arXiv subjects

E. Dudas

Publications and source records attributed to E. Dudas.

At least 19 recordsLinked to original sources

arXiv2025

Supersymmetry Breaking with Fields, Strings and Branes

The first part of this review tries to provide a self-contained view of supersymmetry breaking from the bottom-up perspective. We thus describe N=1 supersymmetry in four dimensions, the Standard Model and the MSSM, with emphasis on the ``soft terms'' that can link it to supergravity. The second part deals with the top-down perspective. It addresses, insofar as possible in a self-contained way, the basic setup provided by ten-dimensional strings and their links with supergravity, toroidal orbifolds, Scherk-Schwarz deformations and Calabi-Yau reductions, before focusing on a line of developments that is closely linked to our own research. Its key input is drawn from ten-dimensional non-tachyonic string models where supersymmetry is absent or non-linearly realized, and runaway ``tadpole potentials'' deform the ten-dimensional Minkowski vacua. We illustrate the perturbative stability of the resulting most symmetrical setups, which are the counterparts of circle reduction but involve internal intervals. We then turn to a discussion of fluxes in Calabi-Yau vacua and the KKLT setup, and conclude with some aspects of Cosmology, emphasizing some intriguing clues that the tadpole potentials can provide for the onset of inflation. The appendices collect some useful material on global and local N=1 supersymmetry, in components and in superspace, on string vacuum amplitudes, and on convenient tools used to examine the fluctuations of non-supersymmetric string vacua.

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arXiv2024

Rigid Vacua with Brane Supersymmetry Breaking

We construct new string vacua featuring Brane Supersymmetry Breaking, based on $T^4/\mathbb{Z}_N$ orientifolds with $\text{O}5_+$ planes and $\overline{\text{D}5}$ branes. Differently from the original construction, in these vacua the cancellation of twisted R-R charges of D-branes and orientifold planes is achieved in a non-trivial way, and results in rigid configurations with few open-string moduli, which highly restrict the possible deformations of the model. The breaking of supersymmetry and, consequently, the non-vanishing untwisted and twisted NS-NS tadpoles, generates a rich potential both for the dilaton and the blown-up moduli. We also uncover the stringy origin of the $J$ form entering the gauge kinetic functions in the low-energy effective action, and display its relation to the NS-NS tadpoles for the scalars in the tensor multiplets. As a result, the $J$ form can be consistently identified also when supersymmetry is broken, thus solving an embarrassing puzzle related to its very existence. We also discuss the unitarity constraints for one-dimensional defects in these vacua, where the Ka$\check{\text{c}}$-Moody algebra for D9 and $\overline{\text{D}5}$ can be realised both in the left-moving and right-moving sectors.

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arXiv2020

Chiral Froggatt-Nielsen models, gauge anomalies and flavourful axions

We study UV-complete Froggatt-Nielsen-like models for the generation of mass and mixing hierarchies, assuming that the integrated heavy fields are chiral with respect to an abelian Froggatt-Nielsen symmetry. It modifies the mixed anomalies with respect to the Standard Model gauge group, which opens up the possibility to gauge the Froggatt-Nielsen symmetry without the need to introduce additional spectator fermions, while keeping mass matrices usually associated to anomalous flavour symmetries. We give specific examples where this happens, and we study the flavourful axion which arises from an accidental Peccei-Quinn symmetry in some of those models. Such an axion is typically more coupled to matter than in models with spectator fermions.

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arXiv2017

A superfield constraint for N=2 --> N=0 breaking

We identify a cubic holomorphic constraint that subtends the total breaking of N=2 supersymmetry in a vector multiplet and exhibit its microscopic origin. The new constraint leaves behind, at low energies, a vector and the two goldstini, in a non-linear Lagrangian that generalizes the N=2 Volkov-Akulov model.

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arXiv2016

On the origin of constrained superfields

In this work we analyze constrained superfields in supersymmetry and supergravity. We propose a constraint that, in combination with the constrained goldstino multiplet, consistently removes any selected component from a generic superfield. We also describe its origin, providing the operators whose equations of motion lead to the decoupling of such components. We illustrate our proposal by means of various examples and show how known constraints can be reproduced by our method.

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arXiv2015

Properties of Nilpotent Supergravity

We construct Supergravity models where the goldstino multiplet has a gravitational origin, being dual to the chiral curvature superfield. Supersymmetry is nonlinearly realized due to a nilpotent constraint, while the goldstino arises from $γ$-traces of the gauge-invariant gravitino field strength. After duality transformations one recovers, as expected, the standard Volkov-Akulov Lagrangian coupled to Supergravity, but the gravitational origin of the goldstino multiplet restricts the available types of matter couplings. We also construct explicitly some inflationary models of this type, which contain both the inflaton and the nilpotent superfield.

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arXiv2015

Effective operators in SUSY, superfield constraints and searches for a UV completion

We discuss the role of a class of higher dimensional operators in 4D N=1 supersymmetric effective theories. The Lagrangian in such theories is an expansion in momenta below the scale of "new physics" ($Λ$) and contains the effective operators generated by integrating out the "heavy states" above $Λ$ present in the UV complete theory. We go beyond the "traditional" leading order in this momentum expansion (in $\partial/Λ$). Keeping manifest supersymmetry and using superfield {\it constraints} we show that the corresponding higher dimensional (derivative) operators in the sectors of chiral, linear and vector superfields of a Lagrangian can be "unfolded" into second-order operators. The "unfolded" formulation has only polynomial interactions and additional massive superfields, some of which are ghost-like if the effective operators were {\it quadratic} in fields. Using this formulation, the UV theory emerges naturally and fixes the (otherwise unknown) coefficient and sign of the initial (higher derivative) operators. Integrating the massive fields of the "unfolded" formulation generates an effective theory with only polynomial effective interactions relevant for phenomenology. We also provide several examples of "unfolding" of theories with higher derivative {\it interactions} in the gauge or matter sectors that are actually ghost-free. We then illustrate how our method can be applied even when including {\it all orders} in the momentum expansion, by using an infinite set of superfield constraints and an iterative procedure, with similar results.

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arXiv2014

The Minimal Volkov - Akulov - Starobinsky Supergravity

We construct a supergravity model whose scalar degrees of freedom arise from a chiral superfield and are solely a scalaron and an axion that is very heavy during the inflationary phase. The model includes a second chiral superfield $X$, which is subject however to the constraint $X^2=0$ so that it describes only a Volkov - Akulov goldstino and an auxiliary field. We also construct the dual higher - derivative model, which rests on a chiral scalar curvature superfield ${\cal R}$ subject to the constraint ${\cal R}^2=0$, where the goldstino dual arises from the gauge - invariant gravitino field strength as $γ^{mn} {\cal D}_m ψ_n$. The final bosonic action is an $R+R^2$ theory involving an axial vector $A_m$ that only propagates a physical pseudoscalar mode.

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arXiv2012

CMB Imprints of a Pre-Inflationary Climbing Phase

We discuss the implications for cosmic microwave background (CMB) observables, of a class of pre-inflationary dynamics suggested by string models where SUSY is broken due to the presence of D-branes and orientifolds preserving incompatible portions of it. In these models the would-be inflaton is forced to emerge from the initial singularity climbing up a mild exponential potential, until it bounces against a steep exponential potential of "brane SUSY breaking" scenarios, and as a result the ensuing descent gives rise to an inflationary epoch that begins when the system is still well off its eventual attractor. If a pre-inflationary climbing phase of this type had occurred within 6-7 e-folds of the horizon exit for the largest observable wavelengths, displacement off the attractor and initial-state effects would conspire to suppress power in the primordial scalar spectrum, enhancing it in the tensor spectrum and typically superposing oscillations on both. We investigate these imprints on CMB observables over a range of parameters, examine their statistical significance, and provide a semi-analytic rationale for our results. It is tempting to ascribe at least part of the large-angle anomalies in the CMB to pre-inflationary dynamics of this type.

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arXiv2012

On non-universal Goldstino couplings to matter

Using the constrained superfields formalism to describe the interactions of a light goldstino to matter fields in supersymmetric models, we identify generalised, higher-order holomorphic superfield constraints that project out the superpartners and capture the non-universal couplings of the goldstino to matter fields. These arise from microscopic theories in which heavy superpartners masses are of the order of the supersymmetry breaking scale (\sqrt f). In the decoupling limit of infinite superpartners masses, these constraints reduce to the familiar, lower-order universal constraints discussed recently, that describe the universal goldstino-matter fields couplings, suppressed by inverse powers of \sqrt f. We initiate the study of the couplings of the Standard Model (SM) fields to goldstino in the constrained superfields formalism.

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arXiv2011

Non-linear MSSM

Using the formalism of constrained superfields, we derive the most general effective action of a light goldstino coupled to the minimal supersymmetric standard model (MSSM) and study its phenomenological consequences. The goldstino-induced couplings become important when the (hidden sector) scale of spontaneous supersymmetry breaking, $\sqrt f$, is relatively low, of the order of few TeV. In particular, we compute the Higgs potential and show that the (tree level) mass of the lightest Higgs scalar can be increased to the LEP bound for $\sqrt f\sim 2$ TeV to 7 TeV. Moreover, the effective quartic Higgs coupling is increased due to additional tree-level contributions proportional to the ratio of visible to hidden sector supersymmetry breaking scales. This increase can alleviate the amount of fine tuning of the electroweak scale that exists in the MSSM. Among the new goldstino couplings, beyond those in MSSM, the most important ones generate an invisible decay of the Higgs boson into a goldstino and neutralino (if m_h>m_{χ_1^0}), with a partial decay rate that can be comparable to the SM channel h^0-> γγ. A similar decay of Z boson is possible if m_Z>m_{χ_1^0} and brings a lower bound on $\sqrt f$ that must be of about 700 GeV. Additional decay modes of the Higgs or Z bosons into a pair of light goldstinos, while possible, are suppressed by an extra 1/f factor and have no significant impact on the model.

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arXiv2011

Beyond the MSSM Higgs with d=6 effective operators

We continue a previous study of the MSSM Higgs Lagrangian extended by all effective operators of dimension d=6 that can be present beyond the MSSM, consistent with its symmetries. By supersymmetry, such operators also extend the neutralino and chargino sectors, and the corresponding component fields Lagrangian is computed onshell. The corrections to the neutralino and chargino masses, due to these operators, are computed analytically in function of the MSSM corresponding values. For individual operators, the corrections are small, of few GeV for the constrained MSSM (CMSSM) viable parameter space. We investigate the correction to the lightest Higgs mass, which receives, from individual operators, a supersymmetric correction of up to 4 (6) GeV above the 2-loop leading-log CMSSM value, from those CMSSM phase space points with: EW fine tuning Delta<200, consistent with WMAP relic density (3$σ$), and for a scale of the operators of M=10 (8) TeV, respectively. Applied to the CMSSM point of minimal fine tuning (Delta=18), such increase gives an upper limit $m_h=120(122)\pm 2$ GeV, respectively. The increase of m_h from individual operators can be larger ($\sim$ 10-30 GeV) for those CMSSM phase space points with Delta>200; these can now be phenomenologically viable, with reduced Delta, and this includes those points that would have otherwise violated the LEP2 bound by this value. The neutralino/chargino Lagrangian extended by the effective operators can be used in studies of dark matter relic density within extensions of the MSSM, by implementing it in public codes like micrOMEGAs.

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arXiv2011

Goldstino and sgoldstino in microscopic models and the constrained superfields formalism

We examine the exact relation between the superconformal symmetry breaking chiral superfield (X) and the goldstino superfield in microscopic models of an arbitrary Kahler potential (K) and in the presence of matter fields. We investigate the decoupling of the massive sgoldstino and scalar matter fields and the offshell/onshell-SUSY expressions of their superfields in terms of the fermions composites. For general K of two superfields, we study the properties of the superfield X after integrating out these scalar fields, to show that in the infrared it satisfies (offshell) the condition $X^3=0$ and $X^2\not=0$. We then compare our results to those of the well-known method of constrained superfields discussed in the literature, based on the conjecture $X^2=0$. Our results can be used in applications, to couple offshell the (s)goldstino fields to realistic models such as the MSSM.

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arXiv2010

On Climbing Scalars in String Theory

In string models with "brane supersymmetry breaking" exponential potentials emerge at (closed-string) tree level but are not accompanied by tachyons. Potentials of this type have long been a source of embarrassment in flat space, but can have interesting implications for Cosmology. For instance, in ten dimensions the logarithmic slope |V'/V| lies precisely at a "critical" value where the Lucchin--Matarrese attractor disappears while the scalar field is \emph{forced} to climb up the potential when it emerges from the Big Bang. This type of behavior is in principle perturbative in the string coupling, persists after compactification, could have trapped scalar fields inside potential wells as a result of the cosmological evolution and could have also injected the inflationary phase of our Universe.

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arXiv2010

Non-perturbative Vacuum Destabilization and D-brane Dynamics

We analyze the process of string vacuum destabilization due to instanton induced superpotential couplings which depend linearly on charged fields. These non-perturbative instabilities result in potentials for the D-brane moduli and lead to processes of D-brane recombination, motion and partial moduli stabilization at the non-perturbative vacuum. By using techniques of D-brane instanton calculus, we explicitly compute this scalar potential in toroidal orbifold compactifications with magnetized D-branes by summing over the possible discrete instanton configurations. We illustrate explicitly the resulting dynamics in globally consistent models. These instabilities can have phenomenological applications to breaking hidden sector gauge groups, open string moduli stabilization and supersymmetry breaking. Our results suggest that breaking supersymmetry by Polonyi-like models in string theory is more difficult than expected.

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arXiv2010

MSSM Higgs with dimension-six operators

We investigate an extension of the MSSM Higgs sector by including the effects of all dimension-five and dimension-six effective operators and their associated supersymmetry breaking terms. The corrections to the masses of the neutral CP-even and CP-odd Higgs bosons due to the d=5 and d=6 operators are computed. When the d=5 and d=6 operators are generated by the same physics (i.e. when suppressed by powers of the same scale M), due to the relative $\tanβ$ enhancement of the latter, which compensates their extra scale suppression (1/M), the mass corrections from d=6 operators can be comparable to those of d=5 operators, even for conservative values of the scale M. We identify the effective operators with the largest individual corrections to the lightest Higgs mass and discuss whether at the microscopic level and in the simplest cases, these operators are generated by "new physics" with a sign consistent with an increase of m_h. Simple numerical estimates easily allow an increase of m_h due to d=6 operators alone in the region of 10-30 GeV, while for a much larger increase light new states beyond MSSM may be needed, in which case the effective description is unreliable. Special attention is paid to the treatment of the effective operators with higher derivatives. These can be removed by non-linear field redefinitions or by an "unfolding" technique, which effectively ensure that any ghost degrees of freedom (of mass $\geqsim M$) are integrated out and absent in the effective theory at scales much smaller than M. Considering general coefficients of the susy operators with a scale of new physics above the LHC reach, it is possible to increase the tree-level prediction for the Higgs mass to the LEPII bound, thus alleviating the MSSM fine-tuning.

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arXiv2009

Stringy Instanton Effects in Models with Rigid Magnetised D-branes

We compute instantonic effects in globally consistent T^6/Z2xZ2 orientifold models with discrete torsion and magnetised D-branes. We consider fractional branes and instantons wrapping the same rigid cycles. We clarify and analyse in detail the low-energy effective action on D-branes in these models. We provide explicit examples where instantons induce linear terms in the charged fields, or non-perturbative mass terms are generated. We also find examples where the gauge theory on fractional branes has conformal symmetry at one-loop, broken by instantonic mass terms at a hierarchically small energy scale.

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arXiv2009

(In)visible Z' and dark matter

We study the consequences of an extension of the standard model containing an invisible extra gauge group under which the SM particles are neutral. We show that effective operators, generated by loops of heavy chiral fermions charged under both gauge groups and connecting the new gauge sector to the Standard Model, can give rise to a viable dark matter candidate. Its annihilations produce clean visible signals through a gamma-ray line. This would be a smoking gun signature of such models observable by actual experiments.

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