; Petrov, A.Yu.

2013-01-01

In this paper, we consider the perturbative generation of the CPT-even aether-like Lorentz-breaking term in the extended Lorentz-breaking QED within different approaches and discuss its ambiguities. (orig.)

Analytic determination at one loop of the energy-momentum tensor for lattice QCD

International Nuclear Information System (INIS)

Caracciolo, S.; Menotti, P.; Pelissetto, A.

1991-01-01

We give a completely analytical determinaton of the corrections to the naive energy-momentum tensor for lattice QCD at one loop. This tenor is conserved and gives rise to the correct trace anomaly. (orig.)

General QED/QCD aspects of simple systems

International Nuclear Information System (INIS)

Telegdi, V.L.; Brodsky, S.J.

1989-09-01

This paper discusses the following topics: renormalization theory; the Kinoshita-Lee-Nauenberg theorem; the Yennie-Frautschi-Suura relation; scale invariance at large momentum transfer; scaling and scaling violation at large momentum transfers; low-energy theorem in Compton scattering; does the perturbation series in QED converge; renormalization of the weak angle Θ w ; the Nambu-Bethe-Salpeter (NBS) equation; the decay rate of 3 S, positronium; radiative corrections to QCD Born cross section; and progress on the relativistic 2-body equation

OpenQ∗D simulation code for QCD+QED

DEFF Research Database (Denmark)

Campos, Isabel; Fritzsch, Patrick; Hansen, Martin

2018-01-01

The openQ∗D code for the simulation of QCD+QED with C∗ boundary conditions is presented. This code is based on openQCD-1.6, from which it inherits the core features that ensure its efficiency: the locally-deflated SAP-preconditioned GCR solver, the twisted-mass frequency splitting of the fermion....... An alpha version of this code is publicly available and can be downloaded from http://rcstar.web.cern.ch/....

Realization of arbitrary positive-operator-value measurement of single atomic qubit via cavity QED

International Nuclear Information System (INIS)

Han Yang; Wu Wei; Wu Chunwang; Dai Hongyi; Li Chengzu

2008-01-01

Positive-operator-value measurement (POVM) is the most general class of quantum measurement. We propose a scheme to deterministically implement arbitrary POVMs of single atomic qubit via cavity QED catalysed by only one ancilla atomic qubit. By appropriately entangling two atomic qubits and sequentially measuring the ancilla qubit, any POVM can be implemented step by step. As an application of our scheme, the realization of a specific POVM for optimal unambiguous discrimination (OUD) between two nonorthogonal states is given. (authors)

Two aspects of one loop structure: Unitarity delay in the Standard Model and modular invariance in string theory

Energy Technology Data Exchange (ETDEWEB)

Ahn, C.

1989-08-01

We study two aspects of one loop structures in quantum field theories which describe two different areas of particle physics: the one loop unitarity behavior of the Standard Model of electroweak interactions and modular invariance of string model theory. Loop expansion has its importance in that it contains quantum fluctuations due to all physical states in the theory. Therefore, by studying the various models to one loop, we can understand how the contents of the theory can contribute to physically measurable quantities and how the consistency at quantum level restricts the physical states of the theory, as well. In the first half of the thesis, we study one loop corrections to the process {ital e}{sup +}{ital e}{sup {minus}} {yields} {ital W}{sup +}{ital W}{sup {minus}}. In this process, there is a delicate unitarity-saving cancellation between s-channel and t-channel tree level Feynman diagrams. If the one loop contribution due to heavy particles corrects the channels asymmetrically, the cancellation, hence unitarity, will be delayed up to the mass scale of these heavy particles. We refer to this phenomena as the unitarity delay effect. Due to this effect, cross section below these mass scales can have significant radiative corrections which may provide an appropriate window through which we can see the high energy structure of the Standard Model from relatively low energy experiments. In the second half, we will show how quantum consistency can restrict the physical states in string theory. 53 refs., 13 figs.

Thermal phase transition with full 2-loop effective potential

Science.gov (United States)

Laine, M.; Meyer, M.; Nardini, G.

2017-07-01

Theories with extended Higgs sectors constructed in view of cosmological ramifications (gravitational wave signal, baryogenesis, dark matter) are often faced with conflicting requirements for their couplings; in particular those influencing the strength of a phase transition may be large. Large couplings compromise perturbative studies, as well as the high-temperature expansion that is invoked in dimensionally reduced lattice investigations. With the example of the inert doublet extension of the Standard Model (IDM), we show how a resummed 2-loop effective potential can be computed without a high-T expansion, and use the result to scrutinize its accuracy. With the exception of Tc, which is sensitive to contributions from heavy modes, the high-T expansion is found to perform well. 2-loop corrections weaken the transition in IDM, but they are moderate, whereby a strong transition remains an option.

Lattice artifacts in the non-Abelian Debye screening mass in one-loop order

International Nuclear Information System (INIS)

Kaste, P.; Rothe, H.J.

1997-01-01

We compute the electric screening mass in lattice QCD with Wilson fermions at finite temperature and chemical potential to one-loop order, and show that lattice artifacts arising from a finite lattice spacing result in an enhancement of the screening mass as compared to the continuum. We discuss the magnitude of this enhancement as a function of the temperature and chemical potential for lattices with a different number of lattice sites in the temporal direction that can be implemented in lattice simulations. Most of the enhancement is found to be due to the fermion loop contribution. copyright 1997 The American Physical Society

Fingerprinting the extended Higgs sector using one-loop corrected Higgs boson couplings and future precision measurements

Directory of Open Access Journals (Sweden)

Shinya Kanemura

2015-07-01

Full Text Available We calculate radiative corrections to a full set of coupling constants for the 125 GeV Higgs boson at the one-loop level in two Higgs doublet models with four types of Yukawa interaction under the softly-broken discrete Z2 symmetry. The renormalization calculations are performed in the on-shell scheme, in which the gauge dependence in the mixing parameter which appears in the previous calculation is consistently avoided. We first show the details of our renormalization scheme, and present the complete set of the analytic formulae of the renormalized couplings. We then numerically demonstrate how the inner parameters of the model can be extracted by the future precision measurements of these couplings at the high luminosity LHC and the International Linear Collider.

SU-E-J-85: Leave-One-Out Perturbation (LOOP) Fitting Algorithm for Absolute Dose Film Calibration

International Nuclear Information System (INIS)

Chu, A; Ahmad, M; Chen, Z; Nath, R; Feng, W

2014-01-01

Purpose: To introduce an outliers-recognition fitting routine for film dosimetry. It cannot only be flexible with any linear and non-linear regression but also can provide information for the minimal number of sampling points, critical sampling distributions and evaluating analytical functions for absolute film-dose calibration. Methods: The technique, leave-one-out (LOO) cross validation, is often used for statistical analyses on model performance. We used LOO analyses with perturbed bootstrap fitting called leave-one-out perturbation (LOOP) for film-dose calibration . Given a threshold, the LOO process detects unfit points (“outliers”) compared to other cohorts, and a bootstrap fitting process follows to seek any possibilities of using perturbations for further improvement. After that outliers were reconfirmed by a traditional t-test statistics and eliminated, then another LOOP feedback resulted in the final. An over-sampled film-dose- calibration dataset was collected as a reference (dose range: 0-800cGy), and various simulated conditions for outliers and sampling distributions were derived from the reference. Comparisons over the various conditions were made, and the performance of fitting functions, polynomial and rational functions, were evaluated. Results: (1) LOOP can prove its sensitive outlier-recognition by its statistical correlation to an exceptional better goodness-of-fit as outliers being left-out. (2) With sufficient statistical information, the LOOP can correct outliers under some low-sampling conditions that other “robust fits”, e.g. Least Absolute Residuals, cannot. (3) Complete cross-validated analyses of LOOP indicate that the function of rational type demonstrates a much superior performance compared to the polynomial. Even with 5 data points including one outlier, using LOOP with rational function can restore more than a 95% value back to its reference values, while the polynomial fitting completely failed under the same conditions

SU-E-J-85: Leave-One-Out Perturbation (LOOP) Fitting Algorithm for Absolute Dose Film Calibration

Energy Technology Data Exchange (ETDEWEB)

Chu, A; Ahmad, M; Chen, Z; Nath, R [Yale New Haven Hospital/School of Medicine Yale University, New Haven, CT (United States); Feng, W [New York Presbyterian Hospital, Tenafly, NJ (United States)

2014-06-01

Purpose: To introduce an outliers-recognition fitting routine for film dosimetry. It cannot only be flexible with any linear and non-linear regression but also can provide information for the minimal number of sampling points, critical sampling distributions and evaluating analytical functions for absolute film-dose calibration. Methods: The technique, leave-one-out (LOO) cross validation, is often used for statistical analyses on model performance. We used LOO analyses with perturbed bootstrap fitting called leave-one-out perturbation (LOOP) for film-dose calibration . Given a threshold, the LOO process detects unfit points (“outliers”) compared to other cohorts, and a bootstrap fitting process follows to seek any possibilities of using perturbations for further improvement. After that outliers were reconfirmed by a traditional t-test statistics and eliminated, then another LOOP feedback resulted in the final. An over-sampled film-dose- calibration dataset was collected as a reference (dose range: 0-800cGy), and various simulated conditions for outliers and sampling distributions were derived from the reference. Comparisons over the various conditions were made, and the performance of fitting functions, polynomial and rational functions, were evaluated. Results: (1) LOOP can prove its sensitive outlier-recognition by its statistical correlation to an exceptional better goodness-of-fit as outliers being left-out. (2) With sufficient statistical information, the LOOP can correct outliers under some low-sampling conditions that other “robust fits”, e.g. Least Absolute Residuals, cannot. (3) Complete cross-validated analyses of LOOP indicate that the function of rational type demonstrates a much superior performance compared to the polynomial. Even with 5 data points including one outlier, using LOOP with rational function can restore more than a 95% value back to its reference values, while the polynomial fitting completely failed under the same conditions

Oblique photon expansion of QED structure functions

International Nuclear Information System (INIS)

Chahine, C.

1986-01-01

In the oblique photon expansion, the collinear part of photon emission is summed up to all orders in perturbation theory. The number of oblique or non-collinear photons is the expansion order. Unlike in perturbation theory, every term of the expansion is both infrared finite and gauge invariant. The zero oblique photon contribution to the electromagnetic structure tensor in QED is computed in detail. The behaviors of the structure functions F1 and F2 are discussed in the soft and ultra-soft limits

Testing of QED-Theory and Precise Measurements of the Rydberg Series for the He-Like Multicharged Ions

Energy Technology Data Exchange (ETDEWEB)

Pal' chikov, V. G. [VNIIFTRI, Mendeleevo, National Research Institute for Physical-Technical and Radiotechnical Measurements - (Russian Federation)], E-mail: vitpal@mail.ru

2001-01-15

The wavelengths of the 1snp{sup 1}P{sub 1}-1s{sup 21}S{sub 0} transitions in He-like Mg XI, F VIII (n= 4-8) and Al XII (n=6,9) have been calculated in the framework of the 1/Z expansion method including relativistic effects and QED contributions. It is found that QED corrections to the ground-state ionization energy are significant at the present level of experimental accuracy.

Zero field Quantum Hall Effect in QED3

International Nuclear Information System (INIS)

Raya, K; Sánchez-Madrigal, S; Raya, A

2013-01-01

We study analytic structure of the fermion propagator in the Quantum Electrodynamics in 2+1 dimensions (QED3) in the Landau gauge, both in perturbation theory and nonperturbatively, by solving the corresponding Schwinger-Dyson equation in rainbow approximation. In the chiral limit, we found many nodal solutions, which could be interpreted as vacuum excitations. Armed with these solutions, we use the Kubo formula and calculate the filling factor for the zero field Quantum Hall Effect

Multi-flavor massless QED{sub 2} at finite densities via Lefschetz thimbles

Energy Technology Data Exchange (ETDEWEB)

Tanizaki, Yuya [RIKEN BNL Research Center, Brookhaven National Laboratory,Upton, NY 11973-5000 (United States); Tachibana, Motoi [Department of Physics, Saga University,Saga 840-8502 (Japan)

2017-02-15

We consider multi-flavor massless (1+1)-dimensional QED with chemical potentials at finite spatial length and the zero-temperature limit. Its sign problem is solved using the mean-field calculation with complex saddle points.

Nuclear polarization study: new frontiers for tests of QED in heavy highly charged ions.

Science.gov (United States)

Volotka, Andrey V; Plunien, Günter

2014-07-11

A systematic investigation of the nuclear polarization effects in one- and few-electron heavy ions is presented. The nuclear polarization corrections in the zeroth and first orders in 1/Z are evaluated to the binding energies, the hyperfine splitting, and the bound-electron g factor. It is shown that the nuclear polarization contributions can be substantially canceled simultaneously with the rigid nuclear corrections. This allows for new prospects for probing the QED effects in a strong electromagnetic field and the determination of fundamental constants.

Hydrogen atom spectrum and the Lamb shift in noncommutative QED

International Nuclear Information System (INIS)

Chaichian, M. . Helsinki Institute of Physics, Helsinki; Tureanu, A. . Helsinki Institute of Physics, Helsinki; FI)

2000-10-01

We have calculated the energy levels of the hydrogen atom and as well the Lamb shift within the noncommutative quantum electrodynamics theory. The results show deviations from the usual QED both on the classical and on the quantum levels. On both levels, the deviations depend on the parameter of space/space noncommutativity. (author)

Exploring photonic topological insulator states in a circuit-QED lattice

Science.gov (United States)

Li, Jing-Ling; Shan, Chuan-Jia; Zhao, Feng

2018-04-01

We propose a simple protocol to explore the topological properties of photonic integer quantum Hall states in a one-dimensional circiut-QED lattice. By periodically modulating the on-site photonic energies in such a lattice, we demonstrate that this one-dimensional lattice model can be mapped into a two-dimensional integer quantum Hall insulator model. Based on the lattice-based cavity input-output theory, we show that both the photonic topological protected edge states and topological invariants can be clearly measured from the final steady state of the resonator lattice after taking into account cavity dissipation. Interestingly, we also find that the measurement signals associated with the above topological features are quite unambitious even in five coupled dissipative resonators. Our work opens up a new prospect of exploring topological states with a small-size dissipative quantum artificial lattice, which is quite attractive to the current quantum optics community.

On the construction of QED using ERG

International Nuclear Information System (INIS)

Sonoda, H

2007-01-01

It has been known for some time that a smooth momentum cutoff is compatible with local gauge symmetries. In this paper, we show concretely how to construct QED using the exact renormalization group (ERG). First, we give a new derivation of the Ward identity for the Wilson action using the technique of composite operators. Second, parametrizing the theory by its asymptotic behaviour for a large cutoff, we show how to fine tune the parameters to satisfy the identity. Third, we recast the identity as an invariance of the Wilson action under a nonlinear BRST transformation

Entanglement concentration and purification of two-mode squeezed microwave photons in circuit QED

Science.gov (United States)

Zhang, Hao; Alsaedi, Ahmed; Hayat, Tasawar; Deng, Fu-Guo

2018-04-01

We present a theoretical proposal for a physical implementation of entanglement concentration and purification protocols for two-mode squeezed microwave photons in circuit quantum electrodynamics (QED). First, we give the description of the cross-Kerr effect induced between two resonators in circuit QED. Then we use the cross-Kerr media to design the effective quantum nondemolition (QND) measurement on microwave-photon number. By using the QND measurement, the parties in quantum communication can accomplish the entanglement concentration and purification of nonlocal two-mode squeezed microwave photons. We discuss the feasibility of our schemes by giving the detailed parameters which can be realized with current experimental technology. Our work can improve some practical applications in continuous-variable microwave-based quantum information processing.

Two-loop planar master integrals for Higgs →3 partons with full heavy-quark mass dependence

International Nuclear Information System (INIS)

Bonciani, Roberto; Duca, Vittorio Del; Frellesvig, Hjalte; Henn, Johannes M.; Moriello, Francesco; Smirnov, Vladimir A.

2016-01-01

We present the analytic computation of all the planar master integrals which contribute to the two-loop scattering amplitudes for Higgs→3 partons, with full heavy-quark mass dependence. These are relevant for the NNLO corrections to fully inclusive Higgs production and to the NLO corrections to Higgs production in association with a jet, in the full theory. The computation is performed using the differential equations method. Whenever possible, a basis of master integrals that are pure functions of uniform weight is used. The result is expressed in terms of one-fold integrals of polylogarithms and elementary functions up to transcendental weight four. Two integral sectors are expressed in terms of elliptic integrals. We show that by introducing a one-dimensional parametrization of the integrals the relevant second order differential equation can be readily solved, and the solution can be expressed to all orders of the dimensional regularization parameter in terms of iterated integrals over elliptic kernels. We express the result for the elliptic sectors in terms of two and three-fold iterated integrals, which we find suitable for numerical evaluations. This is the first time that four-point multiscale Feynman integrals have been computed in a fully analytic way in terms of elliptic integrals.

Two-loop planar master integrals for Higgs →3 partons with full heavy-quark mass dependence

Energy Technology Data Exchange (ETDEWEB)

Bonciani, Roberto [Dipartimento di Fisica, Sapienza - Università di Roma,Piazzale Aldo Moro 5, 00185, Rome (Italy); INFN Sezione di Roma, Piazzale Aldo Moro 2, 00185, Rome (Italy); Duca, Vittorio Del [ETH Zurich, Institut fur theoretische Physik, Wolfgang-Paulistr. 27, 8093, Zurich (Switzerland); INFN Laboratori Nazionali di Frascati, 00044 Frascati, Roma (Italy); Frellesvig, Hjalte [Institute of Nuclear and Particle Physics, NCSR Demokritos, Agia Paraskevi, 15310 (Greece); Henn, Johannes M. [PRISMA Cluster of Excellence, Johannes Gutenberg University, 55099 Mainz (Germany); Moriello, Francesco [Dipartimento di Fisica, Sapienza - Università di Roma,Piazzale Aldo Moro 5, 00185, Rome (Italy); INFN Sezione di Roma, Piazzale Aldo Moro 2, 00185, Rome (Italy); ETH Zurich, Institut fur theoretische Physik, Wolfgang-Paulistr. 27, 8093, Zurich (Switzerland); Smirnov, Vladimir A. [Skobeltsyn Institute of Nuclear Physics of Moscow State University, 119991 Moscow (Russian Federation)

2016-12-19

We present the analytic computation of all the planar master integrals which contribute to the two-loop scattering amplitudes for Higgs→3 partons, with full heavy-quark mass dependence. These are relevant for the NNLO corrections to fully inclusive Higgs production and to the NLO corrections to Higgs production in association with a jet, in the full theory. The computation is performed using the differential equations method. Whenever possible, a basis of master integrals that are pure functions of uniform weight is used. The result is expressed in terms of one-fold integrals of polylogarithms and elementary functions up to transcendental weight four. Two integral sectors are expressed in terms of elliptic integrals. We show that by introducing a one-dimensional parametrization of the integrals the relevant second order differential equation can be readily solved, and the solution can be expressed to all orders of the dimensional regularization parameter in terms of iterated integrals over elliptic kernels. We express the result for the elliptic sectors in terms of two and three-fold iterated integrals, which we find suitable for numerical evaluations. This is the first time that four-point multiscale Feynman integrals have been computed in a fully analytic way in terms of elliptic integrals.

Gauge-invariant dressed fermion propagator in massless QED3

International Nuclear Information System (INIS)

Mitra, Indrajit; Ratabole, Raghunath; Sharatchandra, H.S.

2006-01-01

The infrared behaviour of the gauge-invariant dressed fermion propagator in massless QED 3 is discussed for three choices of dressing. It is found that only the propagator with the isotropic (in three Euclidean dimensions) choice of dressing is acceptable as the physical fermion propagator. It is explained that the negative anomalous dimension of this physical fermion does not contradict any field-theoretical requirement

One-loop polarization operator of the quantum gauge superfield for 𝒩 = 1 SYM regularized by higher derivatives

Science.gov (United States)

Kazantsev, A. E.; Skoptsov, M. B.; Stepanyantz, K. V.

2017-11-01

We consider the general 𝒩 = 1 supersymmetric gauge theory with matter, regularized by higher covariant derivatives without breaking the BRST invariance, in the massless limit. In the ξ-gauge we obtain the (unrenormalized) expression for the two-point Green function of the quantum gauge superfield in the one-loop approximation as a sum of integrals over the loop momentum. The result is presented as a sum of three parts: the first one corresponds to the pure supersymmetric Yang-Mills theory in the Feynman gauge, the second one contains all gauge-dependent terms, and the third one is the contribution of diagrams with a matter loop. For the Feynman gauge and a special choice of the higher derivative regulator in the gauge fixing term, we analytically calculate these integrals in the limit k → 0. In particular, in addition to the leading logarithmically divergent terms, which are determined by integrals of double total derivatives, we also find the finite constants.

Fermion bag approach to the sign problem in strongly coupled lattice QED with Wilson fermions

OpenAIRE

Chandrasekharan, Shailesh; Li, Anyi

2010-01-01

We explore the sign problem in strongly coupled lattice QED with one flavor of Wilson fermions in four dimensions using the fermion bag formulation. We construct rules to compute the weight of a fermion bag and show that even though the fermions are confined into bosons, fermion bags with negative weights do exist. By classifying fermion bags as either simple or complex, we find numerical evidence that complex bags with positive and negative weights come with almost equal probabilities and th...

QED the strange theory of light and matter

CERN Document Server

Feynman, Richard Phillips

2006-01-01

Celebrated for his brilliantly quirky insights into the physical world, Nobel laureate Richard Feynman also possessed an extraordinary talent for explaining difficult concepts to the general public. Here Feynman provides a classic and definitive introduction to QED (namely quantum electrodynamics), that part of quantum field theory describing the interactions of light with charged particles. Using everyday language, spatial concepts, visualizations, and his renowned ""Feynman diagrams"" instead of advanced mathematics, Feynman clearly and humorously communicates both the substance and spiri

Meson-meson scattering in lattice QED2+1

International Nuclear Information System (INIS)

Fiebig, H.R.; Woloshyn, R.M.

1993-01-01

Scattering phase shifts of a meson-meson system in staggered 3-dimensional lattice QED are computed. The main task of the simulation is to obtain a discrete set of two-body energy levels. These are extracted from a 4-point time correlation matrix and then used to obtain scattering phase shifts. The results for the l = 0 and l = 2 partial waves are consistent with short-range repulsion and intermediate-range attraction of the residual meson-meson interaction. (orig.)

One-turn stub-loaded loop patch antenna on a small ground plane

DEFF Research Database (Denmark)

Thaysen, Jesper; Jakobsen, Kaj Bjarne

2005-01-01

A small 1.1-cm3 one-turn loop patch antenna located 2.5 mm above an 18 × 25 mm ground plane separated by a dielectric substrate with relative permittivity of 9.8 is presented. By varying the length of a thin quarter-wavelength matching line, it is possible to change the resonant frequency. An RLC...

Refined counting of necklaces in one-loop N=4 SYM

Science.gov (United States)

Suzuki, Ryo

2017-06-01

We compute the grand partition function of N=4 SYM at one-loop in the SU(2) sector with general chemical potentials, extending the results of Pólya's theorem. We make use of finite group theory, applicable to all orders of perturbative 1 /N c expansion. We show that only the planar terms contribute to the grand partition function, which is therefore equal to the grand partition function of an ensemble of {XXX}_{1/2} spin chains. We discuss how Hagedorn temperature changes on the complex plane of chemical potentials.

Effects of one-loop corrections in the Weinberg-Salam theory

International Nuclear Information System (INIS)

Bardin, D.Y.; Fedorenko, O.M.; Christova, P.C.

1982-01-01

We have studied the one-loop effects in the Weinberg-Salam theory in the natural renormalization scheme which we have generalized to the case of an arbitrary unitary mixing of the fermion fields. We have discussed in detail the problems which are connected with carrying out the renormalization program in the Weinberg-Salam theory. We have calculated the masses of the W and Z bosons. We present a description of the finite renormalizations which relate to each other the three definitions of the Weinberg parameter sin 2 theta/sub W/

Pair creation in inhomogeneous fields from worldline instantons

International Nuclear Information System (INIS)

Dunne, Gerald V.; Schubert, Christian

2006-01-01

We show how to do semiclassical nonperturbative computations within the worldline approach to quantum field theory using ''worldline instantons''. These worldline instantons are classical solutions to the Euclidean worldline loop equations of motion, and are closed spacetime loops parametrized by the proper-time. Specifically, we compute the imaginary part of the one loop effective action in scalar and spinor QED using worldline instantons, for a wide class of inhomogeneous electric field backgrounds

QED corrections in deep-inelastic scattering from tensor polarized deuteron target

CERN Document Server

Gakh, G I

2001-01-01

The QED correction in the deep inelastic scattering from the polarized tensor of the deuteron target is considered. The calculations are based on the covariant parametrization of the deuteron quadrupole polarization tensor. The Drell-Yan representations in the electrodynamics are used for describing the radiation real and virtual particles

Chiral anomalies in QED and QCD at finite temperature

International Nuclear Information System (INIS)

Alvarez-Estrada, R.F.

1991-01-01

Chiral anomalies (a) for QED and QCD at finite temperature are analyzed in imaginary- and real-time formalisms. Both triangle diagrams and functional methods are used. It is found that the expressions for a in terms of finite-temperature fields are formally similar to that for the zero-temperature anomaly as a function of zero-temperature fields, thereby generalizing previous work by other authors. (author). 20 refs.; 1 fig

Transverse Momentum Distributions of Electron in Simulated QED Model

Science.gov (United States)

Kaur, Navdeep; Dahiya, Harleen

2018-05-01

In the present work, we have studied the transverse momentum distributions (TMDs) for the electron in simulated QED model. We have used the overlap representation of light-front wave functions where the spin-1/2 relativistic composite system consists of spin-1/2 fermion and spin-1 vector boson. The results have been obtained for T-even TMDs in transverse momentum plane for fixed value of longitudinal momentum fraction x.

Massless spectra and gauge couplings at one-loop on non-factorisable toroidal orientifolds

Science.gov (United States)

Berasaluce-González, Mikel; Honecker, Gabriele; Seifert, Alexander

2018-01-01

So-called 'non-factorisable' toroidal orbifolds can be rewritten in a factorised form as a product of three two-tori by imposing an additional shift symmetry. This finding of Blaszczyk et al. [1] provides a new avenue to Conformal Field Theory methods, by which the vector-like massless matter spectrum - and thereby the type of gauge group enhancement on orientifold invariant fractional D6-branes - and the one-loop corrections to the gauge couplings in Type IIA orientifold theories can be computed in addition to the well-established chiral matter spectrum derived from topological intersection numbers among three-cycles. We demonstrate this framework for the Z4 × ΩR orientifolds on the A3 ×A1 ×B2-type torus. As observed before for factorisable backgrounds, also here the one-loop correction can drive the gauge groups to stronger coupling as demonstrated by means of a four-generation Pati-Salam example.

Actinide collisions for QED and superheavy elements with the time-dependent Hartree-Fock theory and the Balian-Vénéroni variational principle

Directory of Open Access Journals (Sweden)

Kedziora David J.

2011-10-01

Full Text Available Collisions of actinide nuclei form, during very short times of few zs (10−21 s, the heaviest ensembles of interacting nucleons available on Earth. Such collisions are used to produce super-strong electric fields by the huge number of interacting protons to test spontaneous positron-electron pair emission (vacuum decay predicted by the quantum electrodynamics (QED theory. Multi-nucleon transfer in actinide collisions could also be used as an alternative way to fusion in order to produce neutron-rich heavy and superheavy elements thanks to inverse quasifission mechanisms. Actinide collisions are studied in a dynamical quantum microscopic approach. The three-dimensional time-dependent Hartree-Fock (TDHF code tdhf3d is used with a full Skyrme energy density functional to investigate the time evolution of expectation values of one-body operators, such as fragment position and particle number. This code is also used to compute the dispersion of the particle numbers (e.g., widths of fragment mass and charge distributions from TDHF transfer probabilities, on the one hand, and using the BalianVeneroni variational principle, on the other hand. A first application to test QED is discussed. Collision times in 238U+238U are computed to determine the optimum energy for the observation of the vacuum decay. It is shown that the initial orientation strongly affects the collision times and reaction mechanism. The highest collision times predicted by TDHF in this reaction are of the order of ~ 4 zs at a center of mass energy of 1200 MeV. According to modern calculations based on the Dirac equation, the collision times at Ecm > 1 GeV are sufficient to allow spontaneous electron-positron pair emission from QED vacuum decay, in case of bare uranium ion collision. A second application of actinide collisions to produce neutron-rich transfermiums is discussed. A new inverse quasifission mechanism associated to a specific orientation of the nuclei is proposed to

Evidence for a critical behavior in 4D pure compact QED

International Nuclear Information System (INIS)

Jersak, J.; Neuhaus, T.

1995-01-01

We present evidence about a critical behavior of 4D compact QED (CQED) pure gauge theory. Regularizing the theory on lattices homotopic to a sphere, we present evidence for a critical, i.e. second order like behavior at the deconfinement phase transition for certain values of the coupling parameter γ. ((orig.))

Dirac dark matter with a charged mediator: a comprehensive one-loop analysis of the direct detection phenomenology

International Nuclear Information System (INIS)

Ibarra, Alejandro; Wild, Sebastian

2015-01-01

We analyze the direct detection signals of a toy model consisting of a Dirac dark matter particle which couples to one Standard Model fermion via a scalar mediator. For all scenarios, the dark matter particle scatters off nucleons via one loop-induced electromagnetic and electroweak moments, as well as via the one-loop exchange of a Higgs boson. Besides, and depending on the details of the model, the scattering can also be mediated at tree level via the exchange of the scalar mediator or at one loop via gluon-gluon interactions. We show that, for thermally produced dark matter particles, the current limits from the LUX experiment on these scenarios are remarkably strong, even for dark matter coupling only to leptons. We also discuss future prospects for XENON1T and DARWIN and we argue that multi-ton xenon detectors will be able to probe practically the whole parameter space of the model consistent with thermal production and perturbativity. We also discuss briefly the implications of our results for the dark matter interpretation of the Galactic GeV excess

Loop calculations in the three dimensional Gribov-Zwanziger Lagrangian

International Nuclear Information System (INIS)

Gracey, J.A.

2010-01-01

The three dimensional Gribov-Zwanziger Lagrangian is analysed at one and two loops. Specifically, the two loop gap equation is evaluated and the Gribov mass is expressed in terms of the coupling constant. The one loop corrections to the propagators of all the fields are determined. It is shown that when the gap equation is satisfied the Faddeev-Popov ghost and both Bose and Grassmann localizing ghosts all enhance in the infrared limit at one loop. This verifies that the Kugo-Ojima confinement criterion holds to this order and we also show that both Grassmann ghosts are enhanced at two loops. For the Bose ghost we determine the full form of the propagator in the zero momentum limit for both the transverse and longitudinal pieces and confirm Zwanziger's recent general analysis for the low energy behaviour. We provide an alternative but equivalent version of the horizon condition expressing it as the vacuum expectation value of an operator involving only the localizing Bose ghost field. The one loop static potential is also determined. (orig.)

Gauge dependence of the infrared behaviour of massless QED3

International Nuclear Information System (INIS)

Mitra, Indrajit; Ratabole, Raghunath; Sharatchandra, H.S.

2006-01-01

Using the Zumino identities it is shown that in a class of non-local gauges, massless QED 3 has an infrared behaviour of a conformal field theory with a continuously varying anomalous dimension of the fermion. In the usual Lorentz gauge, the fermion propagator falls off exponentially for a large separation, but this apparent fermion mass is a gauge artifact

Compact lattice QED with staggered fermions and chiral symmetry breaking

International Nuclear Information System (INIS)

Hoferichter, A.; Mitrjushkin, V.K.; Mueller-Preussker, M.

1994-07-01

Different formulations of the 4d compact lattice QED with staggered fermions (standard Wilson and modified by suppression of lattice artifacts) are investigated by Monte Carlo simulations within the quenched approximation. We show that after suppressing lattice artifacts the system undergoes a phase transition from the Coulomb phase into a presumably weakly chirally broken phase only at (unphysical) negative β-values. (orig.)

First-order signals in compact QED with monopole suppressed boundaries

International Nuclear Information System (INIS)

Lippert, T.; Schilling, K.; Forschungszentrum Juelich GmbH

1995-01-01

Pure gauge compact QED on hypercubic lattices is considered with periodically closed monopole currents suppressed. We compute observables on sublattices which are nested around the centre of the lattice in order to locate regions where translation symmetry is approximately recovered. Our Monte Carlo simulations on 24 4 -lattices give indications for a first-order nature of the U(1) phase transition. ((orig.))

NNLO O(α4s) results for heavy quark pair production in quark-antiquark collisions. The one-loop squared contributions

International Nuclear Information System (INIS)

Koerner, J.G.

2008-02-01

We calculate the NNLO O(α 4 s ) one-loop squared corrections to the production of heavy quark pairs in quark-antiquark annihilations. These are part of the NNLO O(α 4 s ) radiative QCD corrections to this process. Our results, with the full mass dependence retained, are presented in a closed and very compact form, in the dimensional regularization scheme. We find very intriguing factorization properties for the finite part of the amplitudes. (orig.)

One-loop tensor Feynman integral reduction with signed minors

International Nuclear Information System (INIS)

Fleischer, J.; Yundin, V.

2011-12-01

We present an algebraic approach to one-loop tensor integral reduction. The integrals are presented in terms of scalar one- to four-point functions. The reduction is worked out explicitly until five-point functions of rank five. The numerical C++ package PJFry evaluates tensor coefficients in terms of a basis of scalar integrals, which is provided by an external library, e.g. QCDLoop. We shortly describe installation and use of PJFry. Examples for numerical results are shown, including a special treatment for small or vanishing inverse four-point Gram determinants. An extremely efficient application of the formalism is the immediate evaluation of complete contractions of the tensor integrals with external momenta. This leads to the problem of evaluating sums over products of signed minors with scalar products of chords. Chords are differences of external momenta. These sums may be evaluated analytically in a systematic way. The final expressions for the numerical evaluation are then compact combinations of the contributing basic scalar functions. (orig.)

One-loop tensor Feynman integral reduction with signed minors

Energy Technology Data Exchange (ETDEWEB)

Fleischer, J. [Bielefeld Univ. (Germany). Fakultaet fuer Physik; Riemann, T. [Deutsches Elektronen-Synchrotron (DESY), Zeuthen (Germany); Yundin, V. [Copenhagen Univ. (Denmark). Niels Bohr International Academy and Discovery Center

2011-12-15

We present an algebraic approach to one-loop tensor integral reduction. The integrals are presented in terms of scalar one- to four-point functions. The reduction is worked out explicitly until five-point functions of rank five. The numerical C++ package PJFry evaluates tensor coefficients in terms of a basis of scalar integrals, which is provided by an external library, e.g. QCDLoop. We shortly describe installation and use of PJFry. Examples for numerical results are shown, including a special treatment for small or vanishing inverse four-point Gram determinants. An extremely efficient application of the formalism is the immediate evaluation of complete contractions of the tensor integrals with external momenta. This leads to the problem of evaluating sums over products of signed minors with scalar products of chords. Chords are differences of external momenta. These sums may be evaluated analytically in a systematic way. The final expressions for the numerical evaluation are then compact combinations of the contributing basic scalar functions. (orig.)

Tiling arbitrarily nested loops by means of the transitive

Directory of Open Access Journals (Sweden)

Bielecki Włodzimierz

2016-12-01

Full Text Available A novel approach to generation of tiled code for arbitrarily nested loops is presented. It is derived via a combination of the polyhedral and iteration space slicing frameworks. Instead of program transformations represented by a set of affine functions, one for each statement, it uses the transitive closure of a loop nest dependence graph to carry out corrections of original rectangular tiles so that all dependences of the original loop nest are preserved under the lexicographic order of target tiles. Parallel tiled code can be generated on the basis of valid serial tiled code by means of applying affine transformations or transitive closure using on input an inter-tile dependence graph whose vertices are represented by target tiles while edges connect dependent target tiles. We demonstrate how a relation describing such a graph can be formed. The main merit of the presented approach in comparison with the well-known ones is that it does not require full permutability of loops to generate both serial and parallel tiled codes; this increases the scope of loop nests to be tiled.

One-loop renormalization of Lee-Wick gauge theory

International Nuclear Information System (INIS)

Grinstein, Benjamin; O'Connell, Donal

2008-01-01

We examine the renormalization of Lee-Wick gauge theory to one-loop order. We show that only knowledge of the wave function renormalization is necessary to determine the running couplings, anomalous dimensions, and vector boson masses. In particular, the logarithmic running of the Lee-Wick vector boson mass is exactly related to the running of the coupling. In the case of an asymptotically free theory, the vector boson mass runs to infinity in the ultraviolet. Thus, the UV fixed point of the pure gauge theory is an ordinary quantum field theory. We find that the coupling runs more quickly in Lee-Wick gauge theory than in ordinary gauge theory, so the Lee-Wick standard model does not naturally unify at any scale. Finally, we present results on the beta function of more general theories containing dimension six operators which differ from previous results in the literature.

Loop Quantum Cosmology.

Science.gov (United States)

Bojowald, Martin

2008-01-01

Quantum gravity is expected to be necessary in order to understand situations in which classical general relativity breaks down. In particular in cosmology one has to deal with initial singularities, i.e., the fact that the backward evolution of a classical spacetime inevitably comes to an end after a finite amount of proper time. This presents a breakdown of the classical picture and requires an extended theory for a meaningful description. Since small length scales and high curvatures are involved, quantum effects must play a role. Not only the singularity itself but also the surrounding spacetime is then modified. One particular theory is loop quantum cosmology, an application of loop quantum gravity to homogeneous systems, which removes classical singularities. Its implications can be studied at different levels. The main effects are introduced into effective classical equations, which allow one to avoid the interpretational problems of quantum theory. They give rise to new kinds of early-universe phenomenology with applications to inflation and cyclic models. To resolve classical singularities and to understand the structure of geometry around them, the quantum description is necessary. Classical evolution is then replaced by a difference equation for a wave function, which allows an extension of quantum spacetime beyond classical singularities. One main question is how these homogeneous scenarios are related to full loop quantum gravity, which can be dealt with at the level of distributional symmetric states. Finally, the new structure of spacetime arising in loop quantum gravity and its application to cosmology sheds light on more general issues, such as the nature of time. Supplementary material is available for this article at 10.12942/lrr-2008-4.

Protein intercalation in DNA as one of main modes of fixation of the most stable chromatin loop domains

Directory of Open Access Journals (Sweden)

М. I. Chopei

2014-08-01

Full Text Available The main mechanism of DNA track formation during comet assay of nucleoids, obtained after removal of cell membranes and most of proteins, is the extension to anode of negatively supercoiled DNA loops attached to proteins, remaining in nucleoid after lysis treatment. The composition of these residual protein structures and the nature of their strong interaction with the loop ends remain poorly studied. In this work we investigated the influence of chloroquine intercalation and denaturation of nucleoid proteins on the efficiency of electrophoretic track formation during comet assay. The results obtained suggest that even gentle protein denaturation is sufficient to reduce considerably the effectiveness of the DNA loop migration due to an increase in the loops size. The same effect was observed under local DNA unwinding upon chloroquine intercalation around the sites of the attachment of DNA to proteins. The topological interaction (protein intercalation into the double helix between DNA loop ends and nucleoid proteins is discussed.

Natively unstructured loops differ from other loops.

Directory of Open Access Journals (Sweden)

Avner Schlessinger

2007-07-01

Full Text Available Natively unstructured or disordered protein regions may increase the functional complexity of an organism; they are particularly abundant in eukaryotes and often evade structure determination. Many computational methods predict unstructured regions by training on outliers in otherwise well-ordered structures. Here, we introduce an approach that uses a neural network in a very different and novel way. We hypothesize that very long contiguous segments with nonregular secondary structure (NORS regions differ significantly from regular, well-structured loops, and that a method detecting such features could predict natively unstructured regions. Training our new method, NORSnet, on predicted information rather than on experimental data yielded three major advantages: it removed the overlap between testing and training, it systematically covered entire proteomes, and it explicitly focused on one particular aspect of unstructured regions with a simple structural interpretation, namely that they are loops. Our hypothesis was correct: well-structured and unstructured loops differ so substantially that NORSnet succeeded in their distinction. Benchmarks on previously used and new experimental data of unstructured regions revealed that NORSnet performed very well. Although it was not the best single prediction method, NORSnet was sufficiently accurate to flag unstructured regions in proteins that were previously not annotated. In one application, NORSnet revealed previously undetected unstructured regions in putative targets for structural genomics and may thereby contribute to increasing structural coverage of large eukaryotic families. NORSnet found unstructured regions more often in domain boundaries than expected at random. In another application, we estimated that 50%-70% of all worm proteins observed to have more than seven protein-protein interaction partners have unstructured regions. The comparative analysis between NORSnet and DISOPRED2 suggested

A mapping between Feynman and string motivated one-loop rules in gauge theories

International Nuclear Information System (INIS)

Bern, Z.

1992-01-01

Recently, computationally efficient rules for one-loop gauge theory amplitudes have been derived from string theory. We demonstrate the relationship of the compact string organization of the amplitude to Feynman diagrams. In particular, we explicitly show how large cancellations inherent in conventional Feynman diagram computations are avoided by the string motivated rules. (orig.)

Electron-electron bound states in Maxwell-Chern-Simons-Proca QED3

International Nuclear Information System (INIS)

Belich, H.; Helayel-Neto, J.A.; Ferreira, M.M. Jr.; Maranhao Univ., Sao Luis, MA

2002-10-01

We start from a parity-breaking MCS QED 3 model with spontaneous breaking of the gauge symmetry as a framework for evaluation of the electron-electron interaction potential and for attainment of numerical values for the e - e - - bound state. Three expressions V eff↓↓ , V eff↓↑ , V eff↓↓ ) are obtained according to the polarization state of the scattered electrons. In an energy scale compatible with condensed matter electronic excitations, these potentials become degenerated. The resulting potential is implemented in the Schroedinger equation and the variational method is applied to carry out the electronic binding energy. The resulting binding energies in the scale of 10-100 meV and a correlation length in the scale of 10 - 30 Angstrom are possible indications that the MCS-QED 3 model adopted may be suitable to address an eventual case of e - e - pairing in the presence of parity-symmetry breakdown. The data analyzed here suggest an energy scale of 10-100 meV to fix the breaking of the U(1)-symmetry. (author)

Harmonic polylogarithms for massive Bhabha scattering

International Nuclear Information System (INIS)

Czakon, M.; Riemann, T.

2005-08-01

One- and two-dimensional harmonic polylogarithms, HPLs and GPLs, appear in calculations of multi-loop integrals. We discuss them in the context of analytical solutions for two-loop master integrals in the case of massive Bhabha scattering in QED. For the GPLs we discuss analytical representations, conformal transformations, and also their transformations corresponding to relations between master integrals in the s- and t-channel. (orig.)

Gauge-invariant dressed fermion propagator in massless QED{sub 3}

Energy Technology Data Exchange (ETDEWEB)

Mitra, Indrajit [Theory Group, Saha Institute of Nuclear Physics, 1/AF Bidhan-Nagar, Kolkata 700064 (India)]. E-mail: indrajit.mitra@saha.ac.in; Ratabole, Raghunath [Institute of Mathematical Sciences, C.I.T. Campus, Taramani P.O., Chennai 600113 (India)]. E-mail: raghu@imsc.res.in; Sharatchandra, H.S. [Institute of Mathematical Sciences, C.I.T. Campus, Taramani P.O., Chennai 600113 (India)]. E-mail: sharat@imsc.res.in

2006-04-27

The infrared behaviour of the gauge-invariant dressed fermion propagator in massless QED{sub 3} is discussed for three choices of dressing. It is found that only the propagator with the isotropic (in three Euclidean dimensions) choice of dressing is acceptable as the physical fermion propagator. It is explained that the negative anomalous dimension of this physical fermion does not contradict any field-theoretical requirement.

The one loop calculation of the strong coupling β function in the Toy Model

International Nuclear Information System (INIS)

Bai Zhiming; Jiang Yuanfang

1991-01-01

The background field quantization is used to calculate the one-loop β function in the Toy Model which has the strong coupling and the SU(3) symmetry. The function obtained is consistent with the Appalquist-Carrazone theorem in the low energy condition

Appell functions and the scalar one-loop three-point integrals in Feynman diagrams

Energy Technology Data Exchange (ETDEWEB)

Cabral-Rosetti, L G [Departamento de Posgrado, Centro Interdisciplinario de Investigacion y Docencia en Educacion Tecnica (CIIDET), Av. Universidad 282 Pte., Col. Centro, A. Postal 752, C.P. 76000, Santiago de Queretaro, Qro. (Mexico); Sanchis-Lozano, M A [Departamento de Fisica Teorica and IFIC, Centro Mixto Universidad de Valencia-CSIC, 46100 Burjassot, Valencia (Spain)

2006-05-15

The scalar three-point function appearing in one-loop Feynman diagrams is compactly expressed in terms of a generalized hypergeometric function of two variables. Use is made of the connection between such Appell function and dilogarithms coming from a previous investigation. Special cases are obtained for particular values of internal masses and external momenta.

Renormalization of the one-loop theory of fluctuations in polymer blends and diblock copolymer melts.

Science.gov (United States)

Grzywacz, Piotr; Qin, Jian; Morse, David C

2007-12-01

Attempts to use coarse-grained molecular theories to calculate corrections to the random-phase approximation (RPA) for correlations in polymer mixtures have been plagued by an unwanted sensitivity to the value of an arbitrary cutoff length, i.e., by an ultraviolet (UV) divergence. We analyze the UV divergence of the inverse structure factor S(-1)(k) predicted by a "one-loop" approximation similar to that used in several previous studies. We consider both miscible homopolymer blends and disordered diblock copolymer melts. We show, in both cases, that all UV divergent contributions can be absorbed into a renormalization of the values of the phenomenological parameters of a generalized self-consistent field theory (SCFT). This observation allows the construction of an UV convergent theory of corrections to SCFT phenomenology. The UV-divergent one-loop contribution to S(-1)(k) is shown to be the sum of (i) a k -independent contribution that arises from a renormalization of the effective chi parameter, (ii) a k-dependent contribution that arises from a renormalization of monomer statistical segment lengths, (iii) a contribution proportional to k(2) that arises from a square-gradient contribution to the one-loop fluctuation free energy, and (iv) a k-dependent contribution that is inversely proportional to the degree of polymerization, which arises from local perturbations in fluid structure near chain ends and near junctions between blocks in block copolymers.

One-loop renormalisation for the second moment of GPDs with Wilson fermions

International Nuclear Information System (INIS)

Goeckeler, M.; Horsley, R.; Perlt, H.; Rakow, P.E.L.; Schaefer, A.; Schierholz, G.; Schiller, A.

2005-01-01

We calculate the non-forward quark matrix elements for operators with two covariant derivatives in one-loop lattice perturbation theory using Wilson fermions. These matrix elements are needed in the renormalisation of the second moment of generalised parton distributions measured in lattice QCD. For some commonly used representations of the hypercubic group we determine the sets of all mixing operators and find the matrices of mixing and renormalisation factors

Effects of the fermionic vacuum polarization in QED

Energy Technology Data Exchange (ETDEWEB)

Medeiros, M.F.X.P.; Barone, F.A. [IFQ-Universidade Federal de Itajuba, Itajuba, MG (Brazil); Barone, F.E.

2018-01-15

Some effects of vacuum polarization in QED due to the presence of field sources are investigated. We focus on effects with no counter-part in Maxwell electrodynamics. The Uehling interaction energy between two stationary point-like charges is calculated exactly in terms of Meijer-G functions. Effects induced on a hydrogen atom by the vacuum polarization in the vicinity of a Dirac string are considered. We also calculate the interaction between two parallel Dirac strings and corrections to the energy levels of a quantum particle constrained to move on a ring circumventing a solenoid. (orig.)

Dynamical breakdown of chiral symmetry in vectorial theories: QED and QCD

International Nuclear Information System (INIS)

Garcia, J.C.M.

1987-01-01

Using a variational approach for the Effective Potential for composite operators we dicuss the dynamical breakdown of chiral symmetry in two vectorial theories: Quantum Electrodynamics (QED) and Quantum Chromodynamics (QCD). We study the energetic aspects of the problem calculating the Effective Potential with the asymptotic nonperturbative solutions of the Schwinger-Dyson equation for the fermion selfenergy. (author) [pt

QED's School Market Trends: Teacher Buying Behavior & Attitudes, 2001-2002. Research Report.

Science.gov (United States)

Quality Education Data, Inc., Denver, CO.

This study examined teachers' classroom material buying behaviors and trends. Data came from Quality Education Data's National Education Database, which includes U.S. K-12 public, private, and Catholic schools and districts. Researchers surveyed K-8 teachers randomly selected from QED's National Education Database. Results show that teachers spend…

Package-X 2.0: A Mathematica package for the analytic calculation of one-loop integrals

Science.gov (United States)

Patel, Hiren H.

2017-09-01

This article summarizes new features and enhancements of the first major update of Package-X. Package-X 2.0 can now generate analytic expressions for arbitrarily high rank dimensionally regulated tensor integrals with up to four distinct propagators, each with arbitrary integer weight, near an arbitrary even number of spacetime dimensions, giving UV divergent, IR divergent, and finite parts at (almost) any real-valued kinematic point. Additionally, it can generate multivariable Taylor series expansions of these integrals around any non-singular kinematic point to arbitrary order. All special functions and abbreviations output by Package-X 2.0 support Mathematica's arbitrary precision evaluation capabilities to deal with issues of numerical stability. Finally, tensor algebraic routines of Package-X have been polished and extended to support open fermion chains both on and off shell. The documentation (equivalent to over 100 printed pages) is accessed through Mathematica's Wolfram Documentation Center and contains information on all Package-X symbols, with over 300 basic usage examples, 3 project-scale tutorials, and instructions on linking to FEYNCALC and LOOPTOOLS. Program files doi:http://dx.doi.org/10.17632/yfkwrd4d5t.1 Licensing provisions: CC by 4.0 Programming language: Mathematica (Wolfram Language) Journal reference of previous version: H. H. Patel, Comput. Phys. Commun 197, 276 (2015) Does the new version supersede the previous version?: Yes Summary of revisions: Extension to four point one-loop integrals with higher powers of denominator factors, separate extraction of UV and IR divergent parts, testing for power IR divergences, construction of Taylor series expansions of one-loop integrals, numerical evaluation with arbitrary precision arithmetic, manipulation of fermion chains, improved tensor algebraic routines, and much expanded documentation. Nature of problem: Analytic calculation of one-loop integrals in relativistic quantum field theory. Solution

Single atoms on demand for cavity QED experiments

International Nuclear Information System (INIS)

Dotsenko, I.

2007-01-01

Cavity quantum electrodynamics (cavity QED) describes electromagnetic fields in a confined space and the radiative properties of atoms in such fields. The simplest example of such system is a single atom interacting with one mode of a high-finesse resonator. Besides observation and exploration of fundamental quantum mechanical effects, this system bears a high potential for applications quantum information science such as, e.g., quantum logic gates, quantum communication and quantum teleportation. In this thesis I present an experiment on the deterministic coupling of a single neutral atom to the mode of a high-finesse optical resonator. In Chapter 1 I describe our basic techniques for trapping and observing single cesium atoms. As a source of single atoms we use a high-gradient magneto-optical trap, which captures the atoms from background gas in a vacuum chamber and cools them down to millikelvin temperatures. The atoms are then transferred without loss into a standing-wave dipole trap, which provides a conservative potential required for experiments on atomic coherence such as quantum information processing and metrology on trapped atoms. Moreover, shifting the standing-wave pattern allows us to deterministically transport the atoms (Chapter 2). In combination with nondestructive fluorescence imaging of individual trapped atoms, this enables us to control their position with submicrometer precision over several millimeters along the dipole trap. The cavity QED system can distinctly display quantum behaviour in the so-called strong coupling regime, i.e., when the coherent atom-cavity coupling rate dominates dissipation in the system. This sets the main requirements on the resonator's properties: small mode volume and high finesse. Chapter 3 is devoted to the manufacturing, assembling, and testing of an ultra-high finesse optical Fabry-Perot resonator, stabilized to the atomic transition. In Chapter 4 I present the transportation of single atoms into the cavity

Single atoms on demand for cavity QED experiments

Energy Technology Data Exchange (ETDEWEB)

Dotsenko, I.

2007-09-06

Cavity quantum electrodynamics (cavity QED) describes electromagnetic fields in a confined space and the radiative properties of atoms in such fields. The simplest example of such system is a single atom interacting with one mode of a high-finesse resonator. Besides observation and exploration of fundamental quantum mechanical effects, this system bears a high potential for applications quantum information science such as, e.g., quantum logic gates, quantum communication and quantum teleportation. In this thesis I present an experiment on the deterministic coupling of a single neutral atom to the mode of a high-finesse optical resonator. In Chapter 1 I describe our basic techniques for trapping and observing single cesium atoms. As a source of single atoms we use a high-gradient magneto-optical trap, which captures the atoms from background gas in a vacuum chamber and cools them down to millikelvin temperatures. The atoms are then transferred without loss into a standing-wave dipole trap, which provides a conservative potential required for experiments on atomic coherence such as quantum information processing and metrology on trapped atoms. Moreover, shifting the standing-wave pattern allows us to deterministically transport the atoms (Chapter 2). In combination with nondestructive fluorescence imaging of individual trapped atoms, this enables us to control their position with submicrometer precision over several millimeters along the dipole trap. The cavity QED system can distinctly display quantum behaviour in the so-called strong coupling regime, i.e., when the coherent atom-cavity coupling rate dominates dissipation in the system. This sets the main requirements on the resonator's properties: small mode volume and high finesse. Chapter 3 is devoted to the manufacturing, assembling, and testing of an ultra-high finesse optical Fabry-Perot resonator, stabilized to the atomic transition. In Chapter 4 I present the transportation of single atoms into the

Measurement of the Proton Structure Function $F_{2}$ at low $Q^{2}$ in QED Compton Scattering at HERA

CERN Document Server

Aktas, A.; Anthonis, T.; Asmone, A.; Babaev, A.; Backovic, S.; Bahr, J.; Baranov, P.; Barrelet, E.; Bartel, W.; Baumgartner, S.; Becker, J.; Beckingham, M.; Behnke, O.; Behrendt, O.; Belousov, A.; Berger, Ch.; Berger, N.; Berndt, T.; Bizot, J.C.; Bohme, J.; Boenig, M.-O.; Boudry, V.; Bracinik, J.; Brisson, V.; Broker, H.-B.; Brown, D.P.; Bruncko, D.; Busser, F.W.; Bunyatyan, A.; Buschhorn, G.; Bystritskaya, L.; Campbell, A.J.; Caron, S.; Cassol-Brunner, F.; Cerny, K.; Chekelian, V.; Collard, C.; Contreras, J.G.; Coppens, Y.R.; Coughlan, J.A.; Cox, B.E.; Cozzika, G.; Cvach, J.; Dainton, J.B.; Dau, W.D.; Daum, K.; Delcourt, B.; Demirchyan, R.; De Roeck, A.; Desch, K.; De Wolf, E.A.; Diaconu, C.; Dingfelder, J.; Dodonov, V.; Dubak, A.; Duprel, C.; Eckerlin, Guenter; Efremenko, V.; Egli, S.; Eichler, R.; Eisele, F.; Ellerbrock, M.; Elsen, E.; Erdmann, M.; Erdmann, W.; Faulkner, P.J.W.; Favart, L.; Fedotov, A.; Felst, R.; Ferencei, J.; Fleischer, M.; Fleischmann, P.; Fleming, Y.H.; Flucke, G.; Flugge, G.; Fomenko, A.; Foresti, I.; Formanek, J.; Franke, G.; Frising, G.; Gabathuler, E.; Gabathuler, K.; Garutti, E.; Garvey, J.; Gayler, J.; Gerhards, R.; Gerlich, C.; Ghazaryan, Samvel; Goerlich, L.; Gogitidze, N.; Gorbounov, S.; Grab, C.; Grassler, H.; Greenshaw, T.; Gregori, M.; Grindhammer, Guenter; Gwilliam, C.; Haidt, D.; Hajduk, L.; Haller, J.; Hansson, M.; Heinzelmann, G.; Henderson, R.C.W.; Henschel, H.; Henshaw, O.; Heremans, R.; Herrera, G.; Herynek, I.; Heuer, R.-D.; Hildebrandt, M.; Hiller, K.H.; Hoting, P.; Hoffmann, D.; Horisberger, R.; Hovhannisyan, A.; Ibbotson, M.; Ismail, M.; Jacquet, M.; Janauschek, L.; Janssen, X.; Jemanov, V.; Jonsson, L.; Johnson, D.P.; Jung, H.; Kant, D.; Kapichine, M.; Karlsson, M.; Katzy, J.; Keller, N.; Kennedy, J.; Kenyon, I.R.; Kiesling, Christian M.; Klein, M.; Kleinwort, C.; Klimkovich, T.; Kluge, T.; Knies, G.; Knutsson, A.; Koblitz, B.; Korbel, V.; Kostka, P.; Koutouev, R.; Kropivnitskaya, A.; Kroseberg, J.; Kuckens, J.; Kuhr, T.; Landon, M.P.J.; Lange, W.; Lastovicka, T.; Laycock, P.; Lebedev, A.; Leiner, B.; Lemrani, R.; Lendermann, V.; Levonian, S.; Lindfeld, L.; Lipka, K.; List, B.; Lobodzinska, E.; Loktionova, N.; Lopez-Fernandez, R.; Lubimov, V.; Lueders, H.; Luke, D.; Lux, T.; Lytkin, L.; Makankine, A.; Malden, N.; Malinovski, E.; Mangano, S.; Marage, P.; Marks, J.; Marshall, R.; Martisikova, M.; Martyn, H.-U.; Maxfield, S.J.; Meer, D.; Mehta, A.; Meier, K.; Meyer, A.B.; Meyer, H.; Meyer, J.; Michine, S.; Mikocki, S.; Milcewicz-Mika, I.; Milstead, D.; Mohamed, A.; Moreau, F.; Morozov, A.; Morozov, I.; Morris, J.V.; Mozer, Matthias Ulrich; Muller, K.; Murin, P.; Nagovizin, V.; Naroska, B.; Naumann, J.; Naumann, Th.; Newman, Paul R.; Niebuhr, C.; Nikiforov, A.; Nikitin, D.; Nowak, G.; Nozicka, M.; Oganezov, R.; Olivier, B.; Olsson, J.E.; Ossoskov, G.; Ozerov, D.; Pascaud, C.; Patel, G.D.; Peez, M.; Perez, E.; Perieanu, A.; Petrukhin, A.; Pitzl, D.; Placakyte, R.; Poschl, R.; Portheault, B.; Povh, B.; Raicevic, N.; Ratiani, Z.; Reimer, P.; Reisert, B.; Rimmer, A.; Risler, C.; Rizvi, E.; Robmann, P.; Roland, B.; Roosen, R.; Rostovtsev, A.; Rurikova, Z.; Rusakov, S.; Rybicki, K.; Sankey, D.P.C.; Sauvan, E.; Schatzel, S.; Scheins, J.; Schilling, F.-P.; Schleper, P.; Schmidt, S.; Schmitt, S.; Schneider, M.; Schoeffel, L.; Schoning, A.; Schroder, V.; Schultz-Coulon, H.-C.; Schwanenberger, C.; Sedlak, K.; Sefkow, F.; Sheviakov, I.; Shtarkov, L.N.; Sirois, Y.; Sloan, T.; Smirnov, P.; Soloviev, Y.; South, D.; Spaskov, V.; Specka, Arnd E.; Spitzer, H.; Stamen, R.; Stella, B.; Stiewe, J.; Strauch, I.; Straumann, U.; Tchoulakov, V.; Thompson, Graham; Thompson, P.D.; Tomasz, F.; Traynor, D.; Truoel, Peter; Tsipolitis, G.; Tsurin, I.; Turnau, J.; Tzamariudaki, E.; Uraev, A.; Urban, Marcel; Usik, A.; Utkin, D.; Valkar, S.; Valkarova, A.; Vallee, C.; Van Mechelen, P.; Van Remortel, N.; Vargas Trevino, A.; Vazdik, Y.; Veelken, C.; Vest, A.; Vinokurova, S.; Volchinski, V.; Wacker, K.; Wagner, J.; Weber, G.; Weber, R.; Wegener, D.; Werner, C.; Werner, N.; Wessels, M.; Wessling, B.; Winter, G.-G.; Wissing, Ch.; Woehrling, E.-E.; Wolf, R.; Wunsch, E.; Xella, S.; Yan, W.; Yeganov, V.; Zacek, J.; Zalesak, J.; Zhang, Z.; Zhokin, A.; Zohrabyan, H.; Zomer, F.

2004-01-01

The proton structure function F_2(x,Q^2) is measured in inelastic QED Compton scattering using data collected with the H1 detector at HERA. QED Compton events are used to access the kinematic range of very low virtualities of the exchanged photon, Q^2, down to 0.5 GeV^2, and Bjorken x up to \\sim 0.06, a region which has not been covered previously by inclusive measurements at HERA. The results are in agreement with the measurements from fixed target lepton-nucleon scattering experiments.

Reduction method for one-loop tensor 5- and 6-point integrals revisited

International Nuclear Information System (INIS)

Diakonidis, Theodoros

2009-01-01

A complete analytical reduction of general one-loop Feynman integrals with five legs for tensors up to rank R=3 and six legs for tensors up to rank 4 is reviewed. An elegant formalism with extensive use of signed minors was developed for the cancellation of leading inverse Gram determinants. The resulting compact formulae allow both for a study of analytical properties and for efficient numerical programming. Here some special numerical examples are presented. (orig.)

Reduction method for one-loop tensor 5- and 6-point integrals revisited

Energy Technology Data Exchange (ETDEWEB)

Diakonidis, Theodoros [Deutsches Elektronen-Synchrotron (DESY), Hamburg (Germany)

2009-01-15

A complete analytical reduction of general one-loop Feynman integrals with five legs for tensors up to rank R=3 and six legs for tensors up to rank 4 is reviewed. An elegant formalism with extensive use of signed minors was developed for the cancellation of leading inverse Gram determinants. The resulting compact formulae allow both for a study of analytical properties and for efficient numerical programming. Here some special numerical examples are presented. (orig.)

Alternative loop rings

CERN Document Server

Goodaire, EG; Polcino Milies, C

1996-01-01

For the past ten years, alternative loop rings have intrigued mathematicians from a wide cross-section of modern algebra. As a consequence, the theory of alternative loop rings has grown tremendously. One of the main developments is the complete characterization of loops which have an alternative but not associative, loop ring. Furthermore, there is a very close relationship between the algebraic structures of loop rings and of group rings over 2-groups. Another major topic of research is the study of the unit loop of the integral loop ring. Here the interaction between loop rings and group ri

Four-loop vacuum energy density of the SU($N_c$) + adjoint Higgs theory

CERN Document Server

Kajantie, Keijo; Rummukainen, K; Schröder, Y

2003-01-01

We compute the dimensionally regularised four-loop vacuum energy density of the SU(N_c) gauge + adjoint Higgs theory, in the disordered phase. ``Scalarisation'', or reduction to a small set of master integrals of the type appearing in scalar field theories, is carried out in d dimensions, employing general partial integration identities through an algorithm developed by Laporta, while the remaining scalar integrals are evaluated in d = 3 - 2\\epsilon dimensions, by expanding in \\epsilon << 1 and evaluating a number of coefficients. The results have implications for the thermodynamics of finite temperature QCD, allowing to determine perturbative contributions of orders O(g^6 ln(1/g)), O(g^6) to the pressure, while the general methods are applicable also to studies of critical phenomena in QED-like statistical physics systems.

Overview on the anomaly and Schwinger term in two dimensional QED

International Nuclear Information System (INIS)

Adam, C.; Bertlmann, R.A.; Hofer, P.

1993-01-01

The axial anomaly of two-dimensional QED is computed in different ways (perturbative, via dispersion integrals, path integral and index theorem) and their relation is discussed as well as the relation between anomaly, Schwinger term and the Dirac vacuum. Some features of the special case of massless fermions (Schwinger model) and some methods of exactly solving it are demonstrated. (authors)

Gauge dependence of the infrared behaviour of massless QED{sub 3}

Energy Technology Data Exchange (ETDEWEB)

Mitra, Indrajit [Theory Group, Saha Institute of Nuclear Physics, 1/AF Bidhan-Nagar, Kolkata 700064 (India)]. E-mail: indrajit.mitra@saha.ac.in; Ratabole, Raghunath [The Institute of Mathematical Sciences, CIT Campus, Taramani PO, Chennai 600113 (India)]. E-mail: raghu@imsc.res.in; Sharatchandra, H.S. [The Institute of Mathematical Sciences, CIT Campus, Taramani PO, Chennai 600113 (India)]. E-mail: sharat@imsc.res.in

2006-03-23

Using the Zumino identities it is shown that in a class of non-local gauges, massless QED{sub 3} has an infrared behaviour of a conformal field theory with a continuously varying anomalous dimension of the fermion. In the usual Lorentz gauge, the fermion propagator falls off exponentially for a large separation, but this apparent fermion mass is a gauge artifact.

Status and prospects of (g-2)μ and ΔαQED

International Nuclear Information System (INIS)

Teubner, Thomas

2008-01-01

A brief review of the status of the anomalous magnetic moment of the muon, (g-2) μ , and the running of the electromagnetic coupling, α QED (q 2 ), is given. The discrepancy between the Standard Model prediction of g-2 and the measurement from BNL is discussed. The prospects for further improvements in the determination of the vacuum polarisation contributions are outlined.

SUSY non-Abelian gauge models: exact beta function from one loop of perturbation theory

International Nuclear Information System (INIS)

Shifman, M.A.; Vajnshtejn, A.I.; Zakharov, V.I.

1985-01-01

The method for calculating the exact β function (to all orders in the coupling constant) proposed earlier in supersymmetric electrodynamics is extended. The starting point is the observation that the low-energy effective action is exhausted by one loop provided that the theory is regularized supersymmetrically both in the ultraviolet and infrared domains in four dimensions. The Pouli-Villars method of the ultraviolet regularization is used. Two methods for the infrared regularization are considered. The first one - quantization in a box with a finite volume L 3 - is universally applicable to anygauge theory. The second method is based on the effective Higgs mechanism for mass generation and requires the presence of certain matter superfields in the lagrangian. Within this method the necessary condition is the existence of flat directions, so called valeys, along which the vacuum energy vanishes. The theory is quantized near epsilon non-vanishing value of the scalar field from the bottom of the valley. After calculating the one-loop effective action one and the same exact expression is obtained for the β function within the both approaches, and it also coincides with our earlier result extracted from instanton calculus. A few remarks on the problem of anomalies in SUSY gauge theories are presented

NGluon. A package to calculate one-loop multi-gluon amplitudes

Energy Technology Data Exchange (ETDEWEB)

Badger, S. [Deutsches Elektronen-Synchrotron (DESY), Zeuthen (Germany); Niels Bohr Institute, Copenhagen (Denmark). Niels Bohr International Academy and Discovery Center; Biedermann, B.; Uwer, P. [Humboldt Univ., Berlin (Germany). Inst. fuer Physik

2010-11-15

We present a computer library for the numerical evaluation of colour-ordered n-gluon amplitudes at one-loop order in pure Yang-Mills theory. The library uses the recently developed technique of generalised unitarity. Running in double precision the library yields reliable results for up to 14 gluons with only a small fraction of events requiring a re-evaluation using extended floating point arithmetic. We believe that the library presented here provides an important contribution to future LHC phenomenology. The program may also prove useful in cross checking results obtained by other methods. In addition, the code provides a sample implementation which may serve as a starting point for further developments. (orig.)

Reduction formalism for dimensionally regulated one-loop N-point integrals

International Nuclear Information System (INIS)

Binoth, T.; Guillet, J.Ph.; Heinrich, G.

2000-01-01

We consider one-loop scalar and tensor integrals with an arbitrary number of external legs relevant for multi-parton processes in massless theories. We present a procedure to reduce N-point scalar functions with generic 4-dimensional external momenta to box integrals in (4-2ε) dimensions. We derive a formula valid for arbitrary N and give an explicit expression for N=6. Further a tensor reduction method for N-point tensor integrals is presented. We prove that generically higher dimensional integrals contribute only to order ε for N≥5. The tensor reduction can be solved iteratively such that any tensor integral is expressible in terms of scalar integrals. Explicit formulas are given up to N=6

NGluon. A package to calculate one-loop multi-gluon amplitudes

International Nuclear Information System (INIS)

Badger, S.; Niels Bohr Institute, Copenhagen; Biedermann, B.; Uwer, P.

2010-11-01

We present a computer library for the numerical evaluation of colour-ordered n-gluon amplitudes at one-loop order in pure Yang-Mills theory. The library uses the recently developed technique of generalised unitarity. Running in double precision the library yields reliable results for up to 14 gluons with only a small fraction of events requiring a re-evaluation using extended floating point arithmetic. We believe that the library presented here provides an important contribution to future LHC phenomenology. The program may also prove useful in cross checking results obtained by other methods. In addition, the code provides a sample implementation which may serve as a starting point for further developments. (orig.)

Phase diagram of a QED-cavity array coupled via a N-type level scheme

Energy Technology Data Exchange (ETDEWEB)

Jin, Jiasen; Rossini, Davide [CNR, NEST, Scuola Normale Superiore and Istituto di Nanoscienze, Pisa (Italy); Fazio, Rosario [CNR, NEST, Scuola Normale Superiore and Istituto di Nanoscienze, Pisa (Italy); National University of Singapore, Center for Quantum Technologies, Singapore (Singapore)

2015-01-01

We study the zero-temperature phase diagram of a one-dimensional array of QED cavities where, besides the single-photon hopping, an additional coupling between neighboring cavities is mediated by an N-type four-level system. By varying the relative strength of the various couplings, the array is shown to exhibit a variety of quantum phases including a polaritonic Mott insulator, a density-wave and a superfluid phase. Our results have been obtained by means of numerical density-matrix renormalization group calculations. The phase diagram was obtained by analyzing the energy gaps for the polaritons, as well as through a study of two-point correlation functions. (orig.)

Circuit QED with 3D cavities

Energy Technology Data Exchange (ETDEWEB)

Xie, Edwar; Baust, Alexander; Zhong, Ling; Gross, Rudolf [Walther-Meissner-Institut, Bayerische Akademie der Wissenschaften, Garching (Germany); Physik-Department, TU Muenchen, Garching (Germany); Nanosystems Initiative Munich (NIM), Muenchen (Germany); Anderson, Gustav; Wang, Lujun; Eder, Peter; Fischer, Michael; Goetz, Jan; Haeberlein, Max; Schwarz, Manuel; Wulschner, Karl Friedrich; Deppe, Frank; Fedorov, Kirill; Huebl, Hans; Menzel, Edwin [Walther-Meissner-Institut, Bayerische Akademie der Wissenschaften, Garching (Germany); Physik-Department, TU Muenchen, Garching (Germany); Marx, Achim [Walther-Meissner-Institut, Bayerische Akademie der Wissenschaften, Garching (Germany)

2015-07-01

In typical circuit QED systems on-chip superconducting qubits are coupled to integrated coplanar microwave resonators. Due to the planar geometry, the resonators are often a limiting factor regarding the total coherence of the system. Alternatively, similar hybrid systems can be realized using 3D microwave cavities. Here, we present design considerations for the 3D microwave cavity as well as the superconducting transmon qubit. Moreover, we show experimental data of a high purity aluminum cavity demonstrating quality factors above 1.4 .10{sup 6} at the single photon level and a temperature of 50 mK. Our experiments also demonstrate that the quality factor is less dependent on the power compared to planar resonator geometries. Furthermore, we present strategies for tuning both the cavity and the qubit individually.

Compact QED tree-level amplitudes from dressed BCFW recursion relations

International Nuclear Information System (INIS)

Badger, Simon D.; Henn, Johannes M.

2010-05-01

We construct a modified on-shell BCFW recursion relation to derive compact analytic representations of tree-level amplitudes in QED. As an application, we study the amplitudes of a fermion pair coupling to an arbitrary number of photons and give compact formulae for the NMHV and N 2 MHV case. We demonstrate that the new recursion relation reduces the growth in complexity with additional photons to be exponential rather than factorial. (orig.)

Compact QED tree-level amplitudes from dressed BCFW recursion relations

Energy Technology Data Exchange (ETDEWEB)

Badger, Simon D. [Deutsches Elektronen-Synchrotron (DESY), Zeuthen (Germany); Henn, Johannes M. [Humboldt Univ., Berlin (Germany). Inst. fuer Physik

2010-05-15

We construct a modified on-shell BCFW recursion relation to derive compact analytic representations of tree-level amplitudes in QED. As an application, we study the amplitudes of a fermion pair coupling to an arbitrary number of photons and give compact formulae for the NMHV and N{sup 2}MHV case. We demonstrate that the new recursion relation reduces the growth in complexity with additional photons to be exponential rather than factorial. (orig.)

On a manifestation of the anomalies in the massless QED

International Nuclear Information System (INIS)

Gorskij, A.S.

1989-01-01

The questions concerned with the axial and conformal anomalies in the massless QED are discussed. It is shown that the interaction of the longitudinal real photons is proportional to the β function of the theory and the corresponding matrix element L |Θ αβ |γ L > where Θ αβ is energy-momentum tensor has a common features with the nonvanishing matrix element α |γ> in the massless limit. 7 refs.; 2 figs

One-loop QCD and Higgs bosons to partons processes using six-dimensional helicity and generalized unitarity

International Nuclear Information System (INIS)

Davies, Scott

2011-01-01

We combine the six-dimensional helicity formalism of Cheung and O'Connell with D-dimensional generalized unitarity to obtain a new formalism for computing one-loop amplitudes in dimensionally regularized QCD. With this procedure, we simultaneously obtain the pieces that are constructible from four-dimensional unitarity cuts and the rational pieces that are missed by them, while retaining a helicity formalism. We illustrate the procedure using four- and five-point one-loop amplitudes in QCD, including examples with external fermions. We also demonstrate the technique's effectiveness in next-to-leading order QCD corrections to Higgs processes by computing the next-to-leading order correction to the Higgs plus three positive-helicity gluons amplitude in the large top-quark mass limit.

GoSam-2.0. A tool for automated one-loop calculations within the Standard Model and beyond

International Nuclear Information System (INIS)

Cullen, Gavin; Deurzen, Hans van; Greiner, Nicolas

2014-05-01

We present the version 2.0 of the program package GoSam for the automated calculation of one-loop amplitudes. GoSam is devised to compute one-loop QCD and/or electroweak corrections to multi-particle processes within and beyond the Standard Model. The new code contains improvements in the generation and in the reduction of the amplitudes, performs better in computing time and numerical accuracy, and has an extended range of applicability. The extended version of the ''Binoth-Les-Houches-Accord'' interface to Monte Carlo programs is also implemented. We give a detailed description of installation and usage of the code, and illustrate the new features in dedicated examples.

On μe-scattering at NNLO in QED

Directory of Open Access Journals (Sweden)

Mastrolia P.

2018-01-01

Full Text Available We report on the current status of the analytic evaluation of the two-loop corrections to the μescattering in Quantum Electrodynamics, presenting state-of-the art techniques which have been developed to address this challenging task.

Fried-Yennie gauge in dimensionally regularized QED

International Nuclear Information System (INIS)

Adkins, G.S.

1993-01-01

The Fried-Yennie gauge in QED is a covariant gauge with agreeable infrared properties. That is, the mass-shell renormalization scheme can be implemented without introducing artificial infrared divergences, and terms having spuriously low orders in α disappear in certain bound-state calculations. The photon propagator in the Fried-Yennie gauge has the form D β μν (k)=(-1/k 2 )[g μν +βk μ kν/k 2 ], where β is the gauge parameter. In this work, I show that the Fried-Yennie gauge parameter is β=2/(1-2ε) when dimensional regularization (with n=4-2ε dimensions of spacetime) is used to regulate the theory

Closed-loop fault detection for full-envelope flight vehicle with measurement delays

Directory of Open Access Journals (Sweden)

Wang Zhaolei

2015-06-01

Full Text Available A closed-loop fault detection problem is investigated for the full-envelope flight vehicle with measurement delays, where the flight dynamics are modeled as a switched system with delayed feedback signals. The mode-dependent observer-based fault detection filters and state estimation feedback controllers are derived by considering the delays’ impact on the control system and fault detection system simultaneously. Then, considering updating lags of the controllers/filters’ switching signals which are introduced by the delayed measurement of altitude and Mach number, an asynchronous H∞ analysis method is proposed and the system model is further augmented to be an asynchronously switched time-delay system. Also, the global stability and desired performance of the augmented system are guaranteed by combining the switched delay-dependent Lyapunov–Krasovskii functional method with the average dwell time method (ADT, and the delay-dependent existing conditions for the controllers and fault detection filters are obtained in the form of the linear matrix inequalities (LMIs. Finally, numerical example based on the hypersonic vehicles and highly maneuverable technology (HiMAT vehicle is given to demonstrate the merits of the proposed method.

Dimensioning the EVITA semi-open loop at BR2 for qualification of full size JHR fuel elements

International Nuclear Information System (INIS)

Gouat, Philippe

2011-01-01

Research highlights: → Research reactor fuel (LEU) qualification as part of the licensing process of the JHR reactor. → Thermal-hydraulic dimensioning process of fuel irradiation installation. → We compare the predicted pressure profile in the installation with in situ measured values. - Abstract: The Jules Horowitz Reactor (JHR) is the next generation research reactor from CEA and which commissioning is foreseen in 2014. Prior to acquiring the exploitation license, the fuel elements have to be qualified for their intended functioning power. The only facility capable to perform this task is the Belgian research reactor BR2, due to its similar thermal-hydraulic parameters. At the moment, one has already tested the fuel plates separately. The preparation of the JHR safety report still needs the test of full size elements. This JHR fuel element is broader and more powerful than a standard BR2 fuel element, and one cannot perform an irradiation by simply interchanging them. However, BR2 has 200 mm channels at its disposal, which can be adapted to give the correct hydraulic diameter. One also needs an additional pump to deliver the necessary cooling flow rate for the higher power. This paper describes the dimensioning of the EVITA semi-open loop, which has been built at BR2 to irradiate full size JHR fuel elements and qualify them for the foreseen exploitation parameters. One explains here the followed methodology to quantify the required additional head for the booster pump and to determine the pressure profile along the circuit and the safety margin on the fuel. This methodology relies only on a priori calculations without any measurement on full size installation subpart as usual before the assembly in controlled zone. The article also explains how the original JHR thermal hydraulic safety calculation scheme was adapted to the BR2 environment. One also compares the measurement results on the fully built installation with our previsions. Our models compare well

Perturbation theory for BAO reconstructed fields: One-loop results in the real-space matter density field

Science.gov (United States)

Hikage, Chiaki; Koyama, Kazuya; Heavens, Alan

2017-08-01

We compute the power spectrum at one-loop order in standard perturbation theory for the matter density field to which a standard Lagrangian baryonic acoustic oscillation (BAO) reconstruction technique is applied. The BAO reconstruction method corrects the bulk motion associated with the gravitational evolution using the inverse Zel'dovich approximation (ZA) for the smoothed density field. We find that the overall amplitude of one-loop contributions in the matter power spectrum substantially decreases after reconstruction. The reconstructed power spectrum thereby approaches the initial linear spectrum when the smoothed density field is close enough to linear, i.e., the smoothing scale Rs≳10 h-1 Mpc . On smaller Rs, however, the deviation from the linear spectrum becomes significant on large scales (k ≲Rs-1 ) due to the nonlinearity in the smoothed density field, and the reconstruction is inaccurate. Compared with N-body simulations, we show that the reconstructed power spectrum at one-loop order agrees with simulations better than the unreconstructed power spectrum. We also calculate the tree-level bispectrum in standard perturbation theory to investigate non-Gaussianity in the reconstructed matter density field. We show that the amplitude of the bispectrum significantly decreases for small k after reconstruction and that the tree-level bispectrum agrees well with N-body results in the weakly nonlinear regime.

Beyond-one-loop quantum gravity action yielding both inflation and late-time acceleration

Directory of Open Access Journals (Sweden)

E. Elizalde

2017-08-01

Full Text Available A unified description of early-time inflation with the current cosmic acceleration is achieved by means of a new theory that uses a quadratic model of gravity, with the inclusion of an exponential F(R-gravity contribution for dark energy. High-curvature corrections of the theory come from higher-derivative quantum gravity and yield an effective action that goes beyond the one-loop approximation. It is shown that, in this theory, viable inflation emerges in a natural way, leading to a spectral index and tensor-to-scalar ratio that are in perfect agreement with the most reliable Planck results. At low energy, late-time accelerated expansion takes place. As exponential gravity, for dark energy, must be stabilized during the matter and radiation eras, we introduce a curing term in order to avoid nonphysical singularities in the effective equation of state parameter. The results of our analysis are confirmed by accurate numerical simulations, which show that our model does fit the most recent cosmological data for dark energy very precisely.

Proof of the relativistic covariance of the fermion Green function in QED

International Nuclear Information System (INIS)

Nguyen Suan Han.

1995-02-01

This paper is devoted to the calculation of the fermion Green function in QED in the framework of the Minimal Quantization Method, based on an explicit solution of the constraint equations and the gauge-invariance principle. The relativistic invariant expression for the fermion Green function which has the right analytical properties is obtained. (author). 24 refs

Quantum Key Distribution Based on a Weak-Coupling Cavity QED Regime

International Nuclear Information System (INIS)

Li Chun-Yan; Li Yan-Song

2011-01-01

We present a quantum key distribution scheme using a weak-coupling cavity QED regime based on quantum dense coding. Hybrid entanglement states of photons and electrons are used to distribute information. We just need to transmit photons without storing them in the scheme. The electron confined in a quantum dot, which is embedded in a microcavity, is held by one of the legitimate users throughout the whole communication process. Only the polarization of a single photon and spin of electron measurements are applied in this protocol, which are easier to perform than collective-Bell state measurements. Linear optical apparatus, such as a special polarizing beam splitter in a circular basis and single photon operations, make it more flexible to realize under current technology. Its efficiency will approach 100% in the ideal case. The security of the scheme is also discussed. (general)

Inflationary magnetogenesis and non-local actions: the conformal anomaly

Energy Technology Data Exchange (ETDEWEB)

El-Menoufi, Basem Kamal, E-mail: bmahmoud@physics.umass.edu [Department of Physics, University of Massachusetts Amherst, MA 01003 (United States)

2016-02-01

We discuss the possibility of successful magnetogenesis during inflation by employing the one-loop effective action of massless QED. The action is strictly non-local and results from the long distance fluctuations of massless charged particles present at the inflationary scale. Most importantly, it encodes the conformal anomaly of QED which is crucial to avoid the vacuum preservation in classical electromagnetism. In particular, we find a blue spectrum for the magnetic field with spectral index n{sub B} ≅ 2 − α{sub e} where α{sub e} depends on both the number of e-folds during inflation as well as the coefficient of the one-loop beta function. In particular, the sign of the beta function has important bearing on the final result. A low reheating temperature is required for the present day magnetic field to be consistent with the lower bound inferred on the field in the intergalactic medium.

The one-loop six-dimensional hexagon integral and its relation to MHV amplitudes in N=4 SYM

CERN Document Server

Dixon, Lance J.; Henn, Johannes M.

2011-01-01

We provide an analytic formula for the (rescaled) one-loop scalar hexagon integral $\\tilde\\Phi_6$ with all external legs massless, in terms of classical polylogarithms. We show that this integral is closely connected to two integrals appearing in one- and two-loop amplitudes in planar $\\\\mathcal{N}=4$ super-Yang-Mills theory, $\\Omega^{(1)}$ and $\\Omega^{(2)}$. The derivative of $\\Omega^{(2)}$ with respect to one of the conformal invariants yields $\\tilde\\Phi_6$, while another first-order differential operator applied to $\\tilde\\Phi_6$ yields $\\Omega^{(1)}$. We also introduce some kinematic variables that rationalize the arguments of the polylogarithms, making it easy to verify the latter differential equation. We also give a further example of a six-dimensional integral relevant for amplitudes in $\\\\mathcal{N}=4$ super-Yang-Mills.

Two-loop SL(2) form factors and maximal transcendentality

International Nuclear Information System (INIS)

Loebbert, Florian; Sieg, Christoph; Wilhelm, Matthias; Yang, Gang

2016-01-01

Form factors of composite operators in the SL(2) sector of N=4 SYM theory are studied up to two loops via the on-shell unitarity method. The non-compactness of this subsector implies the novel feature and technical challenge of an unlimited number of loop momenta in the integrand’s numerator. At one loop, we derive the full minimal form factor to all orders in the dimensional regularisation parameter. At two loops, we construct the complete integrand for composite operators with an arbitrary number of covariant derivatives, and we obtain the remainder functions as well as the dilatation operator for composite operators with up to three covariant derivatives. The remainder functions reveal curious patterns suggesting a hidden maximal uniform transcendentality for the full form factor. Finally, we speculate about an extension of these patterns to QCD.

Two-loop SL(2) form factors and maximal transcendentality

Energy Technology Data Exchange (ETDEWEB)

Loebbert, Florian [Institut für Physik, Humboldt-Universität zu Berlin,Zum Großen Windkanal 6, 12489 Berlin (Germany); Sieg, Christoph [Institut für Physik, Humboldt-Universität zu Berlin,Zum Großen Windkanal 6, 12489 Berlin (Germany); Institut für Mathematik, Humboldt-Universität zu Berlin,Zum Großen Windkanal 6, 12489 Berlin (Germany); Wilhelm, Matthias [Institut für Physik, Humboldt-Universität zu Berlin,Zum Großen Windkanal 6, 12489 Berlin (Germany); Institut für Mathematik, Humboldt-Universität zu Berlin,Zum Großen Windkanal 6, 12489 Berlin (Germany); Niels Bohr Institute, Copenhagen University,Blegdamsvej 17, 2100 Copenhagen Ø (Denmark); Yang, Gang [CAS Key Laboratory of Theoretical Physics,Institute of Theoretical Physics, Chinese Academy of Sciences,Beijing 100190 (China); Institut für Physik, Humboldt-Universität zu Berlin,Zum Großen Windkanal 6, 12489 Berlin (Germany)

2016-12-19

Form factors of composite operators in the SL(2) sector of N=4 SYM theory are studied up to two loops via the on-shell unitarity method. The non-compactness of this subsector implies the novel feature and technical challenge of an unlimited number of loop momenta in the integrand’s numerator. At one loop, we derive the full minimal form factor to all orders in the dimensional regularisation parameter. At two loops, we construct the complete integrand for composite operators with an arbitrary number of covariant derivatives, and we obtain the remainder functions as well as the dilatation operator for composite operators with up to three covariant derivatives. The remainder functions reveal curious patterns suggesting a hidden maximal uniform transcendentality for the full form factor. Finally, we speculate about an extension of these patterns to QCD.

Lorentz and CPT violation in QED revisited: A missing analysis

Energy Technology Data Exchange (ETDEWEB)

Del Cima, Oswaldo M., E-mail: wadodelcima@if.uff.b [Universidade Federal Fluminense (UFF), Polo Universitario de Rio das Ostras, Rua Recife s/n, 28890-000, Rio das Ostras, RJ (Brazil); Fonseca, Jakson M., E-mail: jakson.fonseca@ufv.b [Universidade Federal de Vicosa (UFV), Departamento de Fisica, Avenida Peter Henry Rolfs s/n, 36570-000, Vicosa, MG (Brazil); Franco, Daniel H.T., E-mail: daniel.franco@ufv.b [Universidade Federal de Vicosa (UFV), Departamento de Fisica, Avenida Peter Henry Rolfs s/n, 36570-000, Vicosa, MG (Brazil); Piguet, Olivier, E-mail: opiguet@pq.cnpq.b [Universidade Federal do Espirito Santo (UFES), Departamento de Fisica, Campus Universitario de Goiabeiras, 29060-900, Vitoria, ES (Brazil)

2010-05-03

We investigate the breakdown of Lorentz symmetry in QED by a CPT violating interaction term consisting of the coupling of an axial fermion current with a constant vector field b, in the framework of algebraic renormalization - a regularization-independent method. We show, to all orders in perturbation theory, that a CPT-odd and Lorentz violating Chern-Simons-like term, definitively, is not radiatively induced by the axial coupling of the fermions with the constant vector b.

Lorentz and CPT violation in QED revisited: A missing analysis

International Nuclear Information System (INIS)

Del Cima, Oswaldo M.; Fonseca, Jakson M.; Franco, Daniel H.T.; Piguet, Olivier

2010-01-01

We investigate the breakdown of Lorentz symmetry in QED by a CPT violating interaction term consisting of the coupling of an axial fermion current with a constant vector field b, in the framework of algebraic renormalization - a regularization-independent method. We show, to all orders in perturbation theory, that a CPT-odd and Lorentz violating Chern-Simons-like term, definitively, is not radiatively induced by the axial coupling of the fermions with the constant vector b.

A Test of QED in Electron-Positron Annihilation at Energies around the Z Mass

CERN Document Server

Spartiotis, C

1992-01-01

A study of the reaction e+ e- -t 11( /) at center-of-mass energies around the mass of the z 0 boson(91.2Ge V) has been performed. The total and differential cross sections have been measured cor- responding to an integrated luminosity of 14.42pb- 1 . The results are in good agreement with QED predictions. Lower limits were set , at 95% confidence level, on the QED cutoff parameters of A+ >130 GeV, A_ >112 GeV and on the mass of an excited elec- tron of me* > 120 Ge V. z 0 rare decays with photonic signatures in the final state were also searched for. Upper limits, at 953 confi- dence level, for the branching ratio of z 0 decaying into 7ro/ /11, TJI and /// are 1.2 x 10-4, 1.7 x 10-4, 3.3 x 10- 5 respectively.

Cancellation of soft and collinear divergences in noncommutative QED

International Nuclear Information System (INIS)

Mirza, B.; Zarei, M.

2006-01-01

In this paper, we investigate the behavior of noncommutative IR divergences and will also discuss their cancellation in the physical cross sections. The commutative IR (soft) divergences existing in the nonplanar diagrams will be examined in order to prove an all-order cancellation of these divergences using the Weinberg's method. In noncommutative QED, collinear divergences due to triple photon splitting vertex, were encountered, which are shown to be canceled out by the noncommutative version of KLN theorem. This guarantees that there is no mixing between the Collinear, soft divergences and noncommutative IR divergences

One-loop adjoint masses for non-supersymmetric intersecting branes

Energy Technology Data Exchange (ETDEWEB)

Anastasopoulos, P. [Technische Univ., Vienna (Austria). 1. Inst. fuer Theoretische Physik; Antoniadis, I. [European Organization for Nuclear Research (CERN), Geneva (Switzerland); Benakli, K. [CNRS, UPMC Univ. Paris (France). Lab. de Physique Theorique et Haute Energies; Goodsell, M.D. [Deutsches Elektronen-Synchrotron (DESY), Hamburg (Germany); Vichi, A. [Institute de Theorie des Phenomenes Physiques, EPFL, Lausanne (Switzerland)

2011-05-15

We consider breaking of supersymmetry in intersecting D-brane configurations by slight deviation of the angles from their supersymmetric values. We compute the masses generated by radiative corrections for the adjoint scalars on the brane world-volumes. In the open string channel, the string two-point function receives contributions only from the infrared and the ultraviolet limits. The latter is due to tree-level closed string uncanceled NS-NS tadpoles, which we explicitly reproduce from the effective Born-Infeld action. On the other hand, the infrared region reproduces the one-loop mediation of supersymmetry breaking in the effective gauge theory, via messengers and their Kaluza-Klein excitations. In the toroidal set-up considered here, it receives contributions only from N {approx} 4 and N {approx} 2 supersymmetric configurations, and thus always leads at leading order to a tachyonic direction, in agreement with effective field theory expectations. (orig.)

Simulation of QED effects in ultrahigh intensity laser-plasma interaction

International Nuclear Information System (INIS)

Kostyukov, I.; Nerush, E.

2010-01-01

Complete text of publication follows. Due to an impressive progress in laser technology, laser pulses with peak intensity of nearly 2 x 10 22 W/cm 2 are now available in laboratory. When the matter is irradiated by so intense laser pulses high energy density plasma is produced. Besides of fundamental interest such plasma is the efficient source of particles and radiation with extreme parameters that opens bright perspectives in developments of advanced particle accelerators, next generation of radiation sources, laboratory modelling of astrophysics phenomena etc. Even high laser intensity the radiation reaction and QED effects become important. One of the QED effects, which recently attracts much attention, is the electron-positron plasma creation in strong laser field. The plasma can be produced via electromagnetic cascades: the seeded charged particles is accelerated in the field of counter-propagating laser pulses, then they emit energetic photons, the photons by turn decay in the laser field and create electron-positron pairs. The pair particles accelerated in the laser field produce new generation of the photons and pairs. For self-consistent study of the electron-positron plasma dynamics in the laser field we develop 2D code based on particle-in-cell and Monte-Carlo methods. The electron, positron and photon dynamics as well as evolution of the plasma and laser fields are calculated by PIC technique while photon emission and pair production are calculated by Monte-Carlo method. We simulate pair production in the field of counter-propagating linearly polarized laser pulses. It is shown that for the laser intensity above threshold the plasma production becomes so intense that the laser pulse are strongly absorbed in the plasma. The laser intensity threshold and the rate of laser field absorption are calculated. Acknowledgements. This work has been supported by federal target 'The scientific and scientific-pedagogical personnel of innovation in Russia' and by

A covariant technique for the calculation of the one-loop effective action

International Nuclear Information System (INIS)

Avramidi, I.G.

1991-01-01

We develop a manifestly covariant technique for a heat kernel calculation in the presence of arbitrary background fields in a curved space. The four lowest-order coefficients of the Schwinger-De Witt asymptotic expansion are explicitly computed. We also calculate the heat kernel asymptotic expansion up to terms of third order in rapidly varying background fields (curvatures). This approximate series is summed and covariant nonlocal expressions for the heat kernel, ξ-function and one-loop effective action are obtained. Other related problems are discussed. (orig.)

Circuit QED with 3D cavities

Energy Technology Data Exchange (ETDEWEB)

Xie, Edwar; Eder, Peter; Fischer, Michael; Goetz, Jan; Deppe, Frank; Gross, Rudolf [Walther-Meissner-Institut, Bayerische Akademie der Wissenschaften, 85748 Garching (Germany); Physik-Department, TU Muenchen, 85748 Garching (Germany); Nanosystems Initiative Munich (NIM), 80799 Muenchen (Germany); Haeberlein, Max; Wulschner, Karl Friedrich [Walther-Meissner-Institut, Bayerische Akademie der Wissenschaften, 85748 Garching (Germany); Physik-Department, TU Muenchen, 85748 Garching (Germany); Fedorov, Kirill; Marx, Achim [Walther-Meissner-Institut, Bayerische Akademie der Wissenschaften, 85748 Garching (Germany)

2016-07-01

In typical circuit QED systems, on-chip superconducting qubits are coupled to integrated coplanar microwave resonators. Due to the planar geometry, the resonators are often a limiting factor regarding the total coherence of the system. Alternatively, similar hybrid systems can be realized using 3D microwave cavities. Here, we present studies on transmon qubits capacitively coupled to 3D cavities. The internal quality factors of our 3D cavities, machined out of high purity aluminum, are above 1.4 .10{sup 6} at the single photon level and a temperature of 50 mK. For characterization of the sample, we perform dispersive shift measurements up to the third energy level of the qubit. We show simulations and data describing the effect of the transmon geometry on it's capacitive properties. In addition, we present progress towards an integrated quantum memory application.

High-temperature expansion of the one-loop effective action induced by scalar and Dirac particles

Energy Technology Data Exchange (ETDEWEB)

Kalinichenko, Igor; Kazinski, Peter [Tomsk State University, Physics Faculty, Tomsk (Russian Federation)

2017-12-15

The complete nonperturbative expressions for the high-temperature expansion of the one-loop effective action induced by the charged scalar and the charged Dirac particles both at zero and finite temperatures are derived with account of possible nontrivial boundary conditions. The background electromagnetic field is assumed to be stationary and such that the corresponding Klein-Gordon operator or the Dirac Hamiltonian is self-adjoint. The contributions of particles and antiparticles are obtained separately. The explicit expressions for the C-symmetric and the non-C-symmetric vacuum energies of the Dirac fermions are derived. The leading corrections to the high-temperature expansion due to the nontrivial boundary conditions are explicitly found. The corrections to the logarithmic divergence of the effective action that come from the boundary conditions are derived. The high-temperature expansion of the naive one-loop effective action induced by charged fermions turns out to be divergent in the limit of a zero fermion mass. (orig.)

Ward identities at finite temperature

International Nuclear Information System (INIS)

DOlivo, J.C.; Torres, M.; Tututi, E.

1996-01-01

The Ward identities for QED at finite temperature are derived using the functional real-time formalism. They are verified by an explicit one-loop calculation. An effective causal vertex is constructed which satisfy the Ward identity with the associated retarded self-energy. copyright 1996 American Institute of Physics

NNLO O({alpha}{sup 4}{sub s}) results for heavy quark pair production in quark-antiquark collisions. The one-loop squared contributions

Energy Technology Data Exchange (ETDEWEB)

Koerner, J.G. [Mainz Univ. (Germany). Inst. fuer Physik; Merebashvili, Z. [Hamburg Univ. (Germany). 2. Inst. fuer Theoretische Physik; Rogal, M. [Deutsches Elektronen-Synchrotron (DESY), Zeuthen (Germany)

2008-02-15

We calculate the NNLO O({alpha}{sup 4}{sub s}) one-loop squared corrections to the production of heavy quark pairs in quark-antiquark annihilations. These are part of the NNLO O({alpha}{sup 4}{sub s}) radiative QCD corrections to this process. Our results, with the full mass dependence retained, are presented in a closed and very compact form, in the dimensional regularization scheme. We find very intriguing factorization properties for the finite part of the amplitudes. (orig.)

Renormalization of QED with planar binary trees

International Nuclear Information System (INIS)

Brouder, C.

2001-01-01

The Dyson relations between renormalized and bare photon and electron propagators Z 3 anti D(q)=D(q) and Z 2 anti S(q)=S(q) are expanded over planar binary trees. This yields explicit recursive relations for the terms of the expansions. When all the trees corresponding to a given power of the electron charge are summed, recursive relations are obtained for the finite coefficients of the renormalized photon and electron propagators. These relations significantly decrease the number of integrals to carry out, as compared to the standard Feynman diagram technique. In the case of massless quantum electrodynamics (QED), the relation between renormalized and bare coefficients of the perturbative expansion is given in terms of a Hopf algebra structure. (orig.)

Hardware-efficient fermionic simulation with a cavity-QED system

Science.gov (United States)

Zhu, Guanyu; Subaşı, Yiǧit; Whitfield, James D.; Hafezi, Mohammad

2018-03-01

In digital quantum simulation of fermionic models with qubits, non-local maps for encoding are often encountered. Such maps require linear or logarithmic overhead in circuit depth which could render the simulation useless, for a given decoherence time. Here we show how one can use a cavity-QED system to perform digital quantum simulation of fermionic models. In particular, we show that highly nonlocal Jordan-Wigner or Bravyi-Kitaev transformations can be efficiently implemented through a hardware approach. The key idea is using ancilla cavity modes, which are dispersively coupled to a qubit string, to collectively manipulate and measure qubit states. Our scheme reduces the circuit depth in each Trotter step of the Jordan-Wigner encoding by a factor of N2, comparing to the scheme for a device with only local connectivity, where N is the number of orbitals for a generic two-body Hamiltonian. Additional analysis for the Fermi-Hubbard model on an N × N square lattice results in a similar reduction. We also discuss a detailed implementation of our scheme with superconducting qubits and cavities.

Innovative hybrid pile oscillator technique in the Minerve reactor: open loop vs. closed loop

Directory of Open Access Journals (Sweden)

Geslot Benoit

2018-01-01

Full Text Available Pile oscillator techniques are powerful methods to measure small reactivity worth of isotopes of interest for nuclear data improvement. This kind of experiments has long been implemented in the Mineve experimental reactor, operated by CEA Cadarache. A hybrid technique, mixing reactivity worth estimation and measurement of small changes around test samples is presented here. It was made possible after the development of high sensitivity miniature fission chambers introduced next to the irradiation channel. A test campaign, called MAESTRO-SL, took place in 2015. Its objective was to assess the feasibility of the hybrid method and investigate the possibility to separate mixed neutron effects, such as fission/capture or scattering/capture. Experimental results are presented and discussed in this paper, which focus on comparing two measurements setups, one using a power control system (closed loop and another one where the power is free to drift (open loop. First, it is demonstrated that open loop is equivalent to closed loop. Uncertainty management and methods reproducibility are discussed. Second, results show that measuring the flux depression around oscillated samples provides valuable information regarding partial neutron cross sections. The technique is found to be very sensitive to the capture cross section at the expense of scattering, making it very useful to measure small capture effects of highly scattering samples.

Leading-order hadronic contributions to aμ and αQED from Nf=2+1+1 twisted mass fermions

International Nuclear Information System (INIS)

Feng, Xu; Hotzel, Grit; Renner, Dru B.

2012-11-01

We present the first four-flavour lattice calculation of the leading-order hadronic vacuum-polarisation contribution to the anomalous magnetic moment of the muon, a hvp μ , and the hadronic running of the QED coupling constant, Δα hvp QED (Q 2 ). In the heavy sector a mixed-action setup is employed. The bare quark masses are determined from matching the K- and D-meson masses to their physical values. Several light quark masses are used in order to yield a controlled extrapolation to the physical pion mass by utilising a recently proposed improved method. We demonstrate that this method also works in the four-flavour case.

One-loop corrections to the process e+e-→tt including hard bremsstrahlung

International Nuclear Information System (INIS)

Fleischer, J.; Riemann, T.; Werthenbach, A.; Leike, A.

2002-03-01

Radiative corrections to the process e + e - → t anti t are calculated in one-loop approximation of the Standard Model. There exist results from several groups. This talk provides further comparisons of the complete electroweak contributions, including hard bremsstrahlung. The excellent final agreement of the different groups allows to continue by working on a code for an event generator for TESLA and an extension to e + e - → 6 fermions. (orig.)

On the classical dynamics of charges in non-commutative QED

International Nuclear Information System (INIS)

Fatollahi, A.H.; Mohammadzadeh, H.

2004-01-01

Following Wong's approach to formulating the classical dynamics of charged particles in non-Abelian gauge theories, we derive the classical equations of motion of a charged particle in U(1) gauge theory on non-commutative space, the so-called non-commutative QED. In the present use of the procedure, it is observed that the definition of the mechanical momenta should be modified. The derived equations of motion manifest the previous statement about the dipole behavior of the charges in non-commutative space. (orig.)

One-loop stabilization of the fuzzy four-sphere via softly broken SUSY

Energy Technology Data Exchange (ETDEWEB)

Steinacker, Harold C. [Faculty of Physics, University of Vienna,Boltzmanngasse 5, A-1090 Vienna (Austria)

2015-12-17

We describe a stabilization mechanism for fuzzy S{sub N}{sup 4} in the Euclidean IIB matrix model due to vacuum energy in the presence of a positive mass term. The one-loop effective potential for the radius contains an attractive contribution attributed to supergravity, while the mass term induces a repulsive contribution for small radius due to SUSY breaking. This leads to a stabilization of the radius. The mechanism should be pertinent to recent results on the genesis of 3+1-dimensional space-time in the Minkowskian IIB model.

Derivative expansion of one-loop effective energy of stiff membranes with tension

Science.gov (United States)

Borelli, M. E. S.; Kleinert, H.; Schakel, Adriaan M. J.

1999-03-01

With help of a derivative expansion, the one-loop corrections to the energy functional of a nearly flat, stiff membrane with tension due to thermal fluctuations are calculated in the Monge parametrization. Contrary to previous studies, an arbitrary tilt of the surface is allowed to exhibit the nontrivial relations between the different, highly nonlinear terms accompanying the ultraviolet divergences. These terms are shown to have precisely the same form as those in the original energy functional, as necessary for renormalizability. Also infrared divergences arise. These, however, are shown to cancel in a nontrivial way.

Electron-electron bound states in Maxwell-Chern-Simons-Proca QED{sub 3}

Energy Technology Data Exchange (ETDEWEB)

Belich, H.; Helayel-Neto, J.A. [Grupo de Fisica Teorica Jose Leite Lopes, Petropolis, RJ (Brazil)]|[Centro Brasileiro de Pesquisas Fisicas (CBPF), Rio de Janeiro, RJ (Brazil). Coordenacao de Teoria de Campos e Particulas]. E-mail: belich@cbpf.br; helayel@gft.ucp.br; Del Cima, O.M. [Grupo de Fisica Teorica Jose Leite Lopes, Petropolis, RJ (Brazil)]. E-mail: delcima@gft.ucp.br; Ferreira, M.M. Jr. [Grupo de Fisica Teorica Jose Leite Lopes, Petropolis, RJ (Brazil)]|[Maranhao Univ., Sao Luis, MA (Brazil). Dept. de Fisica]. E-mail: manojr@cbpf.br

2002-10-01

We start from a parity-breaking MCS QED{sub 3} model with spontaneous breaking of the gauge symmetry as a framework for evaluation of the electron-electron interaction potential and for attainment of numerical values for the e{sup -}e{sup -} - bound state. Three expressions (V{sub eff{down_arrow}}{sub {down_arrow}}, V{sub eff{down_arrow}}{sub {up_arrow}}, V{sub eff{down_arrow}}{sub {down_arrow}}) are obtained according to the polarization state of the scattered electrons. In an energy scale compatible with condensed matter electronic excitations, these potentials become degenerated. The resulting potential is implemented in the Schroedinger equation and the variational method is applied to carry out the electronic binding energy. The resulting binding energies in the scale of 10-100 meV and a correlation length in the scale of 10 - 30 Angstrom are possible indications that the MCS-QED{sub 3} model adopted may be suitable to address an eventual case of e{sup -}e{sup -} pairing in the presence of parity-symmetry breakdown. The data analyzed here suggest an energy scale of 10-100 meV to fix the breaking of the U(1)-symmetry. (author)

3-D numerical simulations of coronal loops oscillations

Directory of Open Access Journals (Sweden)

M. Selwa

2009-10-01

Full Text Available We present numerical results of 3-D MHD model of a dipole active region field containing a loop with a higher density than its surroundings. We study different ways of excitation of vertical kink oscillations by velocity perturbation: as an initial condition, and as an impulsive excitation with a pulse of a given position, duration, and amplitude. These properties are varied in the parametric studies. We find that the amplitude of vertical kink oscillations is significantly amplified in comparison to horizontal kink oscillations for exciters located centrally (symmetrically below the loop, but not if the exciter is located a significant distance to the side of the loop. This explains why the pure vertical kink mode is so rarely observed in comparison to the horizontally polarized one. We discuss the role of curved magnetic field lines and the pulse overlapping at one of the loop's footpoints in 3-D active regions (AR's on the excitation and the damping of slow standing waves. We find that footpoint excitation becomes more efficient in 3-D curved loops than in 2-D curved arcades and that slow waves can be excited within an interval of time that is comparable to the observed one wave-period due to the combined effect of the pulse inside and outside the loop. Additionally, we study the effect of AR topology on the excitation and trapping of loop oscillations. We find that a perturbation acting directly on a single loop excites oscillations, but results in an increased leakage compared to excitation of oscillations in an AR field by an external source.

3-D numerical simulations of coronal loops oscillations

Directory of Open Access Journals (Sweden)

M. Selwa

2009-10-01

Full Text Available We present numerical results of 3-D MHD model of a dipole active region field containing a loop with a higher density than its surroundings. We study different ways of excitation of vertical kink oscillations by velocity perturbation: as an initial condition, and as an impulsive excitation with a pulse of a given position, duration, and amplitude. These properties are varied in the parametric studies. We find that the amplitude of vertical kink oscillations is significantly amplified in comparison to horizontal kink oscillations for exciters located centrally (symmetrically below the loop, but not if the exciter is located a significant distance to the side of the loop. This explains why the pure vertical kink mode is so rarely observed in comparison to the horizontally polarized one. We discuss the role of curved magnetic field lines and the pulse overlapping at one of the loop's footpoints in 3-D active regions (AR's on the excitation and the damping of slow standing waves. We find that footpoint excitation becomes more efficient in 3-D curved loops than in 2-D curved arcades and that slow waves can be excited within an interval of time that is comparable to the observed one wave-period due to the combined effect of the pulse inside and outside the loop. Additionally, we study the effect of AR topology on the excitation and trapping of loop oscillations. We find that a perturbation acting directly on a single loop excites oscillations, but results in an increased leakage compared to excitation of oscillations in an AR field by an external source.

Kinetics of Internal-Loop Formation in Polypeptide Chains: A Simulation Study

Science.gov (United States)

Doucet, Dana; Roitberg, Adrian; Hagen, Stephen J.

2007-01-01

The speed of simple diffusional motions, such as the formation of loops in the polypeptide chain, places one physical limit on the speed of protein folding. Many experimental studies have explored the kinetics of formation of end-to-end loops in polypeptide chains; however, protein folding more often requires the formation of contacts between interior points on the chain. One expects that, for loops of fixed contour length, interior loops will form more slowly than end-to-end loops, owing to the additional excluded volume associated with the “tails”. We estimate the magnitude of this effect by generating ensembles of randomly coiled, freely jointed chains, and then using the theory of Szabo, Schulten, and Schulten to calculate the corresponding contact formation rates for these ensembles. Adding just a few residues, to convert an end-to-end loop to an internal loop, sharply decreases the contact rate. Surprisingly, the relative change in rate increases for a longer loop; sufficiently long tails, however, actually reverse the effect and accelerate loop formation slightly. Our results show that excluded volume effects in real, full-length polypeptides may cause the rates of loop formation during folding to depart significantly from the values derived from recent loop-formation experiments on short peptides. PMID:17208979

A theory of desynchronisable closed loop system

Directory of Open Access Journals (Sweden)

Harsh Beohar

2010-10-01

Full Text Available The task of implementing a supervisory controller is non-trivial, even though different theories exist that allow automatic synthesis of these controllers in the form of automata. One of the reasons for this discord is due to the asynchronous interaction between a plant and its controller in implementations, whereas the existing supervisory control theories assume synchronous interaction. As a consequence the implementation suffer from the so-called inexact synchronisation problem. In this paper we address the issue of inexact synchronisation in a process algebraic setting, by solving a more general problem of refinement. We construct an asynchronous closed loop system by introducing a communication medium in a given synchronous closed loop system. Our goal is to find sufficient conditions under which a synchronous closed loop system is branching bisimilar to its corresponding asynchronous closed loop system.

Present status and prospect of the experimental study of QED in high Z ions

International Nuclear Information System (INIS)

Briand, J.P.

1993-01-01

I summarize in this paper the present status of our experimental knowledge on the Lamb shift of high Z hydrogenlike ions. Some tentative prospect on the future improvements with the new large accelerators and ion sources are discussed and compared with the present accuracy of QED corrections. (orig.)

Multiphoton production and tests of QED at LEP-II

International Nuclear Information System (INIS)

Winter, M.

2001-01-01

Data collected by the 4 LEP collaboration from 1995 to 2000 at collision energies ranging from 130 to 208 GeV were used to measure the cross-section of the process e + e - →γγ(γ). QED predictions for this reaction were tested with a few per-cent accuracy and manifestations of physics beyond the Standard Model (SM) were investigated. Preliminary lower bounds on the cut-off parameter Λ ± , the mass of an excited electron, the string mass scale underlying low-scale Quantum Gravity and on energy scales expression various contact interactions were derived. (author)

ORIENTATION: KEY TO THE OODA LOOP – THE CULTURE FACTOR

Directory of Open Access Journals (Sweden)

Donald A. MACCUISH

2012-01-01

Full Text Available The late Colonel John Boyd developed what he called the OODA-Loop as both a learning and decision making model to help us better understand how we make decisions and learn. His OODA-Loop model consists of non-sequential elements: Observe – Orient – Decide – Action. He contended if one could cycle through these phases quicker and more accurately than one’s adversary you could then get inside your adversary’s OODA-Loop and “win”. The key to the OODA-Loop he noted is Orientation. He only drew one diagram of his OODA-Loop. Only in the Orientation phase did he elaborate component elements. These elements are: Cultural Traditions, Genetic Heritage, Analysis/Synthesis, New Information, and Previous Experience. All of these elements he contended are interconnected. Thus, the interaction of all these factors effects how we orient ourselves to the situation at hand. In this article I will share my view of the “Culture Factor” in Orientation.

Study of open-charm 0{sup +} states in unitarized chiral effective theory with one-loop potentials

Energy Technology Data Exchange (ETDEWEB)

Du, Meng-Lin [Universitaet Bonn, Helmholtz-Institut fuer Strahlen- und Kernphysik and Bethe Center for Theoretical Physics, Bonn (Germany); Guo, Feng-Kun [Chinese Academy of Sciences, CAS Key Laboratory of Theoretical Physics, Institute of Theoretical Physics, Beijing (China); University of Chinese Academy of Sciences, School of Physical Sciences, Beijing (China); Meissner, Ulf G. [Universitaet Bonn, Helmholtz-Institut fuer Strahlen- und Kernphysik and Bethe Center for Theoretical Physics, Bonn (Germany); Forschungszentrum Juelich, Institute for Advanced Simulation, Institut fuer Kernphysik and Juelich Center for Hadron Physics (Germany); Yao, De-Liang [Forschungszentrum Juelich, Institute for Advanced Simulation, Institut fuer Kernphysik and Juelich Center for Hadron Physics (Germany); Instituto de Fisica Corpuscular (Centro mixto CSIC-UV), Institutos de Investigacion de Paterna, Valencia (Spain)

2017-11-15

Chiral potentials are derived for the interactions between Goldstone bosons and pseudo-scalar charmed mesons up to next-to-next-to-leading order in a covariant chiral effective field theory with explicit vector charmed-meson degrees of freedom. Using the extended-on-mass-shell scheme, we demonstrate that the ultraviolet divergences and the so-called power counting breaking terms can be properly absorbed by the low-energy constants of the chiral Lagrangians. We calculate the scattering lengths by unitarizing the one-loop potentials and fit them to the data extracted from lattice QCD. The obtained results are compared to the ones without an explicit contribution of vector charmed mesons given previously. It is found that the difference is negligible for S-wave scattering in the threshold region. This validates the use of D*-less one-loop potentials in the study of the pertinent scattering lengths. We search for dynamically generated open-charm states with J{sup P} = 0{sup +} as poles of the S-matrix on various Riemann sheets. The trajectories of those poles for varying pion masses are presented as well. (orig.)

Single and two-phase similarity analysis of a reduced-scale natural convection loop relative to a full-scale prototype

International Nuclear Information System (INIS)

Botelho, David A.; Faccini, Jose L.H.

2002-01-01

The main topic in this paper is a new device being considered to improve nuclear reactor safety employing the natural circulation. A scaled experiment used to demonstrate the performance of the device is also described. We also applied a similarity analysis method for single and two-phase natural convection loop flow to the IEN CCN experiment and to an APEX like experiment to verify the degree of similarity relative to a full-scale prototype like the AP600. Most of the CCN similarity numbers that represent important single and two-phase similarity conditions are comparable to the APEX like loop non-dimensional numbers calculated employing the same methodology. Despite the much smaller geometric, pressure, and power scales, we conclude that the IEN CCN has single and two-phase natural circulation similarity numbers that represent fairly well the full-scale prototype. even lacking most complementary primary and safety systems, this IEN circuit provided a much valid experience to develop human, experimental, and analytical resources, besides its utilization as a training tool. (author)

Comments on confinement criteria

International Nuclear Information System (INIS)

Kurak, V.; Schroer, B.; Swieca, J.A.

1977-01-01

For a QED 2 model with SU(n) flavour, the nature of the physical states space is more subtle than one expects on the basis of the loop criterion for confinement. One may have colour confinement without confinement of the fundamental flavour representation. Attempts to formulate confinement criteria in which the quark fields play a more fundamental role are discussed [pt

Probabilistic Teleportation of an Arbitrary Two-Atom State in Cavity QED

Institute of Scientific and Technical Information of China (English)

LIU Jin-Ming

2007-01-01

We propose a scheme for the teleportation of an arbitrary two-atom state by using two pairs of two-atom nonmaximally entangled states as the quantum channel in cavity QED.It is shown that no matter whether the arbitrary two-atom pure state to be teleported is entangled or not,our teleportation scheme can always be probabilistically realized.The success probability of teleportation is determined by the smaller coefficients of the two initially entangled atom pairs.