Ref HAL: hal-05240961_v1
DOI: 10.48550/arXiv.2509.03293
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Instanton contributions in 2d string theory are known to include subtle numerical factors $ζ_n$ closely related to a contour prescription in multi-instanton string amplitudes. Both ingredients appear to be ambiguous due to a degeneracy between $(1,n)$-ZZ instantons and $n$ (1,1)-ZZ instantons in the linear dilaton background. We resolve this ambiguity using insights from the dual matrix quantum mechanics where the multipliers $ζ_n$ can be derived from an integral representation of the scattering phase and follow from the median resummation prescribed by resurgence theory. We evaluate multi-instanton string amplitudes in the theory compactified on a circle of finite radius for arbitrary number of instantons and show that they reproduce the matrix model predictions provided the Lorentzian contour prescription is used for their evaluation. We also show that the non-perturbative free energy matches the structure of the D-instanton induced string field theory effective action, which suggests the vanishing of contributions from worldsheet topologies of negative Euler number.

Ref HAL: hal-05184942_v1
Ref Arxiv: 2507.16908
Ref INSPIRE: 2953431
DOI: 10.48550/arXiv.2507.16908
Ref. & Cit.: NASA ADS
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Refined BPS indices give rise to a quantum Riemann-Hilbert problem that is inherently related to a non-commutative deformation of moduli spaces arising in gauge and string theory compactifications. We reformulate this problem in terms of a non-commutative deformation of a TBA-like equation and obtain its formal solution as an expansion in refined indices. As an application of this construction, we derive a generating function of solutions of the TBA equation in the unrefined case.

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We study Effect of top metallic contacts on energy conversion performances for near-field thermophotovoltaics. We find behaviors differing substantially from those predicted by previous simplistic approaches, with significant impact on the net radiative power absorbed by the cell and, consequently, on the generated electrical power. The design of metallic contact grids on the front side of thermophotovoltaic cells is critical since it can cause significant optical and electrical resistive losses, particularly in the near field. However, from the theoretical point of view, this effect has been either discarded or studied by means of extremely simplified models like the shadowing methods, that consist in simply ignoring the fraction of the semiconductor surface covered by metal. Our study [1], based on a rigorous three-body theoretical framework and implemented using the scattering matrix approach with the Fourier modal method augmented with adaptive spatial resolution, provides deeper insight into the influence of the front metal contact grid. This approach allows direct access to the radiative power absorbed by the semiconductor, enabling the proposal of an alternative definition for the thermophotovoltaic cell efficiency. By modeling this grid as a metallic grating, we demonstrate its significant impact on the net radiative power absorbed by the cell and, consequently, on the generated electrical power. Our analysis reveals behaviors differing substantially from those predicted by previous simplistic approaches. References1.Youssef Jeyar, Kevin Austry, Minggang Luo, Brahim Guizal, Yi Zheng, Riccardo Messina, Rodolphe Vaillon, and Mauro Antezza, arXiv:2412.04258 (2024)

Ref HAL: hal-05176981_v1
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We study Effect of top metallic contacts on energy conversion performances for near-field thermophotovoltaics. We find behaviors differing substantially from those predicted by previous simplistic approaches, with significant impact on the net radiative power absorbed by the cell and, consequently, on the generated electrical power.

Ref HAL: hal-05165381_v1
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The high chemical specificity, minimal sample preparationand the ability to use advanced optical technologies in thevisible or near-infrared spectral range have led in the lastyears to an increase in the biomedical applications of Ramanspectroscopy. Raman spectroscopy measures the inelasticscattering of light by vibrating molecules, providing thechemical fingerprints of cells, tissues or biofluids. However,as Raman scattering efficiency is quite low, requiringrelatively long acquisition times, new technologies based onBroadband Coherent Anti-Stokes Raman scattering(BCARS) was proposed [1]. This coherent Raman imagingtechnique is based on the detection of the fingerprint regionof molecules (500-1800 cm-1), as well as the higher-energyCH-/OH-stretch region (~2,700 cm−1 to 3,300 cm−1) andcould probe multiple Raman transitions simultaneously toallow imaging of biological tissues with improved molecularcontrast. When compared to spontaneous Ramanmicroscopy, BCARS microscopy provided 10-100x fasterimage acquisition for quantitative and qualitative assessmentof pharmaceuticals at much higher spatiochemical resolutionand with spectra of much higher signal-to noise ratio [2]. Inthis talk, I will present the principles of the BCARSmicroscopy we’ve developed in our laboratory and someexamples of biological applications. BCARS imaging is usedto evaluate changes underlying the lesion of a spinal cordinjury in a murine model. After injury the axonalregeneration in spinal cord is inhibited by a glial and afibrous scar, acting as a physical and chemical barrier.Recently we have reported that the signal exhibited byfibrillar collagen enabled to specifically monitor it as abiomarker of a spinal cord lesion [3]. However, the injuryand the scarring process involves also other elements as themyelin sheets, microglia, astrocytes and extracellular matrixcomponents. We demonstrate the versatility of BCARSimaging to assess the additional structural and metabolicmodifications of the injured tissue in excised murine spinalcord samples at different time points (1, 2, 4, 6 weeks) afterinjury.1) Camp Jr CH et al. Nat. Photonics 8(8), 627 (2014).2) Hartshorn CM et al. Anal. Chem. 85(17), 8102 (2013)3) C. Manesco, et al. Nanomedicine: Nanotechnology,Biology, and Medicine 53 (2023) 102699.

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DOI: 10.1016/j.optmat.2025.117293
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The normalization of multi-instanton effects in two-dimensional string theory involves numerical factors that are hard to determine. I'll show how they can be found using a chiral representation of the dual matrix quantum mechanics.The result is confirmed by a string field theory calculation of annuli amplitudes and nicely agrees with a median resummation of the Gamma function.