We constrain a primordial magnetic field (PMF) generated during a phase transition (PT) using the big bang nucleosynthesis bound on the relativistic energy density. The amplitude of the PMF at large scales is determined by the shape of the PMF spectrum outside its maximal correlation length scale. Even if the amplitude of the PMF at 1 Mpc is small, PT-generated PMFs can leave observable signatures in the potentially detectable relic gravitational wave background if a large enough fraction ($1-10%$) of the thermal energy is converted into the PMF.
We estimate the chirality of the cosmological medium due to parity violating decays of standard model particles, focusing on the example of tau leptons. The non-trivial chirality is however too small to make a significant contribution to the cosmological magnetic field via the chiral-magnetic effect.
It is well known that gravitons can convert into photons, and vice versa, in the presence of cosmological magnetic fields. We study this conversion process in the context of atomic dark matter scenario. In this scenario, we can expect cosmological dark magnetic fields, which are free from the stringent constraint from the cosmic microwave observations. We find that gravitons can effectively convert into dark photons in the presence of cosmological dark magnetic fields. The graviton-dark photon conversion effect may open up a new window for ultra high frequency gravitational waves.
We study the evolution of magnetic fields in turbulent hot plasma of the early Universe accounting for the chiral magnetic effect. The magnetohydrodynamic turbulence is modeled by replacing the matter velocity in the advection term in the Faraday equation with the Lorentz force. The system of the kinetic equations for the spectra of the densities of the magnetic helicity and the magnetic energy, as well as for the chiral imbalance, is derived. The amplification of the magnetic field is shown to result from the presence of the chiral magnetic effect solely. The system of the kinetic equations i…
It has been recently argued \cite{Barvinsky:2017lfl} that the de Sitter phase in cosmology might be naturally generated as a result of dynamics of the topologically nontrivial sectors in a strongly coupled QCD-like gauge theory in expanding universe. It is known that the de Sitter phase is realized in the history of our Universe twice: the first occurrence is coined as the inflation, while the second time (which is occurring now) is dubbed as the dark energy (DE). The crucial element of the proposal \cite{Barvinsky:2017lfl} is the presence of a nontrivial gauge holonomy which is the source of …
A variety of observations impose upper limits at the nano Gauss level on magnetic fields that are coherent on inter-galactic scales while blazar observations indicate a lower bound $\sim 10^{-16}$ Gauss. Such magnetic fields can play an important astrophysical role, for example at cosmic recombination and during structure formation, and also provide crucial information for particle physics in the early universe. Magnetic fields with significant energy density could have been produced at the electroweak phase transition. The evolution and survival of magnetic fields produced on sub-horizon scal…
We explore the possibility that matter bulk flows could generate the required vorticity in the electron-proton-photon plasma to source cosmic magnetic fields through the Harrison mechanism. We analyze the coupled set of perturbed Maxwell and Boltzmann equations for a plasma in which the matter and radiation components exhibit relative bulk motions at the background level. We find that, to first order in cosmological perturbations, bulk flows with velocities compatible with current Planck limits ($β<8.5\times 10^{-4}$ at $95\%$ CL) could generate magnetic fields with an amplitude $10^{-21}$ G o…
Effects of simulated cosmological magnetic fields on the galaxy population
我们调查的原始磁种子场的强度变化的影响，在理想的磁流体动力学宇宙学模拟与移动网格代码AREPO进行的星系人口的全球性质。我们在计算中改变了种子场，使其值的范围仍然与当前宇宙学的上限相兼容。我们表明，以上的$\simeq 10^{-9}\,{\rm G}$的临界强度，从外地产生的额外的压力强烈影响的气体结构的演变，导致宇宙恒星形成历史的抑制，\rev{which is stronger for larger seed fields. This directly reflects into a lower total galaxy count above a fixed stellar mass threshold at all redshifts, and}一个较低的星系数密度在固定的恒星质量和质量较小的恒星组件在所有质量尺度上固定维里质量。除了现有的方法之外，这些签名可以用于导出对原始磁种子场强度的更严格的约束。
Secondary Production of Photons from ALP Dark Matter interacting with a Cosmological Magnetic Field
McGill University（麦吉尔大学）；Instituto de Fisica Teorica, UNESP-Universidade Estadual Paulista（圣保罗州立大学理论物理研究所）；Trottier Space Institute, Department of Physics, McGill University（麦吉尔大学特罗蒂尔空间研究所）；Department of Physics, Institute of Science Tokyo（东京科学大学物理系）
We study the effect of magnetic braking due to a primordial magnetic field in the context of the formation of massive ($\gtrsim 10^{4} M_\odot$) direct collapse black holes (DCBHs) at high redshifts. Under the assumption of axial symmetry, we analytically compute the effect of magnetic braking on the angular momentum of gas collapsing into the potential well of massive dark matter haloes ($\simeq 10^{7-9} M_\odot$) which are spun up by gravitational tidal torques. We find that a primordial magnetic field of strength $B_0\simeq 0.1$~nG (comoving) can remove the initial angular momentum gained b…
A primordial magnetic field with the strength in the 1-10 pG range can resolve the tension between different measurements of the Hubble constant and provide an explanation for the excess opacity in the 21 cm line at redshift $15<z<20$, if it is present during the recombination and reionization epochs. This field can also survive in the voids of the large-scale Structure in the present day universe. We study the sensitivity reach of the gamma-ray technique for measurement of such relatively strong cosmological magnetic field using deep exposure(s) of the nearest hard spectrum blazar(s) with CTA…
It is usually assumed that when Weyl invariance is unbroken in the electromagnetic sector, the energy density of primordial magnetic fields will redshift as radiation. Here we show that primordial magnetic fields do not exhibit radiation-like redshifting in the presence of stronger electric fields, as a consequence of Faraday's law of induction. In particular for the standard Maxwell theory, magnetic fields on super-horizon scales can redshift as $B^2 \propto a^{-6} H^{-2}$, instead of the usually assumed $a^{-4}$. Taking into account this effect for inflationary magnetogenesis can correct pre…
Cosmological magnetic helicity and birefrigence from primordial torsion in Lorentz violation theories
宇宙学磁螺旋度被认为是宇宙中磁场放大的基本因素。最近Semikoz和Sokoloff [Phys Rev Lett 92（2004）：131.301.]表明种子场的弱并不一定意味着磁宇宙螺旋度的弱。本文推导了Riemann-Cartan时空中基于平扭光子非最小耦合的发电机方程。从这个推导，我们可以从宇宙学的磁螺旋度，计算出一个平坦的扭转场产生银河发电机种子的必要条件。这个发电机方程的一个特点是电阻率依赖于Ricci标量曲率。这一特征也存在于湍流发电机模型中。这里的有效电导率是利用$R(Γ)F^{2}$拉格朗日的平扭模得到的，其中R是指Ricci-Cartan时空。计算了磁场的功率谱。光子的双折射与挠率的半极小耦合自然地产生洛伦兹破坏。尽管Dobado和Maroto [Mod Phys Lett A 12：3003（1997）]之前已经研究了原始扭转在光传播各向异性中的作用，但他们使用QED拉格朗日的费米子部分进行了研究，而我们使用光子部分获得了类似的结果。他们也使用了伪挠迹，而我们这里用挠迹本身来计算。
The origin of cosmic magnetic fields is an unsolved problem and magnetogenesis could have occurred in the early Universe. We study the evolution of such primordial magnetic fields across the cosmological recombination epoch via 3D magnetohydrodynamic numerical simulations. We compute the effective or net heating rate of baryons due to decaying magnetic fields and its dependence on the magnetic field strength and spectral index. In the drag-dominated regime ($z \gtrsim 1500$), prior to recombination, we find no real heating is produced. Our simulations allow us to smoothly trace a new transitio…
The recent claim by the NANOGrav collaboration of a possible detection of an isotropic gravitational wave background stimulated a series of investigations searching for the origin of such a signal. The QCD phase transition appears as a natural candidate and in this paper the gravitational spectrum generated during the conversion of quarks into hadrons is calculated. Here, contrary to recent studies, equations of state for the quark-gluon plasma issued from the lattice approach were adopted. The duration of the transition, an important parameter affecting the amplitude of the gravitational wave…
The aim of this thesis is to study the effects on the CMB anisotropy due to primordial magnetic fields and to analyze some favorable scenarios of magnetogenesis constrained by those signatures, including limits on the amplitude of the fields from bounds on CMB non-Gaussianity and background models. In fact, we found out that helicity in the fields plays an important role in the analysis PMFs origin, by generating significant features in the cross-correlation polarization pattern and the increasing of the signal in the reduced CMB bispectrum. In the latter case, we reported that non-causal fiel…
