Exotic Models Research Articles

An Examination on the Planning and Practice of Bilingual Education in Primary and Secondary Schools in Taiwan

Over the past few years, several reforms in language education have been outlined to implement the full-scale bilingualization of the education system in Taiwan. Among the 3392 public primary and secondary schools, nearly one-third of them have been implementing bilingual education in certain subjects. The vast majority of these schools have adopted Immersion, CLIL, or EMI as models for bilingual education. It has been argued that these exotic models cannot be “transplanted” to the education context of Taiwan, and he proposes the FERTILE model. Adopting this model as the theoretical framework, this qualitative study aims to examine how school practitioners plan and practice bilingual education in Taiwan. Data were collected through the document analysis of the progress reports from thirty-five primary and secondary schools and three focus group discussions (FGDs) with nine subject teachers. The findings show that the participants made considerable efforts to construct a bilingual environment and have an identical understanding about the strategies for bilingual instruction that emphasize subject knowledge and students’ comprehension. However, the participants experienced a diverse ecology of bilingual teacher learning communities and received differential support from the principals. Qualified and stable teaching manpower was identified as the key to sustain bilingual education. Implications to different education stakeholders are also discussed.

Gravitational Wave Constraints on Planetary-Mass Primordial Black Holes Using LIGO O3a Data.

Gravitational waves from subsolar mass inspiraling compact objects would provide almost smoking-gun evidence for primordial black holes (PBHs). We perform the first search for inspiraling planetary-mass compact objects in equal-mass and highly asymmetric mass-ratio binaries using data from the first half of the LIGO-Virgo-KAGRA third observing run. Though we do not find any significant candidates, we determine the maximum luminosity distance reachable with our search to be of O(0.1-100) kpc, and corresponding model-independent upper limits on the merger rate densities to be O(10^{3}-10^{-7}) kpc^{-3} yr^{-1} for systems with chirp masses of O(10^{-4}-10^{-2})M_{⊙}, respectively. Furthermore, we interpret these rate densities as arising from PBH binaries and constrain the fraction of dark matter that such objects could comprise. For equal-mass PBH binaries, we find that these objects would compose less than 4%-100% of DM for PBH masses of 10^{-2}M_{⊙} to 2×10^{-3}M_{⊙}, respectively. For asymmetric binaries, assuming one black hole mass corresponds to a peak in the mass function at 2.5M_{⊙}, a PBH dark-matter fraction of 10% and a second, much lighter PBH, we constrain the mass function of the second PBH to be less than 1 for masses between 1.5×10^{-5}M_{⊙} and 2×10^{-4}M_{⊙}. Our constraints, recently released, are robust enough to be applied to any PBH or exotic compact object binary formation models, and complement existence microlensing results.

T-duality and flavor symmetries in Little String Theories

We explore the T-duality web of 6D Heterotic Little String Theories, focusing on flavor algebra reducing deformations. A careful analysis of the full flavor algebra, including Abelian factors, shows that the flavor rank is preserved under T-duality. This suggests a new T-duality invariant in addition to the Coulomb branch dimension and the two-group structure constants. We also engineer Little String Theories with non-simply laced flavor algebras, whose appearance we attribute to certain discrete 3-form fluxes in M-theory. Geometrically, these theories are engineered in F-theory with non-Kähler favorable K3 fibers. This geometric origin leads us to propose that freezing fluxes are preserved across T-duality. Along the way, we discuss various exotic models, including two inequivalent Spin(32)/ℤ2 models that are dual to the same E8 × E8 theory, and a family of self-T-dual models.

Strange higher-spin topological systems in 3D

Motivated by the generation of action principles from off-shell dualisation, we present a general class of free, topological theories in three dimensional Minkowski spacetime that exhibit higher-spin gauge invariance. In the spin-two case, we recover a dual reformulation of the triplet system already known, while the higher-spin systems that we obtain seem to be new. They are associated with wild quivers. We study in which situations these exotic (or strange) higher-spin models can be extended to dS3 and AdS3 backgrounds, revealing that the flat limit of such models, when they exist, admits a one-parameter freedom. Interactions are studied in the simplest higher-spin case featuring spin-2 and spin-3 fields. We then give several higher-spin generalizations of these strange systems.

Disentangling the primordial nature of stochastic gravitational wave backgrounds with CMB spectral distortions

ABSTRACT The recent detection of a stochastic gravitational wave background (SGWB) at nanohertz frequencies by pulsar timing arrays (PTAs) has sparked a flurry of interest. Beyond the standard interpretation that the progenitor is a network of supermassive black hole binaries, many exotic models have also been proposed, some of which can potentially offer a better fit to the data. We explore how the various connections between gravitational waves (GWs) and cosmic microwave background (CMB) spectral distortions (SDs) can be leveraged to help determine whether an SGWB was generated primordially or astrophysically. To this end, we present updated k-space window functions that can be used for distortion parameter estimation on enhancements to the primordial scalar power spectrum. These same enhancements can also source GWs directly at second order in perturbation theory, so-called scalar-induced GWs (SIGWs), and indirectly through the formation of primordial black holes (PBHs). We perform a mapping of scalar power spectrum constraints into limits on the GW parameter space of SIGWs for δ-function features. We highlight that broader features in the scalar spectrum can explain the PTA results while simultaneously producing an SD within reach of future experiments. We additionally update PBH constraints from μ- and y-type SDs. Refined treatments of the distortion window functions widen existing SD constraints, and we find that a future CMB spectrometer could play a pivotal role in unravelling the origin of GWs imprinted at or below CMB anisotropy scales.

Identifying topological corner states in two-dimensional metal-organic frameworks

Due to the diversity of molecular building blocks, the two-dimensional (2D) metal-organic frameworks (MOFs) are ideal platforms to realize exotic lattice models in condensed matter theory. In this work, we demonstrate the universal existence of topological corner states in 2D MOFs with a star lattice configuration, and confirm the intriguing higher-order nontrivial topology in the energy window between two Kagome-bands, or between Dirac-band and four-band. Furthermore, combining first-principles calculations and scanning tunneling microscopy measurements, the unique topological corner state is directly identified in monolayer Ni3(HITP)2 (HITP = 2,3,6,7,10,11-hexaiminotriphenylene) grown on the Au(111) substrate. Our results not only illustrate the first organic topological state in the experiments, but also offer an exciting opportunity to study higher-order topology in 2D MOFs with the large insulating band gap.

Constraining exotic dark matter models with the dark ages 21-cm signal

ABSTRACT The dark ages 21-cm signal is a powerful tool for precision cosmology and probing new physics. We study two non-standard models: an excess radio background (ERB) model (possibly generated by dark matter decay) and the millicharged dark matter (mDM) model. These models were inspired by the possible EDGES detection of a strong global 21-cm absorption during cosmic dawn, but more generally they provide a way to anticipate the potential discovery space. During the dark ages the 21-cm global signal in the ERB model reaches a saturated form for an amplitude Ar = 0.4, where Ar is the radio background intensity at cosmic dawn relative to the cosmic microwave background. This amplitude is one fifth of the minimum required to explain the EDGES signal, and corresponds to just 0.1 per cent of the observed extragalactic background; it would give a signal that can be detected at 5.9σ significance (compared to 4.1σ for the standard signal) and can be distinguished from the standard (no ERB) signal at 8.5σ, all with a 1000 h global signal measurement. The 21-cm power spectrum has potentially more information, but far greater resources would be required for comparable constraints. For the mDM model, over a range of viable parameters, the global signal detection significance would be $4.7-7.2\, \sigma$, and it could be distinguished from standard at $2.2-9.3\, \sigma$. With an array of global signal antennas achieving an effective 100 000 h integration, the significance would be 10× better. Our analysis helps motivate the development of lunar and space-based dark ages experiments.

Coexistence of stable and unstable population dynamics in a nonlinear non-Hermitian mechanical dimer.

Non-Hermitian two-site dimers serve as minimal models in which to explore the interplay of gain and loss in dynamical systems. In this paper, we experimentally and theoretically investigate the dynamics of non-Hermitian dimer models with nonreciprocal hoppings between the two sites. We investigate two types of non-Hermitian couplings; one is when asymmetric hoppings are externally introduced, and the other is when the nonreciprocal hoppings depend on the population imbalance between the two sites, thus introducing the non-Hermiticity in a dynamical manner. We engineer the models in our synthetic mechanical setup comprised of two classical harmonic oscillators coupled by measurement-based feedback. For fixed nonreciprocal hoppings, we observe that, when the strength of these hoppings is increased, there is an expected transition from a PT-symmetric regime, where oscillations in the population are stable and bounded, to a PT-broken regime, where the oscillations are unstable and the population grows/decays exponentially. However, when the non-Hermiticity is dynamically introduced, we also find a third intermediate regime in which these two behaviors coexist, meaning that we can tune from stable to unstable population dynamics by simply changing the initial phase difference between the two sites. As we explain, this behavior can be understood by theoretically exploring the emergent fixed points of a related dimer model in which the nonreciprocal hoppings depend on the normalized population imbalance. Our study opens the way for the future exploration of non-Hermitian dynamics and exotic lattice models in synthetic mechanical networks.

Cross-diffusion models in complex frameworks from microscopic to macroscopic

This paper deals with the micro–macro derivation of models from the underlying description provided by methods of the kinetic theory for active particles. We consider the so-called exotic models according to the definition proposed in [ N. Bellomo, N. Outada, J. Soler, Y. Tao and M. Winkler, Chemotaxis and cross diffusion models in complex environments: Modeling towards a multiscale vision, Math. Models Methods Appl. Sci. 32 (2022) 713–792]. The first part of the presentation focuses on a survey and a critical analysis of some phenomenological models known in the literature. We refer to a selection of case studies, in detail, the transport of virus models, social dynamics, and Keller–Segel in a fluid. The second part shows how a Hilbert-type approach can be developed to derive models at the macroscale from the underlying description provided by the kinetic theory of active particles. The third part deals with the derivation of macroscopic models corresponding to the selected case studies. Finally, a forward look into the future research perspectives is proposed.

Simulating Dynamical Phases of Chiral p+ip Superconductors with a Trapped ion Magnet

Two-dimensional p+ip superconductors and superfluids are systems that feature chiral behavior emerging from the Cooper pairing of electrons or neutral fermionic atoms with nonzero angular momentum. Their realization has been a longstanding goal because they offer great potential utility for quantum computation and memory. However, they have so far eluded experimental observation both in solid-state systems as well as in ultracold quantum gases. Here, we propose to leverage the tremendous control offered by rotating two-dimensional trapped-ion crystals in a Penning trap to simulate the dynamical phases of two-dimensional p+ip superfluids. This is accomplished by mapping the presence or absence of a Cooper pair into an effective spin-1/2 system encoded in the ions’ electronic levels. We show how to infer the topological properties of the dynamical phases, and discuss the role of beyond mean-field corrections. More broadly, our work opens the door to use trapped-ion systems to explore exotic models of topological superconductivity and also paves the way to generate and manipulate skyrmionic spin textures in these platforms.Received 21 April 2022Revised 16 September 2022Accepted 31 October 2022DOI:https://doi.org/10.1103/PRXQuantum.3.040324Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article's title, journal citation, and DOI.Published by the American Physical SocietyPhysics Subject Headings (PhySH)Research AreasPenning trapsQuantum information with trapped ionsQuantum simulationSuperconductivityTopological superconductorsp-waveAtomic, Molecular & OpticalCondensed Matter, Materials & Applied Physics

Do We Need Exotic Models? Engineering Metrics to Enable Green Machine Learning from Tackling Accuracy-Energy Trade-offs

Machine learning (ML) has been shown to bypass key limitations of traditional methods (i.e., physical testing and numerical simulations) and hence presents itself as an attractive technology in engineering. While the integration of ML brings exciting opportunities, it also introduces unique challenges. One such challenge is related to the heavy reliance of ML on large datasets and computing facilities – for algorithm development, training, deployment, and storage. To realize Green ML (GML), this paper argues that ML users are to be cognizant of the hidden costs of energy consumption and subsequent carbon emissions arising from ML modeling, and hence they are ethically bound to apply ML responsibly. In this pursuit, a series of simple and exotic ML algorithms are examined, and their performance on a relatively large dataset (∼8000 observations) is documented on five fronts; predictive performance, model size, training time, energy consumption, and generatedcarbon emissions. In addition, this work also examines the influence of algorithmic architecture, processing language, number of features, as well as dataset size on model predictivity and energy consumption. Findings from this investigation infer that a 23–99% reduction in energy consumption and carbon emissions can be attained (while maintaining a comparable level of accuracy) by adopting simple as opposed to exotic ML models. The same findings have also led to the development of two new metrics that can tie the predictivity (i.e., level of accuracy) to the amount of energy consumed per algorithm. These metrics can be used to compare model performance in a similar manner to that traditionally used to assess the accuracy of ML predictions, thereby integrating energy-based awareness as a key dimension for model comparison.

Fractons on graphs and complexity

We introduce two exotic lattice models on a general spatial graph. The first one is a matter theory of a compact Lifshitz scalar field, while the second one is a certain rank-2 $U(1)$ gauge theory of fractons. Both lattice models are defined via the discrete Laplacian operator on a general graph. We unveil an intriguing correspondence between the physical observables of these lattice models and graph theory quantities. For instance, the ground state degeneracy of the matter theory equals the number of spanning trees of the spatial graph, which is a common measure of complexity in graph theory ("GSD = complexity"). The discrete global symmetry is identified as the Jacobian group of the graph. In the gauge theory, superselection sectors of fractons are in one-to-one correspondence with the divisor classes in graph theory. In particular, under mild assumptions on the spatial graph, the fracton immobility is proven using a graph-theoretic Abel-Jacobi map.

Event-Based Anomaly Detection for Searches for New Physics

This paper discusses model-agnostic searches for new physics at the Large Hadron Collider using anomaly-detection techniques for the identification of event signatures that deviate from the Standard Model (SM). We investigate anomaly detection in the context of a machine-learning approach based on autoencoders. The analysis uses Monte Carlo simulations for the SM background and several selected exotic models. We also investigate the input space for the event-based anomaly detection and illustrate the shapes of invariant masses in the outlier region which will be used to perform searches for resonant phenomena beyond the SM. Challenges and conceptual limitations of this approach are discussed.

Semantics of quantum programming languages: Classical control, quantum control

This chapter is devoted to a discussion on the semantics of quantum programming languages. We will discuss two main paradigms: the usual, standard co-processor model, and more exotic models based on quantum superposition of executions. We will discuss how these two systems can –or cannot– be unified, and how this relates to languages.

A comprehensive Bayesian reanalysis of the SARAS2 data from the epoch of reionization

ABSTRACT We present a Bayesian re-analysis of the sky-averaged 21-cm experimental data from SARAS2 using nested sampling implemented with polychord, spectrally smooth foreground modelling implemented with maxsmooth, detailed systematic modelling and rapid signal emulation with globalemu. Our analysis differs from previous analysis of the SARAS2 data through the use of a full Bayesian framework and separate modelling of the foreground and non-smooth systematics. We use the most up-to-date signal models, including Lyman-α and CMB heating parametrized by astrophysical parameters such as star formation efficiency, X-ray heating efficiency, minimal virial circular velocity of star forming galaxies, CMB optical depth, and the low energy cutoff of the X-ray spectral energy distribution. We consider models with an excess radio background above the CMB produced via radio emission from early galaxies and parametrized by a radio production efficiency. A non-smooth systematic is identified and modelled as both a frequency damped sinusoid introduced by the electronics and separately from the sky. The latter is modulated by the total efficiency of the antenna and marginally favoured by the data. We consider three different models for the noise in the data. The SARAS2 constraints on individual astrophysical parameters are extremely weak, however, we identify classes of disfavoured signals. We weakly disfavour standard astrophysical models with high Lyman-α fluxes and weak heating and more confidently disfavour exotic models with high Lyman-α fluxes, low X-ray efficiencies, and high radio production efficiencies in early galaxies.

Chemotaxis and cross-diffusion models in complex environments: Models and analytic problems toward a multiscale vision

This paper proposes a review focused on exotic chemotaxis and cross-diffusion models in complex environments. The term exotic is used to denote the dynamics of models interacting with a time-evolving external system and, specifically, models derived with the aim of describing the dynamics of living systems. The presentation first, considers the derivation of phenomenological models of chemotaxis and cross-diffusion models with particular attention on nonlinear characteristics. Then, a variety of exotic models is presented with some hints toward the derivation of new models, by accounting for a critical analysis looking ahead to perspectives. The second part of the paper is devoted to a survey of analytical problems concerning the application of models to the study of real world dynamics. Finally, the focus shifts to research perspectives within the framework of a multiscale vision, where different paths are examined to move from the dynamics at the microscopic scale to collective behaviors at the macroscopic scale.

Accounting for scalar non-Gaussianity in secondary gravitational waves

It is well known that enhancement in the primordial scalar perturbations over small scales generates detectable amplitudes of secondary gravitational waves (GWs), by sourcing the tensor perturbations at the second order. These stochastic gravitational waves are expected to carry the imprints of primordial non-Gaussianities. The scalar bispectrum that is typically produced in models of inflation leading to significant secondary GWs is nontrivial and highly scale dependent. In this work, we present a method to account for such general scale-dependent scalar bispectrum arising from inflationary models in the calculation of the spectral density of secondary GWs. Using this method, we compute the contributions arising from the scalar bispectrum to the amplitude of secondary GWs in two specific models of inflation driven by the canonical scalar field. We find that these non-Gaussian contributions can be highly model dependent and have to be consistently taken into account while estimating the total amplitude of the secondary GWs. Beyond the models considered, we emphasize that the method discussed is robust and free from assumptions about the shape of the bispectrum and generalizes earlier approaches adopted in the literature. We argue that this method of accounting for the scalar bispectrum shall be helpful in future computations for exotic models generating larger amplitudes of scalar non-Gaussianities along with a significant amount of secondary GWs.

Dark Matter Search with the Nuclear Isomer 180mTa

There is compelling cosmological and astrophysical evidence of dark matter comprising 27% of the energy budget of the Universe. However, dark matter has never been observed in direct detection experiments. The long-time favorite model of Weakly Interacting Massive Particles saw a large experimental effort with steady progress over recent decades. Since also these large-scale searches remain unsuccessful to date, it is compelling to look at more exotic dark matter models which can be constrained with new approaches and much less scientific resources. Using nuclear isomers is one of these approaches. 180m Ta is the rarest known isotope with the longest-lived meta-stable state whose partial half-life limits are on the order of 1014016 yr. We investigate how strongly interacting dark matter and inelastic dark dark matter collides with 180m Ta, leading to its de-excitation. The energy stored in the meta-stable state is released in the transition, which becomes the signature for thermalized dark matter in a well-shielded underground experiment.We report on a direct detection experiment searching for these dark-matter-induced decay signatures which has further constrained the open parameter space. We also propose an indirect geochemical experiment to search for decay products of 180mTa in tantalum minerals accumulated over 1 billion years.

Searching for leptoquarks at future muon colliders

A high energy muon collider can provide new and complementary discovery potential to the LHC or future hadron colliders. Leptoquarks are a motivated class of exotic new physics models, with distinct production channels at hadron and lepton machines. We study a vector leptoquark model at a muon collider with sqrt{s} = 3, 14 TeV within a set of both UV and phenomenologically motivated flavor scenarios. We compute which production mechanism has the greatest reach for various values of the leptoquark mass and the coupling between leptoquark and Standard Model fermions. We find that we can probe leptoquark masses up to an order of magnitude beyond sqrt{s} with perturbative couplings. Additionally, we can also probe regions of parameter space unavailable to flavor experiments. In particular, all of the parameter space of interest to explain recent low-energy anomalies in B meson decays would be covered even by a sqrt{s} = 3 TeV collider.

Role of MicroRNAs in Extreme Animal Survival Strategies.

The critical role microRNAs play in modulating global functions is emerging, both in the maintenance of homeostatic mechanisms and in the adaptation to diverse environmental stresses. When stressed, cells must divert metabolic requirements toward immediate survival and eventual recovery and the unique features of miRNAs, such as their relatively ATP-inexpensive biogenesis costs, and the quick and reversible nature of their action, renders them excellent "master controllers" for rapid responses. Many animal survival strategies for dealing with extreme environmental pressures involve prolonged retreats into states of suspended animation to extend the time that they can survive on their limited internal fuel reserves until conditions improve. The ability to retreat into such hypometabolic states is only possible by coupling the global suppression of nonessential energy-expensive functions with an activation of prosurvival networks, a process in which miRNAs are now known to play a major role. In this chapter, we discuss the activation, expression, biogenesis, and unique attributes of miRNA regulation required to facilitate profound metabolic rate depression and implement stress-specific metabolic adaptations. We examine the role of miRNA in strategies of biochemical adaptation including mammalian hibernation, freeze tolerance, freeze avoidance, anoxia and hypoxia survival, estivation, and dehydration tolerance. By comparing these seemingly different adaptive programs in traditional and exotic animal models, we highlight both unique and conserved miRNA-meditated mechanisms for survival. Additional topics discussed include transcription factor networks, temperature dependent miRNA-targeting, and novel species-specific and stress-specific miRNAs.