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The TAROGE-M observatory is an autonomous antenna array on the top of Mt. Melbourne (∼2700 m altitude) in Antarctica, designed to detect radio pulses from ultra-high energy (over 1017 eV) air showers coming from near-horizon directions. The targeted sources include cosmic rays, Earth-skimming tau neutrinos, and most of all, the anomalous near-horizon upward-going events of yet unknown origin discovered by ANITA experiments. The detection concept follows that of ANITA: monitoring large area of ice from high-altitude and taking advantage of strong geomagnetic field and quiet radio background in Antarctica, whereas having significantly greater livetime and scalability. The TAROGE-M station, upgraded from its prototype built in 2019, was deployed in January 2020, and consists of 6 log-periodic dipole antennas pointing horizontally with bandwidth of 180-450 MHz. The station is then calibrated with drone-borne transmitter, with which the event reconstruction obtained ∼0.3° angular resolution. The station was then smoothly operating in the following month, with the live time of ∼ 30 days, before interrupted by a power problem, and its online filtering has identified several candidate cosmic-ray events and sent out via satellite communication. In this paper, the instrumentation of the station for polar and high-altitude environment, its radio-locating performance, the preliminary result on cosmic-ray detection, and the future extension plan are presented.

TAROGE-M is a self-triggered radio antenna array atop the 2700 m high Mt.Melbourne in Antarctica, designed to detect impulsive geomagnetic emission fromextensive air showers induced by ultra-high energy (UHE) particles beyond 0.1EeV, including cosmic rays (CRs), Earth-skimming tau neutrinos, andparticularly, the "ANITA anomalous events" (AAEs) from near and below thehorizon, which origin remains uncertain and requires more experimental inputsfor clarification. The detection concept of TAROGE-M takes advantage of a high altitude withsynoptic view toward the horizon as an efficient signal collector, and theradio quietness as well as strong and near vertical geomagnetic field inAntarctica. This approach has a low energy threshold, high duty cycle, and iseasy to extend for quickly enlarging statistics. Here we report experimentalresults from the first TAROGE-M station deployed in 2020, corresponding to$25.3$-days of livetime. The station consists of six receiving antennasoperating at 180-450 MHz, and can reconstruct source directions with$\sim0.3^\circ$ angular resolution. To demonstrate its ability to detect UHEair showers, a search for CR signals in the data was conducted, resulting inseven identified events. These events have a mean reconstructed energy of$0.95_{-0.31}^{+0.46}$ EeV and zenith angles between $25^\circ-82^\circ$, withboth distributions agreeing with simulations. The estimated CR flux is alsoconsistent with results of other experiments. The TAROGE-M sensitivity to AAEsis approximated by the tau neutrino exposure with simulations, suggestingcomparable sensitivity as ANITA's at $~1$ EeV energy with a few station-yearsof operation. These first results verified the station design and performancein a polar and high-altitude environment, and are promising for furtherdiscovery of tau neutrinos and AAEs after an extension in the near future.

Though wakefield acceleration in crystal channels has been previouslyproposed, x-ray wakefield acceleration has only recently become a realisticpossibility since the invention of the single-cycled optical laser compressiontechnique. We investigate the acceleration due to a wakefield induced by acoherent, ultrashort x-ray pulse guided by a nanoscale channel inside a solidmaterial. By two-dimensional particle in- cell computer simulations, we showthat an acceleration gradient of TeV/cm is attainable. This is about 3 ordersof magnitude stronger than that of the conventional plasma-based wakefieldaccelerations, which implies the possibility of an extremely compact scheme toattain ultrahigh energies. In addition to particle acceleration, this schemecan also induce the emission of high energy photons at ~O(10-100) MeV. Oursimulations confirm such high energy photon emissions, which is in contrastwith that induced by the optical laser driven wakefield scheme. In addition tothis, the significantly improved emittance of the energetic electrons has beendiscussed.

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 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 an information-preserving one. At early times, the former dominates EPI, while at the late times, the latter becomes dominant. By doing so, 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. [ABSTRACT FROM AUTHOR]

We discuss that a scheme of nonperturbative pair production by high energy photons (ω ≳ m) in a strong external field is achievable at the next high intensity laser experiments. The pair momentum is boosted, and for ω ≳ 1.2 m , the pair yield is increased when the external field is formed by two laser pulses converging at a small angle. These characteristics are nonperturbative in origin and related to the presence of magnetic field in addition to electric field. By enhancing the signal over perturbative backgrounds, these features allow the employment of above-threshold photons ω > 2 m , which further increases the pair yield. We note the close relation of this photon-pair conversion mechanism to spontaneous pair creation, recommending it as an accessible stepping stone experiment using state-of-the-art or soon-to-be laser technology. [ABSTRACT FROM AUTHOR]

Accelerating relativistic mirrors have long been recognized as viable settings where the physics mimic those of the black hole Hawking radiation. In 2017, Chen and Mourou proposed a novel method to realize such a system by traversing an ultra-intense laser through a plasma target with a decreasing density. An international AnaBHEL (Analog Black Hole Evaporation via Lasers) collaboration was formed with the objectives of observing the analog Hawking radiation, shedding light on the information loss paradox. To reach these goals, we plan to first verify the dynamics of the flying plasma mirror and characterize the correspondence between the plasma density gradient and the trajectory of the accelerating plasma mirror. We will then attempt to detect the analog Hawking radiation photons and measure the entanglement between the Hawking photons and their "partner particles". In this paper, we describe our vision and strategy of AnaBHEL using the Apollon laser as a reference, and we report on the progress of our R&D concerning the key components in this experiment, including the supersonic gas jet with a graded density profile, and the superconducting nanowire single-photon Hawking detector. In parallel to these hardware efforts, we performed computer simulations to estimate the potential backgrounds, and derived analytic expressions for modifications to the blackbody spectrum of the Hawking radiation for a perfectly reflecting point mirror, due to the semi-transparency and finite-size effects specific to flying plasma mirrors. Based on this more realistic radiation spectrum, we estimate the Hawking photon yield to guide the design of the AnaBHEL experiment, which appears to be achievable. [ABSTRACT FROM AUTHOR]

The information loss paradox remains unresolved ever since Hawking's seminal discovery of black hole evaporation. In this paper, we revisit the entanglement entropy via Euclidean path integral (EPI) and allow for the branching of semi-classical histories during the Lorentzian evolution. We posit that there exist two histories that contribute to EPI, where one is information-losing that dominates at early times, while the other is information-preserving that dominates at late times. By so doing, we recover the Page curve and preserve the unitarity, albeit with the Page time shifted significantly towards the late time. One implication is that the entropy bound may thus be violated. We compare our approach with string-based islands and replica wormholes concepts. [ABSTRACT FROM AUTHOR]

10.3390/photonics10020099 7 Jiang K., Wang W., Feng K., Li R. Review of Quality Optimization of Electron Beam Based on Laser Wakefield Acceleration. Roa et al. [[11]] focused on potential applications of fiber-optic-based laser Wakefield accelerated electron beams for radiotherapy cancer treatment, while Papp et al. [[12]] introduced the idea of LWFA-driven photoneutron generation aspired by high-impact societal applications. Another critical challenge is the production of high-quality electron beams in laser acceleration, whose optimization scheme was nicely examined by Jiang et al. [[7]]. [Extracted from the article]

Flying plasma mirrors induced by intense lasers via laser wake field acceleration scheme have been proposed as a promising way to generate few-cycle EUV or x-ray lasers. In addition, if such a relativistic plasma mirror can accelerate, then it would serve as an analog black hole to investigate the information loss paradox associated with the black hole Hawking evaporation. Among these applications, the reflectivity, which is usually frequency-dependent, would affect the outgoing photon spectrum and, therefore, impact on the analysis of the physics under investigation. In this paper, these two issues are investigated analytically and numerically with one-dimensional particle-in-cell simulations. Based on our simulation results, we propose a new model that provides a better estimate of the reflectivity than those studied previously. Moreover, we found that the peak frequency of the reflected spectrum of a Gaussian incident wave deviates from the expected value, 4 γ 2 ω , due to the dependence of reflectivity on the frequency of the incident wave. [ABSTRACT FROM AUTHOR]

It has been proposed that laser-induced relativistic plasma mirror can accelerate if the plasma has a properly tailored density profile. Such accelerating plasma mirrors can serve as analog black holes to investigate Hawking evaporation and the associated information loss paradox. Here we reexamine the underlying dynamics of mirror motion in a graded-density plasma to provide an explicit trajectory as a function of the plasma density and its gradient. Specifically, a decreasing plasma density profile (down-ramp) along the direction of laser propagation would in general accelerate the mirror. In particular, a constant-plus-exponential density profile would generate the Davies–Fulling trajectory with a well-defined analog Hawking temperature, which is sensitive to the plasma density gradient but not to the density itself. We show that without invoking nano-fabricated thin-films, a much lower density gas target at, for example, ∼ 1 × 10 17 cm − 3 , would be able to induce an analog Hawking temperature, k B T H ∼ 3.1 × 10 − 2 eV , in the far-infrared region. We hope that this would help to better realize the experiment proposed by Chen and Mourou. [ABSTRACT FROM AUTHOR]