arXiv subjects

Aiichi Iwazaki

Publications and source records attributed to Aiichi Iwazaki.

At least 37 records · Page 2Linked to original sources

arXiv2019

Chiral Symmetry Breaking by Monopole Condensation

Under the assumption of Abelian dominance in QCD, we show that either color charge or chirality of quark is not conserved, when the low energy massless quark collides with QCD monopole. Because the color charge is conserved in reality, the chirality is not conserved. We show by using chiral anomaly that chiral non symmetric quark pair production takes place when a classical color charge is putted in a vacuum with monopole condensation, while chiral symmetric pair production takes place in a vacuum with no monopole condensation. Our results indicate that the chiral symmetry is broken by the monopole condensation.

hep-ph↗

arXiv2018

Axion Stars and Repeating Fast Radio Bursts with Finite Bandwidths

We have proposed a model of non repeating fast radio bursts ( FRBs ); the collisions between axion stars and neutron stars generate the bursts. In this paper, we propose a model of repeating FRBs which shows that they arise from the several collisions between magnetized accretion disk of a black hole and an axion star orbiting the black hole. There would be many axions stars condensing as dark matter in an early stage galaxy so that such collisions arises repeatedly. The radiations are emitted by coherent oscillations of electrons in the accretion disk. The oscillations are caused by oscillating electric fields, which are induced by axion stars under strong magnetic field $\sim O(10^{11})$G. The emissions are terminated by the thermal fluctuations of the electrons which result from the thermalization of the oscillation energies. Although the radiations are monochromatic, the thermal Doppler effects broaden the spectral lines; their spectra $S(ν)$ are given by $S(ν) \propto \exp(-(ν-ν_c)^2/2(δν)^2)$ with the center frequency $ν_c$. The bandwidth $δν=ν_c\sqrt{T_c/m_e}$ with electron mass $m_e$ is determined by the critical temperature $T_c$ at which the thermal fluctuations terminate the coherent emissions. The observed bandwidths $(3\sim5)\times10^2$MHz are originated from the strong magnetic fields $\sim O(10^{11})$G. With such strong magnetic fields, large amount of the burst energies are produced. Various center frequencies $ν_c$ of the bursts in the repeating FRB 121102 come from the various rotation speeds in the disk which make an intrinsic frequency of the bursts being Doppler shifted. The recent observation showing an extreme magneto-ionic environment around the source of FRB 121102 supports our model.

astro-ph.HE↗

arXiv2017

Chiral Symmetry Breaking by Monopole Condensation

Under the assumption of Abelian dominance in QCD, we have shown that chiral condensate is locally present around each QCD monopole. The essence is that either of charge or chirality of a quark is not conserved, when the low energy massless quark collides with QCD monopole. In reality, the charge is conserved so that the chirality is not conserved. Reviewing the presence of the local chiral condensate, we show by using chiral anomaly that chiral non symmetric quark pair production takes place when a quark is putted in a vacuum with monopole condensation, while chiral symmetric pair production takes place in a vacuum with no monopole condensation. Our results strongly indicate that the chiral symmetry is broken by the monopole condensation.

hep-ph↗

arXiv2017

QCD monopole and sigma meson coupling

Under the assumption of the Abelian dominance in QCD, we show that chiral condensate is locally present around a QCD monopole. The appearance of the chiral condensate around a GUT monopole was shown in the previous analysis of the Rubakov effect. We apply a similar analysis to the QCD monopole. It follows that the condensation of the monopole carrying the chiral condensate leads to the chiral symmetry breaking as well as quark confinement. To realize the result explicitly, we present a phenomenological linear sigma model coupled with the monopoles, in which the monopole condensation causes the chiral symmetry breaking as well as confinement. The monopoles are assumed to be described by a model of dual superconductor. Because the monopoles couple with mesons, we point out the presence of an observable color singlet monopole coupled with the mesons.

hep-ph↗

arXiv2017

Monopole and Polyakov loop

We propose a new order parameter of a $Z_N$ symmetry in SU(N) gauge theories in $4$ dimensional Minkowski space-time, assuming spatial periodic boundary conditions. It is given by $Tr(P\exp(i\int_c A_μdx^μ))$ where the spatial path $c$ is taken, for example, along $x_1$ axis. The parameter vanishes when the $Z_N$ symmetry is preserved. We calculate the contribution of QCD monopoles to the order parameter and show that when the monopoles condense $\langleΦ\rangle\neq 0$, it vanishes, while it does not vanish when they do not condense. These calculations are performed using a monopole field $Φ$ canonically quantized in a model of dual superconductor.

hep-th↗

arXiv2016

Production of Semi Quark Gluon Monopole Plasma by Glasma Decay

Using the standard Lagrangian of gluons and a model of dual superconductor for magnetic monopoles, we calculate the number densities of the gluons and monopoles produced by the decay of background color electric $E$ and magnetic $B$ fields ( glasma ). We find that gluons are dominant decay products when the initial values of the gauge fields are large such that $gE=gB>(0.5\mbox{GeV})^2$, while they are suppressed and monopoles are dominant decay products when the initial values are small such that $gE=gB<(0.4\mbox{GeV})^2$. The feature of the gluon dominance at large $gE=gB$ and the monopole dominance at small $gE=gB$ is similar to the one of thermalized quark gluon monopole plasmas proposed recently, if we identify $\sqrt{gE}=\sqrt{gB}$ as temperatures of the plasmas. Although the model of the monopoles is phenomenological, our analysis suggests that the monopoles play important roles in the decay of the glasmas with small saturation momenta, to which classical statistical field theories are not applicable.

hep-ph↗

arXiv2015

FRBs and dark matter axions

We have proposed a model of a progenitor of fast radio bursts (FRBs): The FRBs are emitted by electrons in atmospheres of neutron stars when neutron stars collide with dark matter axion stars. We reexamine the model by taking account of the tidal forces of the neutron stars. The axion stars are distorted by the forces so that they become like long sticks when they are close to the neutron stars. Although the tidal forces fairly distort the axion stars, our model is still consistent with present observations. We explain a distinctive feature of our model that the FRBs are not broadband, but narrowband. We also show that two-component FRBs may arise when the axion stars collide with binary neutron stars. FRBs would most frequently arise in centers of galaxies since the dark matter concentrates in the centers.

hep-ph↗

arXiv2015

Fast Radio Bursts from Axion Stars

Axions are one of the most promising candidates of dark matter. The axions have been shown to form miniclusters with masses $\sim 10^{-12}M_{\odot}$ and to become dominant component of dark matter. Some of the axion miniclusters condense to form axion stars. We have recently shown a possible origin of fast radio bursts ( FRBs ) by assuming that the axion stars are main component of halos: FRBs arise from the collisions between the axion stars and neutron stars. It is remarkable that the masses of the axion stars obtained by the comparison of the theoretical and observational event rates are coincident with the mass $\sim 10^{-12}M_{\odot}$. In this paper, we describe our model of FRBs in detail. We derive the approximate solutions of the axion stars with large radii and constraint their masses for the approximation to be valid. The FRBs are emitted by electrons in atmospheres of neutron stars. By calculating the optical depth of the atmospheres, we show that they are transparent for the radiations with the frequency given by the axion mass $m_a$ such as $m_a/2π\simeq 2.4$GHz$(m_a/10^{-5}\rm eV)$. Although the radiations are linearly polarized when they are emitted, they are shown to be circularly polarized after they pass magnetospheres of neutron stars. We also show that the FRBs are not broadband and their frequencies have finite bandwidths owing to the thermal fluctuations of the electrons in the atmospheres of the neutron stars. The presence of the finite bandwidths is a distinctive feature of our model and can be tested observationally. Furthermore, we show that similar FRBs may arise when the axion stars collide with magnetic white dwarfs $B\sim 10^9$G. The distinctive feature is that the durations of the bursts are of the order of $0.1$second.

hep-ph↗

arXiv2014

Proton Mass Shift in Muonic Hydrogen Atom

We show that the value of the proton mass depends on each bound state of muonic or electronic hydrogen atom. The charged particle bound to the proton produces magnetic field inside the proton. This makes a change to the amount of chiral condensate inside the proton. The change gives rise to the shift in the value of the proton mass. Numerically, the shift in the $2S$ state of the muonic hydrogen atom can be of the order of $0.1$ meV. The effect may solve the puzzle of the proton radius.

hep-ph↗

arXiv2014

Monopole Production and Glasma Decay

It has been discussed that quark gluon plasma is produced following the rapid decay of coherent color gauge fields generated immediately after high energy heavy ion collisions. But there are no convincing mechanisms known for the rapid decay of the gauge fields which satisfy phenomenological constraints on their lifetime. We show by using classical statistical field theory that the gauge fields rapidly decay into magnetic monopoles. For comparison, we show how fast they decay into Nielsen-Olesen unstable modes. We find that the rapid decay of the glasma is caused by the monopole production.

hep-ph↗

arXiv2014

Rapid Decay of Color Gauge Fields by Production of Magnetic Monopoles

It has been argued that the rapid decay of coherent color gauge fields generated immediately after high energy heavy ion collisions produces quark gluon plasma. But there are no convincing mechanisms for the rapid decay of the gauge fields which satisfy phenomenological constraints on their life time. We show by using classical statistical field theory that the production of magnetic monopoles cause the rapid decay of the gauge fields. The monopoles are unstable modes just like Nielsen-Olesen modes and are enormously produced by dual Schwinger mechanism.

hep-ph↗

arXiv2013

Anomalous Gluon Production and Condensation in Glasma

The collinear color electric and magnetic fields have been discussed to be produced immediately after high energy heavy ion collisions. We discuss anomalous gluon production under the background gauge fields. The gluons are Nielsen-Olesen unstable modes. The production rate of the modes by Schwinger mechanism has recently been found to be anomalously larger than the rate of quarks or other stable gluons. Analyzing classical evolutions of the modes with initial conditions given by vacuum fluctuations, we find that their production makes the color electric field decay very rapidly. The life time of the field is approximately given by the inverse of saturation momentum in the collisions. We also show that the mode with zero momentum form a Bose condensate and its gluon number density grows up to be of the order of $1/α_g$. After the saturation of the gluon number density, the condensate melts into quark gluon plasma owing to nonlinear interactions in QCD.

hep-ph↗

arXiv2012

A Model of Vanishing Cosmological Constant

We propose a model in which there exists a real scalar field $q$ satisfying a condition $\dot{q} =MH$ and its energy density is given by $(1/2)\dot{q}^2+V(q)$, where $H$ is the Hubble parameter ($H=\dot{a}/a$) and $M$ is a mass scale characterizing the field. We show that the potential $V(q)$ of the field is uniquely determined by the condition. The potential depends on the energy densities of background matters. We find that the vacuum energy of the matters is cancelled by the potential of the field. As a result, the minimum of the total energy density of the matters and the field vanishes and is located at the infinite scale factor $a=\infty$. This remarkable property results without a supersymmetry. We show that the present tiny dark energy is caused by early inflation, while the energy is comparable to Planck scale before the inflation. As our model is reduced to the $Λ$CDM model in the limit $M\to 0$, it is a natural generalization of the $Λ$CDM model.

astro-ph.CO↗

arXiv2012

Quark Pair Production in Expanding Glasma

Glasma in high energy heavy ion collisions is longitudinal classical color electric and magnetic fields. The color electric field has been shown to produces quark and anti-quark pairs by the Schwinger mechanism and to oscillate with time in non-expanding glasma, that is, plasma oscillation. On the other hand, in the expanding glasma we show that the field decreases with the plasma oscillation. We can explicitly obtain the solutions representing such temporal behaviors in the system with $τ$ and $η$ coordinates. We show these results by using massless QED as a simplified model of QCD.

hep-ph↗

arXiv2011

Schwinger Mechanism with Energy Dissipation in Glasma

Initial states of glasma in high energy heavy ion collisions are longitudinal classical color electric and magnetic fields. Assuming finite color electric conductivity, we show that the color electric field decays by quark pair production with the life time of the order of $Q_s^{-1}$, i.e. the inverse of the saturation momentum. Quarks and anti-quarks created in the pair production are immediately thermalized as far as their temperature $β^{-1}$ is lower than $Q_s$. Namely, a relaxation time of the quarks to be thermalized is much shorter than $Q_s^{-1}$ when $β^{-1} \ll Q_s$. We also show that the quarks acquire longitudinal momentum of the order of $Q_s$ by the acceleration of the electric field. To discuss the quark pair production, we use chiral anomaly which has been shown to be very powerful tool in the presence of strong magnetic field.

hep-ph↗

arXiv2010

A Quintessence with Tiny Dark Energy Induced by Inflation

We propose a postulate $\dot{q} =MH$ concerning temporal variation of quintessence field $q$ where $H$ is Hubble parameter ($=\dot{a}/a$) and $M$ is the scale characterizing the field. Using the postulate we uniquely determines a dynamical model of the field. The potential of the field satisfies the tracking condition. The minimum of the total energy density of matter and the field is located at $a=\infty$. We show that the present tiny dark energy is caused by early inflation, while the energy is comparable to Planck scale before the inflation. Since the model is reduced to $Λ$CDM model in the limit $M\to 0$, it is a natural generalization of $Λ$CDM model.

hep-ph↗

arXiv2009

Pair Creation of Massless Fermions in Electric Flux Tube

Using chiral anomaly, we discuss the pair creation of massless fermions in an electric flux tube $\vec{E}$ under homogeneous magnetic field $\vec{B}$ parallel to $\vec{E}$. The tube is axial symmetric and infinitely long in longitudinal direction. In the limit $B\gg E$, we can analytically obtain the spatial and temporal behaviors of the electric field and azimuthal magnetic field generated by the produced fermions. We find that the life time $t_c$ of the electric field is shorter as the width of the tube is narrower. Applying it to the glasma in high-energy heavy-ion collisions, we find that color electric field decays fast such as $t_c\simeq Q_s^{-1}$ with saturation momentum $Q_s$.

hep-ph↗

arXiv2009

Chiral Anomaly and Decay of Color Electric Field

Using the formula of chiral anomaly, we discuss the pair production of quarks under color electric field $\vec{E}$ without addressing explicit formula of quark's wavefunctions. The production is assumed to occur under the effect of color magnetic field $\vec{B}$ as well as the color electric field. We obtain the life time $t_c$ of the color electric field in the limit of $B\gg E$. Applying it to the glasma in high-energy heavy-ion collisions, we find that $t_c\simeq 10Q_s^{-1}$ with saturation momentum $Q_s$.

hep-ph↗