arXiv subjects

Wen Yin

Publications and source records attributed to Wen Yin.

At least 91 records · Page 5Linked to original sources

arXiv2022

Stability of domain wall network with initial inflationary fluctuations, and its implications for cosmic birefringence

We study the formation and evolution of domain walls with initial inflationary fluctuations by numerical lattice calculations that, for the first time, correctly take into account correlations on superhorizon scales. We find that, contrary to the widely-held claim {over the past few tens of years}, the domain wall network exhibits remarkable stability even when the initial distribution is largely biased toward one of the minima. This is due to the fact that the domain wall network retains information about initial conditions on superhorizon scales, and that the scaling solution is not a local attractor in this sense. Our finding immediately implies that such domain walls will have a significant impact on cosmology, including the production of gravitational waves, baryogenesis, and dark matter from domain walls. Applying this result to the axion-like particle domain wall, we show that it not only explains the isotropic cosmic birefringence suggested by the recent analysis, but also predicts anisotropic cosmic birefringence that is nearly scale-invariant on large scales and can be probed by future CMB observations.

hep-ph↗

arXiv2022

Weak-Scale Higgs Inflation

The present measurement of the standard model (SM) parameters suggests that the Higgs effective potential has a maximum at the intermediate scale, and the electroweak (EW) vacuum is not absolutely stable. The simplest possibility for absolute EW stability may be introducing a very large Higgs-Ricci scalar non-minimal coupling. In this extension of the SM, I study the cosmic inflation driven by the Higgs field. Since the resulting Hubble parameter happens to be around the weak scale, I call this scenario $weak\text{-}scale\text{ }Higgs\text{ }inflation$. It is pointed out that the cosmic-microwave background normalization of the scalar density perturbation can be enhanced compared with the conventional Higgs inflation prediction, thanks to the potential maximum predicted by the SM. It turns out in the Palatini formulation of the gravity with various higher dimensional terms suppressed by the scale close to the Planck scale that the inflation is successful, with a prediction of the running of the spectral index, $α_s=-(3-4)\times 10^{-3}$, which can be tested in the future. I also argue the UV (in)sensitivity of the prediction, the fact that the parameter region for successful inflation is very close to the criticality for potential shapes for eternal and non-eternal inflation, and the phenomenological applications.

hep-ph↗

arXiv2022

Axion dark matter from first-order phase transition, and very high energy photons from GRB 221009A

We study an axion-like particle (ALP) that experiences the first-order phase transition with respect to its mass or potential minimum. This can be realized if the ALP obtains a potential from non-perturbative effects of SU($N$) gauge theory that is confined via the first-order phase transition, or if the ALP is trapped in a false vacuum at high temperatures until it starts to oscillate about the true minimum. The resulting ALP abundance is significantly enhanced compared to the standard misalignment mechanism, explaining dark matter in a broader parameter space that is accessible to experiments e.g. IAXO, ALPS-II, and DM-radio. Furthermore, the viable parameter space includes a region of the mass $m_a \simeq 10^{-7} - 10^{-8}$ eV and the ALP-photon coupling $g_{a γγ} \simeq 10^{-11} {\rm GeV}^{-1}$ that can explain the recent observation of very high energy photons from GRB221009A via axion-photon oscillations. The parameter region suggests that the FOPT can generate the gravitational wave that explains the NANOGrav hint. If the ALP in this region explains dark matter, then the ALP has likely experienced a first-order phase transition.

hep-ph↗

arXiv2022

Challenges for heavy QCD axion inflation

We examine the theoretical possibility for the heavy QCD axion to induce slow-roll inflation while solving the strong CP problem through the Peccei-Quinn mechanism. If the cancellation between contributions from a small-size instanton and another Peccei-Quinn symmetry breaking occurs with high accuracy, the potential can be flattened enough near its maximum to achieve hilltop inflation. This comes at the cost of severe fine-tuning of their relative size and phase, but it also allows us to relate the high quality problem of the Peccei-Quinn symmetry to the fine-tuning problem of the hilltop inflation. There are two classes of such axion hilltop inflation, each giving a different relation between the axion mass at the minimum and the decay constant. The first class predicts the relation $m_ϕ\sim 10^{-6}f_ϕ$, and the axion can decay via the gluon coupling and reheat the universe. Most of the predicted parameter region will be covered by various experiments such as CODEX, DUNE, FASER, LHC, MATHUSLA, and NA62 where the production and decay proceed through the same coupling that induced reheating. The second class predicts the relation $m_ϕ\sim 10^{-6} f^2_ϕ/ M_{\rm pl}$. In this case, the axion mass is much lighter than in the previous case, and one needs another mechanism for successful reheating. The viable decay constant is restricted to be $10^8{\rm GeV} \lesssim f_ϕ\lesssim 10^{10}\,$GeV, which will be probed by future experiments on the electric dipole moment of nucleons. In both cases, requiring the axion hilltop inflation results in the strong CP phase that is close to zero.

hep-ph↗

arXiv2022

Glassy crystals with colossal multi-baroresponsivities

As a nontrivial solid state of matter, the glassy-crystal state embraces physical features of both crystalline and amorphous solids, where a long-range ordered periodic structure formed by the mass centers of constituent molecules accommodates orientational glasses. Here, we discover and validate a glassy-crystal state in 2-amino-2-methyl-1,3-propanediol (AMP, C4H11NO2) by neutron scattering and complementary broadband dielectric spectroscopy (BDS) measurements. The freezing process of the dynamic orientational disorder is manifested at relaxation times well described by the Vogel-Fulcher-Tammann (VFT) law and the strongly frequency-dependent freezing temperature ranging from around 225 K at 0.1 Hz to above room temperature in the GHz region. At room temperature, the supercooled state is extremely sensitive to pressure such that a few MPa pressure can induce crystallization to the ordered crystal state, eventually leading to a temperature increase by 48 K within 20 s, a significant reduction of visible light transmittance from about 95% to a few percentages, and a remarkable decrease of electrical conductivity by three orders of magnitude. These ultrasensitive baroresponsivities might find their applications in low-grade waste heat recycling, pressure sensors and non-volatile memory devices. It is expected that glassy crystals serve as an emerging platform for exploiting exotic states of matter and the associated fantastic applications.

cond-mat.mtrl-sci↗

arXiv2022

Early dark energy by dark Higgs, and axion-induced non-thermal trapping

We propose a new scenario of early dark energy (EDE) with a dark Higgs trapped at the origin. To keep this dark Higgs trapped until around the matter-radiation equality, we use dark photons produced non-thermally by coherent oscillations of axions, which have a much stronger trapping effect than thermal mass. When the trapping ends, the dark Higgs quickly decays into dark photons, which are then red-shifted as radiation. The dark Higgs EDE scenario works well for an ordinary Mexican-hat potential, and the dark Higgs naturally sits at the origin from the beginning, since it is the symmetry-enhanced point. Thus, unlike the axion EDE, there is no need for elaborate potentials or fine-tuning with respect to the initial condition. Interestingly, the axion not only produces dark photons, but also explains dark matter. We find the viable parameter region of the axion decay constant and the axion mass where dark matter and the $H_0$ tension can be simultaneously explained. We also discuss the detectability of the axion in the presence of axion-photon coupling, and show that the axion can be the QCD axion.

astro-ph.CO↗

arXiv2022

Atomically engineered cobaltite layers for robust ferromagnetism

Emergent phenomena at heterointerfaces are directly associated with the bonding geometry of adjacent layers. Effective control of accessible parameters, such as the bond length and bonding angles, offers an elegant method to tailor competing energies of the electronic and magnetic ground states. In this study, we construct unit thick syntactic layers of cobaltites within a strongly tilted octahedral matrix via atomically precise synthesis. The octahedral tilt patterns of adjacent layers propagate into cobaltites, leading to a continuation of octahedral tilting while maintaining significant misfit tensile strain. These effects induce severe rumpling within an atomic plane of neighboring layers triggers the electronic reconstruction between the splitting orbitals. First-principles calculations reveal that the cobalt ions transits to a higher spin state level upon octahedral tilting, resulting in robust ferromagnetism in ultrathin cobaltites. This work demonstrates a design methodology for fine-tuning the lattice and spin degrees of freedom in correlated quantum heterostructures by exploiting epitaxial geometric engineering.

cond-mat.mtrl-sci↗

arXiv2022

Ultra-relativistic bubbles from the simplest Higgs portal and their cosmological consequences

We analyze the phase transitions in the minimal extension of the SM with a real singlet scalar field. The novelty of our study is that we identify and analyze in details the region of parameter space where the first order phase transition can occur and in particular when the bubbles with true vacuum can reach relativistic velocities. This region is interesting since it can lead to the new recently discussed baryogenesis and Dark Matter production mechanisms. We fully analyze different models for the production of Dark Matter and baryogenesis as well as the possibilities of discovery at the current and future experiments.

hep-ph↗

arXiv2022

Instability of the Electroweak Vacuum in Starobinsky Inflation

We study the stability of the electroweak vacuum during and after the Starobinsky inflation, assuming the existence of the non-minimal Higgs coupling to the Ricci scalar. In the Starobinsky inflation, there exists $R^2$ term (with $R$ being the Ricci scalar), which modifies the evolution equation of the Higgs field. We consider the case that the non-minimal coupling is sizable so that the quantum fluctuation of the Higgs field is suppressed and that the Higgs amplitude is settled near the origin during the inflation. In such a case, the Higgs amplitude may be amplified in the preheating epoch after inflation because of the parametric resonance due to the non-minimal coupling. We perform a detailed analysis of the evolution of the Higgs field in the preheating epoch by a numerical lattice simulation and derive an upper bound on the non-minimal coupling constant $ξ$ in order to realize the electroweak vacuum in the present universe. We find that the upper bound on $ξ$ in the Starobinsky inflation model is more stringent than that in conventional inflation models without the $R^2$ term.

hep-ph↗

arXiv2022

High Energy Sphalerons for Baryogenesis at Low Temperatures

We discuss baryogenesis in scenarios where the Universe is reheated to temperatures $\lesssim 100\,$GeV by the decay of long-lived massive particles into energetic SM particles. Before its thermalization, the center-of-mass energy in collisions between such a particle and a particle from the ambient plasma can be higher than the typical sphaleron mass, even if the temperature of the plasma itself is much lower. Optimistic estimates for the high energy enhancement of the sphaleron cross section suggest that successful baryogenesis is possible for reheating temperatures as low as $0.1\text{-}1\,$GeV. With a simple extension of the SM, sufficient baryon production can be achieved even if more pessimistic results for the sphaleron rate are correct. In both cases this scenario can be probed in collider and cosmic-ray experiments. We briefly discuss the possible origin of the required CP violation.

hep-ph↗

arXiv2022

Power spectrum of domain-wall network and its implications for isotropic and anisotropic cosmic birefringence

Recently, based on a novel analysis of the Planck satellite data, a hint of a uniform rotation of the polarization of cosmic microwave background photons, called isotropic cosmic birefringence, has been reported. The suggested rotation angle of polarization of about $0.2-0.4$ degrees strongly suggests that it is determined by the fine structure constant, which can be naturally explained over a very wide parameter range by the domain walls of axion-like particles. Interestingly, the axion-like particle domain walls predict not only isotropic cosmic birefringence but also anisotropic one that reflects the spatial distribution of the axion-like particle field on the last scattering surface. In this Letter, we perform lattice simulations of the formation and evolution of domain walls in the expanding universe and obtain for the first time the two-point correlation function and power spectrum of the scalar field that constitutes the domain walls. We find that while the power spectrum is generally consistent with analytical predictions based on random wall distributions, there is a predominant excess on the scale corresponding to the Hubble radius. Applying our results to the anisotropic cosmic birefringence, we predict the power spectrum of the rotation angles induced by the axion-like particle domain walls and show that it is within the reach of future observations of the cosmic microwave background.

astro-ph.CO↗

arXiv2022

Singlet extensions and W boson mass in the light of the CDF II result

Recently, the CDF collaboration has reported the precise measurement of the W boson mass, $M_W = 80433.5\pm 9.4 \,$MeV, based on $8.8$ fb$^{-1}$ of $\sqrt{s}=1.96$ TeV $p\bar{p}$ collision data from the CDF II detector at the Fermilab Tevatron. This is about $7σ$ away from the Standard Model prediction, $M_{W}^{\rm SM}=80357 \pm 6 \,$MeV. Such a large discrepancy may be partially due to exotic particles that radiatively alter the relation between the W and Z boson masses. In this Letter, we study singlet extensions of the Standard Model focusing on the shift of the W boson mass. In the minimal extension with a real singlet field, using the bounds from the electroweak oblique parameters, B meson decays, LEP, and LHC, we find that the W boson mass shift is at most a few MeV, and therefore it does not alleviate the tension between the CDF II result and the SM prediction. We then examine how much various bounds are relaxed when the singlet is allowed to decay invisibly and find that the increase of the W boson mass does not exceed $5$ MeV due to the bound from the Higgs signal strength. We also discuss phenomenological and cosmological implications of the singlet extensions such as the muon $g-2$ anomaly, axion/hidden photon dark matter, and self-interacting dark radiation as a possible alleviation of the Hubble tension.

hep-ph↗

arXiv2022

Suppression of Higgs Mixing by Quantum Zeno Effect

The Higgs portal interaction to a singlet sector of the standard model (SM) gauge group is widely-studied. In this Letter, we show that a quantum effect is important if the Higgs field mixes with another singlet scalar field whose decay rate is larger than the mass difference between the two mass eigenstates. This effect may be interpreted as the quantum Zeno effect. In either the quantum mechanics or the quantum field theory, we show that the resulting propagating mode is not the eigenstate of the mass matrix, but it is approximately the eigenstate of the interaction. As a consequence, the decoupling of the mixing effect happens at the infinity limit of the decay width of the exotic scalar even if the naïve mixing parameter is not small. With a finite decay width of the exotic scalar, we derive the effective mass of the propagating mode in the SM sector, its decay rate, and the couplings at the 1-loop level. It turns out that the mixed mass eigenstates can mimic the discovered 125 GeV Higgs boson. This fuzzy Higgs boson can be obtained in a simple perturbative renormalizable model. It is consistent with the 125 GeV SM Higgs boson when the mass difference is smaller than ${\cal O}(0.1)$GeV (${\cal O}(1)$GeV) for ${\cal O}(1)$ (${\cal O}(0.01)$) mixing. We argue the possible natural scenario for the tiny mass splitting and the possibility that the upper bound of the mass difference is larger for a strongly-coupled singlet sector. To probe the fuzzy Higgs boson scenario, it is difficult to directly produce the singlet sector particles. Nevertheless, the future Higgs factories may probe this scenario by precisely measuring the Higgs boson invisible decay rate and the deviation of the Higgs coupling. Applications of the mechanism are also mentioned.

hep-ph↗

arXiv2022

On the Robustness of "Robust reversible data hiding scheme based on two-layer embedding strategy"

In the paper "Robust reversible data hiding scheme based on two-layer embedding strategy" published in INS recently, Kumar et al. proposed a robust reversible data hiding (RRDH) scheme based on two-layer embedding. Secret data was embedded into the most significant bit (MSB) planes to increase robustness, and a sorting strategy based on local complexity was adopted to reduce distortion. However, Kumar et al.'s reversible data hiding (RDH) scheme is not as robust against joint photographic experts group (JPEG) compression as stated and can not be called RRDH. This comment first gives a brief description of their RDH scheme, then analyses their scheme's robustness from the perspective of JPEG compression principles. JPEG compression will change pixel values, thereby destroying auxiliary information and pixel value ordering required to extract secret data correctly, making their scheme not robust. Next, the changes in both bit plane and pixel value ordering after JPEG compression are shown and analysed by different robustness-testing experiments. Finally, some suggestions are given to improve the robustness.

cs.MM↗

arXiv2021

Cosmological implications of $n_s\approx 1$ in light of the Hubble tension

Recently, a low-$z$ measurement of the Hubble constant, $H_0 = 73.04 \pm 1.04 {\rm ~km/s/Mpc}$, was reported by the SH0ES Team. The long-standing Hubble tension, i.e. the difference between the Hubble constant from the local measurements and that inferred from the cosmic microwave background data based on the $Λ$CDM model, was further strengthened. There are many cosmological models modifying the cosmology after and around the recombination era to alleviate this tension. In fact, some of the models alter the small-scale fluctuation amplitude relative to larger scales, and thus require a significant modification of the primordial density perturbation, especially the scalar spectral index, $n_s$. In certain promising models, $n_s$ is favored to be larger than the $Λ$CDM prediction, and even the scale-invariant one, $n_s=1$, is allowed. In this Letter, we focus on the very early Universe models to study the implication of such unusual $n_s$. In particular, we find that an axiverse with an axion in the equilibrium distribution during inflation can be easily consistent with $n_s = 1$. This is because the axion behaves as a curvaton with mass much smaller than the inflationary Hubble parameter. We also discuss other explanations of $n_s$ different from that obtained based on the $Λ$CDM.

astro-ph.CO↗

arXiv2021

Topological Superconductivity in Rashba Spin-Orbital Coupling Suppressed Monolayer \{beta}-Bi2Pd

The weak interlayer Van Der Waals material \{beta}-Bi2Pd has recently been established as a strong topological superconductor candidate with unconventional spin-triplet pairing and Majorana zero modes at vortices. In this letter, we study the topological characters and the superconducting pairing, which are still obscure in monolayer \{beta}-Bi2Pd, in light of our effective theoretical model. We find that the non-Rashba spin-orbital coupling plays a critical role in realizing and tuning various novel topological natures. In particular, the spin-triplet p-wave superconducting pairing with Majorana zero mode is revealed in monolayer \{beta}-Bi2Pd. Our studies deepen the understanding of topology and superconductivity in monolayer \{beta}-Bi2Pd and indicate it is a promising platform for achieving low-dimentional topological superconductivity.

cond-mat.mes-hall↗

arXiv2021

Phenomenology of CP-even ALP

Axion or axion-like particle (ALP) has been usually considered as a CP-odd Nambu-Goldstone boson (NGB) from the spontaneous breakdown of a global U(1) symmetry. In this paper, we point out that the NGB behaves as a CP-even particle coupled to the SM particles in a large class of simple (or perhaps the simplest) renormalizable models. We provide a first study of the collider phenomenology and cosmology of the CP-even ALP. In a natural parameter region, the CP-even ALP can be produced from the Higgs boson decay in colliders. When the mass is not very light, the signals will be Higgs exotic decays, Higgs decay to displaced vertex $\times 2$, Higgs decay to displaced vertex + missing energy. The signal can be discriminated from other models, e.g. hidden photon, by measuring the decay length and the decay products of the light new particle. In addition, when $ m_a\lesssim \,$MeV, in which case the Higgs boson invisible decay may be probed in the colliders, the CP-even ALP is a nice Dark matter (DM) candidate. The DM can be probed by 21cm line measurement, the future measurement of the Milky way mass halo function in the Vera Rubin Observatory, as well as X- or $γ$-ray observations. The DM production mechanisms are discussed.

hep-ph↗

arXiv2021

Shining ALP Dark Radiation

String scenarios typically not only predict axion-like particles (ALPs) but also significant amounts of ALP dark radiation originating from the decay of the inflaton or a more general modulus. In this paper, we study the decay of such non-thermally produced relativistic (but massive) ALPs to photons. If the ALPs are sufficiently highly energetic, contribute to $ΔN_{\rm eff} \gtrsim {\cal O}(0.001)$ and have a mass $m_a\gtrsim$ MeV we find that, using observations of X-, and $γ$-rays, the CMB and BBN, very small values of the ALP-photon coupling can be probed, corresponding to an origin of this coupling at the string (or even Planck) scale.

hep-ph↗