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We report the observation of new properties of primary cosmic rays He, C, and O measured in the rigidity (momentum/charge) range 2 GV to 3 TV with $90\times {10}^6$ helium, $8.4\times {10}^6$ carbon, and $7.0\times {10}^6$ oxygen nuclei collected by the Alpha Magnetic Spectrometer (AMS) during the first five years of operation. Above 60 GV, these three spectra have identical rigidity dependence. They all deviate from a single power law above 200 GV and harden in an identical way.

A precision measurement by AMS of the positron fraction in primary cosmic rays in the energy range from 0.5 to 500 GeV based on 10.9 million positron and electron events is presented. This measurement extends the energy range of our previous observation and increases its precision. The new results show, for the first time, that above $\sim 200\mathrm{GeV}$ the positron fraction no longer exhibits an increase with energy.

The cosmological primordial power spectrum is known to be one of the most promising observable to probe quantum gravity effects. In this article, we investigate how the tensor power spectrum is modified by loop-quantum-gravity corrections. The two most important quantum terms, holonomy and inverse volume, are explicitly taken into account in a unified framework. The equation of propagation of gravitational waves is derived and solved for one set of parameters.

Precision measurements of cosmic ray positrons are presented up to 1 TeV based on 1.9 million positrons collected by the Alpha Magnetic Spectrometer on the International Space Station. The positron flux exhibits complex energy dependence. Its distinctive properties are (a) a significant excess starting from $25.2\pm 1.8\mathrm{GeV}$ compared to the lower-energy, power-law trend, (b) a sharp dropoff above $284_{-64}^{+91}\mathrm{GeV}$, (c) in the entire energy range the positron flux is well described by the sum of a term associated with the positrons produced in the collision of cosmic rays, which dominates at low energies, and a new source term of positrons, which dominates at high energies, and (d) a finite energy cutoff of the source term of $E_s=810_{-180}^{+310}\mathrm{GeV}$ is established with a significance of more than $4\sigma$. These experimental data on cosmic ray positrons show that, at high energies, they predominantly originate either from dark matter annihilation or from other astrophysical sources.

Precision measurements by the Alpha Magnetic Spectrometer on the International Space Station of the primary cosmic-ray electron flux in the range 0.5 to 700 GeV and the positron flux in the range 0.5 to 500 GeV are presented. The electron flux and the positron flux each require a description beyond a single power-law spectrum. Both the electron flux and the positron flux change their behavior at $\sim 30\mathrm{GeV}$ but the fluxes are significantly different in their magnitude and energy dependence. Between 20 and 200 GeV the positron spectral index is significantly harder than the electron spectral index. The determination of the differing behavior of the spectral indices versus energy is a new observation and provides important information on the origins of cosmic-ray electrons and positrons.

A precision measurement by AMS of the antiproton flux and the antiproton-to-proton flux ratio in primary cosmic rays in the absolute rigidity range from 1 to 450 GV is presented based on $3.49\times 10^5$ antiproton events and $2.42\times 10^9$ proton events. The fluxes and flux ratios of charged elementary particles in cosmic rays are also presented. In the absolute rigidity range $\sim 60$ to $\sim 500\mathrm{GV}$, the antiproton $\overline{p}$, proton $p$, and positron $e^{+}$ fluxes are found to have nearly identical rigidity dependence and the electron $e^{-}$ flux exhibits a different rigidity dependence. Below 60 GV, the ($\overline{p}/p$), ($\overline{p}/e^{+}$), and ($p/e^{+}$) flux ratios each reaches a maximum. From $\sim 60$ to $\sim 500\mathrm{GV}$, the ($\overline{p}/p$), ($\overline{p}/e^{+}$), and ($p/e^{+}$) flux ratios show no rigidity dependence. These are new observations of the properties of elementary particles in the cosmos.

The fluxes of light antinuclei $A\le 4$ induced near Earth by cosmic ray interactions with the interstellar matter in the Galaxy and with the Earth’s atmosphere are calculated in a phenomenological framework. The hadronic production cross section for antinucleons is based on a recent parametrization of a wide set of accelerator data. The production of light nuclei is calculated using coalescence models. For the standard coalescence model, the coalescence radius is fitted to the available experimental data. The nonannihilating inelastic scattering process for the antideuterons is discussed and taken into account for the first time via a more realistic procedure than used so far for antiprotons.

Precision measurements by the Alpha Magnetic Spectrometer (AMS) on the International Space Station of ${}^3\mathrm{He}$ and ${}^4\mathrm{He}$ fluxes are presented. The measurements are based on 100 million ${}^4\mathrm{He}$ nuclei in the rigidity range from 2.1 to 21 GV and 18 million ${}^3\mathrm{He}$ from 1.9 to 15 GV collected from May 2011 to November 2017. We observed that the ${}^3\mathrm{He}$ and ${}^4\mathrm{He}$ fluxes exhibit nearly identical variations with time. The relative magnitude of the variations decreases with increasing rigidity. The rigidity dependence of the ${}^3\mathrm{He}/{}^4\mathrm{He}$ flux ratio is measured for the first time. Below 4 GV, the ${}^3\mathrm{He}/{}^4\mathrm{He}$ flux ratio was found to have a significant long-term time dependence. Above 4 GV, the ${}^3\mathrm{He}/{}^4\mathrm{He}$ flux ratio was found to be time independent, and its rigidity dependence is well described by a single power law $\propto R^{\mathrm{\Delta }}$ with $\mathrm{\Delta }=-0.294\pm 0.004$. Unexpectedly, this value is in agreement with the B/O and B/C spectral indices at high energies.

Knowledge of the precise rigidity dependence of the helium flux is important in understanding the origin, acceleration, and propagation of cosmic rays. A precise measurement of the helium flux in primary cosmic rays with rigidity (momentum/charge) from 1.9 GV to 3 TV based on 50 million events is presented and compared to the proton flux. The detailed variation with rigidity of the helium flux spectral index is presented for the first time. The spectral index progressively hardens at rigidities larger than 100 GV. The rigidity dependence of the helium flux spectral index is similar to that of the proton spectral index though the magnitudes are different. Remarkably, the spectral index of the proton to helium flux ratio increases with rigidity up to 45 GV and then becomes constant; the flux ratio above 45 GV is well described by a single power law.

Precision results on cosmic-ray electrons are presented in the energy range from 0.5 GeV to 1.4 TeV based on $28.1\times {10}^6$ electrons collected by the Alpha Magnetic Spectrometer on the International Space Station. In the entire energy range the electron and positron spectra have distinctly different magnitudes and energy dependences. The electron flux exhibits a significant excess starting from $42.1_{-5.2}^{+5.4}\mathrm{GeV}$ compared to the lower energy trends, but the nature of this excess is different from the positron flux excess above $25.2\pm 1.8\mathrm{GeV}$. Contrary to the positron flux, which has an exponential energy cutoff of $810_{-180}^{+310}\mathrm{GeV}$, at the $5\sigma$ level the electron flux does not have an energy cutoff below 1.9 TeV. In the entire energy range the electron flux is well described by the sum of two power law components. The different behavior of the cosmic-ray electrons and positrons measured by the Alpha Magnetic Spectrometer is clear evidence that most high energy electrons originate from different sources than high energy positrons.

We present the precision measurement from May 2011 to May 2017 (79 Bartels rotations) of the proton fluxes at rigidities from 1 to 60 GV and the helium fluxes from 1.9 to 60 GV based on a total of $1\times {10}^9$ events collected with the Alpha Magnetic Spectrometer aboard the International Space Station. This measurement is in solar cycle 24, which has the solar maximum in April 2014. We observed that, below 40 GV, the proton flux and the helium flux show nearly identical fine structures in both time and relative amplitude. The amplitudes of the flux structures decrease with increasing rigidity and vanish above 40 GV. The amplitudes of the structures are reduced during the time period, which started one year after solar maximum, when the proton and helium fluxes steadily increase. Above $\sim 3\mathrm{GV}$ the $p/\mathrm{He}$ flux ratio is time independent. We observed that below $\sim 3\mathrm{GV}$ the ratio has a long-term decrease coinciding with the period during which the fluxes start to rise.

Together with holonomy corrections, inverse volume terms should be taken into account when studying the primordial universe in loop quantum cosmology. We investigate how the tensor power spectrum is modified with respect to the standard general relativistic prediction by those semiclassical corrections. Depending on the values of the free parameters of the model, it is shown that the spectrum can exhibit a very large deviation from its usual shape, in particular, with a very red slope and a strong running in the infrared limit.

Knowledge of the rigidity dependence of the boron to carbon flux ratio (B/C) is important in understanding the propagation of cosmic rays. The precise measurement of the $\mathrm{B}/\mathrm{C}$ ratio from 1.9 GV to 2.6 TV, based on 2.3 million boron and 8.3 million carbon nuclei collected by AMS during the first 5 years of operation, is presented. The detailed variation with rigidity of the $\mathrm{B}/\mathrm{C}$ spectral index is reported for the first time. The $\mathrm{B}/\mathrm{C}$ ratio does not show any significant structures in contrast to many cosmic ray models that require such structures at high rigidities. Remarkably, above 65 GV, the $\mathrm{B}/\mathrm{C}$ ratio is well described by a single power law $R^{\mathrm{\Delta }}$ with index $\mathrm{\Delta }=-0.333\pm 0.014(\text{fit})\pm 0.005(\text{syst})$, in good agreement with the Kolmogorov theory of turbulence which predicts $\mathrm{\Delta }=-1/3$ asymptotically.

This Letter aims at showing that the observation of evaporating black holes should allow the usual Hawking behavior to be distinguished from loop quantum gravity (LQG) expectations. We present a full Monte Carlo simulation of the evaporation in LQG and statistical tests that discriminate between competing models. We conclude that contrarily to what was commonly thought, the discreteness of the area in LQG leads to characteristic features that qualify evaporating black holes as objects that could reveal quantum gravity footprints.

We present a measurement of the cosmic ray $(e^{+}+e^{-})$ flux in the range 0.5 GeV to 1 TeV based on the analysis of 10.6 million $(e^{+}+e^{-})$ events collected by AMS. The statistics and the resolution of AMS provide a precision measurement of the flux. The flux is smooth and reveals new and distinct information. Above 30.2 GeV, the flux can be described by a single power law with a spectral index $\gamma =-3.170\pm 0.008(\text{stat}+\text{syst})\pm 0.008(\text{energy}\text{scale})$.

A precise measurement of the proton flux in primary cosmic rays with rigidity (momentum/charge) from 1 GV to 1.8 TV is presented based on 300 million events. Knowledge of the rigidity dependence of the proton flux is important in understanding the origin, acceleration, and propagation of cosmic rays. We present the detailed variation with rigidity of the flux spectral index for the first time. The spectral index progressively hardens at high rigidities.

Gravitinos are expected to be produced in any local supersymmetric model. Using their abundance prediction as a function of the reheating energy scale, we argue that the next generation of cosmic microwave background experiments could exclude supergravity or strongly favor “thermal-like” inflation models if B mode polarized radiation were detected. Galactic cosmic-ray production by evaporating primordial black holes is also investigated as a way of constraining the Hubble mass at the end of inflation. Subsequent limits on the gravitino mass and on the related grand unification parameters are derived.

In this paper, we extend the idea that the spectrum of Hawking radiation can reveal valuable information on a number of parameters that characterize a particular black hole background—such as the dimensionality of spacetime and the value of coupling constants—to gain information on another important aspect: the curvature of spacetime. We investigate the emission of Hawking radiation from a $D$-dimensional Schwarzschild–de Sitter black hole emitted in the form of scalar fields, and employ both analytical and numerical techniques to calculate greybody factors and differential energy emission rates on the brane and in the bulk. The energy emission rate of the black hole is significantly enhanced in the high-energy regime with the number of spacelike dimensions. On the other hand, in the low-energy part of the spectrum, it is the cosmological constant that leaves a clear footprint, through a characteristic, constant emission rate of ultrasoft quanta determined by the values of black hole and cosmological horizons. Our results are applicable to “small” black holes arising in theories with an arbitrary number and size of extra dimensions, as well as to pure 4-dimensional primordial black holes, embedded in a de Sitter spacetime.

The primordial spectrum of cosmological tensor perturbations is considered as a possible probe of quantum gravity effects. Together with string theory, loop quantum gravity is one of the most promising frameworks to study quantum effects in the early universe. We show that the associated corrections should modify the potential seen by gravitational waves during the inflationary amplification. The resulting power spectrum should exhibit a characteristic tilt. This opens a new window for cosmological tests of quantum gravity.

Lovelock gravity is an important extension of general relativity that provides a promising framework to study curvature corrections to the Einstein action, while avoiding ghosts and keeping second order field equations. This paper derives the greybody factors for $D$-dimensional black holes arising in a theory with a Gauss-Bonnet curvature-squared term. These factors describe the nontrivial coupling between black holes and quantum fields during the evaporation process: they can be used both from a theoretical viewpoint to investigate the intricate space-time structure around such a black hole, and for phenomenological purposes in the framework of braneworld models with a low Planck scale. We derive exact spectra for the emission of scalar, fermion and gauge fields emitted on the brane, and for scalar fields emitted in the bulk, and demonstrate how the Gauss-Bonnet term can change the bulk-to-brane emission rates ratio in favor of the bulk channel in particular frequency regimes.