Ref HAL: hal-04771155_v1
Ref Arxiv: 2410.22400
Ref INSPIRE: 2843841
Ref. & Cit.: NASA ADS
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Flux compactifications that give three- or four-dimensional Anti de Sitter vacua with a parametrically small negative cosmological constant are claimed to be ubiquitous in String Theory. However, the 1+1 and 2+1 dimensional CFT duals to such vacua should have very large central charges and rather unusual properties. We construct brane configurations that source these would-be AdS flux compactifications, and identify certain UV AdS geometries that these branes source. The central charge of the CFT duals to these UV AdS geometries place lower bounds on the absolute values of the cosmological constants of the AdS vacua. These bounds are incompatible with the scale separation needed to construct realistic cosmological models.

Ref HAL: hal-04745819_v1
Ref Arxiv: 2410.09033
Ref INSPIRE: 2839391
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The current Large Hadron Collider (LHC) data show no clear indication of new physics and only incremental improvements are anticipated at the energy frontier in the near future. However, while the focus of the LHC has been on constraining TeV scale physics, new particles could still be hiding below the electroweak scale. In order to obtain sensitivity to a new light boson with couplings to SM fermions, a potentially promising decay channel, for resonances with mass $\gtrsim {\cal O}(10)$ GeV, would be the decay to $b\bar b$ pairs. The measurement of such signatures is challenging due to the trigger requirements at the LHC. In this work, we explore the LHC sensitivity to a light pseudoscalar, or axion-like particle (ALP), in the $b\bar{b}$ final state with an associated photon, using jet substructure techniques, in the mass range between 10 GeV and 100 GeV. We obtain projected exclusions on the ALP-fermion coupling in a region of phase space which has not so far been probed by direct searches. We further discuss the impact that lower trigger thresholds may have on the LHC reach.

Commentaires: 26 pages, 10 figures, 5 tables

Ref HAL: hal-04745663_v1
Ref Arxiv: 2309.07549
DOI: 10.1016/j.wavemoti.2024.103422
Ref. & Cit.: NASA ADS
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The scattering of scalar waves by a set of scatterers is considered. It is proven that the scattered field can be represented as an integral supported by any smooth surface enclosing the scatterers. This is a generalization of the series expansion over spherical harmonics and spherical Bessel functions for spherical geometries. More precisely, given a set of scatterers, the field scattered by any subset can be expressed as an integral over any smooth surface enclosing the given subset alone. It is then possible to solve the multiple scattering problem by using this integral representation instead of an expansion over spherical harmonics. This result is used to develop an extension of the Fast Multipole Method in order to deal with subsets that are not enclosed within non-intersecting balls.

Résumé:

Twistor space provides an efficient description of quaternion-Kahler (QK) manifolds. In physics, the latter appear as supergravity moduli spaces and often carry an isometric action of the S-duality group SL(2,Z). I’ll show that a lift of S-duality to the twistor space gives rise to a rich and interesting structure, and describe its consequences for a class of QK manifolds arising in Calabi-Yau string compactifications. In particular, this includes mock modularity of generating functions of DT invariants and the weak/strong coupling duality of topological string partition function.

Ref HAL: hal-04701156_v1
Ref Arxiv: 2409.02721
Ref INSPIRE: 2824764
Ref. & Cit.: NASA ADS
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Majorana neutrinos may have transitional dipole moments, which violate lepton number as well as lepton flavour. We estimate the sensitivity of future colliders to the electron-muon neutrino dipole moment, $\lambda_{e\mu}$, by considering same-sign dilepton final states. We find that hadron colliders, even the proposed FCC-hh upgrade, are sensitive only to $|\lambda_{e\mu}|\gtrsim 10^{-9}\mu_B$ (with $\mu_B$ the Bohr magneton), a value two-three orders of magnitude larger than current bounds from astrophysics and low-energy neutrino-scattering experiments. In the case of a future muon collider, we show that the sensitivity varies from $|\lambda_{e\mu}|\sim 5\cdot 10^{-9}\mu_B$ for energy $\sqrt{s}\simeq 3$ TeV, to $\sim 10^{-12}\mu_B$ for $\sqrt{s}\simeq 50$ TeV, matching the current laboratory bounds for $\sqrt{s}\simeq 30$ TeV. The singular advantage of the muon collider signal would be a direct, clean identification of lepton number and flavour violation. We also show that a muon collider would improve by orders of magnitude the direct bounds on $m_{e\mu}$ and $m_{\mu\mu}$, two of the entries of the Majorana neutrino mass matrix. These bounds could be as strong as $\sim 50$ keV, still far above the neutrino mass scale.

Ref HAL: hal-04694631_v1
Ref Arxiv: 2408.16819
Ref INSPIRE: 2823269
Ref. & Cit.: NASA ADS
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Generating functions of BPS indices, counting states of D4-D2-D0 black holes in Calabi-Yau compactifications of type IIA string theory and identified with rank 0 Donaldson- Thomas invariants, are examples of mock modular forms. They have a quite complicated modular anomaly expressed as a sum over three different types of trees weighted by generalized error functions and their derivatives. We show that this anomaly can be significantly simplified, which in turn simplfies finding the corresponding mock modular generating functions.

Ref HAL: hal-04693176_v1
Ref Arxiv: 2408.16674
Ref INSPIRE: 2822771
Ref. & Cit.: NASA ADS
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We extend previous next-to-next-to leading order (NNLO) calculations of the QCD pressure at zero temperature and non-zero baryonic densities using the renormalization group optimized perturbation theory (RGOPT), which entails an all-order RG-invariant resummation. First, we consider the approximation of three massless quark flavors, and then adding the running strange quark mass dependence. The resulting pressure displays a sizeably reduced sensitivity to variations of the arbitrary renormalization scale as compared to the state-of-the-art NNLO results. This confirms previous NLO investigations that the RGOPT resummation scheme provides improved convergence properties and reduced renormalization scale uncertainties, thus being a promising prescription to improve perturbative QCD at high and mid range baryonic densities.