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Improving the performance of cryogenic calorimeters with nonlinear multivariate noise cancellation algorithms
No full textState-of-the-art physics experiments require high-resolution, low-noise, and low-threshold detectors to achieve competitive scientific results. However, experimental environments invariably introduce sources of noise, such as electrical interference or microphonics. The sources of this environmental noise can often be monitored by adding specially designed "auxiliary devices" (e.g. microphones, accelerometers, seismometers, magnetometers, and antennae). A model can then be constructed to predict the detector noise based on the auxiliary device information, which can then be subtracted from the true detector signal. Here, we present a multivariate noise cancellation algorithm which can be used in a variety of settings to improve the performance of detectors using multiple auxiliary devices. To validate this approach, we apply it to simulated data to remove noise due to electromagnetic interference and microphonic vibrations. We then employ the algorithm to a cryogenic light detector in the laboratory and show an improvement in the detector performance. Finally, we motivate the use of nonlinear terms to better model vibrational contributions to the noise in thermal detectors. We show a further improvement in the performance of a particular channel of the CUORE detector when using the nonlinear algorithm in combination with optimal filtering techniques
A quantum fluctuation description of charge qubits
No full textWe consider a specific instance of a superconducting circuit, the so-called charge-qubit, consisting of a capacitor and a Josephson junction that we describe by means of the BCS microscopic model in terms of two tunnelling superconducting systems in the strong-coupling quasi-spin formulation. Then, by means of collective observables we derive the Hamiltonian governing the quantum behaviour of the circuit in the limit of a large number N of quasi-spins. Our approach relies on suitable quantum fluctuations, i.e. on collective quasi-spin operators, different from mean-field observables, that retain a quantum character in the large-N limit. These collective operators generate the Heisenberg algebra on the circle and we show that their dynamics reproduces the phenomenological one generated by the charge qubit Hamiltonian obtained by quantizing the macroscopic classical Hamiltonian of the circuit. The microscopic derivation of the emergent, large-N behaviour provides a rigorous setting to investigate more in detail both general quantum circuits and quantum macroscopic scenarios; in particular, in the specific case of charge-qubits, it allows to explicitly obtain the temperature dependence of the critical Josephson current in the strong coupling regime, a result not accessible using standard approximation techniques
Using the motion of S2 to constrain vector clouds around Sgr A*
No full textThe dark compact object at the centre of the Milky Way is well established to be a supermassive black hole with mass ||, but the nature of its environment is still under debate. In this work, we used astrometric and spectroscopic measurements of the motion of the star S2, one of the closest stars to the massive black hole, to determine an upper limit on an extended mass composed of a massive vector field around Sagittarius A*. For a vector with effective mass ||, our Markov chain Monte Carlo analysis shows no evidence for such a cloud, placing an upper bound || at 3σ confidence level. We show that dynamical friction exerted by the medium on S2 motion plays no role in the analysis performed in this and previous works, and can be neglected thus
Measurement of the cosmic <math display="inline"><mrow><mi>p</mi><mo>+</mo><mi>He</mi></mrow></math> energy spectrum from 50 GeV to 0.5 PeV with the DAMPE space mission
No full textRecent observations of the light component of the cosmic-ray spectrum have revealed unexpected features that motivate further and more precise measurements up to the highest energies. The Dark Matter Particle Explorer is a satellite-based cosmic-ray experiment that has been operational since December 2015, continuously collecting data on high-energy cosmic particles with very good statistics, energy resolution, and particle identification capabilities. In this work, the latest measurements of the energy spectrum of proton+helium in the energy range from 46 GeV to 464 TeV are presented. Among the most distinctive features of the spectrum, a spectral hardening at 600 GeV has been observed, along with a softening at 29 TeV measured with a 6.6σ significance. Moreover, the detector features and the analysis approach allowed for the extension of the spectral measurement up to the sub-PeV region. Even if with small statistical significance due to the low number of events, data suggest a new spectral hardening at about 150 TeV
Linear and nonlinear clusterings of Horndeski-inspired dark energy models with fast transition
No full textWe analyze time-dependent dark energy equations of state through linear and nonlinear structure formation and their quintessence potentials, characterized by fast, recent transitions, inspired by parameter space studies of selected classes of the more general Horndeski models. The influence of dark energy on structures comes from modifications to the background expansion rate and from perturbations as well. In order to compute the structures growth, we employ a generalization of the spherical collapse formalism that includes perturbations of fluids with pressure. We numerically solve the equations of motion for the perturbations and the field. Our analysis suggests that a true Heaviside step transition is a good approximation for most of the considered models, since most of the quantities weakly depend on the transition speed. We find that transitions occurring at redshifts zt≳2 cannot be distinguished from the ΛCDM model if dark energy is freezing, i.e., the corresponding equation of state tends to -1. For fast, recent transitions, the redshift at which the properties of dark energy have the most significant effect is z=0.6±0.2. We also find that in the freezing regime, the σ8 values can be lowered by about 8%, suggesting that those models could relieve the σ8-tension. Additionally, freezing models generally predict faster late-time merging rates but a lower number of massive galaxies at z=0. Finally, the nonlinear matter power spectrum for smooth dark energy shows a valley centered in k≈1h Mpc-1 which in the clustering case is replaced by a sharp increase for k≳0.2h Mpc-1 and a peak at k≈2h Mpc-1
Extending Cosmic Ray Background in the LiteBIRD Experiment using Generative Adversarial Networks
No full text<p>Cosmic rays (CR) reaching telescope detectors in outer space are known to induce glitches and background noise, as the High-Frequency Telescope (HFT) of the LiteBIRD experiment, designed to measure the B modes polarization of the Cosmic Microwave Background (CMB). The presence of CR noise significantly influenced the Planck experiment, which shared similarities in detector design with LiteBIRD. Detecting the faint CMB signal, excluding data affected by CR noise from analysis, is impractical. In order to address this challenge, it is imperative to accurately simulate the CR background throughout the duration of LiteBIRD's three-year mission. However, state-of-the-art Monte Carlo simulations of CR background incur significant computational overhead, typically requiring 30 times the simulated period, rendering complete coverage of the mission infeasible. To overcome this limitation, we propose augmenting Monte Carlo simulations with Generative Adversarial Networks (GANs). By leveraging GANs, we can efficiently generate a sufficient number of genuine, statistically independent images, unlike traditional noise analysis techniques together with template expansion methods.</p>
Studying QGP transport properties in a concurrent minijet+hydro framework
No full textMinijets are ubiquitous in heavy-ion collision experiments. However, they are often excluded from the hydrodynamic simulations of QGP as they do not thermalize at short time scales and are not treated as part of the collective medium. Using a concurrent jet+hydro framework, we show that the minijets could account for a significant portion of particle multiplicity. Therefore, the energy deposition from minijet-medium interactions can substantially modify the QGP transport properties inferred from model-to-data comparison
On the renormalization of Poincaré gauge theories
No full textPoincaré Gauge Theories are a class of Metric-Affine Gravity theories with a metric-compatible (i.e. Lorentz) connection and with an action quadratic in curvature and torsion. We perform an explicit one-loop calculation starting with a single term of each type and show that not only are all other terms generated, but also many others. In our particular model all terms containing torsion are redundant and can be eliminated by field redefinitions, but there remains a new term quadratic in curvature, making the model non-renormalizable. We discuss the likely behavior of more general theories of this type
Many-Body Dynamics in Monitored Atomic Gases without Postselection Barrier
No full textWe study the properties of a monitored ensemble of atoms driven by a laser field and in the presence of collective decay. The properties of the quantum trajectories describing the atomic cloud drastically depend on the monitoring protocol and are distinct from those of the average density matrix. By varying the strength of the external drive, a measurement-induced phase transition occurs separating two phases with entanglement entropy scaling subextensively with the system size. Incidentally, the critical point coincides with the superradiance transition of the trajectory-averaged dynamics. Our setup is implementable in current light-matter interaction devices, and most notably, the monitored dynamics is free from the postselection measurement problem, even in the case of imperfect monitoring
Kerr black hole in Einstein–æther gravity
No full textWhile nonrotating black-hole solutions are well known in Einstein–æther gravity, no axisymmetric solutions endowed with Killing horizons have been so far found outside of the slowly rotating limit. Here we show that the Kerr spacetime is also an exact vacuum solution of Einstein–æther gravity in a phenomenologically viable corner of the parameter space; the corresponding æther flow is characterized by a vanishing expansion. Such a solution displays all the characteristic features of the Kerr metric (inner and outer horizons, ergoregion, etc.) with the remarkable exception of the causality-violating region in proximity of the ring singularity. However, due to the associated æther flow, it is endowed with a special surface, inside the Killing horizon, which exhibits many features normally related to the universal horizon of the nonrotating solutions—to which it tends in the limit of zero angular momentum. Hence, these Kerr black holes are very good mimickers of their general relativistic counterparts while sporting important differences and specific structures. As such, they appear particularly well-suited candidates for future phenomenological studies