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Salvatore Esposito

Publications and source records attributed to Salvatore Esposito.

At least 19 recordsLinked to original sources

ROOM: A Physics-Based Continuum Robot Simulator for Photorealistic Medical Datasets Generation

Continuum robots are advancing bronchoscopy procedures by accessing complex lung airways and enabling targeted interventions. However, their development is limited by the lack of realistic training and test environments: Real data is difficult to collect due to ethical constraints and patient safety concerns, and developing autonomy algorithms requires realistic imaging and physical feedback. We present ROOM (Realistic Optical Observation in Medicine), a comprehensive simulation framework designed for generating photorealistic bronchoscopy training data. By leveraging patient CT scans, our pipeline renders multi-modal sensor data including RGB images with realistic noise and light specularities, metric depth maps, surface normals, optical flow and point clouds at medically relevant scales. We validate the data generated by ROOM in two canonical tasks for medical robotics: multi-view pose estimation and monocular depth estimation, demonstrating diverse challenges that state-of-the-art methods must overcome to transfer to these medical settings. Furthermore, we show that the data produced by ROOM can be used to fine-tune existing depth estimation models to overcome these challenges, also enabling other downstream applications such as navigation. We expect that ROOM will enable large-scale data generation across diverse patient anatomies and procedural scenarios that are challenging to capture in clinical settings. Code and data: https://github.com/iamsalvatore/room.

cs.RO↗

VesselSDF: Distance Field Priors for Vascular Network Reconstruction

Accurate segmentation of vascular networks from sparse CT scan slices remains a significant challenge in medical imaging, particularly due to the thin, branching nature of vessels and the inherent sparsity between imaging planes. Existing deep learning approaches, based on binary voxel classification, often struggle with structural continuity and geometric fidelity. To address this challenge, we present VesselSDF, a novel framework that leverages signed distance fields (SDFs) for robust vessel reconstruction. Our method reformulates vessel segmentation as a continuous SDF regression problem, where each point in the volume is represented by its signed distance to the nearest vessel surface. This continuous representation inherently captures the smooth, tubular geometry of blood vessels and their branching patterns. We obtain accurate vessel reconstructions while eliminating common SDF artifacts such as floating segments, thanks to our adaptive Gaussian regularizer which ensures smoothness in regions far from vessel surfaces while producing precise geometry near the surface boundaries. Our experimental results demonstrate that VesselSDF significantly outperforms existing methods and preserves vessel geometry and connectivity, enabling more reliable vascular analysis in clinical settings.

eess.IV↗

CrossSDF: 3D Reconstruction of Thin Structures From Cross-Sections

Reconstructing complex structures from planar cross-sections is a challenging problem, with wide-reaching applications in medical imaging, manufacturing, and topography. Out-of-the-box point cloud reconstruction methods can often fail due to the data sparsity between slicing planes, while current bespoke methods struggle to reconstruct thin geometric structures and preserve topological continuity. This is important for medical applications where thin vessel structures are present in CT and MRI scans. This paper introduces CrossSDF, a novel approach for extracting a 3D signed distance field from 2D signed distances generated from planar contours. Our approach makes the training of neural SDFs contour-aware by using losses designed for the case where geometry is known within 2D slices. Our results demonstrate a significant improvement over existing methods, effectively reconstructing thin structures and producing accurate 3D models without the interpolation artifacts or over-smoothing of prior approaches.

cs.CV↗

GeoGen: Geometry-Aware Generative Modeling via Signed Distance Functions

We introduce a new generative approach for synthesizing 3D geometry and images from single-view collections. Most existing approaches predict volumetric density to render multi-view consistent images. By employing volumetric rendering using neural radiance fields, they inherit a key limitation: the generated geometry is noisy and unconstrained, limiting the quality and utility of the output meshes. To address this issue, we propose GeoGen, a new SDF-based 3D generative model trained in an end-to-end manner. Initially, we reinterpret the volumetric density as a Signed Distance Function (SDF). This allows us to introduce useful priors to generate valid meshes. However, those priors prevent the generative model from learning details, limiting the applicability of the method to real-world scenarios. To alleviate that problem, we make the transformation learnable and constrain the rendered depth map to be consistent with the zero-level set of the SDF. Through the lens of adversarial training, we encourage the network to produce higher fidelity details on the output meshes. For evaluation, we introduce a synthetic dataset of human avatars captured from 360-degree camera angles, to overcome the challenges presented by real-world datasets, which often lack 3D consistency and do not cover all camera angles. Our experiments on multiple datasets show that GeoGen produces visually and quantitatively better geometry than the previous generative models based on neural radiance fields.

cs.CV↗

The development of the concept of exchange forces in the 1930s: close encounters between Europe and Japan and the birth of nuclear theory

The onset and the development of the concept of exchange force in quantum physics are historically reconstructed, starting from Heisenberg's seminal contributions in 1926 and going through the great developments in nuclear physics, which allowed the emergence of the idea of force mediating virtual quanta. Although most of such work was performed in Europe, the last and decisive effort in this long path was carried out by Japanese scientists in the 1930s. This is the main focus of the present work, which retraces the achievements of Yukawa and Tomonaga, whose results and mutual interactions are carefully analyzed and related to those of European physicists.

physics.hist-ph↗

Towards detecting gravitational waves: a contribution by Richard Feynman

An account of Richard Feynman's work on gravitational waves is given. Feynman's involvement with this subject can be traced backto 1957, when he attended the famous Chapel Hill conference on the Role of Gravitation in Physics. At that conference, he presented in particular the celebrated sticky bead argument, which was devised to intuitively argue that gravitational waves must carry energy, if they exist at all. While giving a simple argument in favor of the existence of gravitational waves, Feynman's thought experiment paved the way for their detection and stimulated subsequent efforts in building a practical detecting device. Feynman's contributions were systematically developed in a letter to Victor Weisskopf, completed in February 1961, as well as in his Caltech Lectures on Gravitation, delivered in 1962-63. There, a detailed calculation of the power radiated as gravitational radiation was performed, using both classical and quantum field theoretical tools, leading to a derivation of the quadrupole formula and its application to gravitational radiation by a binary star system. A comparison between the attitudes of Feynman and of the general relativity community to the problems of gravitational wave physics is drawn as well.

physics.hist-ph↗

A look inside Feynman's route to gravitation

In this contribution we report about Feynman's approach to gravitation, starting from the records of his interventions at the Chapel Hill Conference of 1957. As well known, Feynman was concerned about the relation of gravitation with the rest of physics. Probably for this reason, he promoted an unusual, field theoretical approach to general relativity, in which, after the recognition that the interaction must be mediated by the quanta of a massless spin-$2$ field, Einstein's field equations should follow from the general properties of Lorentz-invariant quantum field theory, plus self-consistency requirements. Quantum corrections would then be included by considering loop diagrams. These ideas were further developed by Feynman in his famous lectures on gravitation, delivered at Caltech in 1962-63, and in a handful of published papers, where he also introduced some field theoretical tools which were soon recognized to be of general interest, such as ghosts and the tree theorem. Some original pieces of Feynman's work on gravity are also present in a set of unpublished lectures delivered at Hughes Aircraft Company in 1966-67 and devoted primarily to astrophysics and cosmology. Some comments on the relation between Feynman's approach to gravity and his ideas on the quantum foundations of the fundamental interactions are included.

physics.hist-ph↗

A glimpse into Feynman's contributions to the debate on the foundations of quantum mechanics

The broad debate on foundational issues in quantum mechanics, which took place at the famous 1957 Chapel Hill conference on \textit{The Role of Gravitation in Physics}, is here critically analyzed with an emphasis on Richard Feynman's contributions. One of the most debated questions at Chapel Hill was whether the gravitational field had to be quantized and its possible role in wave function collapse. Feynman's arguments in favor of the quantization of the gravitational field, based essentially on a series of gedanken experiments, are here discussed. Then the related problem of the wave function collapse, for which Feynman hints to decoherence as a possible solution, is discussed. Finally, another topic is analyzed, concerning the role of the observer in a closed Universe. In this respect, Feynman's many-worlds characterization of Everett's approach at Chapel Hill is discussed, together with later contributions of his, including a kind of Schrödinger's cat paradox, which are scattered throughout the 1962-63 Lectures on Gravitation. Philosophical implications of Feynman's ideas in relation to foundational issues are also discussed.

physics.hist-ph↗

A road map for Feynman's adventures in the land of gravitation

Richard P. Feynman's work on gravitation, as can be inferred from several published and unpublished sources, is reviewed. Feynman was involved with this subject at least from late 1954 to the late 1960s, giving several pivotal contributions to it. Even though he published only three papers, much more material is available, beginning with the records of his many interventions at the Chapel Hill conference in 1957, which are here analyzed in detail, and show that he had already considerably developed his ideas on gravity. In addition he expressed deep thoughts about fundamental issues in quantum mechanics which were suggested by the problem of quantum gravity, such as superpositions of the wave functions of macroscopic objects and the role of the observer. Feynman also lectured on gravity several times. Besides the famous lectures given at Caltech in 1962-63, he extensively discussed this subject in a series of lectures delivered at the Hughes Aircraft Company in 1966-67, whose focus was on astronomy and astrophysics. All this material allows to reconstruct a detailed picture of Feynman's ideas on gravity and of their evolution until the late sixties. According to him, gravity, like electromagnetism, has quantum foundations, therefore general relativity has to be regarded as the classical limit of an underlying quantum theory; this quantum theory should be investigated by computing physical processes, as if they were experimentally accessible. The same attitude is shown with respect to gravitational waves, as is evident also from an unpublished letter addressed to Victor F. Weisskopf. In addition, an original approach to gravity, which closely mimics (and probably was inspired by) the derivation of the Maxwell equations given by Feynman in that period, is sketched in the unpublished Hughes lectures.

physics.hist-ph↗

From England to Italy: the intriguing story of Poli's engine for the King of Naples

An interesting, yet unknown, episode concerning the effective permeation of the scientific revolution in the XVIII century Kingdom of Naples (and, more generally, Italy) is recounted. The quite intriguing story of Watt's steam engine prepared for serving a Royal Estate of the King of Naples in Carditello reveals a fascinating piece of the history of that Kingdom, as well as an unknown step in the history of Watt's steam engine, whose final entrepreneurial success for the celebrated Boulton & Watt company was a direct consequence. That story unveils that, contrary to what claimed in the literature, the first introduction in Italy of the most important technological innovation of the XVIII century did not take place with the construction of the first steamship of the Mediterranean Sea, but rather 30 years before that, thanks to the incomparable work of Giuseppe Saverio Poli, a leading scholar and a very influential figure in the Kingdom of Naples. The tragic epilogue of Poli's engine testifies for its vanishing in the historical memory.

physics.hist-ph↗

A new approach to the Thomas-Fermi boundary-value problem

Given the Thomas-Fermi equation sqrt(x)phi''=phi*(3/2), this paper changes first the dependent variable by defining y(x)=sqrt(x phi(x)). The boundary conditions require that y(x) must vanish at the origin as sqrt(x), whereas it has a fall-off behaviour at infinity proportional to the power (1/2)(1-chi) of the independent variable x, chi being a positive number. Such boundary conditions lead to a 1-parameter family of approximate solutions in the form sqrt(x) times a ratio of finite linear combinations of integer and half-odd powers of x. If chi is set equal to 3, in order to agree exactly with the asymptotic solution of Sommerfeld, explicit forms of the approximate solution are obtained for all values of x. They agree exactly with the Majorana solution at small x, and remain very close to the numerical solution for all values of x. Remarkably, without making any use of series, our approximate solutions achieve a smooth transition from small-x to large-x behaviour. Eventually, the generalized Thomas-Fermi equation that includes relativistic, non-extensive and thermal effects is studied, finding approximate solutions at small and large x for small or finite values of the physical parameters in this equation.

hep-th↗

Some insight into Feynman's approach to electromagnetism

We retrace an ab initio relativistic derivation of Maxwell's equations that was developed by Feynman in unpublished notes, clarifying the analogies and the differences with analogous treatments present in the literature. Unlike the latter, Feynman's approach stands out because it considers electromagnetic potentials as primary, reflecting his ideas about the quantum foundations of electromagnetism. Some considerations about the foundations of special relativity, which are naturally suggested by this approach, are given in appendix.

physics.hist-ph↗

The physical leaky tank car problem, revisited

An exhaustive analysis of the leaky tank car problem is presented, pointing out its intriguing physical properties, which well serve to students and teachers for illustrating standard Newtonian mechanics in a highly non-standard fashion. Calculus (at a leading undergraduate level) is effectively required only to examine some details concerning the solution of the equation of motion and interesting limiting cases. Instead we let any student to appreciate all the physical content of the problem, within a proper simple model and its generalization, ranging from the motion of the leaky tank car to that of the water flowing from the car with their peculiarities. Generalizations of the problem to more than one draining hole (even with different sizes), as well as to "two-dimensional" geometries, reveal further intriguing results, culminating into a no-rotation theorem and its corollaries, thus rendering unique the problem at hand for allowing students to fully recognize the power of physical analysis.

physics.class-ph↗

The colours of Newton's Opticks: an advanced project for excellent students

We describe in detail an advanced project devised for outstanding High School (or undergraduate) students with appropriate abilities in physical reasoning (rather than with a good standard preparation), centered around the well-known historical case of Newton's theory of light and colours. The different action lines along which the project is developed are aimed to let the students involved to: 1) think as Newton did, by building step by step all his knowledge and reasoning; 2) work as Newton did, by performing the whole series of his original experiments with prisms; 3) deduce as Newton did about the nature of light and colours; 4) present the results of their activity (including physics demonstrations) to the general public, in order to test abilities in communicating what learned and discovered (including video realization published on YouTube youtube). Such didactic aim is complemented by the purpose to realize a historically informed activity, given the potential key role of the History of Physics in promoting science at a deeper level, especially when no particular training in mathematics or advanced education is required. The highly favourable reception of the project by the students involved, as well as that deserved by the uneducated people to the activities demonstrated by the students in public events, testify for the success of such work.

physics.ed-ph↗

Searching for a response: the intriguing mystery of Feynman's theoretical reference amplifier

We analyze Feynman's work on the response of an amplifier performed at Los Alamos and described in a technical report of 1946, as well as lectured on at the Cornell University in 1946-47 during his course on Mathematical Methods. The motivation for such a work was Feynman's involvement in the Manhattan Project, for which the necessity emerged of feeding the output pulses of counters into amplifiers or several other circuits, with the risk of introducing distortion at each step. In order to deal with such a problem, Feynman designed a theoretical "reference amplifier", thus enabling a characterization of the distortion by means of a benchmark relationship between phase and amplification for each frequency, and providing a standard tool for comparing the operation of real devices. A general theory was elaborated, from which he was able to deduce the basic features of an amplifier just from its response to a pulse or to a sine wave of definite frequency. Moreover, in order to apply such a theory to practical problems, a couple of remarkable examples were worked out, both for high-frequency cutoff amplifiers and for low-frequency ones. A special consideration deserves a mysteriously exceptional amplifier with best stability behavior introduced by Feynman, for which different physical interpretations are here envisaged. Feynman's earlier work then later flowed in the Hughes lectures on Mathematical Methods in Physics and Engineering of 1970-71, where he also remarked on causality properties of an amplifier, that is on certain relations between frequency and phase shift that a real amplifier has to satisfy in order not to allow output signals to appear before input ones. Quite interestingly, dispersion relations to be satisfied by the response function were introduced.

physics.hist-ph↗

Feynman's different approach to electromagnetism

We discuss a previously unpublished description of electromagnetism outlined by Richard P. Feynman in the 1960s in five handwritten pages, recently uncovered among his papers, and partly developed in later lectures. Though similar to the existing approaches deriving electromagnetism from special relativity, the present one extends a long way towards the derivation of Maxwell's equations with minimal physical assumptions. In particular, without postulating Coulomb's law, homogeneous Maxwell's equations are written down by following a route different from the standard one, i.e. first introducing electromagnetic potentials in order to write down a relativistic invariant action, which is just the inverse approach to the usual one. Also, Feynman's derivation of the Lorentz force exclusively follows from its linearity in the charge velocity and from relativistic invariance. Going further, i.e. adding the inhomogeneous Maxwell's equations, requires some more physical input, and can be done by just following conventional lines, hence this task was not pursued here. Despite its incompleteness, this way of proceeding is of great historical and epistemological significance. We also comment about its possible relevance to didactics, as an interesting supplement to usual treatments.

physics.hist-ph↗

When physics meets biology: a less known Feynman

We discuss a less known aspect of Feynman's multifaceted scientific work, centered about his interest in molecular biology, which came out around 1959 and lasted for several years. After a quick historical reconstruction about the birth of molecular biology, we focus on Feynman's work on genetics with Robert S. Edgar in the laboratory of Max Delbruck, which was later quoted by Francis Crick and others in relevant papers, as well as in Feynman's lectures given at the Hughes Aircraft Company on biology, organic chemistry and microbiology, whose notes taken by the attendee John Neer are available. An intriguing perspective comes out about one of the most interesting scientists of the XX century.

physics.hist-ph↗

The Scientific Manuscripts left Unpublished by Ettore Majorana (with outlines of his life and work)

We present a panoramic view of the main scientific manuscripts left unpublished by the brightest Italian theoretical physicist of the XX century, Ettore Majorana. We deal in particular: (i) with his very original "study" notes (the so-called "Volumetti"), already published by us in English, in 2003, c/o Kluwer Acad.Press, Dordrecht & Boston, and in the original Italian language, in 2006, c/o Zanichelli pub., Bologna, Italy; and (ii) with a selection of his research notes (the so-called "Quaderni"), that we shall publish c/o Springer, Berlin. We seize the present opportunity for setting forth also some suitable -scarcely known- information about Majorana's life and work, on the basis of documents (letters, testimonies, different documents...) discovered or collected by ourselves during the last decades. [A finished, enlarged version of this paper will appear as the editors' Preface, at the beginning of the coming book "Ettore Majorana - Unpublished Research Notes on Theoretical Physics", edited by S.Esposito, E.Recami, A.van der Merwe and R.Battiston, to be printed by Springer verlag, Berlin].

physics.hist-ph↗