Symmetry Breaking Mechanism Research Articles

Symmetry and Asymmetry in Mutations and Memory Retention during the Evolutionary Growth of Carbon Nanotubes.

Symmetry is a motif featured in almost all areas of science, and understanding the mechanism of symmetry breaking is challenging. Similar to mutations that disrupt symmetry in evolution, defects in materials offer insight into symmetry breaking. Here, we investigate symmetry in intragenerational mutations and symmetry breaking in transgenerational mutations in the evolutionary growth system of carbon nanotubes (CNTs). Mutations caused by pentagon-heptagon (5-7) pairs in different conformations shorten the lifespans of single-walled carbon nanotubes (SWNTs) by acting as time markers during growth. Symmetric distributions are observed for intragenerational mutations from (n, m) to (n + i, m-i) (where i ∈ caslon Z) with different appearance orders of pentagon and heptagon. Such symmetry breaks occur in transgenerational mutations. Intragenerational mutations occur multiple times on a SWNT, oscillating regularly between i and - i until termination occurs. These types and effects are retained in the form of memory to encode SWNTs during subsequent growth, resulting in a length reduction after each mutation. Our results provide a profound understanding of symmetry breaking and memory retention and offer guidance for the controlled synthesis of materials.

Jahn-Teller Effect on CF3I Photodissociation Dynamics.

The Jahn-Teller (JT) effect, as a spontaneous symmetry-breaking mechanism arising from the coupling between electronic and nuclear degrees of freedom, is a widespread phenomenon in molecular and condensed matter systems. Here, we investigate the influence of the JT effect on the photodissociation dynamics of CF3I molecules. Based on ab initio calculation, we obtain the three-dimensional potential energy surfaces for 3Q0+ and 1Q1 states and establish a diabatic Hamiltonian model to study the wavepacket dynamics in the CF3I photodissociation process. Using the wave function of the final state after dissociation, we calculate the rotational density matrix of the CF3 fragment and analyze its rotational excitation under the JT effect, as well as its partial coherence property and selection rules. Our work paves the way to the experimental observation and quantification of the JT effect in molecular dissociation dynamics beyond the classical ball-and-stick model.

Colloidal substrate-facilitated synthesis of gold nanohelices

Helical nanostructures have unique optical and mechanical properties, yet their syntheses had always been quite challenging. Various symmetry-breaking mechanisms such as chiral templates, strain-restriction and asymmetric ligand-binding have been developed to induce the helical growth at nanoscale. In this work, with neither chiral ligands nor templates, gold (Au) nanohelices were synthesized via a facile wet-chemical method, through an asymmetric Active Surface Growth facilitated by colloidal silica nanoparticles (NPs). The one-dimensional growth followed the Active Surface Growth, which employs a thiolated ligand to direct continuous deposition of Au at the interface, known as the active surface, between the Au nanostructures and the silica NPs – the colloidal substrates. More importantly, the colloidal substrates are crucial for the helical growth, as the diameter of the obtained nanohelices was found proportional to the size of the colloidal substrates. We propose that the nanoscale size and the curvature of the silica NPs would reduce the size of anchoring point between Au nanowires and the substrates, causing partial blockage of the active surface by the substrate and divergence of the activity on the active surface towards Au deposition. The subsequent inequivalent deposition, and the dynamic shifting of the blockage lead to the asymmetric growth and the formation of nanohelices. Factors that would affect the asymmetric Active Surface Growth were also identified and discussed, including the reduction kinetics, substrate treatment and the type and concentration of the ligand. In particular, variation of the size of the active surfaces would change the degree of the surface inequivalence, and thus affect the yield of the nanohelices.

Bosonic multi-Higgs correlations beyond leading order

The production of multiple Higgs bosons at the LHC and beyond is a strong test of the mechanism of electroweak symmetry breaking. Taking inspiration from recent experimental efforts to move toward limits on triple-Higgs production at the Large Hadron Collider, we consider generic bosonic deviations of HH and HHH production from the Standard Model in the guise of Higgs effective field theory (HEFT). Including one-loop radiative corrections within the HEFT and going up to O(p4) in the momentum expansion, we provide a detailed motivation of the parameter range that the LHC (and future hadron colliders) can explore, through accessing nonstandard coupling modifications and momentum dependencies that probe Higgs boson nonlinearities. In particular, we find that radiative corrections can enhance the sensitivity to Higgs self-coupling modifiers and HEFT-specific momentum dependencies can vastly increase triple-Higgs production, thus providing further motivation to consider these processes during the LHC’s high-luminosity phase. Published by the American Physical Society 2024

Distance-Dependent Symmetry-Breaking Charge Transfer in 9,10- Bis(phenylethynyl)anthracene Dimers.

To investigate the effect of the through-bond coupling strength on the symmetry-breaking charge separation (SB-CS) dynamics and mechanism, three 9,10-bis((4-hexylphenyl)ethynyl)anthracene dimers with varying distances, viz., a single-bond linked dimer (0-dimer), a phenylene linked dimer (1-dimer) and a para-biphenylene linked dimer (2-dimer), were synthesized and studied systematically using steady-state and transient spectroscopy. Steady-state absorption spectra revealed that the electronic coupling strength decreased gradually with the increase of the inter-chromophore distance, and the transition of S0→S1 includes the dark charge transfer (CT) excitation. fs-TA spectra demonstrated that SB-CS could be conducted in both weakly and highly polar solvents for 0-dimer, but the SB-CS dynamics has a significant difference. In weakly polar solvents, SB-CS only produces the partial CT (PCT) state, but it could generate the CT state via the PCT state in highly polar solvent. In comparison, SB-CS is only proceeded in highly polar solvents in 1-dimer and 2-dimer to produce the CT state directly. These results demonstrate that the SB-CS dynamics is strongly dependent on the inter-chromophore electronic coupling, and the relatively strong electronic coupling is crucial for the occurrence of SB-CS in weakly polar environment that is commonly presented in photoelectric devices.

Emergence of Optical Activity and Surface Morphology Changes in Racemic Amino Acid Films Under Circularly Polarized Lyman-α Light Irradiation.

The homochirality of life remains one of the most enigmatic issues in the study of the origin of life. A proposed mechanism for symmetry breaking involves irradiation by circularly polarized light (CPL). To investigate the photoreaction of amino acids under CPL irradiation, a vacuum ultraviolet (VUV) CPL irradiation system was developed at the synchrotron light source UVSOR-III. Hydrogen Lyman-α CPL (121.6 nm) is considered a potential asymmetric source in space. Therefore, racemic alanine film samples were irradiated with Lyman-α CPL to explore the photoreaction of biomolecules. Circular dichroism (CD) spectra measurements revealed that irradiation with right- (left-) handed CPL induced a positive (negative) anisotropy factor g in the wavelength range of 180-240 nm. However, the spectra differed from those of enantiopure alanine, exhibiting broad wavelength ranges and no sign change. Liquid chromatography-mass spectrometry (LC-MS) measurements indicate formation of larger molecules, such as oligomeric alanine adducts or modified oligomers after the Lyman-α CPL irradiation. Additionally, CPL irradiation considerably changes the microstructure of the alanine film surface, leading to the formation of circular network aggregates on the scale of 100 nm. The morphology changes in the alanine film and/or the formation of the larger molecules could be possible causes of the modified anisotropy factor spectra compared to those of enantiopure alanine. These findings highlight the need for further research on the photoreaction of biomolecules in solid states under VUV CPL irradiation, particularly in the photoionization energy range, to validate the cosmic scenario of homochirality.

Micro‐ and nanorobots from magnetic particles: Fabrication, control, and applications

AbstractMagnetic microparticles (MPs) and nanoparticles (NPs) have long been used as ideal miniaturized delivery and detection platforms. Their use as micro‐ and nanorobots (MNRs) is also emerging in the recent years with the help of more dedicated external magnetic field manipulations. In this review, we summarize the research progress on magnetic micro‐ and nanoparticle (MNP)‐based MNRs. First, the fabrication of micro‐ and nanorobots from either template‐assisted NP doping methods or directly synthesized MPs is summarized. The external driving torque sources for both types of MNRs are analyzed, and their propulsion control under low Reynolds number flows is discussed by evaluating symmetry breaking mechanisms and interparticle interactions. Subsequently, the use of these MNRs as scientific models, bioimaging agents, active delivery, and treatment platforms (drug and cell delivery, and sterilization), and biomedical diagnostics has also been reviewed. Finally, the perspective of MNPs‐based MNRs was outlined, including challenges and future directions.

Application of Clifford’s Algebra to Describe the Early Universe

This article is a shortened review of previous results obtained by the author. The advantages of describing the geometric nature of the physical properties of the early universe using the Clifford algebra approach are demonstrated. A geometric representation of the wave function of the early universe is used, and a new mechanism of spontaneous symmetry breaking with different degrees of freedom is proposed. A possible supersymmetry is revealed, and it is shown that the energy of the initial vacuum can be considered equal to zero. The origin of baryonic asymmetry and the nature of dark matter can be explained using a geometric representation of the wave function of the early universe.

Localizing Transitions via Interaction-Induced Flat Bands.

This Letter presents a theory of interaction-induced band-flattening in strongly correlated electron systems. We begin by illustrating an inherent connection between flat bands and index theorems, and presenting a generic prescription for constructing flat bands by periodically repeating local Hamiltonians with topological zero modes. Specifically, we demonstrate that a Dirac particle in an external, spatially periodic magnetic field can be cast in this form. We derive a condition on the field to produce perfectly flat bands and provide an exact analytical solution for the flat band wave functions. Furthermore, we explore an interacting model of Dirac fermions in a spatially inhomogeneous field. We show that certain Hubbard-Stratonovich configurations exist that "rectify" the field configuration, inducing band flattening. We present an explicit model where this localization scenario is energetically favorable-specifically in Dirac systems with nearly flat bands, where the energy cost of rectifying textures is quadratic in the order parameter, whereas the energy gain from flattening is linear. In conclusion, we discuss alternative symmetry-breaking channels, especially superconductivity, and propose that these interaction-induced band-flattening scenarios represent a generic nonperturbative mechanism for spontaneous symmetry breaking, pertinent to many strongly correlated electron systems.

Noise-Induced Phase Separation and Time Reversal Symmetry Breaking in Active Field Theories Driven by Persistent Noise.

Within the Landau-Ginzburg picture of phase transitions, scalar field theories develop phase separation because of a spontaneous symmetry-breaking mechanism. This picture works in thermodynamics but also in the dynamics of phase separation. Here we show that scalar nonequilibrium field theories undergo phase separation just because of nonequilibrium fluctuations driven by a persistent noise. The mechanism is similar to what happens in motility-induced phase separation where persistent motion introduces an effective attractive force. We observe that noise-induced phase separation occurs in a region of the phase diagram where disordered field configurations would otherwise be stable at equilibrium. Measuring the local entropy production rate to quantify the time-reversal symmetry breaking, we find that such breaking is concentrated on the boundary between the two phases.

Emergent chirality in active solid rotation of pancreas spheres

Collective cell dynamics play a crucial role in many developmental and physiological contexts. While two-dimensional (2D) cell migration has been widely studied, how three-dimensional (3D) geometry and topology interplay with collective cell behavior to determine dynamics and functions remains an open question. In this work, we elucidate the biophysical mechanism underlying rotation in spherical tissues, a phenomenon widely reported both and . Using murine pancreas-derived organoids as a model system, we find that epithelial spheres exhibit persistent rotation, rotational axis drift, and rotation arrest. Using a 3D vertex model, we demonstrate how the combined action of traction force and polarity alignment can account for these distinct rotational dynamics near a solid to flow transition. Furthermore, our analysis shows that the spherical tissue rotates as an active solid occasionally switching to a flowing state and exhibits spontaneous chiral symmetry breaking. Using a continuum model, we demonstrate how the topological defects in the polarity field underlie this symmetry breaking process, which is revealed by asymmetries in the cell elongation pattern. For cell elongation to reveal the chiral asymmetry, shear flow is required in addition to the solid body rotation. Altogether, our work reveals a robust chiral symmetry breaking mechanism with potential implications for left-right symmetry breaking processes in morphogenetic events. Published by the American Physical Society 2024

Minimal model for chirally induced spin selectivity: spin-orbit coupling, tunneling and decoherence

Here we review a universal model for chirally induced spin-selectivity (CISS) as a standalone effect occurring in chiral molecules. We tie together the results of forward scattering in the gas phase to the results for photoelectrons in chiral self-assembled monolayers, and the more contemporary results in two terminal transport setups. We discuss the ingredients that are necessarily present in all experiments to date, which we identify as: (i) chirality, be it point, helical or configurational, (ii) the spin–orbit coupling as the spin active coupling of atomic origin, (iii) decoherence as a time-reversal symmetry breaking mechanism that avoids reciprocity relations in the linear regime and finally (iv) tunneling that accounts for the magnitude of the spin polarization effect. This proposal does not discard other mechanisms that can yield comparable spin effects related to interactions of the molecule to contacts or substrates that have been proposed but are less universal or apply to specific situations. Finally, we discuss recent results suggesting CISS as a molecular phenomenon in the realms of enantiomer selectivity, coherent electron transfer, and spin effects in chiroptical activity.

Observation of electroweak production of W+W− in association with jets in proton-proton collisions at s\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$ \\sqrt{s} $$\\end{document} = 13 TeV with the ATLAS detector

A measurement of the production of W bosons with opposite electric charges in association with two jets is presented based on 140 fb−1 of data collected by the ATLAS detector in proton-proton collisions at s\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$ \\sqrt{s} $$\\end{document} = 13 TeV. The analysis is sensitive to the scattering of W bosons, which is of particular interest in the ATLAS physics programme as it can be used to probe the electroweak symmetry breaking mechanism of the Standard Model. This signal is observed with a significance of 7.1 standard deviations above the background expectation, while 6.2 standard deviations were expected. The measured cross-section is determined in a signal-enriched fiducial volume and is found to be 2.7 ± 0.5 fb, which is consistent with the theoretical prediction of 2.20−0.13+0.14\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$ {2.20}_{-0.13}^{+0.14} $$\\end{document} fb.

Atomistic phase transition mechanism of zero-strain electrode material: Transmission electron microscopy investigation of Li4Ti5O12 spinel lattice upon lithiation

The lithiation mechanism of electrode materials is important for understanding the basic reactions in Li-ion batteries. In particular, zero-strain materials have garnered interest owing to their stable charge–discharge performances. In this study, we investigated the atomistic phase transition mechanism of spinel Li4Ti5O12, a well-known zero-strain material, using high-resolution transmission electron microscopy. A single-crystalline Li4Ti5O12 (100) specimen was prepared and observed in situ at a lattice resolution under electron-beam-assisted lithiation. The lattice fringes originating from the Li plane of the spinel crystal were anisotropically altered during phase transition, suggesting the asymmetrical site shifting of Li atoms during lithiation. This spontaneous symmetry-breaking mechanism for the phase transition is considered essential for the lithiation of spinel lattice.

Leptogenesis effects on the gravitational waves background:interpreting the NANOGrav measurements and JWST constraints on primordialblack holes

We demonstrate that the leptogenesis mechanisms, which are associated with B-L symmetry breaking mechanism has notable effects on the production of gravitational waves. These gravitational waves align well with the recent observations of a stochastic gravitational wave background by NANOGrav and pulsar-timing arrays (PTAs). For these gravitational waves to match the recent measurements, the critical value of the B-L breaking should be around the GUT scale. Moreover, we consider the generation of primordial gravitational waves from binary systems of Primordial Black Holes (PBHs) which could be predicted by the recent detection of gravitational waves. PBHs with specific masses can be responsible for massive galaxy formation observed at high redshifts reported by the James Webb Space Telescope (JWST). We contemplate the potential for a shared source between the NANOGrav and JWST observations, namely primordial black holes. These black holes could serve as seeds of rapid galaxy formation, offering an explanation for the galaxies observed by JWST.

A Bridge between Trace Anomalies and Deconfinement Phase Transitions

Inspired by the fact that both the dilaton potential encoding the trace anomalies of QCD and the Polyakov loop potential measuring the deconfinement phase transition can be expressed in the logarithmic forms, as well as the fact that the scale symmetry is expected to be restoring and colors are deconfined in extreme conditions such as high temperatures and/or densities, we conjecture a relation between the dilaton potential and the Polyakov loop potential. Explicitly, we start from the Coleman–Weinberg type potential of a real scalar field—a dilaton or conformal compensator—and make an ansatz of the relation between this scalar field and the Polyakov loop to obtain the Polyakov loop potential, which can be parameterized in Lattice QCD (LQCD) in the pure glue sector. We find that the coefficients of Polyakov potential fitted from Lattice data are automatically satisfied in this ansatz, the locations of deconfinement and scale restoration are locked to each other, and the first-order phase transition can be realized. Extensions to the low-energy effective quark models are also discussed. The conjectured relation may deepen our understanding of the evolution of the universe, the mechanism of electroweak symmetry breaking, the phase diagram of QCD matter, and the properties of neutron stars.

Gribov problem in the eletroweak and gluon confined theories

We show that gauge fields after a spontaneous symmetry breaking (SSB) mechanism do not have a Gribov problem along the broken directions. In order to make this proof, we describe a gauge fixing procedure inspired on Morse’s theory leading to the concept of a gauge fixing generating functional. This approach is specially suited in order to understand the unitary gauges of ’t Hooft. The conclusion is that after a SSB process, the generalized Faddeev-Popov operator acquires a positive definite value along the broken directions. We show how this works in the eletroweak SU(2)XU(1) theory, where such a result is in fact expected as in this case the gauge fields acquire masses after the SSB. Then we apply this development to the SL(3,c) confining model of Amaral [A path to confine gluons and fermions through complex gauge theory, ]. The final result explains why such confining mechanism is actually a solution to the Gribov problem for the confined gauge fields. These cases show that although confinement is not a general effect of the solution of the Gribov problem, as we can infer from the eletroweak example, its solution indeed seems to be necessary in order to achieve confinement. In the end, these conclusions allow us to speculate that the strong interaction confinement may be the result of some hidden SSB mechanism yet to be described. Published by the American Physical Society 2024

Steven Weinberg and Higgs physics

As a tribute to Steven Weinberg, we summarize the immense impact that he had on the understanding of the mechanism of spontaneous symmetry breaking and on the physics of the Higgs boson. In particular, four landmark contributions to this field are highlighted. A first one is his early work with Goldstone and Salam on spontaneously broken continuous symmetries that paved the way to the Higgs mechanism. A second towering breakthrough is his model of leptons which later became the Standard Model of particle physics and for which he was awarded the Nobel prize with Glashow and Salam. A third seminal work is the so-called Weinberg-Linde lower bound on the Higgs boson mass that was derived from the requirement of the stability of the electroweak vacuum. Finally, we summarize his important contributions in model-building of new physics with extended Higgs sectors and their possible impact in flavor physics and CP-violation. The historical aspects as well as the contemporary way of viewing these four major topics are summarized and their impact on today Higgs physics, and more generally particle physics, is highlighted.

On-chip topological phononic crystal acoustic waveguide based on lithium niobate thin films

This Letter introduces an on-chip topological phononic crystal (PnC) acoustic waveguide employing lithium niobate thin films. Utilizing a C3v symmetry-breaking mechanism, the topological PnC acoustic waveguide is achieved, operating at frequencies exceeding 430 MHz. A SH0 mode acoustic transceiver is designed, enabling highly efficient on-chip acoustic wave transmission and reception. The fabricated topological PnC waveguide demonstrates a propagation loss of 11.3 dB/mm at the edge mode. An acoustic beam splitter utilizing topological edge mode has been demonstrated, showing the configurability of the topological PnC acoustic waveguide. These results offer significant promise for advancing the development of hybrid phononic circuits tailored for high-frequency acoustic information processing, sensing, and manipulation.

Measuring hhWW coupling at lepton colliders

The quartic Higgs-gauge-boson coupling ghhWW is sensitive to the electroweak symmetry breaking mechanism; however, it is challenging to be measured at the Large Hadron Collider. We show that the coupling can be well probed at future lepton colliders through di-Higgs boson production via the vector boson fusion channel. We perform a detailed simulation of ℓ+ℓ−→νν¯hh→4b+ET with parton showering effects at e+e−, μ+μ− and e−μ+ colliders. We find that the regions of ghhWW/ghhWWSM<0.86 and ghhWW/ghhWWSM>1.32 can be discovered at the 5σ confidence level at the 10 TeV μ+μ− collider with an integrated luminosity of 3 ab−1. We also demonstare that ghhWW/ghhWWSM is constrained within [0.72, 1.66], [0.72, 1.70], [0.84, 1.32], and [0.88, 1.14] at the 1 TeV e+e−, eμ colliders, 2 TeV eμ collider, and 10 TeV μ+μ− collider, respectively, given null excess observed at the 2σ confidence level with an integrated luminosity of 3 ab−1. Published by the American Physical Society 2024