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TAROGE-M is a self-triggered radio antenna array atop the 2700 m high Mt. Melbourne in Antarctica, designed to detect impulsive geomagnetic emission from extensive air showers induced by ultra-high energy (UHE) particles beyond 0.1 EeV, including cosmic rays (CRs), Earth-skimming tau neutrinos, and particularly, the "ANITA anomalous events" (AAEs) from near and below the horizon, which origin remains uncertain and requires more experimental inputs for clarification. The detection concept of TAROGE-M takes advantage of a high altitude with synoptic view toward the horizon as an efficient signal collector, and the radio quietness as well as strong and near vertical geomagnetic field in Antarctica. This approach has a low energy threshold, high duty cycle, and is easy to extend for quickly enlarging statistics. Here we report experimental results from the first TAROGE-M station deployed in 2020, corresponding to $25.3$-days of livetime. The station consists of six receiving antennas operating at 180-450 MHz, and can reconstruct source directions with $\sim0.3^\circ$ angular resolution. To demonstrate its ability to detect UHE air showers, a search for CR signals in the data was conducted, resulting in seven identified events. These events have a mean reconstructed energy of $0.95_{-0.31}^{+0.46}$ EeV and zenith angles between $25^\circ-82^\circ$, with both distributions agreeing with simulations. The estimated CR flux is also consistent with results of other experiments. The TAROGE-M sensitivity to AAEs is approximated by the tau neutrino exposure with simulations, suggesting comparable sensitivity as ANITA's at $~1$ EeV energy with a few station-years of operation. These first results verified the station design and performance in a polar and high-altitude environment, and are promising for further discovery of tau neutrinos and AAEs after an extension in the near future., Comment: 41 pages, 23 figures, submitted to JCAP; minor corrections in references; minor modifications in simulation description in section 5 & 6 for clarity

The information loss paradox associated with black hole Hawking evaporation is an unresolved problem in modern theoretical physics. In a recent brief essay, we revisited the the evolution of the black hole entanglement entropy via the Euclidean path integral (EPI) of the quantum state and allow for the branching of semi-classical histories along the Lorentzian evolution. We posited that there exist at least two histories that contribute to EPI, where one is an information-losing history while the other is information-preserving. At early times, the former dominates EPI, while at late times the latter becomes dominant. By so doing we recovered the essence of the Page curve and thus the unitarity, albeit with the turning point, i.e., the Page time, much shifted toward the late time. In this full-length paper, we fill in the details of our arguments and calculations to strengthen our notion. One implication of this modified Page curve is that the entropy bound may thus be violated. We comment on the similarity and difference between our approach and that of the replica wormholes and the islands conjectures., Comment: 20 pages, 9 figures. arXiv admin note: substantial text overlap with arXiv:2205.08320, arXiv:2111.01005

Analog Hawking radiation emitted by a perfectly reflecting mirror in (1+3)-dimensional flat spacetime is investigated. This is accomplished by studying the reflected frequency and momentum based on Einstein mirror, instead of the canonical way of solving, if possible, wave equations subjected to a dynamical Dirichlet boundary condition. In the case of a finite-size mirror, diffraction pattern appears in the radiation spectrum. Based on the relevant parameters in the proposed AnaBHEL experiment, where the Hawking temperature TH = 0.03 eV and the mirror area A = 0.1 mm2, the Hawking photon yield is estimated to be N = 16 per laser shot (assuming a high reflectivity mirror can be generated in the proposed AnaBHEL experiment)., 8 pages, 4 figures

Production of massless scalar particles by a relativistic semitransparent mirror of finite transverse size and longitudinal thickness in (1+3)D flat spacetime is studied. The derived particle spectrum formula is applied to two specific trajectories. One is the gravitational collapse trajectory invoked in (1+1)D perfectly reflecting moving mirror literature to mimic Hawking radiation, and the other is the plasma mirror trajectory proposed to be realizable in future experiments. It is found that the finiteness of the transverse size leads to diffraction, while the nontrivial thickness amplifies the production rate. We also estimated the particle yield as roughly 3000 in a 20-day data acquisition based on the parameters invoked in the proposed AnaBHEL experiment., Comment: 14 pages, 7 figures, 1 table; title slightly modified, new discussions added, reference added, numerical results updated

The lack of correlations on the large scale cosmic microwave background (CMB) anisotropy provides a potential window to probe beyond the standard inflationary scenario. In this paper, we investigate the primordial power spectrum based on the Hartle-Hawking (HH) no-boundary proposal for a homogeneous, isotropic, and spatially-closed universe that leads to a Starobinsky-type inflation after the classicalization. While we found that there is no suppression at large scales in the standard R + R^2 theory, we also found that it is possible to sufficiently suppress the large-scale power spectrum if a pre-inflation stage is introduced to the Starobinsky-type model. We calculate the C^TT_l correlation function and show that our proposal gives a better fit to the Planck CMB data. l This suggests that our universe might have begun with a compact HH state with a small positive curvature., Comment: 19 pages, 8 figures

The Eddington-inspired-Born-Infeld (EiBI) gravity, which is formulated within the Palatini formalism, is characterized by its ability to cure the big bang singularity in the very beginning of the Universe. We further analyze the EiBI phantom model, and investigate the possible avoidance or alleviation of other dark energy related singularities. We find that except for the big rip singularity and little rip event, most of the cosmological singularities of interest can be partially alleviated in this model. Furthermore, we generalize the EiBI theory by adding a pure trace term to the determinant of the action. This amendment is the most general rank-two tensor composed of up to first order of the Riemann curvature. We find that this model allows the occurrence of primitive bounces and some smoother singularities than that of big bang. Most interestingly, for certain parameter space, the big bang singularity can be followed naturally by an inflationary stage in a radiation dominated universe., Comment: 6 pages; contribution to the proceedings of the "Everything about gravity, Second LeCosPA international Symposium", National Taiwan University, Taipei, December 14-18, 2015, based on a talk delivered at the "Alternative and modified theories of gravity" parallel session

We propose a new scalar-tensor model which induces significant deviation from general relativity inside dense objects like neutron stars, while passing solar-system and terrestrial experiments, extending a model proposed by Damour and Esposito-Farese. Unlike their model, we employ a massive scalar field dubbed asymmetron so that it not only realizes proper cosmic evolution but also can account for the cold dark matter. In our model, asymmetron undergoes spontaneous scalarization inside dense objects, which results in reduction of the gravitational constant by a factor of order unity. This suggests that observational tests of constancy of the gravitational constant in high density phase are the effective ways to look into the asymmetron model., Comment: 22 pages, 3 figures

One longstanding mystery in bio-evolution since Darwin's time is the origin of the Cambrian explosion that happened around 540 million years ago (Mya), where an extremely rapid increase of species occurred. Here we suggest that a nearby GRB event ~500 parsecs away, which should occur about once per 5 Gy, might have triggered the Cambrian explosion. Due to a relatively lower cross section and the conservation of photon number in Compton scattering, a substantial fraction of the GRB photons can reach the sea level and would induce DNA mutations in organisms protected by a shallow layer of water or soil, thus expediting the bio-diversification. This possibility of inducing genetic mutations is unique among all candidate sources for major incidents in the history of bio-evolution. A possible evidence would be the anomalous abundance of certain nuclear isotopes with long half-lives transmuted by the GRB photons in geological records from the Cambrian period. Our notion also imposes constraints on the evolution of exoplanet organisms and the migration of panspermia., Comment: 4 pages, 2 figures

We point out that a new mechanism for radiation should exist if the Bohm theory of quantum mechanics is taken seriously. By traversing a quantum potential, an electron will necessarily be accelerated and radiate. For an illustration, we show that in the double-slit experiment this radiation yields a characteristic spectrum and a distinct pattern on the screen that is complementary to the pattern of the electrons. Experimentally, either the existence or the nonexistence of such a radiation would have important implications for the foundations of quantum mechanics., Comment: 5 pages, 3 figures

We present a simple toy model corresponding to a network of frustrated topological defects of domain walls or cosmic strings that exist previous to the standard slow-roll inflationary era of the universe. Such a network (i) can produce a slower inflationary era than that of the standard scenario if it corresponds to a network of frustrated domain walls or (ii) can induce a vanishing universal acceleration; i.e., the universe would expand at a constant speed, if it corresponds to a network of frustrated cosmic strings red. Those features are phenomenologically modeled by a Chaplygin gas that can interpolate between a network of frustrated topological defects and a de Sitter-like or a power-law inflationary era. We show that this scenario can alleviate the quadruple anomaly of the cosmic microwave background spectrum. Using the method of the Bogoliubov coefficients, we obtain the spectrum of the gravitational waves as would be measured today for the whole range of frequencies. We comment on the possible detection of this spectrum by the planned detectors like BBO and DECIGO., 11 pages, 12 figures. RevTex4-1. Expanded discussion. Version accepted in PRD

We investigate the evolution of the linear cosmological perturbations in f(R) gravity, an alternative to dark energy for explaining the late-time cosmic acceleration. We numerically calculate the early-time evolution with an approximation we contrive to solve a problem that commonly appears when one solves the full evolution equations. With the approximate evolution equations we can fairly assess the effect of the gravity modification on the early-time evolution, thereby examining the validity of the general-relativity (GR) approximation that is widely used for the early universe. In particular, we compare the CMB photon density perturbation and the matter density perturbation obtained respectively by our approximation and the conventional GR approximation. We find that the effect of the gravity modification at early times in f(R) gravity may not be negligible. We conclude that to be self-consistent, in the f(R) theory one should employ the approximation presented in this paper instead of that of GR in the treatment of the early-time evolution., Comment: 14 pages, 3 figures

Recently Disney et al. (2008) found a striking correlation among the five basic parameters that govern the galactic dynamics: R50, R90, Lr, Md, and MHI . They suggested that this is in conflict with the LCDM model, which predicts the hierarchical formation of cosmic structures from bottom up. In light of the importance of the issue, we performed a similar analysis on global parameters of galaxies with a significantly larger database and two additional parameters, LJ and RJ, of the near-infrared J band. We used databases from the Arecibo Legacy Fast Arecibo L-band Feed Array Survey for the atomic gas properties, the Sloan Digital Sky Survey for the optical properties, and the Two Micron All Sky Survey for the near-infrared properties, of the galaxies. We conducted principal component analysis (PCA) to find relations among these observational variables and confirmed that the five parameters in the work of Disney et al. are indeed correlated. The first principal component dominates the correlations among the five parameters and can explain 86% of the variation in the data. When color (g - i) is included, the first component still dominates and the color forms a second principal component that is almost independent of other parameters. The overall trend in our near-infrared PCA is very similar, except that color (i - J) seems even more decoupled from all other parameters. The dominance of the first principal component suggests that the structure of galaxies is governed by a single physical parameter. This confirms the observational results in Disney et al. However, based on the importance of the baryon physics in galaxy formation, we are not convinced that the hierarchical structure formation scenario and the notion of cold dark matter are necessarily flawed., Comment: 8 pages, 9 figures

It has been suggested by Chen and Lai that the proper description of the large scale structure formation of the universe in the post-reionization era, which is conventionally characterized via gas hydrodynamics, should include the plasma collective effects in the formulation. Specifically, it is the combined pressure from the baryon thermal motions and the residual long-range electrostatic potentials resulted from the imperfect Debye shielding, that fights against the gravitational collapse. As a result, at small-scales the baryons would oscillate at the ion-acoustic, instead of the conventional neutral acoustic, frequency. In this paper we extend and improve the Chen-Lai formulation with the attention to the Landau damping of the ion-acoustic oscillations. Since T_e \sim T_i in the post-reionization era, the ion acoustic oscillations would inevitably suffer the Landau damping which severely suppresses the baryon density spectrum in the regimes of intermediate and high wavenumber k. To describe this Landau-damping phenomenon more appropriately, we find it necessary to modify the filtering wavenumber k_f in our analysis. It would be interesting if our predicted Landau damping of the ion-acoustic oscillations can be observed at high redshifts., Comment: 5 pages

One of the most tantalizing questions in astronomy and astrophysics, namely the origin and the evolution of the cosmic accelerators that produce the highest energy cosmic rays (UHECR), may be best addressed through the observation of ultra high energy (UHE) cosmogenic neutrinos. Neutrinos travel from their source undeflected by magnetic fields and unimpeded by interactions with the cosmic microwave background. At high energies, neutrinos could be detected in dense, radio frequency (RF) transparent media via the Askaryan effect. The abundant cold ice covering the geographic South Pole, with its exceptional RF clarity, has been host to several pioneering efforts to develop this approach, including RICE and ANITA. Building on the expertise gained in these efforts, and the infrastructure developed in the construction of the IceCube optical Cherenkov observatory, a low-cost array of radio frequency antenna stations could be deployed near the Pole to efficiently detect a significant number of UHE neutrinos with degree scale angular resolution within the next decade. Such an array, if installed in close proximity to IceCube, could allow cross-calibration on a small but invaluable subset of neutrino events detected by both the optical and radio methods. In addition to providing critical information in the identification of the source of UHECRs, such an observatory could also provide a unique probe of long baseline high energy neutrino interactions unattainable in any man-made neutrino beam., Comment: 7 pages, 3 figures, submitted to US Astronomy Decadal Survey (2010-2020)

We comment on the calculation mistake in the paper "w and w' of scalar field models of dark energy" by Takeshi Chiba [arXiv:astro-ph/0510598], where w is the dark energy equation of state and w' is the time derivative of w in units of the Hubble time. The author made a mistake while rewriting the phantom equation of motion, which led to an incorrect generic bound for the phantom model and an incorrect bound for the tracker phantom model on the w-w' plane., Comment: 3 pages, 2 figures

Magnetowave induced plasma wakefield acceleration (MPWA) in a relativistic astrophysical outflow has been proposed as a viable mechanism for the acceleration of cosmic particles to ultra high energies. Here we present simulation results that demonstrate the viability of this mechanism. We invoke the high frequency and high speed whistler mode for the driving pulse. The plasma wakefield so induced validates precisely the theoretical prediction. This mechanism is shown capable of accelerating charged particles to ZeV energies in Active Galactic Nuclei (AGN)., Comment: Talk presented by G.-L. Lin at Challenges in Particle Astrophysics, XXth RENCONTRES DE BLOIS,18th-23rd May 2008

There has been the suggestion that the cosmological constant as implied by the dark energy is related to the well-known hierarchy between the Planck scale, $M_{\rm Pl}$, and the Standard Model scale, $M_{\rm SM}$. Here we further propose that the same framework that addresses this hierarchy problem must also address the smallness problem of the cosmological constant. Specifically, we investigate the minimal supersymmetric (SUSY) extension of the Randall-Sundrum model where SUSY-breaking is induced on the TeV brane and transmitted into the bulk. We show that the Casimir energy density of the system indeed conforms with the observed dark energy scale.

We show that the cascade limit on ultra high energy cosmic neutrino (UHEC$\nu$) flux imposes a lower bound on the neutrino mass provided that super-GZK events of ultra high energy cosmic rays (UHECRs) are produced from Z-bursts. Based on the data from HiRes and AGASA, the obtained neutrino mass lower bound violates its existing cosmological upper bound. We conclude that the Z-bursts cannot be the dominant source for the observed super-GZK UHECR events. This is consistent with the recent ANITA-lite data., Comment: 6 pages, derivation simplified and main idea consolidated, and appendix added

A new model for the origin of dark energy is proposed based on the Casimir effect in a supersymmetry-breaking brane-world. Supersymmetry is assumed to be preserved in the bulk while broken on a 3-brane. Due to the boundary conditions imposed on the compactified extra dimensions, there is an effective Casimir energy induced on the brane. The net Casimir energy contributed from the graviton and the gravitino modes as a result of supersymmetry-breaking on the brane is identified as the observed dark energy, which in our construction is a cosmological constant. We show that the smallness of the cosmological constant, which results from the huge contrast in the extra-dimensional volumes between that associated with the 3-brane and that of the bulk, is attainable under very relaxed conditions., Comment: 4 pages, 2 figures

Recent years have seen tremendous progress in our understanding of the extreme universe, which in turn points to even deeper questions to be further addressed. History has shown that the symbiosis between direct observations and laboratory investigations is instrumental in the progress of astrophysics. Current frontier astrophysical phenomena related to particle astrophysics and cosmology typically involve one or more of the following conditions: (1) extremely high energy events;(2) very high density, high temperature processes; (3) super strong field environments. Laboratory experiments using high intensity lasers and particle beams can calibrate astrophysical observation or detection processes, investigate the underlying dynamics of astrophysical phenomena, and probe fundamental physics in extreme limits. We give examples of possible laboratory experiments that investigate into the extreme universe.

There have been proposals that primordial black hole remnants (BHRs) are the dark matter, but the idea is somewhat vague. We argue here first that the generalized uncertainty principle (GUP) may prevent black holes from evaporating completely, in a similar way that the standard uncertainty principle prevents the hydrogen atom from collapsing. Secondly we note that the hybrid inflation model provides a plausible mechanism for production of large numbers of small black holes. Combining these we suggest that the dark matter might be composed of Planck-size BHRs and discuss the possible constraints and signatures associated with this notion.

Drees and Godbole have proposed that, at the interaction point of an e+e- linear collider, one expects a high rate of hadron production by gamma-gamma collisions, providing an additional background to studies in e+e- annihilation. Using a simplified model of the gamma-gamma cross section with soft and jet-like components, we estimate the expected rate of these hadronic events for a variety of realistic machine designs. The final background rates are quite small, and they become smaller still when viewed with a realistic detector simulation., Comment: PHYZZX, 39 pages, including 3 tables; 14 figures are not included but are available upon request