arXiv subjects

Stefano Bellucci

Publications and source records attributed to Stefano Bellucci.

At least 19 recordsLinked to original sources

arXiv2026

Spectral Suppression of Asymptotic States in Supersymmetric QFT on de Sitter Backgrounds

We investigate the fate of asymptotic particle states in supersymmetric quantum field theories on de Sitter backgrounds, distinguishing algebraic field content from localized LSZ-like excitations. We study how long-wavelength gravitational fluctuations may suppress pole residues and redistribute spectral weight from isolated contributions toward continuum sectors. The analysis is formulated within a Kallen-Lehmann spectral framework and is intended as a structural infrared mechanism rather than a non-perturbative proof of de Sitter quantum gravity. The paper develops three connected levels. First, we analyze residue suppression in a quasi-de Sitter setting and its possible transmission through Yukawa and gravitational interactions. Second, we formulate the spectral decomposition as a map between the full field-theoretic spectrum and the observable particle sector. Third, we examine a conditional cosmological realization of redistributed spectral weight, including possible effects on expansion, structure growth, and lensing. This cosmological layer is a downstream phenomenological test and is not used as evidence that pole loss has occurred. In the current MCMC analysis we find S8 approximately 0.803 and, when the smooth fraction is varied, fS8 = 0.0025 +/- 0.0017, consistent with the benchmark value 0.00262. These results test the internal consistency of the proposed realization but do not establish the dark-sector assignment or the underlying infrared mechanism.

hep-th↗

arXiv2026

A structural criterion for asymptotic states in Supersymmetry

The occurrence of a field in the formal structure of a quantum field theory does not by itself establish the existence of a corresponding asymptotic particle. We develop a structural criterion separating three logically distinct questions: which field structures are admissible, which survive the dynamics as localized spectral excitations, and which are realized as operational particle states. The revised exterior-polynomial classification of gravitino mass bilinears provides the operator-level prototype for this distinction. Transposing this layered logic from operators to states, we formulate particlehood as the endpoint of an ordered filtration: spacetime geometry and the quantum state determine the spectral environment; the effective algebra fixes the physically realized symmetries and admissible channels; dynamics modifies the dressed two-point function; and spectral analysis determines whether an isolated atomic contribution survives. The localization criterion is thereby given measure-theoretic content: a stable asymptotic particle state requires an isolated spectral atom with non-zero weight. The framework also clarifies two limits of the original formulation. The apparent fermion-scalar asymmetry is channel-specific rather than universal, and no asymmetric realization of particlehood within an exact supersymmetric multiplet is possible while the supercharges act on the physical Hilbert space and annihilate the vacuum. Any split therefore requires supersymmetry breaking, altered background realization, or kinematic and dynamical differences among the relevant channels. The paper establishes necessary structural conditions only; their quantitative realization is deferred to a companion work.

hep-th↗

arXiv2026

Structural Origin of the Gravitino Mass Term: Geometric and Supergravity Perspectives

We identify a minimal superspace projector that uniquely selects the Rarita Schwinger mass bilinear in four-dimensional N=1 supergravity. Working in a reduced superspace with a single fermionic direction, we show that Berezin projection of a canonical even supergeometric form isolates the unique Lorentz-invariant fermionic bilinear compatible with local supersymmetry. The construction is predynamical: it fixes the algebraic structure of the gravitino mass term independently of supersymmetry breaking mechanisms, background geometry, or matter couplings. We show that this projector embeds consistently into curved superspace, extends to N>1 theories, and clarifies the universality of the gravitino mass structure in supergravity.

hep-th↗

arXiv2023

Axiomatic Foundations of Physical Theories

In this paper we give a contribution to the taxonomy of physical theories. We provide here a thorough description of the axiomatic foundations of the most relevant physical theories, Mechanics, Special Relativity, General Relativity, Quantum Mechanics. The corresponding interactions will be dealt with as well, i.e. Gravity in the Minkowskian limit, Electricity without quantized energy, Gravity without quantized energy, Electricity with quantized energy. We pose the problem if the extension of the principle of solidarity to all interactions can impose to consider all variables as dynamic.

physics.gen-ph↗

arXiv2023

A New Insight on Physical Phenomenology: a Review

After a brief digression on the current landscape of theoretical physics and on some open questions pertaining to coherence with experimental results, still to be settled, it is shown that the properties of the Deformed Minkowski space lead to a plurality of potential physical phenomena that should occur, provided that the resulting formalisms can be considered as useful models for the descrip-tion of some aspects of physical reality. A list is given of available experimental evidences not easy to be interpreted, at present, by means of the more established models, such as the standard model with its variants aimed at overcoming its descriptive limits; these evidences could be candidates to verify the predictions stemming from the properties of the Deformed Minkowski space. The list includes: anomalies in the double-slit-like experiments; nuclear metamorphosis; torsional anten-nas, as well as the physical effect of the "geometric vacuum" (as defined in analogy with quantum vacuum), in the absence of external electromagnetic field, when crossing critical thresholds of energy parameter values, energy density in space and energy density in time.

physics.gen-ph↗

arXiv2023

A review of experiments reporting non-conventional phenomena in nuclear matter aiming at identifying common features in view of possible interpretation

The purpose of the present paper is to clarify, as far as it is possible, the overall picture of experimental results in the field of non-conventional phenomena in nuclear matter published in scientific literature, accumulated in the last decades and still missing a widely accepted interpretation. While completeness of the collection of the experiments is not among the aims of the effort, focus is put on adopting a more comprehensive and integral approach through the analysis of the different experimental layouts and the different results, searching for common features and analogous factual outcomes in order to obtain a consistent reading of a lot of experimental evidences that appear, until now, lacking a classification in a logic catalogue which might be compared to a sort of building and not to a collection of single stones. Particular attention is put on the issue of reproducibility of experiments and on the reasons why such a limitation is a frequent characteristic of many experimental activities reported in published papers. This approach is innovative as compared with those already available in the scientific literature. In a synoptical table a comprehensive classification is given of the twenty experiments examined in terms of type of evidences that are ascertained by the experimenters in their published papers but are unexpected according to well established physical theories. Examples of such unexpected evidences (named also non-conventional or weird) are: excess heat generation, isotope production, reduction of radioactivity levels, and production of neutrons or alpha particles.

physics.gen-ph↗

arXiv2017

Thermodynamic Geometry of Yang-Mills Vacua

We study vacuum fluctuation properties of an ensemble of $SU(N)$ gauge theory configurations, in the limit of large number of colors, \textit{viz.} $N_c \rightarrow \infty$, and explore statistical nature of the topological susceptibility by analyzing its critical behavior at a nonzero vacuum parameter $θ$ and temperature $T$. We find that the system undergoes a vacuum phase transition at the chiral symmetry restoration temperature as well as at an absolute value of $θ$. On the other hand, the long range correlation length solely depends on $θ$ for the theories having critical exponent $e=2$ or $T=T_d+1$, where $T_d$ is the decoherence temperature. Further, it is worth noticing that the unit critical exponent vacuum configuration corresponds to a noninteracting statistical basis pertaining to a constant mass of $η^{\prime}$.

hep-th↗

arXiv2015

On the absence of actual plateaus in zero-temperature magnetization curves of quantum spin clusters and chains

We examine the general features of the non-commutativity of the magnetization operator and Hamiltonian for the small quantum spin clusters. The source of this non-commutativity can be a difference in the Landé g-factors for different spins in the cluster, XY-anisotropy in the exchange interaction and the presence of the Dzyaloshinskii-Moriya term in the direction different for the direction of the magnetic field. As a result, a zero-temperature magnetization curve for the small spin clusters mimics that for the macroscopic systems with the band(s) of magnetic excitations, i.e. for the given eigenstate of the spin cluster the corresponding magnetic moment can be an explicit function of the external magnetic field yielding the non-constant (non-plateau) form of the magnetization curve within the given eigenstate. Also, the XY-anisotropy makes the saturated magnetization (the eigenstate when all spins in cluster are aligned along the magnetic field) inaccessible for finite magnetic field magnitude (asymptotical saturation). We demonstrate all these features on three examples: spin-1/2 dimer, mixed spin-(1/2,1) dimer, spin-1/2 ring trimer. We consider the simplest Ising-Heisenberg chain, the XYZ-Ising diamond chain with four different g-factors as well. In the chain model the magnetization curve has more complicated and non trivial structure with than that for clusters.

cond-mat.str-el↗

arXiv2015

Spatial dispersion effects upon local excitation of extrinsic plasmons in a graphene micro-disk

Excitation of surface plasmon waves in extrinsic graphene is studied using a full-wave electromagnetic field solver as analysis engine. Particular emphasis is placed on the role played by spatial dispersion due to the finite size of the two-dimensional material at the micro-scale. A simple instructive set up is considered where the near field of a wire antenna is held at sub-micrometric distance from a disk-shaped graphene patch. The key-input of the simulation is the graphene conductivity tensor at terahertz frequencies, being modeled by the Boltzmann transport equation for the valence and conduction electrons at the Dirac points~(where a linear wave-vector dependence of the band energies is assumed). The conductivity equation is worked out in different levels of approximations, based on the relaxation time ansatz with an additional constraint for particle number conservation. Both drift and diffusion currents are shown to significantly contribute to the spatially dispersive anisotropic features of micro-scale graphene. More generally, spatial dispersion effects are predicted to influence not only plasmon propagation free of external sources, but also typical scanning probe microscopy configurations. The paper set the focus on plasmon excitation phenomena induced by near field probes, being a central issue for the design of optical devices and photonic circuits.

cond-mat.mes-hall↗

arXiv2014

Thermodynamic curvature for a two-parameter spin model with frustration

Microscopic models of realistic thermodynamic systems usually involve a number of parameters, not all of equal macroscopic relevance. We examine a decorated $(1+3)$ Ising spin chain containing two microscopic parameters: a "stiff" $K$ mediating the long-range interactions, and a "sloppy" $J$ operating within local spin groups. $K$ dominates the macroscopic behavior, and varying $J$ has weak effect except in regions where $J$ brings about transitions between phases through its conditioning of the local spin groups with which $K$ interacts. We calculate the heat capacity $C_H$, the magnetic susceptibility $χ_T$, and the thermodynamic curvature $R$. For large $|J/K|$, we identify four magnetic phases: ferromagnetic, antiferromagnetic, and two ferrimagnetic ones, according to the signs of $K$ and $J$. We argue that for characterizing these phases, the strongest picture is offered by the thermodynamic geometric invariant $R$, proportional to the correlation length $ξ$. This picture has correspondences to other cases, such as fluids.

cond-mat.stat-mech↗

arXiv2014

Quantum Rings in Magnetic Fields and Spin Current Generation

We propose three different mechanisms for pumping spin-polarized currents in a ballistic circuit using a time-dependent magnetic field acting on an asymmetrically connected quantum ring at half filling. The first mechanism works thanks to a rotating magnetic field and produces an alternating current with a partial spin polarization. The second mechanism works by rotating the ring in a constant field; like the former case, it produces an alternating charge current but the spin current is d.c.; both methods do not require a spin-orbit interaction to achieve the polarized current, but the rotating ring could be used to measure the spin-orbit interaction in the ring using characteristic oscillations. On the other hand, the last mechanism that we propose depends on the spin-orbit interaction in an essential way, and requires a time-dependent magnetic field in the plane of the ring. This arrangement can be designed to pump a purely spin current. The absence of a charge current is demonstrated analytically. Moreover, a simple formula for the current is derived and compared to the numerical results.

cond-mat.mes-hall↗

arXiv2014

Magnetization non-rational quasi-plateau and spatially modulated spin order in the model of the single-chain magnet, [{(CuL)_2 Dy}{Mo(CN)_8}] 2CH_3CN H_2O

Using the exact solution in terms of the generalized classical transfer matrix method we presented a detailed analysis of the magnetic properties and ground state structure of the simplified model of the single-chain magnet, trimetallic coordination polymer compound, [{(CuL)_2 Dy}{Mo(CN)_8}] 2CH_3CN H_2O is N,N'-propylenebis(3-methoxysalicylideneiminato). Due to appearance of highly anisotropic Dy3+ ion this material is an unique example of the one-dimensional magnets with Ising and Heisenberg bonds, allowing exact statistical-mechanical treatment. We found two zero-temperature ground states corresponding to different part of the magnetization curve of the material. The zero-filed ground state is shown to be an antiferromagnetic configuration with spatial modulation of the local Dy3+(which is proven to posses well defined Ising like properties due two large anisotropy of g-factors) and composite S=1/2 spin of the quantum spin trimer Cu-Mo-Cu in the form "up"-"down"-"down"-"up". Another important feature of this compound is the appearance of the quasi-plateau at non rational value of magnetization due to difference of the g-factors of the Cu- and Mo-ion in quantum spin trimers. The quasi-plateau is an almost horizontal part of the magnetization curve where the corresponding zero-temperature ground state of the chain demonstrate slow but monotonous dependence of the magnetization on the external magnetic field, while the $z$-projection of the total spin is constant.

cond-mat.stat-mech↗

arXiv2013

Magnetization Transfer by a Quantum Ring Device

We show that a tight-binding model device consisting of a laterally connected ring at half filling in a tangent time-dependent magnetic field can in principle be designed to pump a purely spin current. The process exploits the spin-orbit interaction in the ring. This behavior is understood analytically and found to be robust with respect to temperature and small deviations from half filling.

cond-mat.stat-mech↗

arXiv2013

Correlation functions in one-dimensional spin lattices with Ising and Heisenberg bonds

A general technique of exact calculation of any correlation functions for the special class of one-dimensional spin models containing small clusters of quantum spins assembled to a chain by alternating with the single Ising spins is proposed. The technique is a natural generalization of that in the models solved by a classical transfer matrix. The general expressions for corresponding matrix operators which are the key components of the technique are obtained. As it is clear from the general principles, the decay of the correlation functions of various types is explicitly shown to be governed by a single correlation length. The technique is illustrated by two examples: symmetric diamond chain and asymmetric sawtooth chain.

cond-mat.stat-mech↗

arXiv2013

The Coulomb problem on a 3-sphere and Heun polynomials

The paper studies the quantum mechanical Coulomb problem on a 3-sphere. We present a special parametrization of the ellipto-spheroidal coordinate system suitable for the separation of variables. After quantization we get the explicit form of the spectrum and present an algebraic equation for the eigenvalues of the Runge-Lentz vector. We also present the wave functions expressed via Heun polynomials.

hep-th↗

arXiv2012

Isospin particle systems on quaternionic projective spaces

We construct the isospin particle system on $n$-dimensional quaternionic projective spaces in the presence of BPST-instanton by the reduction from the free particle on $(2n+1)$-dimensional complex projective space. Then we add to this system a "quaternionic oscillator potential" and show, that this oscillator-like system is superintegrable. We show, that besides the analogs of quadratic constants of motion of the spherical (Higgs) and $\mathbb{C}P^n $- oscillators, it possesses the third-order constants of motion, which are functionally independent from the quadratic ones.

hep-th↗

arXiv2012

State-space Geometry, Statistical Fluctuations and Black Holes in String Theory

We study the state-space geometry of various extremal and nonextremal black holes in string theory. From the notion of the intrinsic geometry, we offer a new perspective of black hole vacuum fluctuations. For a given black hole entropy, we explicate the intrinsic state-space geometric meaning of the statistical fluctuations, local and global stability conditions and long range statistical correlations. We provide a set of physical motivations pertaining to the extremal and nonextremal black holes, \textit{viz.}, the meaning of the chemical geometry and physics of correlation. We illustrate the state-space configurations for general charge extremal black holes. In sequel, we extend our analysis for various possible charge and anticharge nonextremal black holes. From the perspective of statistical fluctuation theory, we offer general remarks, future directions and open issues towards the intrinsic geometric understanding of the vacuum fluctuations and black holes in string theory. Keywords: Intrinsic Geometry; String Theory; Physics of black holes; Classical black holes; Quantum aspects of black holes, evaporation, thermodynamics; Higher-dimensional black holes, black strings, and related objects; Statistical Fluctuation; Flow Instability. PACS: 02.40.Ky; 11.25.-w; 04.70.-s; 04.70.Bw; 04.70.Dy; 04.50.Gh; 5.40.-a; 47.29.Ky

hep-th↗

arXiv2012

Action-angle variables for the particle near extreme Kerr throat

We construct the action-angle variables for the spherical part of conformal mechanics describing the motion of a particle near extreme Kerr throat. We indicate the existence of the critical point $|p_φ|=mc R_{\rm Sch}$ (with $m$ being the mass of the particle, $c$ denoting the speed of light, $R_{\rm Sch}=2γM /c^2$ being the Schwarzschild radius of a black hole with mass $M$, and $γ$ denoting the gravitational constant), where these variables are expressed in terms of elementary functions. Away from this point the action-angle variables are defined by elliptic integrals. The proposed formulation allows one to easily reconstruct the whole dynamics of the particle both in initial coordinates, as well as in the so-called conformal basis, where the Hamiltonian takes the form of conventional non-relativistic conformal mechanics. The related issues, such as semiclassical quantization and supersymmetrization are also discussed.

hep-th↗