arXiv subjects

Andrea Conti

Publications and source records attributed to Andrea Conti.

At least 37 records · Page 2Linked to original sources

arXiv2025

$\mathcal{N}=6$ supersymmetric AdS$_2 \times \mathbb{CP}^3\times Σ_2 $

We perform a complete classification of AdS$_2$ solutions of Type II supergravity realising $\mathcal{N}=6$ supersymmetry and OSp$(6|2)$ superconformal symmetry on backgrounds that are foliations of AdS$_2 \times \mathbb{CP}^3$ over a Riemann surface $Σ_2$. Such solutions only exist in type IIB supergravity and are in 1 to 1 correspondence with a fourth order PDE that can be locally solved in terms of two holomorphic functions. Particular solutions in the class are the T-duals of the $\text{AdS}_3\times \mathbb{CP}^3$ and $\text{AdS}_2\times \text{S}^7$ solutions to massive Type IIA supergravity found in the literature. We discuss the field theory interpretation of the two sub-classes of solutions related to $\text{AdS}_3\times \mathbb{CP}^3$ by Abelian and non-Abelian T-duality, which provide explicit examples for the Riemann surface an annulus or a strip. In the second case we interpret the solutions as holographic duals to baryon vertex configurations realised in D2-brane box models.

hep-th↗

arXiv2025

Active Stereo in the Wild through Virtual Pattern Projection

This paper presents a novel general-purpose guided stereo paradigm that mimics the active stereo principle by replacing the unreliable physical pattern projector with a depth sensor. It works by projecting virtual patterns consistent with the scene geometry onto the left and right images acquired by a conventional stereo camera, using the sparse hints obtained from a depth sensor, to facilitate the visual correspondence. Purposely, any depth sensing device can be seamlessly plugged into our framework, enabling the deployment of a virtual active stereo setup in any possible environment and overcoming the severe limitations of physical pattern projection, such as the limited working range and environmental conditions. Exhaustive experiments on indoor and outdoor datasets featuring both long and close range, including those providing raw, unfiltered depth hints from off-the-shelf depth sensors, highlight the effectiveness of our approach in notably boosting the robustness and accuracy of algorithms and deep stereo without any code modification and even without re-training. Additionally, we assess the performance of our strategy on active stereo evaluation datasets with conventional pattern projection. Indeed, in all these scenarios, our virtual pattern projection paradigm achieves state-of-the-art performance. The source code is available at: https://github.com/bartn8/vppstereo.

cs.CV↗

arXiv2025

${\cal N}=(4,4)$ supersymmetric AdS$_3$ solutions in $d=11$

We derive necessary and sufficient conditions for AdS$_3$ solutions of $d=11$ supergravity to preserve ${\cal N}=(1,1)$ supersymmetry in terms of G-structures. Such solutions necessarily support an SU(3)-structure on the internal 8-manifold M$_8$, in terms of which we phrase the conditions for supersymmetry preservation. We use this to derive the local form of all ${\cal N}=(4,4)$ supersymmetric AdS$_3$ solutions in $d=11$, for which M$_8$ decomposes as a foliation of a 3-sphere over a 5 dimensional base. There are 3 independent classes, 2 of which preserve the small superconformal algebra and one preserving its large counterpart for which M$_5$ contains a second 3-sphere. We show that for each solution with large (4,4) supersymmetry there are two corresponding solutions with small $(4,4)$, one for which M$_5$ maintains its 3-sphere, one where this blows up to $\mathbb{R}^3$ which can be compactified to $\mathbb{T}^3$. We use our results to construct several new solutions that lie within our derived classes as well as recovering some existing solutions.

hep-th↗

arXiv2025

ToF-Splatting: Dense SLAM using Sparse Time-of-Flight Depth and Multi-Frame Integration

Time-of-Flight (ToF) sensors provide efficient active depth sensing at relatively low power budgets; among such designs, only very sparse measurements from low-resolution sensors are considered to meet the increasingly limited power constraints of mobile and AR/VR devices. However, such extreme sparsity levels limit the seamless usage of ToF depth in SLAM. In this work, we propose ToF-Splatting, the first 3D Gaussian Splatting-based SLAM pipeline tailored for using effectively very sparse ToF input data. Our approach improves upon the state of the art by introducing a multi-frame integration module, which produces dense depth maps by merging cues from extremely sparse ToF depth, monocular color, and multi-view geometry. Extensive experiments on both synthetic and real sparse ToF datasets demonstrate the viability of our approach, as it achieves state-of-the-art tracking and mapping performances on reference datasets.

cs.CV↗

arXiv2025

AdS$_3$ T-duality and evidence for ${\cal N}=5,6$ superconformal quantum mechanics

We construct two families of AdS$_2$ vacua in Type IIB Supergravity performing U(1) and SL(2) T-dualities on the $\text{AdS}_3 \times \text{$ \widehat{\mathbb{CP}}\!\!~^3$} \times $ I solutions to Type IIA recently reported in arXiv:2304.12207. Depending on the T-duality we operate, we find two different classes of solutions of the type $\text{AdS}_2 \times \text{$ \widehat{\mathbb{CP}}\!\!~^3$} \times $ I $\times$ I and $\text{AdS}_3 \times \text{$ \widehat{\mathbb{CP}}\!\!~^3$} \times $ I $\times$ S$^1$. This provides evidence for more general classes of solutions $\text{AdS}_2 \times \text{$ \widehat{\mathbb{CP}}\!\!~^3$} \times Σ$, dual to superconformal quantum mechanics with ${\cal N}=5,6$ supersymmetry.

hep-th↗

arXiv2024

Satellite-Terrestrial Quantum Networks and the Global Quantum Internet

This paper will explore the design and implementation of quantum networks in space integrated with quantum networks on Earth. We propose a three-layer approach, involving GEO and LEO satellites integrated with terrestrial ground stations. We first analyze the channel conditions between the three layers, and then highlight the key role of LEO satellites in the integrated space-terrestrial system - namely the source of entanglement distribution between specified terrestrial stations via direct downlink quantum-optical channels. The GEO satellites in the considered system are used primarily as coordination stations, managing and directing the LEO satellites regarding the positioning and timing of entanglement distribution. Complexity, in the form of entanglement distillation and quantum-state correction, is concentrated at the terrestrial stations, and teleportation is used as the primary quantum channel in the LEO uplinks and the inter-terrestrial channels. Although our designs are futuristic in that they assume limited quantum memory at the transceivers, we also discuss some near-term uses of our network in which no quantum memory is available.

quant-ph↗

arXiv2024

Stoichiometric reconstruction of the Al$_{2}$O$_{3}$(0001) surface

Macroscopic properties of materials stem from fundamental atomic-scale details, yet for insulators, resolving surface structures remains a challenge. The basal (0001) plane of $α$-Al$_{2}$O$_{3}$ was imaged with noncontact atomic force microscopy with an atomically-defined tip apex. The surface forms a complex $({\sqrt31} {\times} {\sqrt31})R{\pm}9°$ reconstruction. The lateral positions of the individual O and Al surface atoms come directly from experiment; how these connect to the underlying crystal bulk was determined based on computational modeling. Before the restructuring, the surface Al atoms assume an unfavorable, threefold planar coordination; the reconstruction allows a rehybridization with subsurface O that leads to a substantial energy gain. The reconstructed surface remains stoichiometric, Al$_{2}$O$_{3}$.

cond-mat.mtrl-sci↗

arXiv2024

Depth on Demand: Streaming Dense Depth from a Low Frame Rate Active Sensor

High frame rate and accurate depth estimation plays an important role in several tasks crucial to robotics and automotive perception. To date, this can be achieved through ToF and LiDAR devices for indoor and outdoor applications, respectively. However, their applicability is limited by low frame rate, energy consumption, and spatial sparsity. Depth on Demand (DoD) allows for accurate temporal and spatial depth densification achieved by exploiting a high frame rate RGB sensor coupled with a potentially lower frame rate and sparse active depth sensor. Our proposal jointly enables lower energy consumption and denser shape reconstruction, by significantly reducing the streaming requirements on the depth sensor thanks to its three core stages: i) multi-modal encoding, ii) iterative multi-modal integration, and iii) depth decoding. We present extended evidence assessing the effectiveness of DoD on indoor and outdoor video datasets, covering both environment scanning and automotive perception use cases.

cs.CV↗

arXiv2024

Half-BPS Janus solutions in AdS$_7$

We study half-BPS flows in gauged minimal 7d supergravity featured by an AdS$_3\times S^3$ slicing of the metric, supported by a dyonic three-form field. We first present a novel strategy for analytic integration of the BPS equations, which makes use of the integrals of motion. Subsequently, we discuss the suitable choice of integration constants that gives rise to smooth geometries. These flows are asymptotically locally AdS$_7$ in their UV limit, while their IR geometry is AdS$_3\times \mathbb{R}^4$. We then discuss their uplifts to 11d and massive IIA supergravity and observe that they describe one-parameter deformations of their AdS$_7\times S^4$ and AdS$_7\times S^3$ vacua, respectively, their holographic interpretation being as conformal defect CFT$_2$'s within the corresponding dual SCFT$_6$'s. We conclude with the computation of the holographic central charge, by focussing on the M-theory interpretation.

hep-th↗

arXiv2024

Deconstruction and surface defects in 6d CFTs

We study the two families of AdS$_3\times S^3\times S^2\times Σ_2$ solutions to massive Type IIA supergravity with small and large $(0,4)$ supersymmetries constructed recently in the literature, in connection with the AdS$_7\times S^2\times I$ solutions to massive Type IIA, to which they asymptote locally. Based on our analysis of various observables, that we study holographically, we propose an interpretation of the first class of solutions as dual to deconstructed 6d (1,0) CFTs dual to AdS$_7$, and of the second class as dual to surface defects in the same 6d theories. Among the observables that we study are baryon vertices and giant graviton configurations in quiver-like constructions.

hep-th↗

arXiv2024

LiDAR-Event Stereo Fusion with Hallucinations

Event stereo matching is an emerging technique to estimate depth from neuromorphic cameras; however, events are unlikely to trigger in the absence of motion or the presence of large, untextured regions, making the correspondence problem extremely challenging. Purposely, we propose integrating a stereo event camera with a fixed-frequency active sensor -- e.g., a LiDAR -- collecting sparse depth measurements, overcoming the aforementioned limitations. Such depth hints are used by hallucinating -- i.e., inserting fictitious events -- the stacks or raw input streams, compensating for the lack of information in the absence of brightness changes. Our techniques are general, can be adapted to any structured representation to stack events and outperform state-of-the-art fusion methods applied to event-based stereo.

cs.CV↗

arXiv2024

NH$_3$ adsorption and competition with H$_2$O on a hydroxylated aluminosilicate surface

The interaction between ammonia (NH$_3$) and (alumino)silicates is of fundamental and applied importance, yet the specifics of NH$_3$ adsorption on silicate surfaces remain largely unexplored, mainly because of experimental challenges related to their electrically insulating nature. An example of this knowledge gap is evident in the context of ice nucleation on silicate dust, wherein the role of NH$_3$ for ice nucleation remains debated. This study explores the fundamentals of the interaction between NH$_3$ and microcline feldspar (KAlSi$_3$O$_8$), a common aluminosilicate with outstanding ice nucleation abilities. Atomically resolved non-contact atomic force microscopy, x-ray photoelectron spectroscopy, and density functional theory-based calculations elucidate the adsorption geometry of NH$_3$ on the lowest-energy surface of microcline, the (001) facet, and its interplay with surface hydroxyls and molecular water. NH$_3$ and H$_2$O are found to adsorb molecularly in the same adsorption sites, creating H-bonds with the proximate surface silanol (Si-OH) and aluminol (Al-OH) groups. Despite the closely matched adsorption energies of the two molecules, NH$_3$ readily yields to replacement by H$_2$O, challenging the notion that ice nucleation on microcline proceeds via the creation of an ordered H$_2$O layer atop pre-adsorbed NH$_3$ molecules.

cond-mat.mes-hall↗

arXiv2024

$p$-adic rigidity of eigenforms of infinite slope

We give a notion of $p$-adic families of Hecke eigenforms that allows for the slope of the forms be infinite at $p$. We prove that, contrary to the case of finite slope when every eigenform lives in a Hida or Coleman family, the only families of infinite slope are either twists of Hida or Coleman families with Dirichlet characters of $p$-power conductor, or non-ordinary families with complex multiplication. Our proof goes via a local study of deformations of potentially trianguline Galois representations, relying on work of Berger and Chenevier, and a global input coming from an analogue of a result of Balasubramanyam, Ghate and Vatsal on a Greenberg-type conjecture for families of Hilbert modular forms.

math.NT↗

arXiv2024

Range-Agnostic Multi-View Depth Estimation With Keyframe Selection

Methods for 3D reconstruction from posed frames require prior knowledge about the scene metric range, usually to recover matching cues along the epipolar lines and narrow the search range. However, such prior might not be directly available or estimated inaccurately in real scenarios -- e.g., outdoor 3D reconstruction from video sequences -- therefore heavily hampering performance. In this paper, we focus on multi-view depth estimation without requiring prior knowledge about the metric range of the scene by proposing RAMDepth, an efficient and purely 2D framework that reverses the depth estimation and matching steps order. Moreover, we demonstrate the capability of our framework to provide rich insights about the quality of the views used for prediction. Additional material can be found on our project page https://andreaconti.github.io/projects/range_agnostic_multi_view_depth.

cs.CV↗

arXiv2023

Revisiting Depth Completion from a Stereo Matching Perspective for Cross-domain Generalization

This paper proposes a new framework for depth completion robust against domain-shifting issues. It exploits the generalization capability of modern stereo networks to face depth completion, by processing fictitious stereo pairs obtained through a virtual pattern projection paradigm. Any stereo network or traditional stereo matcher can be seamlessly plugged into our framework, allowing for the deployment of a virtual stereo setup that is future-proof against advancement in the stereo field. Exhaustive experiments on cross-domain generalization support our claims. Hence, we argue that our framework can help depth completion to reach new deployment scenarios.

cs.CV↗

arXiv2023

How water binds to microcline feldspar (001)

Microcline feldspar (KAlSi$_3$O$_8$) is a common mineral with important roles for Earth's ecological balance. It participates in the carbon, potassium, and water cycles, contributing to CO$_2$ sequestration, soil formation, and atmospheric ice nucleation. To understand the fundamentals of these processes, it is essential to establish microcline's surface atomic structure and its interaction with the omnipresent water molecules. This work presents atomic-scale results on microcline's lowest-energy surface and its interaction with water, combining ultrahigh vacuum investigations by non-contact atomic force microscopy and X-ray photoelectron spectroscopy with density functional theory calculations. An ordered array of hydroxyls bonded to silicon or aluminum readily forms on the cleaved surface at room temperature. The distinct proton affinities of these hydroxyls influence the arrangement and orientation of the first water molecules binding to the surface, holding potential implications for the subsequent condensation of water.

cond-mat.mes-hall↗

arXiv2023

Active Stereo Without Pattern Projector

This paper proposes a novel framework integrating the principles of active stereo in standard passive camera systems without a physical pattern projector. We virtually project a pattern over the left and right images according to the sparse measurements obtained from a depth sensor. Any such devices can be seamlessly plugged into our framework, allowing for the deployment of a virtual active stereo setup in any possible environment, overcoming the limitation of pattern projectors, such as limited working range or environmental conditions. Experiments on indoor/outdoor datasets, featuring both long and close-range, support the seamless effectiveness of our approach, boosting the accuracy of both stereo algorithms and deep networks.

cs.CV↗

arXiv2023

Resolving the intrinsic short-range ordering of K$^+$ ions on cleaved muscovite mica

Muscovite mica, KAl$_2$(Si$_3$Al)O$_{10}$(OH)$_2$, is a common layered phyllosilicate with perfect cleavage planes. The atomically flat surfaces obtained through cleaving lend themselves to scanning probe techniques with atomic resolution and are ideal to model minerals and clays. Despite the importance of the cleaved mica surfaces, several questions remain unresolved. It is established that K$^+$ ions decorate the cleaved surface, but their intrinsic ordering -- unaffected by the interaction with the environment -- is not known. This work presents clear images of the K$^+$ distribution of cleaved mica obtained with low-temperature non-contact atomic force microscopy (AFM) under ultra-high vacuum (UHV) conditions. The data unveil the presence of short-range ordering, contrasting previous assumptions of random or fully ordered distributions. Density functional theory (DFT) calculations and Monte Carlo simulations show that the substitutional subsurface Al$^{3+}$ ions have an important role for the surface K$^+$ ion arrangement.

cond-mat.mtrl-sci↗