Size Scaling Research Articles

Symmetric Mass Generation with Four SU(2) Doublet Fermions

We study a single exactly massless staggered fermion in the fundamental representation of an SU(2) gauge group. We utilize an nHYP-smeared fermion action supplemented with additional heavy Pauli-Villars fields that serve to decrease lattice artifacts. The phase diagram exhibits a clear two-phase structure with a conformal phase at weak coupling and a novel new phase, the symmetric mass generation (SMG) phase, appearing at strong coupling. The SMG phase is confining with all states gapped and chiral symmetry unbroken. Our finite size scaling analysis provides strong evidence that the phase transition between these two phases is continuous, which would allow for the existence of a continuum SMG phase. Furthermore, the renormalization group flows are consistent with a β function that vanishes quadratically at the new fixed point, suggesting that the Nf=4 flavor SU(2) gauge theory lies at the opening of the conformal window. Published by the American Physical Society 2025

Geometric effects in the measurement of the remanent ferroelectric polarization at the nanoscale

A resurgence of research on ferroelectric materials has recently occurred due to their potential to enhance the performance of memory and logic. For the design and commercialization of such technologies, it is important to understand the physical behavior of ferroelectrics and the interplay with device size, geometry, and fabrication processes. Here, we report a study of geometric factors that can influence the measurement of the remanent ferroelectric polarization, an important measurement for understanding wakeup, retention, and endurance in ferroelectric technologies. The areal size scaling of W/Hf0.5Zr0.5O2/W capacitors is compared in two typical structures: an island top electrode with a continuous ferroelectric layer and an island top electrode/ferroelectric layer (etched ferroelectric layer). Error in the evaluation of the switched area leads to anomalous scaling trends and increasing apparent remanent polarization as capacitor sizes decrease, most strongly in continuous ferroelectric layer capacitors. Using TEM and electric field simulations, this is attributed to two effects: a processing artifact from ion milling that creates a foot on the top electrode and a fringe electric field penetrating outside of the capacitor area. With the correction of the switching area, the 2Pr for both samples agree (∼32 μC cm−2) and is invariant in the capacitor sizes used (down to 400 nm diameter). Our work demonstrates that the determination of the actual capacitor structure and local electric field is needed to evaluate the intrinsic ferroelectric behavior at the nanoscale.

Rescaled Free-Volume Theory of Diffusivity of Polystyrene in Various Organic Solvents.

It remains, as yet, far from satisfactory to account for the explicit role of the solvent effect on the transport behaviors of various polymer solutions, especially depending upon the polymer concentration. Here, we exploit the statistical mechanical free-volume theory to describe the diffusivity of polymer solutions in an analytical form in terms of the solvent-solvent, particle-particle, and solvent-particle pair correlation functions as a function of the polymer concentration. To be specific, we introduce a particle size scaling parameter as a measure of the effective polymer-solvent interaction that leads to different polymer globular states, depending on the embedding solvents. Upon applying the theory to the polystyrene (PS) in various organic solvents, the agreement between the theory and experiment is found to be very good over the entire PS volume fraction ϕ investigated by the experiment, i.e., up to ϕ ∼ 0.50. The scaling parameter determined is discussed in association with the Flory-Huggins polymer-solvent interaction parameter χ available in the literature.

Changes in the ideal body shape associated with adolescent rowing-ergometry performance following a 6-week training intervention: New scaling insights using three-dimensional allometry.

Scaling, to remove the effects of body size, is an important methodological approach for enabling an equitable comparison of performance differences between individuals who vary in anthropometric characteristics. Many previous studies using scaling in sport have done so based on only one or two anthropometric characteristics, with only one study to date adopting a three-dimensional approach. To apply a three-dimensional allometric model to rowing ergometer performance (REP) in adolescents, and to detect whether key 'scaling' parameters remain stable when scaling REP both before and after a 6-week training intervention. Novel three-dimensional allometric models were used, incorporating body mass, stature and waist circumference (WC) to detect the most appropriate body size dimension(s) and scaling parameters associated with REP before and after a 6-week training intervention. Using this more flexible and sensitive three-dimensional allometry demonstrated that, following 6-weeks of training, there was a change in the ideal body shape associated with REP. Before training, taller, but not heavier, adolescents performed better. After 6-weeks of training, older participants with a greater body mass but smaller WC performed better. Scaling approaches are important for evaluating performance differences between individuals of differing body size. The findings from the current study (using a novel three-dimensional allometry approach) emphasise that relatively subtle changes in individuals' behavioural characteristics, such as changes in their training/fitness status, can result in quite dramatic changes in the body dimension characteristics and scaling parameters deemed to be key for performance in activities such as REP.

Exact results on the dynamics of the stochastic Floquet-East model*

Abstract We introduce a stochastic generalisation of the classical deterministic Floquet-East model, a discrete circuit with the same kinetic constraint as the East model of glasses. We prove exactly that, in the limit of long time and large size, this model has a large deviation phase transition between active and inactive dynamical phases. We also compute the finite time and size scaling of general space-time fluctuations, which for the case of inactive regions gives rise to dynamical hydrophobicity. We also discuss how, through the Trotter limit, these exact results also hold for the continuous-time East model, thus proving long-standing observations in kinetically constrained models. Our results here illustrate the applicability of exact tensor network methods for solving problems in many-body stochastic systems.

(Invited) Cu-Cu Bonding in Semiconductor Packaging: Utilizing Texture Control for Enhanced Performance

The rapid development of IT markets, including big data, AI, 5G, IoT, smart automotive, and datacenters, has led to an increase in demand for advanced packaging solutions. With the IC density doubling through the shrinking of feature sizes, significant improvements in IC device performance have been achieved. This continuous scaling of feature sizes has prompted changes in packaging technology, with three-dimensional die stacking technologies like through-silicon vias (TSVs) and microbumps emerging as crucial innovations.However, traditional microbumps suffer from issues such as the Kirkendall effect, side wetting, and solder depletion, which compromise both mechanical and electrical properties. Innovative solutions are thus essential to address these challenges effectively. Cu to Cu bonding eliminates the formation of intermetallic compounds, mitigating the problems associated with microbumps. Additionally, Cu to Cu bonding offers superior electrical properties compared to microbumps, further enhancing its appeal.In particular, semiconductor devices requiring high-density packaging, like high bandwidth memory (HBM), have spurred interest in hybrid bonding. Additionally, the growing need for 3D interconnects in advanced packaging is becoming increasingly apparent.To this end, research is focusing on next-generation microbumps, particularly Cu-Cu bonding, as an alternative solution. Understanding the internal characteristics of Cu is crucial for promoting diffusion between Cu atoms at lower temperatures. Thus, nanotwinned Cu with a (111) preferred orientation has garnered significant research attention as a material that promotes diffusion between copper atoms, particularly in Cu-Cu bonding processes. However, research is lacking on the optimal grain orientation for the bonding process.By controlling crystal orientation through plating parameter adjustments, Cu films with three principal preferred orientations have been achieved. These films exhibit distinct mechanical properties based on their preferred orientation, with (111) preferred Cu showing the highest hardness due to the significant presence of nanotwins.In summary, advancements in 3D interconnect technologies, particularly in Cu-Cu bonding, hold promise for addressing the challenges in advanced packaging. By employing innovative solutions and exploring new materials and techniques, the semiconductor industry can continue to meet the evolving demands of the IT market while ensuring the reliability and performance of semiconductor devices.

Size, Scaling, and Sexual Size Dimorphism in Wild South African Thick-Tailed Greater Galagos (Otolemur crassicaudatus)

Size, Scaling, and Sexual Size Dimorphism in Wild South African Thick-Tailed Greater Galagos (Otolemur crassicaudatus)

Size scaling of large landslides from incomplete inventories

Abstract. Landslide inventories have become cornerstones for estimating the relationship between the frequency and size of slope failures, thus informing appraisals of hillslope stability, erosion, and commensurate hazard. Numerous studies have reported how larger landslides are systematically rarer than smaller ones, drawing on probability distributions fitted to mapped landslide areas or volumes. In these models, much uncertainty concerns the larger landslides (defined here as affecting areas ≥ 0.1 km2) that are rarely sampled and often projected by extrapolating beyond the observed size range in a given study area. Relying instead on size-scaling estimates from other inventories is problematic because landslide detection and mapping, data quality, resolution, sample size, model choice, and fitting method can vary. To overcome these constraints, we use a Bayesian multi-level model with a generalised Pareto likelihood to provide a single, objective, and consistent comparison grounded in extreme value theory. We explore whether and how scaling parameters vary between 37 inventories that, although incomplete, bring together 8627 large landslides. Despite the broad range of mapping protocols and lengths of record, as well as differing topographic, geological, and climatic settings, the posterior power-law exponents remain indistinguishable between most inventories. Likewise, the size statistics fail to separate known earthquakes from rainfall triggers and event-based triggers from multi-temporal catalogues. Instead, our model identifies several inventories with outlier scaling statistics that reflect intentional censoring during mapping. Our results thus caution against a universal or solely mechanistic interpretation of the scaling parameters, at least in the context of large landslides.

Catalytic growth in a shared enzyme pool ensures robust control of centrosome size.

Accurate regulation of centrosome size is essential for ensuring error-free cell division, and dysregulation of centrosome size has been linked to various pathologies, including developmental defects and cancer. While a universally accepted model for centrosome size regulation is lacking, prior theoretical and experimental works suggest a centrosome growth model involving autocatalytic assembly of the pericentriolar material. Here we show that the autocatalytic assembly model fails to explain the attainment of equal centrosome sizes, which is crucial for error-free cell division. Incorporating latest experimental findings into the molecular mechanisms governing centrosome assembly, we introduce a new quantitative theory for centrosome growth involving catalytic assembly within a shared pool of enzymes. Our model successfully achieves robust size equality between maturing centrosome pairs, mirroring cooperative growth dynamics observed in experiments. To validate our theoretical predictions, we compare them with available experimental data and demonstrate the broad applicability of the catalytic growth model across different organisms, which exhibit distinct growth dynamics and size scaling characteristics.

The people behind the papers - Saya Furukawa, Akira Satoh and Yoshihiro Morishita.

A remarkable feature of limb regeneration is the ability to regenerate normal limb morphology and anatomical patterning. Although it is thought that regeneration uses similar mechanisms to those employed during development, it is not well understood how this is achieved in the context of varying blastema size. In a new study, Akira Satoh, Yoshihiro Morishita and colleagues investigate the allometric scaling of blastema size and pattern expressions of key genes relative to the size of the limb stump in axolotls. To find out more about the work, we caught up with first author Saya Furukawa, and corresponding authors Akira Satoh, professor at Okayama University, and Yoshihiro Morishita, Principal Investigator at RIKEN, Japan.

Proficient Quantum-Dot Cellular Automata Based XOR Gate Layout Generator for Image Processing Applications

The Conservative lithography-based VLSI technology has been able to increase processing power and achieve proportionate scaling in feature size. However, present work expose that deterioration of these devices (as a result of vital physical confines of CMOS technology) will head to undesirable consequences such as doping fluctuations, power dissipation, short channel effects and electro-migration failures. These repercussions will cause a decline in a number of parameters, including diffusion barriers, off-state leakage, gate depletion, switching performance, and stray capacitances. Furthermore, it is predicted that the 7 nm channel dimension will mark the conclusion of the CMOS technology’s growth process. In order to replace conventional CMOS technology in the near future, extensive nanoscale research has been conducted in recent years. The CMOS technologies can function at frequencies of Tera-Hertz and can attain a consistency of 10 devices/cm2. However, the current strategy of reducing transistor count while maintaining the same design quality may soon be insufficient to overcome the commercial, architectural, and physical barriers. A novel technology that harnesses the advantages of nanoscale physics will have to replace the MOS transistor. A plethora of cutting-edge technologies, such as spin transistors, resonant tunnelling diodes (RTDs), carbon nanotubes (CNTs), and single electron transistors (SETs), are being investigated as potential replacements for conventional CMOS technology. Because nanotechnology has unique features that increase at such small feature sizes, it opens up new computational possibilities. When creating ultra-deep submicron circuits and getting around CMOSs limitations, quantum-dot Cellular Automata (QCA) is a nanotechnology that can take the place of CMOS. It is created on various scientific facts, including Effective QCA Designs and Their Applications. The proposed XOR Gate are compared with existing designs in terms of number of cells area and clock cycles. The proposed design is purely logical, fast and occupies ultra-less area.

Postsynaptic BMP signaling regulates myonuclear properties in Drosophila larval muscles.

The syncytial mammalian muscle fiber contains a heterogeneous population of (myo)nuclei. At the neuromuscular junction (NMJ), myonuclei have specialized positioning and gene expression. However, it remains unclear how myonuclei are recruited and what regulates myonuclear output at the NMJ. Here, we identify specific properties of myonuclei located near the Drosophila larval NMJ. These synaptic myonuclei have increased size in relation to their surrounding cytoplasmic domain (size scaling), increased DNA content (ploidy), and increased levels of transcription factor pMad, a readout for BMP signaling activity. Our genetic manipulations show that local BMP signaling affects muscle size, nuclear size, ploidy, and NMJ size and function. In support, RNA sequencing analysis reveals that pMad regulates genes involved in muscle growth, ploidy (i.e., E2f1), and neurotransmission. Our data suggest that muscle BMP signaling instructs synaptic myonuclear output that positively shapes the NMJ synapse. This study deepens our understanding of how myonuclear heterogeneity supports local signaling demands to fine tune cellular function and NMJ activity.

Reliable Synchronous and Asynchronous Counter Design in QCA

Due to rapid growth in the integrated circuit (IC) industry, the demand for compact digital system design is high. However, the continued technology reductions made the feasibility of further scaling down transistor size more challenging. In response to the growing demand for ultra-compact IC designs, the revolutionary quantum-dot cellular automata (QCA) technology has emerged as a promising solution. In a digital era, the counters are widely adopted in the peer-to-peer process flow to establish a mechanism for generating unique values for each identifier/number. In this work, a unique synchronous and asynchronous counters architecture is proposed with a reliable D and T flip-flop design. The proposed QCA architecture is implemented and validated with the QCA designer tool. Furthermore, in QCA technology, unreliable QCA designs can lead to frequent errors and malfunctions in the implemented logic. To overcome this challenge, the proposed design prioritizes cell placement (the relative positions of QCA cells) to make the circuit more robust. As a result, the circuit can still produce the expected functionality even if some QCA cells malfunction. Hence, to ensure the reliability of the proposed QCA architecture, the missing cell defect analysis is carried out in comparison with existing state-of-the-art designs. Based on comparison results, the unique designs like the proposed multiplexer, D flip-flop and T flip-flop design exhibit success rates of 67.28, 77.04 and 85.15%, respectively. The experimental results demonstrate that the proposed counter-architecture outperforms existing architectures.

Tangentially active polymers in cylindrical channels

We present an analytical and computational study characterizing the structural and dynamical properties of an active filament confined in cylindrical channels. We first outline the effects of the interplay between confinement and polar self-propulsion on the conformation of the chains. We observe that the scaling of the polymer size in the channel, quantified by the end-to-end distance, shows different anomalous behaviours under different confinement and activity conditions. In particular, we report scaling exponents that are markedly different from their passive counterparts. Interestingly, we show that the universal relation, describing the ratio between the end-to-end distance of passive polymer chains in cylindrical channels and in bulk is broken by activity. Finally, we show that the long-time diffusion coefficient under confinement can be rationalised by an analytical model, that takes into account the presence of the channel and the elongated nature of the polymer.

Superconductor to metal quantum phase transition with magnetic field in Josephson coupled lead islands on Graphene

Abstract Superconductor-to-metal transition with magnetic field and gate-voltage is studied in a Josephson junction array comprising of randomly distributed lead islands on exfoliated single-layer graphene. The superconductivity onset temperature at low magnetic-fields is fitted to the Werthamer-Helfand-Hohenberg theory to model the temperature dependence of the upper critical field. The magnetoresistance in the intermediate temperature and field regime is described using thermally activated flux flow dictated by field dependent activation barrier. The barrier also depends on the gate voltage which dictates the inter-island Josephson coupling and disorder. The magnetoresistance near the upper critical field at low temperatures shows signatures of a gate dependent continuous quantum phase transition between superconductor and metal. The finite size scaling analysis shows that this transition belongs to the $(2+1)$D-XY universality class without disorder.

Test of universality at first order phase transitions: The Lebwohl-Lasher model.

Finite size scaling for a first order phase transition, where a continuous symmetry is broken, is tested using an approximation of Gaussian probability distributions with a phenomenological "degeneracy" factor. Predictions are compared to the data from Monte Carlo simulations of the Lebwohl-Lasher model on L × L × L simple cubic lattices. The data show that the intersection of the fourth-order cumulant of the order parameter for different lattice sizes can be expressed in terms of the relative degeneracy q = 4π of the ordered and disordered phases. This result further supports the concept of universality at first order transitions developed recently.

High electroresistance in all-oxide ferroelectric tunnel junctions enabled by a narrow bandgap Mott insulator electrode

Ferroelectric tunnel junctions (FTJs) based on epitaxial complex oxide heterostructures are promising building blocks for developing low power nanoelectronics and neuromorphic computing. FTJs consisting of correlated oxide electrodes have distinct advantages in size scaling but only yield moderate electroresistance (ER) at room temperature due to the challenge in imposing asymmetric interfacial screening and large modulation of the tunneling potential profile. Here, we achieve large ER in all-oxide FTJs by paring a correlated metal with a narrow bandgap Mott insulator as electrodes. We fabricate epitaxial FTJs composed of 2.8 and 4 nm PbZr0.2Ti0.8O3 tunnel barriers sandwiched between correlated oxides LaNiO3 and Sr3Ir2O7 electrodes. An ER of 6500% has been observed at room temperature, which increases to over 105% at 100 K. The high ER can be attributed to ferroelectric polarization induced metal–insulator transition in interfacial Sr3Ir2O7, which enhances the potential asymmetry for the tunnel barrier. The temperature dependence of tunneling current shows that direct tunneling dominates in the on state, while the off-state conduction transitions from thermally activated behavior at high temperatures to Glazman–Matveev defect-mediated inelastic tunneling at low temperatures. Our study provides a viable material strategy for designing all-oxide FTJs with high ER, facilitating their implementation in nonvolatile memories and energy-efficient computing devices.

Finite-size spectrum of the staggered six-vertex model with antidiagonal boundary conditions

The finite-size spectrum of the critical staggered six-vertex model with antidiagonal boundary conditions is studied. Similar to the case of periodic boundary conditions, we identify three different phases. In two of those, the underlying conformal field theory can be identified to be related to the twisted U(1) Kac-Moody algebra. In contrast, the finite size scaling in the third regime, whose critical behaviour with the (quasi-)periodic BCs is related to the 2d black hole CFTs possessing a non-compact degree of freedom, is more subtle. Here with antidiagonal BCs imposed, the corrections to the scaling of the ground state grow logarithmically with the system size, while the energy gaps appear to close logarithmically. Moreover, we obtain an explicit formula for the Q-operator which is useful for numerical implementation.

Cautionary remarks on the planetary boundary visualisation

Abstract. The planetary boundary (PB) concept has captured attention across academia and the public alike. Its unique visual representation has been key to the development of the concept and its dissemination. In this commentary, we outline three areas of concern to facilitate further enhancement in the PB concept’s visualisation. First, the radial bar plot leads to a quadratic scaling of the effect sizes. Second, the colour gradations denoting the risk of each boundary transgression use complex non-linear patterns, which complicates interpretation. Third, non-linearly distorted colour scales and their fading make the visual perception for people suffering from colour-vision deficiency even more challenging or impossible. The conjunction of quadratic effect scaling and specific colour coding may unintentionally amplify the perception of high-risk areas. We recommend a careful revision of the visual language employed in PB communication. Addressing these concerns will make the PB visualisation a more accurate base for decision-makers.

Sparsity-Independent Lyapunov Exponent in the Sachdev-Ye-Kitaev Model.

The saturation of a recently proposed universal bound on the Lyapunov exponent has been conjectured to signal the existence of a gravity dual. This saturation occurs in the low-temperature limit of the dense Sachdev-Ye-Kitaev (SYK) model, N Majorana fermions with q body (q>2) infinite-range interactions. We calculate certain out-of-time-order correlators (OTOCs) for N≤64 fermions for a highly sparse SYK model and find no significant dependence of the Lyapunov exponent on sparsity up to near the percolation limit where the Hamiltonian breaks up into blocks. This provides strong support to the saturation of the Lyapunov exponent in the low-temperature limit of the sparse SYK. A key ingredient to reaching N=64 is the development of a novel quantum spin model simulation library that implements highly optimized matrix-free Krylov subspace methods on graphical processing units. This leads to a significantly lower simulation time as well as vastly reduced memory usage over previous approaches, while using modest computational resources. Strong sparsity-driven statistical fluctuations require both the use of a much larger number of disorder realizations with respect to the dense limit and a careful finite size scaling analysis. The saturation of the bound in the sparse SYK points to the existence of a gravity analog that would enlarge substantially the number of field theories with this feature.