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Quantisation across bubble walls and friction
No full textWe quantise from first principles field theories living on the background of a bubble wall in the planar limit with particular focus on the case of spontaneous breaking of gauge symmetry. Using these tools, we compute the average momentum transfer from transition radiation: the soft emission of radiation by an energetic particle passing across the wall, with a particular focus on the longitudinal polarisation of vectors. We find these to be comparable to transverse polarisations in symmetry-breaking transitions with mild super-cooling, and dominant in broken to broken transitions with thin wall. Our results have phenomenological applications for the expansion of bubbles during first order phase transitions. Our general framework allows for the robust calculation of any particle processes of interest in such translation breaking backgrounds
Relevance of precession for tests of the black hole no hair theorems
No full textThe multipole moments of black holes in general relativity obey certain consistency relations known as the no hair theorems. The details of this multipolar structure are imprinted into the gravitational waves emitted by binary black holes, particularly if the binary is precessing. If black holes do not obey the vacuum field equations of general relativity, then the no hair theorems may be broken, and the observed gravitational waves will be modified, thus providing an important test of the no hair theorems. Recently, analytic solutions to the precession dynamics and inspiral waveforms were computed within the context of binaries possessing nonaxisymmetric mass quadrupole moments, which are parametrized by a modulus qm and phase am with m=1, 2 the azimuthal spherical harmonic number. Here, we use a Fisher analysis to study plausible constraints one may obtain on generic, nonaxisymmetry quadrupole configurations using current and future ground-based detectors. For nonprecessing binaries, we generically find that no meaningful constraints can be placed with current detectors on the nonaxisymmetry parameters (qm,am) due to the presence of strong degeneracies with other waveform parameters, while with next generation detectors, only weak constraints are possible. For precessing configurations, the exact value of the uncertainty is strongly dependent on the sky location, system orientation relative to the line of sight, and initial inclination angle of the orbital angular momentum. After averaging over these parameters, we find that with GWTC-3-like events, one should be able to plausibly constraint nonaxisymmetric mass quadrupole deviations to Δqm∼10-2 for LIGO at design sensitivity, and Δqm∼10-4 for the same sources with Einstein Telescope and Cosmic Explorer
Shell-shaped atomic gases
No full textWe review the quantum statistical properties of two-dimensional shell-shaped gases, produced by cooling and confining atomic ensembles in thin hollow shells. We consider both spherical and ellipsoidal shapes, discussing at zero and at finite temperature the phenomena of Bose–Einstein condensation and of superfluidity, the physics of vortices, and the crossover from the Bardeen–Cooper–Schrieffer regime to a Bose–Einstein condensate. The novel aspects associated to the curved geometry are elucidated in comparison with flat two-dimensional superfluids. We also describe the hydrodynamic excitations and their relation with the Berezinskii–Kosterlitz–Thouless transition for two-dimensional flat and curved superfluids. In the next years, shell-shaped atomic gases will be the leading experimental platform for investigations of quantum many-body physics in curved spatial domains
Detecting a Long-Lived False Vacuum with Quantum Quenches
No full textDistinguishing whether a system supports alternate low-energy (locally stable) states—stable (true vacuum) versus metastable (false vacuum)—by direct observation can be difficult when the lifetime of the state is very long but otherwise unknown. Here we demonstrate, in a tractable model system, that there are physical phenomena on much shorter timescales that can diagnose the difference. Specifically, we study the time evolution of the magnetization following a quench in the tilted quantum Ising model, and show that its magnitude spectrum is an effective diagnostic. Small transition bubbles are more common than large ones, and we see characteristic differences in the size dependence of bubble lifetimes even well below the critical size for false vacuum decay. We expect this sort of behavior to be generic in systems of this kind. We show such signatures persist in a continuum field theory. This also opens the possibility of similar signatures of the potential metastable false vacuum of our universe well before the beginning of a decay process to the true vacuum
A thermal product formula
No full textWe show that holographic thermal two-sided two-point correlators take the form of a product over quasi-normal modes (QNMs). Due to this fact, the two-point function admits a natural dispersive representation with a positive discontinuity at the location of QNMs. We explore the general constraints on the structure of QNMs that follow from the operator product expansion, the presence of the singularity inside the black hole, and the hydrodynamic expansion of the correlator. We illustrate these constraints through concrete examples. We suggest that the product formula for thermal correlators may hold for more general large N chaotic systems, and we check this hypothesis in several models
GroMiT: Planetary Growth and Migration Tracks code
No full text<p>GroMiT is the Growth and Migration Track code of the INAF suite of planet formation codes Arxes, capable of tracking how forming planets accrete pebbles and gas as well as how they migrate depending on the local environment of the native circumstellar disks.</p>
Observation of <math display="inline"><mi>W</mi><mi>Z</mi><mi>γ</mi></math> Production in <math display="inline"><mi>p</mi><mi>p</mi></math> Collisions at <math display="inline"><msqrt><mi>s</mi></msqrt><mo>=</mo><mn>13</mn><mtext> </mtext><mtext> </mtext><mi>TeV</mi></math> with the ATLAS Detector
No full textThis Letter reports the observation of WZγ production and a measurement of its cross section using 140.1±1.2 fb-1 of proton-proton collision data recorded at a center-of-mass energy of 13 TeV by the ATLAS detector at the Large Hadron Collider. The WZγ production cross section, with both the W and Z bosons decaying leptonically, pp→WZγ→ℓ′±νℓ+ℓ-γ (ℓ(′)=e, μ), is measured in a fiducial phase-space region defined such that the leptons and the photon have high transverse momentum and the photon is isolated. The cross section is found to be 2.01±0.30(stat)±0.16(syst) fb. The corresponding standard model predicted cross section calculated at next-to-leading order in perturbative quantum chromodynamics and at leading order in the electroweak coupling constant is 1.50±0.06 fb. The observed significance of the WZγ signal is 6.3σ, compared with an expected significance of 5.0σ
Measurement of the Centrality Dependence of the Dijet Yield in <math display="inline"><mrow><mi>p</mi><mo>+</mo><mi>Pb</mi></mrow></math> Collisions at <math display="inline"><msqrt><msub><mi>s</mi><mrow><mi>NN</mi></mrow></msub></msqrt><mo>=</mo><mn>8.16</mn><mtext> </mtext><mtext> </mtext><mi>TeV</mi></math> with the ATLAS Detector
No full textATLAS measured the centrality dependence of the dijet yield using 165 nb-1 of p+Pb data collected at sNN=8.16 TeV in 2016. The event centrality, which reflects the p+Pb impact parameter, is characterized by the total transverse energy registered in the Pb-going side of the forward calorimeter. The central-to-peripheral ratio of the scaled dijet yields, RCP, is evaluated, and the results are presented as a function of variables that reflect the kinematics of the initial hard parton scattering process. The RCP shows a scaling with the Bjorken x of the parton originating from the proton, xp, while no such trend is observed as a function of xPb. This analysis provides unique input to understanding the role of small proton spatial configurations in p+Pb collisions by covering parton momentum fractions from the valence region down to xp∼10-3 and xPb∼4×10-4
Hard and electromagnetic probes: plans for future measurements at the CERN SPS
No full textThe CERN SuperProtoSynchrotron (SPS) represents an ideal facility for fixed-target heavy-ion experiments exploring the phase diagram of strongly interacting matter in the region MeV. It can deliver high-intensity beams (>10^6 Pb/s), allowing a study of rare probes of the Quark-Gluon Plasma, including electromagnetic and hard processes. The NA61/SHINE experiment is currently active and plans to perform a first direct measurement of open charm production in Pb-Pb collisions at top SPS energy and possibly at lower energies. The project of a new experiment, NA60+, based on a muon spectrometer coupled to a vertex spectrometer is currently being developed, for the study of dimuon and heavy quark production, and a Letter of Intent was recently submitted. In this contribution the physics motivation for the studies of rare probes, the existing and planned experimental set-ups and their expected physics performance will be discussed
Perturbativity in the presence of ultraslow-roll dynamics
No full textWe discuss the issue of perturbativity in single-field inflationary models with a phase of ultraslow-roll (USR) tailor suited to generate an order-one abundance of primordial black holes (PBHs). More in detail, we impose the condition that loop corrections made up of short-wavelength modes enhanced by the USR dynamics do not alter the tree-level power spectrum of curvature perturbations. In our analysis, the USR phase is preceded and followed by two stages of ordinary slow-roll (SR), and we model the resulting SR/USR/SR dynamics using both instantaneous and smooth transitions. Focusing on scales relevant for cosmic microwave background observations, we find that it is not possible, with these arguments, to rule out the scenario of PBH formation via USR, not even in the limit of instantaneous transition. However, we also find that loop corrections of short modes on the power spectrum of long modes, even though not large enough to violate perturbativity requirements, remain appreciable and, most importantly, are not tamed in realistic realizations of smooth SR/USR/SR transitions. This makes perturbativity a powerful theoretical tool to constrain USR dynamics. We extend the analysis at any scale beyond those relevant for cosmic microwave background observations. We find that loop corrections of short modes remain within the few percent if compared to the tree-level power spectrum. However, we also find one notable exception of phenomenological relevance: we show that the so-called dip in the power spectrum of curvature perturbation is significantly reduced beyond the tree-level computation