Cimento Research Articles

The birth of StatPhys: the 1949 Florence conference at the juncture of national and international physics reconstruction after World War II

In spring 1949 about 70 physicists from eight countries met in Florence to discuss recent trends in statistical mechanics. This scientific gathering, co-organized by the Commission on Thermodynamics and Statistical Mechanics of the International Union of Pure and Applied Physics (IUPAP) and the Italian Physical Society (SIF), initiated a tradition of IUPAP-sponsored international conferences on statistical mechanics that lasts to this day. In 1977, when this conference series took the name of StatPhys, the foundational role of the Florence conference was recognized by retrospectively naming it StatPhys1. This paper examines the dual scientific and social significance of the conference, situating it in the broader contexts of the post-World War II reconstruction in Italian physics and of the revitalization of the international science organization. Through an analysis of IUPAP archives and Italian records, we illustrate how the event’s success hinged on the aligned objectives of its organizers. Internationally, it was instrumental in defining the scientific and organizational foundations for the activities of IUPAP commissions during a critical phase of IUPAP’s history, when the Union was resurging on the international scene after the inactivity of the interwar period. Nationally, the conference served as a cornerstone in SIF’s strategy to re-establish Italian physics’ international stature and to aid the domestic revitalization of physics through the internationalization of its activities, notably of its flagship journal, Il Nuovo Cimento. This analysis not only sheds light on the conference’s impact but also informs recent discussions in the history of science about the multiple roles of international scientific conferences.

Sengupta transformations and Carrollian relativistic theory

A detailed and systematic formulation of Carrollian relativity is provided. Based on the transformations, first provided by Sengupta (Nuovo Cim, 54:512, 1966), we construct a mapping between Lorentz relativistic and Carrollian relativistic vectors. Using this map the Carroll theory is built from the standard Maxwell action. We show that we get self-consistent equations of motion from the action, both in electric and magnetic limits. We introduce Carroll electric and magnetic fields. A new set of maps is derived that connects Carroll electric and magnetic fields with the usual Maxwell ones and yields Carroll equations in terms of fields. Consistency of results with the potential formulation is shown. Carroll version of symmetries like duality, gauge, shift, Noether and boost are treated in details and their implications elaborated. Especially, boost symmetry provides a link to the various maps used in this paper.

A Study on Cosmological Model of Anisotropic Universe with Electromagnetic Field and Cloud Strings in the Frame Work of General Relativity

In this study, we have investigated the Bianchi type-III anisotropic cosmological model in the presence of cloud strings with the electromagnetic field in the general theory of relativity. Exact solutions of field equations are obtained using the fact that shear scalar is proportional to scalar expansion and constant decelerating parameter, which is derived from the variation law of Hubble parameter proposed by Berman(Nuovo Cimento B 74, 182 (1983))and linearly varying decelerating parameter proposed by Akarsu and Dereli(International Journal of Theoretical Physics, 51,612(2012)). The dynamics and significance of the physical parameters of the model are discussed using a graphical representation of these parameters. The dynamics and significance of the physical parameters of the models are discussed.

Analytic States in Quantum Field Theory on Curved Spacetimes

We discuss high energy properties of states for (possibly interacting) quantum fields in curved spacetimes. In particular, if the spacetime is real analytic, we show that an analogue of the timelike tube theorem and the Reeh–Schlieder property hold with respect to states satisfying a weak form of microlocal analyticity condition. The former means the von Neumann algebra of observables of a spacelike tube equals the von Neumann algebra of observables of a significantly bigger region that is obtained by deforming the boundary of the tube in a timelike manner. This generalizes theorems by Araki (Helv Phys Acta 36:132–139, 1963) and Borchers (Nuovo Cim (10) 19:787–793, 1961) to curved spacetimes.

Buchdahl-inspired spacetimes and wormholes: Unearthing Hans Buchdahl’s other “hidden” treasure trove

Circa 1962 Hans A. Buchdahl pioneered a program — and made significant progress — seeking vacuo configurations in pure [Formula: see text] gravity (H. A. Buchdahl, Nuovo Cimento 23 (1962) 141). Unfortunately, he deemed the final step in his calculations impassable and prematurely suspended his pursuit. Since then, his achievements on this front have faded into dormancy. Unbeknownst to Buchdahl himself, the [Formula: see text] vacua that he sought were within his striking distance. In our recent three-paper body of work published in Nguyen (Phys. Rev. D 106 (2022) 104004; Phys. Rev. D 107 (2023) 104008; Phys. Rev. D 107 (2023) 104009), we broke this six-decades-old impasse and accomplished his goal: A novel class of metrics, describing non-Schwarzschild spacetimes in quadratic gravity and carrying a hallmark of higher-derivative characteristic. Intriguing properties of Buchdahl-inspired spacetimes and their associated Morris–Thorne–Buchdahl wormholes — summarized herein — embody a new branch of phenomenology that transcends the Einstein–Hilbert paradigm. May this unsung legacy of Hans A. Buchdahl long “forsaken” and “forgotten” finally live on Our essay is a passageway bridging the past and the future. The past is rooted in a research program originated but left unfinished by Buchdahl going back threescore years ago. The future is the new horizons his program brings forth. In between is our labor — summarized in a three-installment “Beyond Schwarzschild–de Sitter spacetimes” series[1–3] — to advance the Buchdahl program and achieve his ultimate goal.

Beyond Schwarzschild–de Sitter spacetimes. II. An exact non-Schwarzschild metric in pure R2 gravity and new anomalous properties of R2 spacetimes

In our recent publication (Phys. Rev. D 106, 104004 (2022)), we advanced a program that Buchdahl originated but prematurely abandoned circa 1962 (Nuovo Cimento 23, 141 (1962)). Therein we obtained an exhaustive class of metrics that constitute the branch of non-trivial solutions to the pure $R^{2}$ field equation in vacuo. The Buchdahl-inspired metrics in general possess non-constant scalar curvature, thereby defeating the generalized Lichnerowicz theorem previously advocated for quadratic gravity. We found that the said theorem makes an overly strong assumption on the asymptotic falloff in the spatial derivatives of the Ricci scalar, rendering it violable against the Buchdahl-inspired metrics. In this paper, we shall further extend our work mentioned above by showing that, within the class of Buchdahl-inspired metrics, the asymptotically flat member takes on an exact closed analytical expression. The new metric is characterized by a horizon radius $r_{\text{s}}$ and the Buchdahl parameter $k$, the latter of which arises via the higher-derivative nature of $R^{2}$ gravity. For $k=0$, the new metric recovers the classic Schwarzschild metric. Equipped with the exact expression of the new metric, we shall analytically construct the Kruskal-Szekeres diagram for pure $R^{2}$ spacetime. We find that the Buchdahl parameter $k$ fundamentally modifies the properties of $R^{2}$ spacetime structures in a variety of ways.

Beyond Schwarzschild–de Sitter spacetimes. III. A perturbative vacuum with nonconstant scalar curvature in R+R2 gravity

In violation of the generalized Lichnerowicz theorem advocated by Nelson and others, quadratic gravity admits vacua with non-constant scalar curvature. In a recent publication [Phys. Rev. D 106, 104004 (2022)], we revitalized a program that Buchdahl originated but prematurely abandoned circa 1962 [Nuovo Cimento 23, 141 (1962)], and uncovered a novel exhaustive class of static spherically symmetric vacua for pure $R^2$ gravity. The Buchdahl-inspired metrics we obtained therein are exact solutions which exhibit non-constant scalar curvature. A product of fourth-order gravity, the metrics entail a new (Buchdahl) parameter $k$ which allows the Ricci scalar to vary on the manifold. The metrics are able to defeat the generalized Lichnerowicz theorem by evading an overly strong restriction on the asymptotic falloff in the Ricci scalar as assumed in the theorem. The Buchdahl parameter $k$ is a new characteristic of pure $R^2$ gravity, a higher-derivative theory. By venturing that the Buchdahl parameter should be a universal hallmark of higher-derivative gravity at large, in this paper we seek to extend the concept to the quadratic action $R^2+\gamma\,(R-2\Lambda)$. We are able to determine that the quadratic field equation admits a perturbative vacuo that is valid up to the order $O(k^2)$. Conforming with our guiding intuition, the Ricci scalar is non-constant, including the asymptotically flat case, as long as $k\neq0$ and $\gamma\neq0$. The existence of such an asymptotically flat vacuo with non-constant scalar curvature defeats the generalized Lichnerowicz theorem in its entirety. Our finding thus warrants restoring the $R^2$ term in the full quadratic action, $\gamma\,R+\beta\,R^2-\alpha\,C^{\mu\nu\rho\sigma}C_{\mu\nu\rho\sigma}$, when applying the L\"u-Perkins-Pope-Stelle ansatz. Implications to the L\"u-Perkins-Pope-Stelle solution are discussed herein.

Classical fermion dynamics in presence of non abelian monopoles

In the present letter, the dynamics of a spin one-half particle with non abelian charge, interacting with a non abelian monopole like configuration, is studied. In the non spinning case, these equations correspond to the Wong ones S Wong (1970, Il Nuovo Cimento LXV, 4 689), and the associated dynamics has been extensively investigated in I Alekseev (1988, Theoret. and Math. Phys. 77 1273), L G Feher (1984, Acta Physica Polonica 15 920). The classical limit of a spinning particle in an abelian was considered in A Davis and W Perkins (1989, Phys. Lett. B 228 37), where an interpretation of the celebrated Callan-Rubakov effect C G Callan (1982, Phys. Rev. D 26 2058); V A Rubakov (1982, Nucl. Phys. B 203 311), V A Rubakov and M S Serebryakov (1983, Nucl. Phys. B 218 240); V A Rubakov (1981, JETP Len. 33 644). was obtained in purely classical terms The present work studies an interpolating situation, in which spin and non abelian charges are turned on. The corresponding equations are obtaining by taking into account some earlier works about spinning particles N Linden, A Macfarlane and J van Holten Czechoslovak (1996, J. Phys. 46 209), A Barducci, R Casalbuoni and L Lusanna (1977, Nuclear Physics B 124 93, A P Balachandran Per Salomson, B -S Skagerstam, and J -O Winnberg (1977, Phys. Rev. D 15 2308). The conservation laws are studied in this context, and it is found that energy and some generalization of angular momentum are conserved just in particular limits. This is a reflection that the non abelian interaction contains gauge field quartic interaction, which spoils the symmetries leading to these conservation laws. The precession of the particle is analyzed and compared with its abelian counterpart in this limit.

Beyond Schwarzschild–de Sitter spacetimes: A new exhaustive class of metrics inspired by Buchdahl for pure R2 gravity in a compact form

Some sixty years ago Buchdahl pioneered a program in search of static spherically symmetric vacua for pure $R^{2}$ gravity (Nuovo Cimento, Vol 23, No 1, pp 141-157 (1962); [https://link.springer.com/article/10.1007/BF02733549]). Surpassing several obstacles, his work culminated in a non-linear second-order ordinary differential equation (ODE) which required being solved. However Buchdahl deemed the ODE intractable and prematurely abandoned his pursuit for an analytical solution. We have finally managed to break this six-decades-old impasse and accomplish his goal. Reformulating the Buchdahl ODE, we obtain a novel exhaustive class of metrics (which we shall call the Buchdahl-inspired metrics hereafter) in a compact form. We are able to verify ex post, via direct inspection, that the metric obtained herein satisfies the $R^{2}$ vacuo field equation, hence establishing its validity. We show why the Buchdahl-inspired metrics, which exhibit non-constant scalar curvature, defeat a Lichnerowicz-type no-go theorem, previously proved for quadratic gravity, by evading the overly strong restriction on the asymptotic falloff of the metric at spatial infinity. Our novel solution thereby completes Buchdahl's six-decades-old program. We also explore the mathematical properties of the Buchdahl-inspired metrics in the limit of small k and in the region around the coordinate origin.

Relativistic free-motion time-of-arrival operator for massive spin-0 particles with positive energy

A relativistic version of the Aharonov-Bohm time-of-arrival operator for spin-0 particles was constructed by Razavi [Il Nuovo Cimento B 63, 271 (1969)]. We study the operator in detail by taking its rigged Hilbert space extension. It is shown that the rigged Hilbert space extension of the operator provides more insights into the time-of-arrival problem that goes beyond Razavi's original results. This allows us to use time-of-arrival eigenfunctions that exhibit unitary arrival to construct time-of-arrival distributions. The expectation value is also calculated and shown that particles can arrive earlier or later than expected classically. Last, the constructed time-of-arrival distribution and expectation value are shown to be consistent with special relativity.

Stabilizing spherical energy shells with angular momentum in gravitational backgrounds

Spherical energy shells in General Relativity tend to collapse due to gravitational effects and/or due to tension effects. Shell stabilization may be achieved by modifying the gravitational properties of the background spacetime. Thus, gravastars consist of stiff matter shells with an interior deSitter space and an exterior Schwarzshild spacetime whose attractive gravity balances the interior repulsive gravity of the interior deSitter spacetime leading to a stable stiff matter shell. Similar stabilization effects may be achieved by considering rotating shells. Here we study the stability of slowly rotating fluid shells. We show that the angular velocity of the shell has stabilizing properties analogous to the repulsive deSitter gravity of the interior of a gravastar. We thus use the Israel junction conditions [W. Israel, Nuovo Cim. B 44S10 (1966) 1, Erratum: Nuovo Cim. B 48 (1967) 463; N. Deruelle, M. Sasaki and Y. Sendouda, Prog. Theor. Phys. 119 (2008) 237, arXiv:0711.1150 [gr-qc]] and the fluid equation of state of the rotating shell to construct the dynamical equations that determine the evolution of the rotating shell radius. These dynamical equations depend on the parameters of the background spacetime and on the angular velocity of the shell. Assuming a rotating interior and a Schwarzschild exterior spacetime we show that the angular velocity of the shell has interesting stabilizing properties on the evolution of its radius R. Thus, rotating matter (or vacuum) shells can imitate black holes while avoiding the presence of a singularity and without the presence of an interior deSitter space.

Hydrogen molecule as seen in electron and positron scattering

By a historical overview, we show the importance of a laconic paper by Kolos and Wolniewicz dating to 1962 [Phys. Lett. 5(2), 222–223 (1962)], in which they applied the variational method for the hydrogen molecule. In the first part of this perspective (say till 1996), the experiments on electron molecule scattering (including hydrogen) developed a vast range of techniques, even if the results were far from being congruent [Riv. Nuovo Cimento 19/3, 1996]. In turn, in the last years, we have observed the quickly rising applicability of theoretical methods, like convergent-close coupling [Zammit et al. Phys. Rev. Lett. 116, 233201 (2016)] and R-matrix [Meltzer & Tennyson, J. Phys. Phys. B 53, 245203 (2020)]. The mutual agreement between theories and experiments allows defining recommended cross-sections for electron and positron scattering from zero to sub-relativistic energies. This, in turn, enables to check the dispersion relation, i.e. the interdependence between the zero-energy integral elastic, the high-energy elastic differential at zero angle, and the integral of the total cross-section from zero to infinity. Such a relation holds, within the experimental uncertainties, for positrons. For electrons, a big discrepancy points to the importance of the exchange effects in the e H scattering.

Particle motion in circularly polarized vacuum pp waves

Bialynicki-Birula and Charzynski argued that a gravitational wave emitted during the merger of a black hole binary may be approximated by a circularly polarized wave which may in turn trap particles (Bialynicki-Birula and Charzynski 2018 Phys. Rev. Lett. 121 171101). In this paper we consider particle motion in a class of gravitational waves which includes, besides circularly polarized periodic waves (CPP) (Stephani et al 2003 Exact Solutions of Einstein’s Field Equations (Cambridge: Cambridge University Press)), also the one proposed by Lukash V N (1975 Sov. Phys. JETP 40 792; 1974 Zh. Eksp. Teor. Fiz. 67 1594–1608; 1974 Astr. Zh. 51 281; 1976 Nuovo Cimento B 35 208) to study anisotropic cosmological models. Both waves have a seven-parameter conformal symmetry which contains, in addition to the generic five-parameter (broken) Carroll group, also a 6th isometry. The Lukash spacetime can be transformed by a conformal rescaling of time to a perturbed CPP problem. Bounded geodesics, found both analytically and numerically, arise when the Lukash wave is of Bianchi type VI. Their symmetries can also be derived from the Lukash–CPP relation. Particle trapping is discussed.

Generalizing Optimal Bell Inequalities.

Bell inequalities are central tools for studying nonlocal correlations and their applications in quantum information processing. Identifying inequalities for many particles or measurements is, however, difficult due to the computational complexity of characterizing the set of local correlations. We develop a method to characterize Bell inequalities under constraints, which may be given by symmetry or other linear conditions. This allows one to search systematically for generalizations of given Bell inequalities to more parties. As an example, we find all possible generalizations of the two-particle inequality by Froissart [Nuovo Cimento Soc. Ital. Fis. B 64, 241 (1981)], also known as I3322 inequality, to three particles. For the simplest of these inequalities, we study their quantum mechanical properties and demonstrate that they are relevant, in the sense that they detect nonlocality of quantum states, for which all two-setting inequalities fail to do so.

Dynamical kernels for optical excitations.

We discuss the physical properties and accuracy of three distinct dynamical (i.e., frequency-dependent) kernels for the computation of optical excitations within linear response theory: (i) an a priori built kernel inspired by the dressed time-dependent density-functional theory kernel proposed by Maitra et al. [J. Chem. Phys. 120, 5932 (2004)], (ii) the dynamical kernel stemming from the Bethe-Salpeter equation (BSE) formalism derived originally by Strinati [Riv. Nuovo Cimento 11, 1-86 (1988)], and (iii) the second-order BSE kernel derived by Zhang et al. [J. Chem. Phys. 139, 154109 (2013)]. The principal take-home message of the present paper is that dynamical kernels can provide, thanks to their frequency-dependent nature, additional excitations that can be associated with higher-order excitations (such as the infamous double excitations), an unappreciated feature of dynamical quantities. We also analyze, for each kernel, the appearance of spurious excitations originating from the approximate nature of the kernels, as first evidenced by Romaniello et al. [J. Chem. Phys. 130, 044108 (2009)]. Using a simple two-level model, prototypical examples of valence, charge-transfer, and Rydberg excited states are considered.

The orbital pericenter precession in the 2PN approximation

Recent article "Revisiting the 2PN Pericenter Precession in View of Possible Future Measurements" published by Iorio (Universe, 2020) argues that calculations of the secular 2PN precession of the orbital pericenter of a binary system accomplished by Damour and Schaefer (Nuovo Cim. B, 1988) and by Kopeikin and Potapov (Astron. Rep., 1994) with different mathematical techniques are inconsistent, differ from each other and do not agree with the result obtained by Iorio (Universe, 2020). The purpose of this communication is to demonstrate that the article by Iorio is erroneous, suffers from misconceptions and cannot be trusted.

Contribution of Academician K.Ya. Kondratyev in the development of meteorology and ecology (to the 100th anniversary)

In connection with the centenary of K.Ya. Kondratyev, the academician of the USSR and RAS, the article examines the scientific path of the outstanding geophysicist, the man who, being a student of the Physics Department of LSU, became an ordinary participant in the second world war and after severe injuries, finished his studies, worked his way from the assistant to the University rector, becoming a scientist whose works were highly appreciated in the world scientific community and are still in demand today. K.Ya. Kondratyev was one of the first to use remote sensing methods of the Earth and atmosphere from manned spaceships, his contribution to the implementation of both national and international research complex experiments, to the consideration of the problems of modern climate change, global ecology and the development of the strategy of global EcoDynamics being great. K.Ya Kondratyev was awarded the State prize of the USSR, was a co-author of scientific discovery "the Phenomenon of vertically-ray structures of day radiation of the upper atmosphere of the Earth”, listed in the State register of discoveries of the USSR under No. 106 with priority from May 19, 1971, was a winner of the Honorary award and was awarded the Grand gold medal of the World Meteorological Organization. He was awarded the Simons Gold medal of the Royal meteorological society of Great Britain. K.Ya Kondratyev was elected an Honorary member of the American Meteorological Society (USA), Royal Meteorological Society (UK), Academy of Natural Sciences "Leopoldina" (Germany), foreign member of the American Academy of Arts and Sciences (USA), member of the International Academy of Astronautics, an honorary doctor of the universities of Lille (France, Budapest (Hungary), Athens (Greece). For many years he has an editor of the "Earth Research from Space" journal, a member of the editorial boards of "Optics of atmosphere and ocean" and "Izvestiya of the Russian geographical society" journals, a member of the editorial boards of foreign journals of "Meteorology and Atmospheric Physics" (Austria), "Idojaras" (Hungary), "II Nuovo Cimento C", "Italy", "Atmosfera" (Mexico), "Energy and Environment" (UK). His scientific and literary heritage consists of 120 monographs and more than 1,500 scientific articles published in the leading scientific journals in Russia and abroad

Interesting QFT Problems Tackled in New Fashion

The Dimensional Regularization technique of Bollini and Giambiagi (BG) [Phys. Lett. B 40, 566 (1972); Il Nuovo Cim. B 12, 20 (1972); Phys. Rev. D 53, 5761 (1996)] cannot be employed for all Schwartz Tempered Distributions Explicitly Lorentz Invariant (STDELI) S′L. We lifted such limitation in [J. Phys. Comm. 2 115029 (2018)], which opens new QFT possibilities, centering in the use of STDELI that allows one to obtain a product in a ring with zero divisors. This in turn, overcomes all problems regrading QFT infinities. We provide here three examples of the application of our STDELI-extension to quantum field theory (A) the exact evaluation of an electron’s self energy to one loop, (B) the exact evaluation of QED’s vacuum polarization, and C) the theory for six dimensions, that is non-renormalizable.

A study on the Friedmann-like Universe with torsion using Noether symmetry

This paper deals with the symmetry analysis of the Einstein Cartan Theory [E. Cartan, C. R. Acad. Sci. (Paris) 174, 593 (1922); E. Cartan, Ann. Sci. Ec. Norm. Super 40, 325 (1923)] which is an extension of the general relativity and it accounts for the spacetime torsion [S. Basilakos et al., Phys. Rev. D 88, 103526 (2013)]. We begin by applying Noether theorem [S. Capozziello, La Rivista del Nuovo Cimento (1978–1999) 19(4), 1 (1996)] to the Lagrangian of the FRW type cosmology with torsion and choose a point transformation: [Formula: see text], such that one of the transformed variables is cyclic [S. Capozziello, M. De Laurentis and S. D. Odintsov, Eur. Phys. J. C 72, 2068 (2012)] for the Lagrangian. Then using the conserved charge [S. Capozziello, M. De Laurentis and S. D. Odintsov, Eur. Phys. J. C 72, 2068 (2012)], which is obtained by applying Noether theorem, and the constant of motion, we get the solutions and conclude that due to the presence of torsion, the FRW type cosmology is in the de Sitter phase [D. Kranas, C. G. Tsagas, J. D. Barrow and D. Iosifidis, Eur. Phys. J. C 79, 341 (2019)].

Bianchi type V Ih Bulk-Viscous String Cosmological Model in f(R) Gravity

In this paper, we derive f(R) gravity field equations with the help of a spatially homogeneous and anisotropic Bianchi type-V Ih space-time, in the presence of a bulk-viscous fluid, containing one-dimensional cosmic strings. Here we obtained the solutions of the field equations, under some specific plausible physical conditions. In particular, cosmological model with bulk-viscous strings in f(R) theory of gravity is obtained by using the special law of variation for Hubble’s parameter proposed by Berman (Nuovo Cimento, B74, 182 (1983)). Some physical and kinematical properties of the models are also discussed.