Breaking Terms Research Articles

Perturbative quantum corrections and flux compactifications

AbstractWe review the results of arxiv:0704.0730, a string theory test of the phenomenologically interesting large volume scenario (LVS) of Balasubramanian et al. In particular, we consider whether the LVS expansion of the string effective action is consistent when the open string one‐loop corrections due to D‐branes and O‐planes are taken into account. The result is that LVS is surprisingly robust. We also review the computation of soft supersymmetry breaking terms, which is only modified at subleading order.

MSSM Higgs sector CP violation at photon colliders: revisited

The CP violating phases in soft SUSY breaking terms may induce indirect CP violation in the neutral Higgs boson sector through SUSY particle loops as well as direct CP violation in the γγ→Hi (i=1,2,3) through CP violating vertices. We present a complete analysis of the MSSM Higgs sector CP violation at photon colliders including the chargino loop contributions in the regime $\tan\beta\lesssim20$ , where the CP violating mixing in the neutral Higgs sector is very strongly influenced by the scalar top loop, more so than the chargino and neutralino ones. However, the CP violating phases of the higgsino and wino mass parameters may still generate direct CP violation in γγ→Hi. In this process, the CP violating phenomena become very rich, and thus we study the production rates and polarization asymmetries in the Higgs production in detail. Photon colliders with high luminosity and well controlled polarized initial photon beams are indispensable in determining the CP properties of neutral Higgs bosons.

Unified Gauge Theories and Reduction of Couplings: from Finiteness to Fuzzy Extra Dimensions

Finite Unified Theories (FUTs) are N = 1 supersymmetric Grand Unified Theories, which can be made all-loop finite, both in the dimensionless (gauge and Yukawa couplings) and dimensionful (soft supersymmetry breaking terms) sectors. This remarkable property, based on the reduction of couplings at the quantum level, provides a drastic reduc- tion in the number of free parameters, which in turn leads to an accurate prediction of the top quark mass in the dimensionless sector, and predictions for the Higgs boson mass and the supersymmetric spectrum in the dimensionful sector. Here we examine the predictions of two such FUTs. Next we consider gauge theories defined in higher dimensions, where the extra dimensions form a fuzzy space (a finite matrix manifold). We reinterpret these gauge theo- ries as four-dimensional theories with Kaluza-Klein modes. We then perform a generalized ` la Forgacs-Manton dimensional reduction. We emphasize some striking features emerging such as (i) the appearance of non-Abelian gauge theories in four dimensions starting from an Abelian gauge theory in higher dimensions, (ii) the fact that the spontaneous symmetry breaking of the theory takes place entirely in the extra dimensions and (iii) the renormaliza- bility of the theory both in higher as well as in four dimensions. Then reversing the above approach we present a renormalizable four dimensional SU(N) gauge theory with a suitable multiplet of scalar fields, which via spontaneous symmetry breaking dynamically develops extra dimensions in the form of a fuzzy sphere S 2 N. We explicitly find the tower of massive Kaluza-Klein modes consistent with an interpretation as gauge theory on M 4 ◊ S 2 , the scalars being interpreted as gauge fields on S 2 . Depending on the parameters of the model the low-energy gauge group can be SU(n), or broken further to SU(n1) ◊ SU(n2) ◊ U(1). Therefore the second picture justifies the first one in a renormalizable framework but in addition has the potential to reveal new aspects of the theory.

Einsteinian gravity from a topological action

The curvature-squared model of gravity, in the affine form proposed by Weyl and Yang, is deduced from a topological action in 4D. More specifically, we start from the Pontrjagin (or Euler) invariant. Using the BRST antifield formalism with a double duality gauge fixing, we obtain a consistent quantization in spaces of double dual curvature as classical instanton type background. However, exact vacuum solutions with double duality properties exhibit a ‘vacuum degeneracy’. By modifying the duality via a scale breaking term, we demonstrate that only Einstein’s equations with an induced cosmological constant emerge for the topology of the macroscopic background. This may have repercussions on the problem of ‘dark energy’ as well as ‘dark matter’ modeled by a torsion induced quintaxion.

First-order restoration ofSU(Nf)×SU(Nf)chiral symmetry with largeNfand an electroweak phase transition

It has been argued by Pisarski and Wilczek that finite temperature restoration of SU(N{sub f})xSU(N{sub f}) chiral symmetry is first order for N{sub f}{>=}3. This type of chiral symmetry with large N{sub f} may appear in the Higgs sector if one considers models such as walking technicolor theories. We examine the first-order restoration of chiral symmetry from the point of view of the electroweak phase transition. The strength of the transition is estimated in a SU(2)xU(1) gauged linear sigma model by means of the finite temperature effective potential at one loop with the ring improvement. Even if the mass of the neutral scalar boson corresponding to the Higgs boson is larger than 114 GeV, the first-order transition can be strong enough for electroweak baryogenesis, as long as the extra massive scalar bosons (required for the linear realization) are kept heavier than the neutral scalar boson. Explicit symmetry breaking terms reduce the strength of the first-order transition, but the transition can remain strongly first order even when the masses of pseudo Nambu-Goldstone bosons become as large as the current lower bound of direct search experiments.

Comparison of mixed-Higgs scenarios in the NMSSM and the MSSM

We study scenarios in the minimal and next-to-minimal supersymmetric models in which the lightest $CP$-even Higgs boson can have mass below the 114 GeV standard model LEP limit by virtue of reduced $ZZ$ coupling due to substantial mixing among the Higgs bosons. We pay particular attention to the size of corrections from superpartners needed for these scenarios to be viable and point to boundary conditions at large scales which lead to these scenarios while at the same time keeping electroweak fine-tuning modest in size. We find that naturalness of electroweak symmetry breaking in the mixed-Higgs scenarios of both models points to the same region of soft supersymmetry breaking terms as in the decoupled scenarios with mass of the $CP$ even Higgs boson above 114 GeV, namely those leading to large mixing in the stop sector at the electroweak scale, especially if we also require that the lightest $CP$-even Higgs explains the Higgs-like LEP events at $\ensuremath{\sim}98\text{ }\text{ }\mathrm{GeV}$.

Is incompressible elasticity a conformal field theory?

In this work, we investigate the theory of linear isotropic incompressible elasticity as a conformal field theory. We calculate the conformal currents, the conservation laws and the balance laws of incompressible elasticity. We investigate the Euler–Lagrange symmetries, variational and divergence symmetries. If the pressure p = 0 , the conformal group is the symmetry group for homogeneous isotropic linear incompressible elasticity without external forces. The additional symmetry is the special conformal transformation. We also discuss the symmetry breaking terms of special conformal transformations in elasticity. To cite this article: M. Lazar, C. Anastassiadis, C. R. Mecanique 336 (2008).

Moduli stabilization, F-term uplifting and soft supersymmetry breaking terms(Summer Institute 2007)

Moduli stabilization, F-term uplifting and soft supersymmetry breaking terms(Summer Institute 2007)

NUCLEI AS SUPERPOSITION OF TOPOLOGICAL SOLITONS

The rational map approximation provides an opportunity to describe light nuclei as classical solitons with baryon number B > 1 in the framework of the Skyrme model. The rational map ansatz yields a possibility of factorization of S3 baryon charge into S1 and S2 parts, the phenomenology of the model being strongly affected by the chosen factorization. Moreover, in the fundamental representation superposition of two different soliton factorizations can be used as solution ansatz. The canonical quantization procedure applied to collective degrees of freedom of the classical soliton leads to anomalous breaking of the chiral symmetry and exponential falloff of the energy density of the soliton at large distance, without explicit symmetry breaking terms included. The evolution of the shape of electric form factor as a function of two different factorization soliton mix ratio is investigated. Numerical results are presented.

Formula omitted] dibaryons in the Einstein–Skyrme model

SU(3) collective coordinate quantization to the regular solution of the B=2 axially symmetric Einstein–Skyrme system is performed. For the symmetry breaking term, exact diagonalization method called Yabu–Ando approach are used. The effect of the gravity on the mass spectra of the SU(3) dibaryons and the symmetry breaking term is studied in detail. In the strong gravity limit, the symmetry breaking term significantly reduces and exact SU(3) flavor symmetry is recovered.

Decoupling and destabilizing in spontaneously broken supersymmetry

The supersymmetric analog of the Goldberger-Treiman relation plays a critical role in the low energy effective theory of models in which supersymmetry is spontaneously broken in a hidden sector. The interactions that connect the hidden and visible sectors break a global symmetry, which implies that the low energy theory must be constructed consistently in inverse powers of the messenger scale. The Goldberger-Treiman relation determines the couplings of the Goldstino to the visible sector fields. These couplings are fixed by the soft supersymmetry breaking terms within a power counting scheme that is stable under radiative corrections. We describe the power counting of the low energy effective theory, first for a toy model of extended technicolor and then for the supersymmetric standard model. One implication of this work for supersymmetry phenomenology is the observation that Goldstino loops can destabilize the weak scale if the low energy theory is not constructed consistently. Another is that Goldstino loops induce all visible sector operators not forbidden by symmetries. The magnitudes of these operators are determined by the consistent power counting of the low energy effective theory.

Quantum Hall ferromagnetism in graphene: SU(4) bosonization approach

We study the quantum Hall effect in graphene at filling factors $\ensuremath{\nu}=0$ and $\ensuremath{\nu}=\ifmmode\pm\else\textpm\fi{}1$, concentrating on the quantum Hall ferromagnetic regime, within a nonperturbative bosonization formalism. We start by developing a bosonization scheme for electrons with two discrete degrees of freedom (spin-$1∕2$ and pseudospin-$1∕2$) restricted to the lowest Landau level. Three distinct phases are considered, namely, the so-called spin-pseudospin, spin, and pseudospin phases. The first corresponds to a quarter-filled $(\ensuremath{\nu}=\ensuremath{-}1)$ lowest Landau level, while the others to a half-filled $(\ensuremath{\nu}=0)$ lowest Landau level. In each case, we show that the elementary neutral excitations can be treated approximately as a set of $n$-independent kinds of boson excitations. The boson representations of the projected electron density, the spin, pseudospin, and mixed spin-pseudospin density operators are derived. We then apply the developed formalism to the effective continuous model, which includes SU(4) symmetry breaking terms, recently proposed by Alicea and Fisher [Phys. Rev. B 74, 075422 (2006)]. For each quantum Hall state, an effective interacting boson model is derived and the dispersion relations of the elementary excitations are analytically calculated. We propose that the charged excitations (quantum Hall skyrmions) can be described as a coherent state of bosons. We calculate the semiclassical limit of the boson model derived from the SU(4) invariant part of the original fermionic Hamiltonian and show that it agrees with the results of Arovas et al. [Phy. Rev. B 59, 13147 (1999)] for $\mathrm{SU}(N)$ quantum Hall skyrmions. We briefly discuss the influence of the SU(4) symmetry breaking terms in the skyrmion energy.

R-symmetry, supersymmetry breaking and metastable vacua in global and local supersymmetric theories

We study N=1 global and local supersymmetric theories with a continuous global $U(1)_R$ symmetry as models of dynamical supersymmetry (SUSY) breaking. We introduce explicit R-symmetry breaking terms into such models, in particular a generalized O'Raifeartaigh model. Such explicit R-symmetry breaking terms can lead to a SUSY preserving minimum. We classify explicit R-symmetry breaking terms by the structure of newly appeared SUSY stationary points as a consequence of the R-breaking effect, which could make the SUSY breaking vacuum metastable. We show that the R-breaking terms are basically divided into two categories. One of them does not generate a SUSY solution, or yields SUSY solutions that disappear in the case of supergravity when we tune a parameter so that the original SUSY breaking minimum becomes a Minkowski vacuum. We also show that the general argument by Nelson and Seiberg for a dynamical SUSY breaking still holds with a local SUSY except for a certain nontrivial case, and present concrete examples of the exception.

Improved actions and asymptotic scaling in lattice Yang-Mills theory

Improved actions in SU(2) and SU(3) lattice gauge theories are investigated with an emphasis on asymptotic scaling. A new scheme for tadpole improvement is proposed. The standard but heuristic tadpole improvement emerges from a mean field approximation from the new approach. Scaling is investigated by means of the large distance static quark potential. Both the generic and the new tadpole scheme yield significant improvements on asymptotic scaling when compared with loop improved actions. A study of the rotational symmetry breaking terms, however, reveals that only the new improvement scheme efficiently eliminates the leading irrelevant term from the action.

On Newton's law in supersymmetric braneworld models

We study the propagation of gravitons within 5-D supersymmetric braneworld models with a bulk scalar field. The setup considered here consists of a 5-D bulk spacetime bounded by two 4-D branes localized at the fixed points of an $S^1/Z_2$ orbifold. There is a scalar field $\phi$ in the bulk which, provided a superpotential $W(\phi)$, determines the warped geometry of the 5-D spacetime. This type of scenario is common in string theory, where the bulk scalar field $\phi$ is related to the volume of small compact extra dimensions. We show that, after the moduli are stabilized by supersymmetry breaking terms localized on the branes, the only relevant degrees of freedom in the bulk consist of a 5-D massive spectrum of gravitons. Then we analyze the gravitational interaction between massive bodies localized at the positive tension brane mediated by these bulk gravitons. It is shown that the Newtonian potential describing this interaction picks up a non-trivial contribution at short distances that depends on the shape of the superpotential $W(\phi)$. We compute this contribution for dilatonic braneworld scenarios $W(\phi) = e^{\alpha \phi}$ (where $\alpha$ is a constant) and discuss the particular case of 5-D Heterotic M-theory: It is argued that a specific footprint at micron scales could be observable in the near future.

Jumping through loops: on soft terms from large volume compactifications

We subject the phenomenologically successful large volume scenario of hep-th/0502058 to a first consistency check in string theory. In particular, we consider whether the expansion of the string effective action is consistent in the presence of D-branes and O-planes. Due to the no-scale structure at tree-level, the scenario is surprisingly robust. We compute the modification of soft supersymmetry breaking terms, and find only subleading corrections. We also comment that for large-volume limits of toroidal orientifolds and fibered Calabi-Yau manifolds the corrections can be more important, and we discuss further checks that need to be performed.

Non-trivial spacetime effects in a supersymmetric model

We study an N = 1 supersymmetric model in an S1 × R3 spacetime. We find that by choosing appropriate boundary conditions for the contributing fields supersymmetry can be preserved. However, if we add a hard supersymmetry breaking term, we observe that for small values of the length of the S1 dimension, supersymmetry remains unbroken and breaks spontaneously when the length exceeds a critical value. The final picture resembles the first-order phase transition picture. A toy cosmological application is discussed.

Supersymmetry for Fermion Masses

It is proposed that supersymmetry (SUSY) may be used to understandfermion mass hierarchies. A family symmetry Z3L is introduced,which is the cyclic symmetry among the three generation SU(2)doublets. SUSY breaks at a high energy scale ∼1011 GeV.The electroweak energy scale ∼100 GeV is unnaturally small. Noadditional global symmetry, like the R-parity, is imposed. The Yukawacouplings and R-parity violating couplings all take their natural values,which are \U0001d4aa(100∼10−2). Under the family symmetry, only the thirdgeneration charged fermions get their masses. This family symmetry isbroken in the soft SUSY breaking terms, which result in a hierarchicalpattern of the fermion masses. It turns out that for the chargedleptons, the τ mass is from the Higgs vacuum expectation value(VEV) and the sneutrino VEVs, the muon mass is due to the sneutrino VEVs,and the electron gains its mass due to both Z3L and SUSY breaking.The large neutrino mixing are produced with neutralinos playing the partialrole of right-handed neutrinos. |Ve3|, which is for νe-ντmixing, is expected to be about 0.1. For the quarks, the third generationmasses are from the Higgs VEVs, the second generation masses are fromquantum corrections, and the down quark mass due to the sneutrino VEVs. Itexplains mc/ms, ms/me, md>mu, and so on. Other aspects of themodel are discussed.

Collider and dark matter phenomenology of models with mirage unification

We examine supersymmetric models with mixed modulus-anomaly mediated SUSY breaking (MM-AMSB) soft terms which get comparable contributions to SUSY breaking from moduli-mediation and anomaly-mediation. The apparent (mirage) unification of soft SUSY breaking terms at Q=mu_mir not associated with any physical threshold is the hallmark of this scenario. The MM-AMSB structure of soft terms arises in models of string compactification with fluxes, where the addition of an anti-brane leads to an uplifting potential and a de Sitter universe, as first constructed by Kachru {\it et al.}. The phenomenology mainly depends on the relative strength of moduli- and anomaly-mediated SUSY breaking contributions, and on the Higgs and matter field modular weights, which are determined by the location of these fields in the extra dimensions. We delineate the allowed parameter space for a low and high value of tan(beta), for a wide range of modular weight choices. We calculate the neutralino relic density and display the WMAP-allowed regions. We show the reach of the CERN LHC and of the International Linear Collider. We discuss aspects of MM-AMSB models for Tevatron, LHC and ILC searches, muon g-2 and b->s \gamma branching fraction. We also calculate direct and indirect dark matter detection rates, and show that almost all WMAP-allowed models should be accessible to a ton-scale noble gas detector. Finally, we comment on the potential of colliders to measure the mirage unification scale and modular weights in the difficult case where mu_mir>>M_GUT.

Flavor Physics in SUSY Grand Unified Theories

Within Supersymmetric Grand Unified theories with soft breaking terms arising at the Planck scale, it is generally possible to link Flavor Changing Neutral Current (FCNC) and CP violating processes occurring in the leptonic and hadronic sectors. So, a correlated analysis of low-energy observables in the leptonic and hadronic sectors, can provide indications of the existence of a Grand Unified theory at high energies. We show how bounds on leptonic FCNC involving the third generation translate into constraints on FCNC B decays. Moreover, we show that, besides FCNC transitions, also lepton-flavor (LF) universality tests in M ℓ 2 decays (with M = π , K , B ), offer a unique opportunity to study the flavour structure of physics beyond the SM.