Kl4K_{l4} at two-loops and CHPT predictions for ππ\pi\pi-scattering

We present the results from our two-loop calculations of masses, decay-constants, vacuum-expectation-values and the $K_{\ell4}$ form-factors in three-flavour Chiral Perturbation Theory (CHPT). We use this to fit the $L_i^r$ to two-loops and discuss the ensuing predictions for $\pi\pi$-threshold parameters.Comment: Talk presented at Chiral Dynamics 2000, Jefferson Lab, Newport News, Virginia, USA, July 17-22, 2000, 2

Compact multigluonic scattering amplitudes with heavy scalars and fermions

Combining the Berends-Giele and on-shell recursion relations we obtain an extremely compact expression for the scattering amplitude of a complex scalar-antiscalar pair and an arbitrary number of positive helicity gluons. This is one of the basic building blocks for constructing other helicity configurations from recursion relations. We also show explicity that the all positive helicity gluons amplitude for heavy fermions is proportional to the scalar one, confirming in this way the recently advocated SUSY-like Ward identities relating both amplitudes.Comment: 7 page

Remarks on the consistency of minimal deviations from General Relativity

We study the consequences of the modification of the phase space structure of General Relativity imposed by breaking the full diffeomorphism invariance but retaining the time foliation preserving diffeomorphisms. We examine the different sectors in phase space that satisfy the new structure of constraints. For some sectors we find an infinite tower of constraints. In spite of that, we also show that these sectors allow for solutions, among them some well known families of black hole and cosmologies which fulfill all the constraints. We raise some physical concerns on the consequences of an absolute Galilean time, on the thermodynamical pathologies of such models and on their unusual vacuum structure.Comment: latex 28 pages, 1 figure. Added comments and a reference. Text improved

Lepton flavor changing Higgs decays in the littlest Higgs model with T-parity

We calculate loop induced lepton flavor violating Higgs decays in the Littlest Higgs model with T-parity. We find that a finite amplitude is obtained only when all contributions from the T-odd lepton sector are included. This is in contrast to lepton fla- vor violating processes mediated by gauge bosons where the partners of the right-handed mirror leptons can be decoupled from the spectrum. These partners are necessary to can- cel the divergence in the Higgs mass introduced by the mirror leptons but are otherwise unnecessary and assumed to be decoupled in previous phenomenological studies. Further- more, as we emphasize, including the partner leptons in the spectrum also introduces a new source of lepton flavor violation via their couplings to the physical pseudo-Goldstone electroweak triplet scalar. Although this extra source also affects lepton flavor changing gauge transitions, it decouples from these amplitudes in the limit of heavy mass for the partner leptons. We find that the corresponding Higgs branching ratio into taus and muons can be as large as ~ 0.2 × 10 -6 for T-odd masses of the order a few TeV, a demanding challenge even for the high luminosity LHC.Peer ReviewedPostprint (author's final draft

Two-point Functions at Two Loops in Three Flavour Chiral Perturbation Theory

The vector and axial-vector two-point functions are calculated to next-to-next-to-leading order in Chiral Perturbation Theory for three light flavours. We also obtain expressions at the same order for the masses, $m_\pi^2$, $m_K^2$ and $m_\eta^2$, and the decay constants, $F_\pi$, $F_K$ and $F_\eta$. We present some numerical results after a simple resonance estimate of some of the new ${\cal O}(p^6)$ constants.Comment: LaTeX2e, 42 page

The full lepton flavor of the littlest Higgs model with T-parity

We thank useful discussions and comments by A. Blondel, A. Falkowski, G. Hernández- Tomé, J. Hubisz, I. Low and J.M. Pérez-Poyatos. This work has been supported in part by the Ministry of Science, Innovation and Universities, under grant numbers FPA2016- 78220-C3-1,2,3-P (fondos FEDER), and by the Junta de Andalucía grant FQM 101 as well as by the Juan de la Cierva program. J.S. and R.V.M. thank the Mainz Institute for Theoretical Physics (MITP) for its hospitality and partial support during the completion of this work. R.V.M. would also like to thank the Fermilab National Accelerator Laboratory and Northwestern University for their hospitality.We re-examine lepton flavor violation (LFV) in the Littlest Higgs model with T-parity (LHT) including the full T-odd (non-singlet) lepton and Goldstone sectors. The heavy leptons induce two independent sources of LFV associated with the couplings necessary to give masses to the T-odd mirror fermions and to their partners in right-handed SO(5) multiplets, respectively. The latter, which have been neglected in the past, can be decoupled from gauge mediated processes but not from Higgs mediated ones and must therefore also be included in a general analysis of LFV in the LHT. We also further extend previous analyses by considering on-shell Z and Higgs LFV decays together with the LFV processes at low momentum transfer. We show that current experimental limits can probe the LHT parameter space up to global symmetry breaking scales f ∼ 10 TeV. For lower f values ≳ 1 TeV, μ − e transitions require the misalignment between the heavy and the Standard Model charged leptons to be ≲ 1%. Future LFV experiments using intense muon beams should be sensitive to misalignments below the per mille level. For τ LFV transitions, which could potentially be observed at Belle II and the LHC as well as future lepton colliders, we find that generically they can not discriminate between the LHT and supersymmetric models though in some regions of parameter space this may be possible.This work has been supported in part by the Ministry of Science, Innovation and Universities, under grant numbers FPA2016- 78220-C3-1,2,3-P (fondos FEDER), and by the Junta de Andalucía grant FQM 10

Consistent and inconsistent truncations. Some results and the issue of the correct uplifting of solutions

We clarify the existence of two different types of truncations of the field content in a theory, the consistency of each type being achieved by different means. A proof is given of the conditions to have a consistent truncation in the case of dimensional reductions induced by independent Killing vectors. We explain in what sense the tracelessness condition found by Scherk and Scharwz is not only a necessary condition but also a {\it sufficient} one for a consistent truncation. The reduction of the gauge group is fully performed showing the existence of a sector of rigid symmetries. We show that truncations originated by the introduction of constraints will in general be inconsistent, but this fact does not prevent the possibility of correct upliftings of solutions in some cases. The presence of constraints has dynamical consequences that turn out to play a fundamental role in the correctness of the uplifting procedure.Comment: Latex, 33 pages, 1 eps fig. v2: typos removed, refs. adde

Truncations driven by constraints: consistency and conditions for correct upliftings

We discuss the mechanism of truncations driven by the imposition of constraints. We show how the consistency of such truncations is controlled, and give general theorems that establish conditions for the correct uplifting of solutions. We show in some particular examples how one can get correct upliftings from 7d supergravities to 10d type IIB supergravity, even in cases when the truncation is not initially consistent by its own.Comment: Latex, 23 page