Natural Fermion Hierarchies from Random Yukawa Couplings

The Standard Model of particle physics requires Yukawa matrices with eigenval- ues that differ by orders of magnitude. We propose a novel way to explain this fact without any small or large parameters. The mechanism is based on the observation that products of matrices of random order one-numbers have hierarchical spectra. The same mechanism can easily account for the hierarchical structure of the quark mixing matrix.Comment: 9 pages. v2: Extended and improved discussion on CKM matrix. References added. Matches published versio

Realistic GUT Yukawa Couplings from a Random Clockwork Model

We present realistic models of flavor in SU(5) and SO(10) grand unified theories (GUTs). The models are renormalizable and do not require any exotic representations in order to accommodate the necessary GUT breaking effects in the Yukawa couplings. They are based on a simple clockwork Lagrangian whose structure is enforced with just two (one) vectorlike U(1) symmetries in the case of SU(5) and SO(10) respectively. The inter-generational hierarchies arise spontaneously from products of matrices with order one random entries.Comment: 18 pages, 2 figure

One-Loop Effective Action in Orbifold Compactifications

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.Comment: 30 pages, 1 figure, 3 tables, v2: appendix on zeta function regularization added, discussion of 6d example expanded, version to appear in JHE

Pension reform in Bolivia : innovative solutions to common problems

Bolivia's bold program of pension reform involved the immediate closing down of the old pay-as-you-go system and its replacement by a defined-contribution system based on individual capitalization accounts and managed by the private sector. The pensions of the old system will be covered by the Bolivian Treasury. Workers will receive compensatory pensions for their contributions to the old system. These will be calculated on the basis of a simple formula that could be improved to reduce the cost of transition. To avoid high marketing costs, Bolivia has entrusted management of the system to two groups selected through international competitive bidding (to minimize fees). Individual accounts have been preallocated to those two groups on a regional basis or, in large cities, on the basis of the birthdays of affiliated workers. Competition for individual accounts will be allowed in the year 2000 and the market will be opened to other private pension-fund administrators (AFPs) in 2002. Proceeds from the capitalization program will be used to pay an annuity to all Bolivians 65 and older. Funds from the capitalization program will also be managed by the two selected AFPs. Custodianship has been entrusted to a multinational group offering global custodial services. AFP investments are only subject to upper limits, including relatively high limits for foreign assets. However, they must initially purchase a certain quantity of treasury bonds to help finance the cost of transition. Bolivian pension reform faces major challenges: a) To create a competitive market for management of pension fund resources and hence achieve competitive returns on investment and higher pensions; b) To eliminate the requirement of investment in treasury bonds; and c) To insulate the system from attempts to use AFP funds and capitalization proceeds for public projects. (One way to achieve this would be to transfer ownership of the capitalization proceeds to individual Bolivians.)Economic Theory&Research,International Terrorism&Counterterrorism,Banks&Banking Reform,Pensions&Retirement Systems,Payment Systems&Infrastructure,Pensions&Retirement Systems,Banks&Banking Reform,Information Technology,International Terrorism&Counterterrorism,Environmental Economics&Policies

Effective theory for neutral resonances and a statistical dissection of the ATLAS diboson excess

We classify the complete set of dimension-5 operators relevant for the resonant production of a singlet of spin 0 or 2 linearly coupled to the Standard Model (SM). We compute the decay width of such states as a function of the effective couplings, and provide the matching to various well-motivated New Physics scenarios. We then investigate the possibility that one of these neutral resonances be at the origin of the excess in diboson production recently reported by the ATLAS collaboration. We perform a shape analysis of the excess under full consideration of the systematic uncertainties to extract the width $\Gamma_{\rm tot}$ of the hypothetical resonance, finding it to be in the range 26 GeV $<\Gamma_{\rm tot}<$ 144 GeV at 95\% C.L. We then point out that the three overlapping selections $WW$, $WZ$, $ZZ$ reported by ATLAS follow a joint trivariate Poisson distribution, which opens the possibility of a thorough likelihood analysis of the event rates. The background systematic uncertainties are also included in our analysis. We show that the data do not require $W\!Z$ production and could thus in principle be explained by neutral resonances. We then use both the information on the width and the cross section, which prove to be highly complementary, to test the effective Lagrangians of singlet resonances. Regarding specific models, we find that neither scalars coupled via the Higgs-portal nor the Randall-Sundrum (RS) radion can explain the ATLAS anomaly. The RS graviton with all matter on the infrared (IR) brane can in principle fit the observed excess, while the RS model with matter propagating in the bulk requires the presence of IR brane kinetic terms for the gauge fields.Comment: 31 page

Anomalous gauge couplings from composite Higgs and warped extra dimensions

We examine trilinear and quartic anomalous gauge couplings (AGCs) generated in composite Higgs models and models with warped extra dimensions. We first revisit the SU(2)_L x U(1)_Y effective Lagrangian and derive the charged and two-photon neutral AGCs. We derive the general perturbative contributions to the pure field-strength operators from spin 0, 1/2, 1 resonances by means of the heat kernel method. In the composite Higgs framework, we derive the pattern of expected deviations from typical SO(N) embeddings of the light composite top partner. We then study a generic warped extra dimension framework with AdS_5 background, recasting in few parameters the features of models relevant for AGCs. We also present a detailed study of the latest bounds from electroweak and Higgs precision observables, with and without brane kinetic terms. For vanishing brane kinetic terms, we find that the S and T parameters exclude KK gauge modes of the RS custodial [non-custodial] scenario below 7.7 [14.7] TeV, for a brane Higgs and below 6.6 [8.1] TeV for a Pseudo Nambu-Goldstone Higgs, at 95% CL. These constraints can be relaxed in presence of brane kinetic terms. The leading AGCs are probing the KK gravitons and the KK modes of bulk gauge fields in parts of the parameter space. In these scenarios, the future CMS and ATLAS forward proton detectors could be sensitive to the effect of KK gravitons in the multi-TeV mass range.Comment: 37 pages, 2 figures, 3 tables. Minor typos fixed, some comments and references added. Matches JHEP versio