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The promise of quantum computers hinges on the ability to scale to large system sizes, e.g., to run quantum computations consisting of more than 100 million operations fault-tolerantly. This in turn requires suppressing errors to levels inversely proportional to the size of the computation. As a step towards this ambitious goal, we present experiments on a trapped-ion QCCD processor where, through the use of fault-tolerant encoding and error correction, we are able to suppress logical error rates to levels below the physical error rates. In particular, we entangled logical qubits encoded in the [[7,1,3]] code with error rates 9.8 times to 500 times lower than at the physical level, and entangled logical qubits encoded in a [[12,2,4]] code with error rates 4.7 times to 800 times lower than at the physical level, depending on the judicious use of post-selection. Moreover, we demonstrate repeated error correction with the [[12,2,4]] code, with logical error rates below physical circuit baselines corresponding to repeated CNOTs, and show evidence that the error rate per error correction cycle, which consists of over 100 physical CNOTs, approaches the error rate of two physical CNOTs. These results signify an important transition from noisy intermediate scale quantum computing to reliable quantum computing, and demonstrate advanced capabilities toward large-scale fault-tolerant quantum computing., Comment: 13 pages, 8 figures

Along the lines of the Einstein-Rosen wave equation of General Relativity (GR), we derive a gravitational wave equation with cylindrical symmetry in the Einstein-aether (EA) theory. We show that the gravitational wave in the EA is periodic in time for both the metric functions $\Psi(r,t)$ and $H(r,t)$. However, in GR, $\Psi(r,t)$ is periodic in time, but $H(r,t)$ is semi-periodic in time, having a secular drifting in the wave frequency. The evolution of wave pulses of a given width is entirely different in both theories in the $H(r,t)$ metric function due to this frequency drifting. Another fundamental difference between the two theories is the gravitational wave velocity. While in GR, the waves propagate with the speed of light, in EA, there is no upper limit to the wave velocity, reaching infinity if $c_{13} \rightarrow 1$ and zero if $c_{13} \rightarrow -\infty$. We also show that energy-momentum pseudotensor and superpotential get contributions from aether in addition to the usual gravitational field part. All these characteristics are observational signatures that differentiate GR and EA., Comment: 26 pages, 10 figures. We have corrected the initial conditions for $H(r,t)$ in order to have $\Psi(r,t)$ not equal to $H(r,t)$

We analysed the nuclear region of all 56 early-type galaxies from the DIVING$^\mathrm{3D}$ Project, which is a statistically complete sample of objects that contains all 170 galaxies of the Southern Hemisphere with B < 12.0 mag and galactic latitude |b| < 15$^{\circ}$. Observations were performed with the Integral Field Unit of the Gemini Multi-Object Spectrograph. Emission lines were detected in the nucleus of 86$\pm$5% of the objects. Diagnostic diagrams were used to classify 52$\pm$7% of the objects as LINERs or Seyferts, while the other 34$\pm$6% galaxies without H$\beta$ or [O III] lines in their spectra were classified as weak emission line objects. Transition Objects are not seen in the sample, possibly because the seeing-limited data cubes of the objects allow one to isolate the nuclei of the galaxies from their circumnuclear regions, avoiding contamination from H II regions. A broad line region is seen in 29$\pm$6% of the galaxies. Of the 48 galaxies with emission-line nuclei, 41 have signs of AGNs. Some objects have also indications of shocks in their nuclei. Lenticular galaxies are more likely to have emission lines than ellipticals. Also, more luminous objects have higher [N II]/H$\alpha$ ratios, which may be associated with the mass-metalicity relation of galaxies. A direct comparison of our results with the Palomar Survey indicates that the detection rates of emission lines and also of type 1 AGNs are higher in the DIVING$^\mathrm{3D}$ objects. This is a consequence of using a more modern instrument with a better spatial resolution than the Palomar Survey observations., Comment: 16 pages (plus appendices), 6 figures, 9 tables, accepted for publication in MNRAS

We attempt to answer whether Birkhoff's theorem (BT) is valid in the Einstein-Aether (EA) theory. The BT states that any spherically symmetric solution of the vacuum field equations must be static, unique, and asymptotically flat. For a general spherically symmetric metric with metric functions $A(r,t)$ \& $B(r,t)$, and aether components $a(r,t)$ \& $b(r,t)$, we prove the conditions for the staticity of spacetime using two different methods. We point out that BT is valid in EA theory only for special values of $c_1+c_3$, $c_1+c_4$, and $c_2$, where we can show that all these special cases are asymptotically flat. In particular, when the aether has only a temporal component, i.e., $b(r,t)=0$ and the $c_{14} \neq 0$ case gives us spherically symmetric static black holes without horizons; that is, they have naked singularities, at least for special values of $c_{14}$. Thus, the cosmic censorship conjecture is violated for the case BT holds. However, when we have an aether vector with temporal and radial components, we only prove that the staticity and the flatness at infinity hold for a special metric and particular combination of the aether parameters. For this case, there exist universal horizons instead of naked singularities., Comment: 19 pages, no figures

We model a compact radiant star that undergoes gravitational collapse from a certain initial static configuration until it becomes a black hole. The star consists of a fluid with anisotropy in pressures, bulk viscosity, in addition to the radial heat flow. A solution of Einstein's field equations with temporal dependence was presented to study the dynamic evolution of physical quantities, such as the mass-energy function, the luminosity seen by an observer at infinity and the heat flow. We checked the acceptability conditions of the initial static configuration to obtain a range of mass-to-radius ratio in which the presented star model is physically reasonable. The energy conditions were analyzed for the dynamic case, in order to guarantee that the model is composed of a physically acceptable fluid within the range of the mass-to-radius ratio obtained for the static configuration or if they will be modified during the collapse, Comment: 35 pages, 19 figures

We report consistent ignition of high-pressure (p > 20-30 bar) hydrogen-oxygen mixtures diluted with helium, using an unfocused Nd:YAG laser. This corresponds to laser irradiances several orders of magnitude below the minimum ignition energies reported in the literature. By placing a mirror inside a cylindrical vessel and filling it up to 100 bar with H2-He or O2-He non-combustible mixtures, we obtain the pressure-dependent absorptivity of the combustible He-H2-O2 mixture. We find no measurable absorption of the laser signal by the medium, for the overall pressure range, to the experimental apparatus sensitivity (about 1% of the laser irradiance). This leads credence to the theory that ignition stems from seed electrons created by autofocusing ionization of dust/impurities in the gas.

We analyze several spherically symmetric exterior vacuum solutions allowed by the Einstein-Aether (EA) theory with a non static aether and study the thermodynamics of their Killing and universal horizons. We show that there are five classes of solutions corresponding to different values of a combination of the free parameters, $c_{2}$, $c_{13}=c_1+c_3$ and $c_{14}=c_1+c_4$, which are: (A) $c_2 \ne 0$ and $c_{13} \ne 0$ and $c_{14}=0$, (B) $c_2 \ne 0$ and $c_{13} = 0$ and $c_{14} = 0$, (C) $c_2 = 0$ and $c_{13} \ne 0$ and $c_{14} = 0$, (D) $c_2 = 0$, $c_{13} = 0$ and $c_{14} \ne 0$, and (E) $c_2 = - c_{13} \ne 0$ and $c_{14} \ne 0$. We present explicit analytical solutions for these five cases. All these cases have singularities at $r=0$ and are asymptotically flat spacetimes and possess both Killing and universal horizons with the universal horizons always being inside the Killing horizons. Finally, we compute the surface gravity, the temperature, the entropy and the first law of thermodynamics for the universal horizons., Comment: 35 pages, 5 figures and 4 tables. We have improved the manuscript with a new solution and a comparison with others authors who have used Eddington-Finkelstein coordinates

This report describes the conceptual design of the DUNE near detector, Comment: 314 pages, 185 figures

In this work we present all the possible solutions for a static cylindrical symmetric spacetime in the Einstein-Aether (EA) theory. As far as we know, this is the first work in the literature that considers cylindrically symmetric solutions in the theory of EA. One of these solutions is the generalization in EA theory of the Levi-Civita (LC) spacetime in General Relativity (GR) theory. We have shown that this generalized LC solution has unusual geodesic properties, depending on the parameter $c_{14}$ of the aether field. The circular geodesics are the same of the GR theory, no matter the values of $c_{14}$. However, the radial and $z$ direction geodesics are allowed only for certain values of $\sigma$ and $c_{14}$. The $z$ direction geodesics are restricted to an interval of $\sigma$ different from those predicted by the GR and the radial geodesics show that the motion is confined between the origin and a maximum radius. The latter is not affected by the aether field but the velocity and acceleration of the test particles are Besides, for $0\leq\sigma<1/2$, when the cylindrical symmetry is preserved, this spacetime is singular at the axis $r=0$, although for $\sigma>1/2$ exists interval of $c_{14}$ where the spacetime is not singular, which is completely different from that one obtained with the GR theory, where the axis $r=0$ is always singular., Comment: 20 pages and 4 figures. Accepted for publication in IJMPD

We investigate some models of compact objects in the general relativity theory with cosmological constant $\Lambda$, based on two density profiles, one of them attributed to Stewart and the other one to Durgapal and Bannerji, proposed in the literature to model "neutron stars". For them, a nonlocal equation of state with cosmological constant is obtained as a consequence of the chosen metric. In another direction, we obtain a solution for configurations with null radial pressure. The first model (based on the Stewart's density profile) turned out to be the most interesting, since surprisingly it admits the presence of dark energy in the interior of the star, in the outermost layers, for a certain range of mass-radius ratio $\gamma$. This dark energy is independent of the cosmological constant, since it is a consequence of the tangential pressure of the fluid be sufficiently negative. Still in this case, for other values of $\gamma$, all the energy conditions are satisfied. Another advantage of this model, as well as that based on the density profile of Durgapal and Bannnerji is the existence of intervals of $\gamma$ compatible with physically acceptable models for $\Lambda < 0$, $\Lambda = 0$ and $\Lambda > 0$, which also allowed us to analyze the influence of $\Lambda$ on the behavior of the fluid with respect to the energy conditions. The other configuration studied here, $P_r=0$, only allow solutions for $\Lambda<0$, in order to ensure a positive mass for the object and to satisfy all the energy conditions in a specific range of $\gamma$., Comment: 32 pages, 15 figures

We discuss the stability and construct dynamical configurations describing the gravitational collapse of unstable neutron stars with realistic equations of state compatible with the recent LIGO-Virgo constraints. Unlike other works that consider the collapse of a stellar configuration without a priori knowledge if it is stable or unstable, we first perform a complete analysis on stellar stability for such equations of state. Negative values of the squared frequency of the fundamental mode indicate us radial instability with respect to the collapse of the unstable star to a black hole. We find numerical solutions corresponding to the temporal and radial behavior during the evolution of the collapse for certain relevant physical quantities such as mass, luminosity, energy density, pressure, heat flow, temperature and quantities that describe bulk viscous processes. Our results show that the equation of state undergoes abrupt changes close to the moment of event horizon formation as a consequence of dissipative effects. During the collapse process all energy conditions are respected, which implies that our model is physically acceptable., Comment: 13 pages, 11 figures

In the present work we analyze all the possible spherically symmetric exterior vacuum solutions allowed by the Einstein-Aether theory with static aether. We show that there are four classes of solutions corresponding to different values of a combination of the free parameters, $c_{14}=c_1+c_4$, which are: $ 0 < c_{14}<2$, $c_{14} < 0$, $c_{14}=2$ and $c_{14}=0$. We present explicit analytical solutions for $c_{14}=3/2, 16/9, 48/25, -16, 2$ and $0$. The first case has some pathological behavior, while the rest have all singularities at $r=0$ and are asymptotically flat spacetimes. For the solutions $c_{14}=16/9, 48/25\, \mathrm{\, and \,}\, -16$ we show that there exist no horizons, neither Killing nor universal horizon, thus we have naked singularities. Finally, the solution for $c_{14}=2$ has a metric component as an arbitrary function of radial coordinate, when it is chosen to be the same as in the Schwarzschild case, we have a physical singularity at finite radius, besides the one at $r=0$. This characteristic is completely different from General Relativity., Comment: 21 pages and 9 figures

Recently, Smirnov published a paper (B. M. Smirnov, "Collision and radiative processes in emission of atmospheric carbon dioxide", 2018, J. Phys. D.: Appl. Phys., Vol. 51, No. 21, pp. 214004) which dismisses the role of increasing concentrations of anthropogenic CO$_2$ on global warming of planet Earth. We show that these conclusions are the consequence of two flaws in Smirnov's theoretical model which neglect the effects of the increased concentrations of CO$_2$ on the absorption of Earth's blackbody radiation in the 12-15$\mu$m region. The influence of doubling the concentration of CO$_2$ in the atmosphere on the surface temperature is not $\Delta$T=0.02K, or even $\Delta$T=0.4K if only one of the two mistakes in Smirnov's analysis is corrected. The correct value lies within $\Delta$T=1.1-1.3K as outlined by other authors analysis using simplified, yet more theoretically consistent models., Comment: 12 pages, 5 figures

Extensively applied to both light and heavy meson decay and standing as one of the most successful strong decay models is the $^{3}P_{0}$ model, in which $q\bar{q}$ pair production is the dominant mechanism. In this paper we evaluate strong decay amplitudes and partial widths of strange $S$ and $D$ state mesons, namely $ \phi(1020)$, $\phi (1680) $, $ \phi (2050) $, $\phi_1 (1850) $, $\phi_2 (1850) $ and $ \phi_3 (1850) $, in the bound-state corrected $^{3}P_{0}$ decay model (C$^{3}P_{0}$). The C$^{3}P_{0}$ model is obtained in the context of the Fock-Tani formalism, which is a mapping technique., Comment: To appear in Phys. Rev. C

How do the global properties of a Lorentzian manifold change when endowed with a vector field? This interesting question is tackled in this paper within the framework of Einstein-Aether (EA) theory which has the most general diffeomorphism-invariant action involving a spacetime metric and a vector field. After classifying all the possible nine vacuum solutions with and without cosmological constant in Friedmann-Lema{\^{\i}}tre-Robertson-Walker (FLRW) cosmology, we show that there exist three singular solutions in the EA theory which are not singular in the General Relativity (GR), all of them for $k=-1$, and another singular solution for $k=1$ in EA theory which does not exist in GR. This result is cross-verified by showing the focusing of timelike geodesics using the Raychaudhuri equation. These new singular solutions show that GR and EA theories can be completely different, even for the FLRW solutions when we go beyond flat geometry ($k=0$). In fact, they have different global structures. In the case where $\Lambda=0$ ($k=\pm 1$) the vector field defining the preferred direction is the unique source of the curvature., Comment: 9 pages and no figures. Some typos are corrected in this version and included an additional discussion in the Conclusions. Accepted for publication in JCAP