{"title":"Solving the missing baryon problem: A review of observational and theoretical advances","authors":"V. Priyadharshini, S. Vijikumar, V. Bhuvaneshwari","doi":"10.1134/S0040577925060017","DOIUrl":"10.1134/S0040577925060017","url":null,"abstract":"<p> The missing baryon problem represents a longstanding challenge in cosmology, highlighting a discrepancy between the amount of baryonic matter predicted by cosmological models and the amount directly observed in the universe. While observations of the cosmic microwave background and Big Bang nucleosynthesis accurately constrain the baryon density of the early universe, only a fraction of this baryonic matter is accounted for in stars, galaxies, and hot gas within galaxy clusters today. Recent advances suggest that much of the missing baryonic matter resides in the warm–hot intergalactic medium (WHIM), a diffuse, filamentary gas with temperatures of <span>(10^5)</span>–<span>(10^7)</span> K. Detecting the WHIM has been challenging due to its low density and weak emissions. However, breakthroughs in observational techniques, such as X-ray and UV spectroscopy, along with cosmological simulations, have provided compelling evidence for its presence. This review synthesizes the latest theoretical and observational efforts to locate the missing baryons, emphasizing the role of the WHIM, novel detection strategies, and their implications for understanding large-scale cosmic structure and galaxy formation. Future missions promise to refine these findings, bringing us closer to resolving this fundamental issue in astrophysics. </p>","PeriodicalId":797,"journal":{"name":"Theoretical and Mathematical Physics","volume":"223 3","pages":"879 - 887"},"PeriodicalIF":1.1,"publicationDate":"2025-06-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145145194","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}
G. Durga Priyadarsini, B. Umesh, G. C. Sankad, G. Murali
{"title":"Enhancing microfluidic transport via pulsatile flow: A study of flow regimes and efficiency optimization","authors":"G. Durga Priyadarsini, B. Umesh, G. C. Sankad, G. Murali","doi":"10.1134/S0040577925060157","DOIUrl":"10.1134/S0040577925060157","url":null,"abstract":"<p> Microfluidic technologies have emerged as transformative diagnostic tools in health care, significantly accelerating diagnostic processes and enhancing patient outcomes. This article explores the principles of fluid dynamics in microfluidic systems, particularly at low Reynolds numbers, and their practical applications. Traditional microfluidic devices often rely on additional hardware for liquid handling, increasing costs, complicating maintenance, and limited accessibility in low-resource settings. To address these challenges, the study introduces a mechanically pulsating heat exchanger utilizing microfluidic technologies, which incorporates internal walls within the flow channel. This innovative design alters the flow patterns of liquid and vapor plugs, significantly improving thermal efficiency in heat pipes. The article highlights the role of flow patterns in preventing blockages and their utility in generating emulsion droplets, blending substances, and separating components through periodic mass flow fluctuations. Furthermore, the advantages of pulsatile flow in microfluidic systems are examined. Unlike steady flows, pulsatile flows offer unique benefits, such as simulating physiological conditions, enhancing cell culture environments, and automating bioassays. These capabilities make pulsatile flows invaluable for advancing biomedical research and diagnostic technologies. However, realizing their full potential requires deeper physics-based insights and further research. This work underscores the promise of microfluidic systems in health care and beyond, paving the way for cost-effective, efficient, and accessible diagnostic solutions. </p>","PeriodicalId":797,"journal":{"name":"Theoretical and Mathematical Physics","volume":"223 3","pages":"1032 - 1047"},"PeriodicalIF":1.1,"publicationDate":"2025-06-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145145141","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}
G. Murali, P. Lakshmi, M. Amarnath, J. Venkata Madhu, A. P. Lingaswamy
{"title":"Three-dimensional MHD flow of a radiative Eyring–Powell nanofluid: Exploring Hall effects and heat transfer","authors":"G. Murali, P. Lakshmi, M. Amarnath, J. Venkata Madhu, A. P. Lingaswamy","doi":"10.1134/S0040577925060170","DOIUrl":"10.1134/S0040577925060170","url":null,"abstract":"<p> In the framework of magnetic fields, thermophoresis, porous media, and Brownian motion, this study examines the rotation and Hall current effects on an electrically conductive, viscous, incompressible, non-Newtonian Eyring–Powell fluid, including nanofluid particles, across a stretched sheet. The governing nonlinear partial differential equations (PDEs) in this work are converted into ordinary differential equations (ODEs) using appropriate similarity transformations. This system of ODEs is then numerically solved using the MATLAB bvp4c solver. Effects of numerous crucial factors on the velocity, temperature, and concentration profiles are shown in graphs. Furthermore, the stretched sheet mass transfer rate, heat transfer rate, and skin-friction coefficient are calculated and shown in tables. The published results and the present findings are compared in a tabular analysis. </p>","PeriodicalId":797,"journal":{"name":"Theoretical and Mathematical Physics","volume":"223 3","pages":"1070 - 1086"},"PeriodicalIF":1.1,"publicationDate":"2025-06-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145144937","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":"Unitary Ramanujan sum for power system applications","authors":"E. Kiran Babu, Y. Rajasekhara Gowd, G. Satheesh","doi":"10.1134/S0040577925060108","DOIUrl":"10.1134/S0040577925060108","url":null,"abstract":"<p> The renowned Indian mathematician Srinivasa Ramanujan introduced a significant summation in 1918, known as the Unitary Ramanujan Sum <span>(C^*_N(L))</span>. In recent years, this sum has garnered considerable attention in the fields of signal and image processing. In this paper, we focus on the application of the Unitary Ramanujan Sum to power systems. A line-to-ground fault is simulated in the MATLAB platform with an IEEE <span>(9)</span>-bus system and the results are presented for the validation of the Unitary Ramanujan Sum application. </p>","PeriodicalId":797,"journal":{"name":"Theoretical and Mathematical Physics","volume":"223 3","pages":"967 - 973"},"PeriodicalIF":1.1,"publicationDate":"2025-06-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145145143","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}
Sk. Nuslin, D. A. Rawoof, P. L. Pallavi, D. Padma, D. Naheed, M. L. Gundagani
{"title":"Radiation influence on transient MHD convection over a permeable surface with thermal diffusion","authors":"Sk. Nuslin, D. A. Rawoof, P. L. Pallavi, D. Padma, D. Naheed, M. L. Gundagani","doi":"10.1134/S0040577925060042","DOIUrl":"10.1134/S0040577925060042","url":null,"abstract":"<p> We investigate the impact of radiation on a transient magnetohydrodynamic (MHD) natural convective flow past an upright permeable surface, considering the thermal diffusion. The fundamental equations, a coupled system of nonlinear partial differential equations, defy analytical solutions. Consequently, a numerical solution employing the Galerkin finite-element method was implemented. We explore the flow behavior under varying conditions, encompassing the thermal diffusion, Schmidt number, Grashof number, magnetic field strength, Prandtl number, heat source parameter, and radiative parameter. Results are presented graphically, illustrating the variations in velocity, temperature, and density profiles. Furthermore, the analysis quantifies the effects on the coefficient of skin friction and the Nusselt number. This comprehensive numerical approach provides valuable insights into the complex interplay of these parameters within the specified MHD free convective flow regime. </p>","PeriodicalId":797,"journal":{"name":"Theoretical and Mathematical Physics","volume":"223 3","pages":"915 - 925"},"PeriodicalIF":1.1,"publicationDate":"2025-06-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145144936","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}
Pudari Chandra Mohan, Y. Suresh Kumar, Anjanna Matta
{"title":"Magnetohydrodynamic unsteady rotating Casson fluid flow with Hall and ion-slip impacts","authors":"Pudari Chandra Mohan, Y. Suresh Kumar, Anjanna Matta","doi":"10.1134/S0040577925060169","DOIUrl":"10.1134/S0040577925060169","url":null,"abstract":"<p> This research explores the influence of Hall ion slip and diffusion thermo effects on the unsteady magnetohydrodynamic (MHD) flow of a viscous, incompressible, electrically conducting, and optically thick radiating Casson fluid through a porous medium in a rotating system. The flow is analyzed under the impact of Joule heating and viscous dissipation, both of which play a crucial role in altering the thermal and hydrodynamic behavior of the fluid. The governing nonlinear equations for velocity, temperature, and concentration are derived and solved using a two-term perturbation technique, subject to physically relevant boundary conditions. The study provides exact solutions to these equations, offering insights into the intricate interplay between key parameters, such as the Hall current, thermal diffusion, porosity, and rotating system’s influence. The variations in velocity, temperature, and concentration profiles with respect to these parameters are illustrated graphically to highlight their effects comprehensively. Furthermore, the skin friction coefficient, the Nusselt number, and the Sherwood number are derived and presented in tabular form, enabling a quantitative assessment of the flow’s thermal and mass transfer characteristics. To validate the proposed solutions, comparisons are made with previously published results, demonstrating excellent agreement and reinforcing the reliability of the analysis. These findings contribute to a deeper understanding of the dynamics of electrically conducting fluids in porous and rotating environments, with potential applications in advanced engineering systems, thermal management, and industrial processes involving MHD flows. </p>","PeriodicalId":797,"journal":{"name":"Theoretical and Mathematical Physics","volume":"223 3","pages":"1048 - 1069"},"PeriodicalIF":1.1,"publicationDate":"2025-06-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145145142","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}
V. R. Prasad, K. Jyothi, C. Sai Pranathi, K. Reddy
{"title":"Heat transfer analysis of a pineapple leaf fiber nanofluid/MWCNT–water convective flow over a disk","authors":"V. R. Prasad, K. Jyothi, C. Sai Pranathi, K. Reddy","doi":"10.1134/S0040577925060121","DOIUrl":"10.1134/S0040577925060121","url":null,"abstract":"<p> We examine the heat and mass transfer characteristics of nanofluid containing a pineapple leaf fiber (PLF) and multi-walled carbon nanotubes (MWCNTs) dispersed in water. We evaluate the Nusselt and Sherwood numbers and the skin friction coefficient under different conditions. The PLF is organic, MWCNTs are widely used for enhancing thermal conductivity. Equations are solved using numerical finite-element methods to analyze the impact of nanoparticles on transfer phenomena. Both nanofluids enhance transfer rates with MWCNTs showing superior thermal properties. The PLF offers sustainability and cost benefits. This study contributes to knowledge on nanofluids, sustainable materials, and applications in thermal management. </p>","PeriodicalId":797,"journal":{"name":"Theoretical and Mathematical Physics","volume":"223 3","pages":"992 - 999"},"PeriodicalIF":1.1,"publicationDate":"2025-06-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145145144","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":"A generalized Sylvester equation and discrete Ablowitz–Kaup–Newell–Segur type equations","authors":"Ya-Nan Hu, Shou-feng Shen, Song-lin Zhao","doi":"10.1134/S004057792505006X","DOIUrl":"10.1134/S004057792505006X","url":null,"abstract":"<p> A generalized Sylvester equation is introduced to revisit the Cauchy matrix schemes of the discrete negative-order Ablowitz–Kaup–Newell–Segur (AKNS) equation and the discrete third-order AKNS equation. Starting from the generalized Sylvester equation, we introduce a master function <span>(boldsymbol{S}^{(i,j)})</span> that admits a recurrence relation under a constraint relation. By imposing the shifts on matrices <span>(boldsymbol{r})</span> and <span>(,^mathrm{t}! {boldsymbol{s}})</span>, the shifts of the master function <span>(boldsymbol{S}^{(i,j)})</span> are derived. By introducing the dependent variables, the above two discrete AKNS equations are constructed as closed forms. For two different choices of the coefficient matrices in the Sylvester equation that preserve the constraint condition, exact solutions in asymmetric and symmetric cases are presented, with one-soliton, two-soliton, and the simplest Jordan-block solutions given explicitly. Continuum limits to the semidiscrete and continuous AKNS-type equations as well as the corresponding exact solutions are also discussed. </p>","PeriodicalId":797,"journal":{"name":"Theoretical and Mathematical Physics","volume":"223 2","pages":"782 - 809"},"PeriodicalIF":1.0,"publicationDate":"2025-05-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144140232","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":"Integration of equations of acoustics of inhomogeneous media","authors":"O. V. Kaptsov","doi":"10.1134/S0040577925050058","DOIUrl":"10.1134/S0040577925050058","url":null,"abstract":"<p> We propose two approaches to integrating linear acoustic equations in inhomogeneous media. The first is based on the Laplace cascade method. For one-dimensional nonstationary equations, new solutions are obtained that depend on two arbitrary functions. These solutions are generalizations of relatively undistorted waves. In the two-dimensional case, conformal maps are used that allow reducing some equations with variable coefficients to equations with constant coefficients. Special three-dimensional equations can also be transformed to a wave equation. </p>","PeriodicalId":797,"journal":{"name":"Theoretical and Mathematical Physics","volume":"223 2","pages":"770 - 781"},"PeriodicalIF":1.0,"publicationDate":"2025-05-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144140202","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":"Butterfly velocity and chaos suppression in de Sitter space","authors":"D. S. Ageev","doi":"10.1134/S0040577925050101","DOIUrl":"10.1134/S0040577925050101","url":null,"abstract":"<p> We study the holographic CFT in the de Sitter static patch at a finite temperature <span>(T)</span> and chemical potential. We find that the butterfly velocity <span>(v_B)</span> in such a field theory degenerates for all values of the Hubble parameter <span>(H)</span> and <span>(T)</span>. We interpret this as a chaos disruption caused by the interplay between the expansion of chaotic correlations constrained by <span>(v_B)</span> and effects caused by the de Sitter curvature. The chemical potential restores healthy butterfly velocity for some range of temperatures. Also, we provide some analogy of this chaos suppression with the Schwinger effect in the de Sitter space and black hole formation from shock wave collisions. </p>","PeriodicalId":797,"journal":{"name":"Theoretical and Mathematical Physics","volume":"223 2","pages":"863 - 871"},"PeriodicalIF":1.0,"publicationDate":"2025-05-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144140254","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}