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Register a new userThe EDGES signal: An imprint from the mirror world?
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Recent results from the Experiment to Detect the Global Epoch of Reionization Signature (EDGES) show an anomalous spectral feature at redshifts $zsim 15-20$ in its 21-cm absorption signal. This deviation from cosmological predictions can be understood as a consequence of physics that either lower the hydrogen spin temperature or increases the radiation temperature through the injection of soft photons in the bath. In the latter case, standard model neutrino decays $ u_i to u_j,gamma$ induced by effective magnetic and electric transition moments ($mu_text{eff}$) are precluded by the tight astrophysical constraints on $mu_text{eff}$. We show that if mirror neutrinos are present in the bath at early times, an analogous mechanism in the mirror sector can lead to a population of mirror photons that are then processed into visible photons through resonant conversion, thus accounting for the EDGES signal. We point out that the mechanism can work for mirror neutrinos which are either heavier than or degenerate with the standard model (SM) neutrinos, a scenario naturally realized in mirror twin Higgs models.
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Dark photons and mirror matter are well-motivated dark matter candidates. It is possible that both of them arose during the compactification and symmetry breaking scenario of the heterotic $E_8times E_8$ string theory and are related to each other. In this case, dark photons can become a natural portal into the mirror world. Unfortunately, the expected magnitude of the induced interactions of ordinary matter with mirror matter is too small to be of phenomenological interest.
In the present paper we have developed a concept of parallel ordinary (O) and mirror (M) worlds. We have shown that in the case of a broken mirror parity (MP), the evolutions of fine structure constants in the O- and M-worlds are not identical. It is assumed that E_6-unification inspired by superstring theory restores the broken MP at the scale sim 10^{18} GeV, what unavoidably leads to the different E_6-breakdowns at this scale: E_6 to SO(10)times U(1)_Z - in the O-world, and E_6 to SU(6)times SU(2)_Z - in the M-world. Considering only asymptotically free theories, we have presented the running of all the inverse gauge constants alpha_i^{-1} in the one-loop approximation. Then a `quintessence scenario is discussed for our model of accelerating universe. Such a scenario is related with an axion (`acceleron) of a new gauge group SU(2)_Z which has a coupling constant g_Z extremely growing at the scale Lambda_Zsim 10^{-3} eV.
The EDGES experiment shows a cooling of baryons at a redshift of $zsim 17$ with an amplitude of 500$_{-500}^{+200}$ mK at 99% C.L. which is a 3.8$sigma$ deviation from what the standard $Lambda$CDM cosmology gives. We present a particle physics model for the baryon cooling where a fraction of the dark matter resides in the hidden sector with a $U(1)$ gauge symmetry and a Stueckelberg mechanism operates mixing the visible and the hidden sectors with the hidden sector consisting of dark Dirac fermions and dark photons. The Stueckelberg mass mixing mechanism automatically generates a millicharge for the hidden sector dark fermions providing a theoretical basis for using millicharged dark matter to produce the desired cooling of baryons seen by EDGES by scattering from millicharged dark matter. We compute the relic density of the millicharged dark matter by solving a set of coupled equations for the dark fermion and dark photon yields and for the temperature ratio of the hidden sector and the visible sector heat baths. For the analysis of baryon cooling, we analyze the evolution equations for the temperatures of baryons and millicharged dark matter as a function of the redshift. We exhibit regions of the parameter space which allow consistency with the EDGES data. A confirmation of the EDGES effect will point to the possibility of the Stueckelberg mechanism operating at early epochs of the universe connecting the visible and hidden sectors.
In the present talk we have developed a concept of parallel ordinary (O) and mirror (M) worlds. We have shown that in the case of a broken mirror parity (MP), the evolutions of fine structure constants in the O- and M-worlds are not identical. It is assumed that E_6-unification inspired by superstring theory restores the broken MP at the scale sim 10^{18} GeV, what unavoidably leads to the different E_6-breakdowns at this scale: E_6 to SO(10)times U(1)_Z - in the O-world, and E_6 to SU(6)times SU(2)_Z - in the M-world. Considering only asymptotically free theories, we have presented the running of all the inverse gauge constants alpha_i^{-1} in the one-loop approximation. Then a `quintessence scenario is discussed for the model of accelerating universe. Such a scenario is related with an axion (`acceleron) of a new gauge group SU(2)_Z which has a coupling constant g_Z extremely growing at the scale Lambda_Zsim 10^{-3} eV.
The redshifted 21-cm signal of neutral Hydrogen is a promising probe into the period of evolution of our Universe when the first stars were formed (Cosmic Dawn), to the period where the entire Universe changed its state from being completely neutral to completely ionized (Reionization). The most striking feature of this line of neutral Hydrogen is that it can be observed across an entire frequency range as a sky-averaged continuous signature, or its fluctuations can be measured using an interferometer. However, the 21-cm signal is very faint and is dominated by a much brighter Galactic and extra-galactic foregrounds, making it an observational challenge. We have used different physical models to simulate various realizations of the 21-cm Global signals, including an excess radio background to match the amplitude of the EDGES 21-cm signal. First, we have used an artificial neural network (ANN) to extract the astrophysical parameters from these simulated datasets. Then, mock observations were generated by adding a physically motivated foreground model and an ANN was used to extract the astrophysical parameters from such data. The $R^2$ score of our predictions from the mock-observations is in the range of 0.65-0.89. We have used this ANN to predict the signal parameters giving the EDGES data as the input. We find that the reconstructed signal closely mimics the amplitude of the reported detection. The recovered parameters can be used to infer the physical state of the gas at high redshifts.
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