Brazilian Journal of Physics最新文献

{"title":"Will We Ever Quantize the Centers of Mass of Heavy Systems? A Case for a Heisenberg Cut in Quantum Mechanics","authors":"Gabriel H. S. Aguiar,&nbsp;George E. A. Matsas","doi":"10.1007/s13538-026-02107-6","DOIUrl":"10.1007/s13538-026-02107-6","url":null,"abstract":"<div><p>The quantum orthodoxy attests that all dynamical degrees of freedom should be quantized, including those associated with the centers of mass of composite/complex systems, such as protons/pebbles. By assuming that the centers of mass of protons/pebbles should be quantized, one implies the existence of a corresponding Fock space, since, according to the present lore, quantum mechanics is a consequence of quantum field theory. Despite the fabulous success of quantum mechanics, it is unreasonable to assume the existence of annihilation and creation operators for pebbles. Fortunately, there are strong reasons to doubt that wave mechanics can describe the centers of mass of systems at or above the Planck scale, thereby jeopardizing the construction of the corresponding Fock space. We argue that isolated (free) systems with masses exceeding the Planck mass would have their centers of mass governed by classical (rather than quantum) mechanics, despite harboring macroscopic quantum phenomena as observed in the laboratory. Here, we briefly revisit (i) the arguments for the need for a Heisenberg cut delimiting the boundary between the quantum and classical realms and (ii) the kind of new physics expected at (the uncharted region of) the Heisenberg cut.</p></div>","PeriodicalId":499,"journal":{"name":"Brazilian Journal of Physics","volume":"56 4","pages":""},"PeriodicalIF":1.8,"publicationDate":"2026-06-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1007/s13538-026-02107-6.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148323705","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"The Concepts of Work and Potential Energy with Application to Continuous Systems","authors":"Filadelfo Cardoso Santos,&nbsp;Oswaldo de Medeiros Ritter","doi":"10.1007/s13538-026-02114-7","DOIUrl":"10.1007/s13538-026-02114-7","url":null,"abstract":"<div><p>In this paper, we discuss how the principle of Galilean invariance, when applied to the conservation principle of total mechanical energy, imposes certain conditions on the choice of the particle system considered. First, changes in kinetic energy are not, generally, Galilean invariant, and second, potential energy must be defined for an interaction. We extend the definition of potential energy for interacting particles and show that total potential energy cannot be defined, in an invariant way, for arbitrary particle systems. These problems can only be solved if we consider closed systems. We also show how this approach is appropriate for applications of the work-energy theorem and the principle of energy conservation to continuous systems.</p></div>","PeriodicalId":499,"journal":{"name":"Brazilian Journal of Physics","volume":"56 4","pages":""},"PeriodicalIF":1.8,"publicationDate":"2026-06-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1007/s13538-026-02114-7.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148323704","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"General Unitary SU(1, 1) Formulation of TFD and its Relation to Tomita-Takesaki Theory","authors":"Alexandre L. Gadelha,&nbsp;Daniel L. Nedel,&nbsp;Carlos R. Senise Jr.","doi":"10.1007/s13538-026-02117-4","DOIUrl":"10.1007/s13538-026-02117-4","url":null,"abstract":"<div><p>We revisit the TFD formulation for finite-temperature field theory and demonstrate its fundamental role in grasping key aspects of real-time finite-temperature field theory. Specifically, we demonstrate that the general unitary <b><i>SU</i></b><b>(1,1)</b> formulation of TFD, in which the conjugation rules are redefined, is consistent with the GNS construction and Tomita-Takesaki theory. We calculate the <b><i>SU</i></b><b>(1,1)</b> thermal propagator and show that the KMS condition is independent of the choice of the <b><i>SU</i></b><b>(1,1)</b> parameters.</p></div>","PeriodicalId":499,"journal":{"name":"Brazilian Journal of Physics","volume":"56 4","pages":""},"PeriodicalIF":1.8,"publicationDate":"2026-06-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1007/s13538-026-02117-4.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148323544","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Influence of the pH on the Synthesis of Carbon Quantum Dots and Graphene Quantum Dots","authors":"Pedro Holland de Oliveira,&nbsp;Ana Champi","doi":"10.1007/s13538-026-02116-5","DOIUrl":"10.1007/s13538-026-02116-5","url":null,"abstract":"<div><p>In this work, we confirmed the presence of Carbon Quantum Dots (CQDs) by optical techniques such as UV-visible and photoluminescence (PL), after filtering the result of carbonization and sulfonation of microcrystalline cellulose (MCC), which are synthesis processes for obtaining these nanomaterials. The high-resolution transmission electron microscopy (HR-TEM) confirmed, not only the size of the particles, but the crystalline pattern of the carbon-based nanoparticles. The HR-TEM also indicates the presence of Graphene Quantum Dots (GQDs), as anisotropic-shaped particles were observed. Fluorescence and absorbance indicate the pH dependence on optical and structural properties, as well as on the production of CQDs and GQDs. The pH may influence the syntheses of CQDs and GQDs and the origin of their fluorescence, due to presence of functional groups such as hydroxyl, carboxyl, carbonyl, epoxy, and sulfoxide at low pH, and in the edge regions of these particles, with sp² hybridization. The Fourier Transform Infrared (FTIR) spectra was also measured, allowing to understand the functional groups present in the samples, and so, understand the groups responsible for the fluorescence.</p></div>","PeriodicalId":499,"journal":{"name":"Brazilian Journal of Physics","volume":"56 4","pages":""},"PeriodicalIF":1.8,"publicationDate":"2026-06-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1007/s13538-026-02116-5.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148281760","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Effects of Transition Metal Elements on the Electronic, Magnetic, and Mechanical Properties of CePd2In4 and CePt2In4","authors":"Ozgur Deniz Kocaoz,&nbsp;Haci Ozisik,&nbsp;Engin Deligoz","doi":"10.1007/s13538-026-02115-6","DOIUrl":"10.1007/s13538-026-02115-6","url":null,"abstract":"<div><p>The effects of transition metal substitution on the structural, electronic, magnetic, mechanical, and lattice dynamical properties of CePd₂In₄ and CePt₂In₄ intermetallic compounds were systematically investigated using first-principles calculations within the generalized gradient approximation. This work constitutes the first comprehensive theoretical study of these materials. The calculated lattice parameters are in agreement with available experimental data. The mechanical stability of both compounds is confirmed as their second-order elastic constants satisfy the Born stability criteria. Furthermore, phonon dispersion calculations reveal no imaginary frequencies throughout the Brillouin zone, confirming the dynamical stability of both compounds. Analysis of the mechanical properties revealed significant elastic anisotropy. Electronic structure calculations indicate metallic behaviour arising from the overlap between valence and conduction bands. The combination of high average atomic mass and relatively weak bond strength leads to low Debye temperatures and low thermal conductivity. The estimated melting temperatures are relatively high for both compounds, indicating their suitability for high-temperature applications. These findings suggest that CePd₂In₄ and CePt₂In₄ compounds may be promising candidates for high-temperature and thermal control applications.</p></div>","PeriodicalId":499,"journal":{"name":"Brazilian Journal of Physics","volume":"56 4","pages":""},"PeriodicalIF":1.8,"publicationDate":"2026-06-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1007/s13538-026-02115-6.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148281418","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Two-Photon Optical Boolean Processor","authors":"M. G. Damaceno,&nbsp;R. C. Souza Pimenta,&nbsp;L. Marques Fagundes,&nbsp;R. Medeiros de Araújo,&nbsp;N. Rubiano da Silva,&nbsp;P. H. Souto Ribeiro","doi":"10.1007/s13538-026-02111-w","DOIUrl":"10.1007/s13538-026-02111-w","url":null,"abstract":"<div><p>We propose an experimental scheme that realizes several Boolean operations nonlocally and simultaneously by exploiting the transverse spatial degrees of freedom (TSDF) of photon pairs generated via spontaneous parametric down-conversion (SPDC). Binary information is encoded as matrices in the TSDF using Digital Micromirror Devices (DMDs) placed in the signal and idler beams. The coincidence counting rate for corresponding matrix elements yields the results of six different Boolean operations. We illustrate a possible implementation, discussing its energy costs and finding its capability to process 25 operations in parallel with only a few hundred photons.</p></div>","PeriodicalId":499,"journal":{"name":"Brazilian Journal of Physics","volume":"56 4","pages":""},"PeriodicalIF":1.8,"publicationDate":"2026-06-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1007/s13538-026-02111-w.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148281388","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Comment on “Comparative Physical and Physicochemical Characterization of Normal Saline Activated by Two Atmospheric-pressure Plasma Systems”","authors":"Fellype do Nascimento","doi":"10.1007/s13538-026-02110-x","DOIUrl":"10.1007/s13538-026-02110-x","url":null,"abstract":"","PeriodicalId":499,"journal":{"name":"Brazilian Journal of Physics","volume":"56 4","pages":""},"PeriodicalIF":1.8,"publicationDate":"2026-06-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148281232","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Thickness-Driven Modulation of Structural, Optical, and UV Photoconductive Properties of ZnO Thin Films for Optoelectronic Applications","authors":"Pranaw Kumar,&nbsp;Mukul Kumar Das","doi":"10.1007/s13538-026-02112-9","DOIUrl":"10.1007/s13538-026-02112-9","url":null,"abstract":"<div><p>Numerous researchers agree that zinc oxide (ZnO) is a highly prospective metal oxide semiconductor for use in gas sensing and optoelectronics. In this work, RF magnetron sputtering was used to deposit ZnO thin films with thicknesses ranging from 40 nm to 200 nm on soda-lime glass substrates. Field emission scanning electron microscopy (FESEM), X-ray diffraction (XRD), photoluminescence (PL), optical spectroscopy, and current–voltage (I–V) measurements under both dark and ultraviolet (UV) illumination conditions were used to systematically examine the impact of film thickness on the structural, morphological, optical, and electrical characteristics. All films had a highly preferred (002) orientation, which indicates <i>c</i>-axis-oriented growth, according to XRD analysis. As thickness increased, crystallite size increased from about 15 nm to about 35 nm. In addition to the beginning of morphological coarsening at 200 nm, FESEM observations revealed a gradual evolution from fine, densely packed grains at lower thickness to larger, coalesced grains at higher thickness. High transparency (&gt; 80%) in the visible region was found in optical studies, and as thickness increased, transmittance gradually decreased, and the absorption edge shifted to the red. Microstructural evolution and potential strain relaxation effects are responsible for the optical band gap’s decrease from 3.41 eV to 3.29 eV. The photoluminescence spectra showed a broad deep-level emission in the visible region and near-band-edge emission in the UV region. While thinner and intermediate thicknesses showed strong near-band-edge emission, thicker films (&gt; 120 nm) showed broadening and decreased intensity of this peak along with increased deep-level emission, indicating a greater contribution from recombination processes related to defects. Ohmic contact behavior and the existence of photoconductive response were indicated by electrical measurements that showed linear and symmetric I-V characteristics under both dark and UV illumination. Up to an intermediate range, the photocurrent increased with thickness; at higher thicknesses, the contrast between illuminated and dark currents decreased. Overall, the results show how ZnO thin-film structural and optoelectronic properties are influenced by film thickness, with intermediate thicknesses providing a balance between crystallinity, optical transparency, and photoconductive response.</p></div>","PeriodicalId":499,"journal":{"name":"Brazilian Journal of Physics","volume":"56 4","pages":""},"PeriodicalIF":1.7,"publicationDate":"2026-06-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148236999","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Acoustic Interaction Force Between Two Identical Compressible Particles Trapped in an Acoustofluidic Nodal Plane","authors":"Glauber T. Silva","doi":"10.1007/s13538-026-02102-x","DOIUrl":"10.1007/s13538-026-02102-x","url":null,"abstract":"<div><p>We derive a closed-form expression for the acoustic interaction force between two identical compressible particles trapped in an acoustofluidic nodal plane. Working in the long-wavelength scattering regime for an ideal fluid, we solve the coupled scattering problem within a fifth-order multipole expansion. The resulting force law extends the Silva–Bruus theory through explicit finite-separation corrections, while recovering it in the weak-density-contrast and large-separation limits. In the close-range regime, the interaction force retains the characteristic inverse-fourth-power dependence on interparticle distance, with a prefactor renormalized by repeated rescattering. Comparison with previous numerical calculations and experiments shows excellent agreement with ideal-fluid numerics in the weak-density-contrast regime, but substantially larger deviations from several experiments, indicating that viscosity, acoustic streaming, and hydrodynamic interactions remain important for quantitative prediction.</p></div>","PeriodicalId":499,"journal":{"name":"Brazilian Journal of Physics","volume":"56 4","pages":""},"PeriodicalIF":1.7,"publicationDate":"2026-06-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1007/s13538-026-02102-x.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148236834","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Effect of Microwave Hybrid Heating on The Structure and Magnetic Properties of Lead Hexaferrite","authors":"D. G. Maldonado,&nbsp;A. Lobo Guerrero,&nbsp;F. J. Santos-López,&nbsp;R. Murillo-Ortiz,&nbsp;J. Guerrero-Paz,&nbsp;M. Vargas-Ramírez","doi":"10.1007/s13538-026-02108-5","DOIUrl":"10.1007/s13538-026-02108-5","url":null,"abstract":"<div><p>In this study, the structural and magnetic properties of lead hexaferrite (PbFe₁₂O₁₉) synthesized via low-power microwave hybrid heating (MHH) were investigated and compared against the conventional solid-state reaction method. Structural properties and phase purity were analyzed using X-ray diffraction and the Rietveld refinement method, while magnetic behavior was evaluated via Vibrating Sample Magnetometry. Kinetically, the rapid heating of the MHH process effectively overcame traditional solid-state diffusion bottlenecks by forming an intermediate plumboferrite (Pb₂Fe₁₁O_18.19) structural scaffold, enabling the complete hexaferrite crystallization in 40 min. Furthermore, Rietveld refinement revealed a 1.13% volumetric compaction of the unit cell in the MHH-processed samples. This structural compaction directly correlated with an intrinsic magnetic hardening, quantitatively supported by a 23% increase in the magnetocrystalline anisotropy constant (<i>K</i>₁) and a nearly 20% increment in the maximum energy product (<i>BH</i>)_max compared to the samples obtained from the solid-state reaction method. Ultimately, the synergetic combination of a refined microstructure and enhanced intrinsic magnetocrystalline anisotropy leads to the improved magnetic performance achieved by the MHH method.</p></div>","PeriodicalId":499,"journal":{"name":"Brazilian Journal of Physics","volume":"56 4","pages":""},"PeriodicalIF":1.7,"publicationDate":"2026-06-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148172756","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}