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Are f(R, Matter) theories really relevant to cosmology?
No full textWe examine f(R, Matter) theories that directly couple the curvature R or R with the matter sector in the action, in addition to the universal coupling. We argue that if the matter sector includes the Standard Model (SM), such theories are either inconsistent or already excluded by experiments unless they are a rewriting of f(R) gravity or general relativity. If these theories genuinely couple the SM to curvature, they suffer from the presence of ghost states at energies within their domain of application for cosmological purposes. Therefore, we raise questions about their relevance to cosmology. Moreover, if such theories do not include the SM, they should just be seen as scalar-tensor, vector-tensor, …, theories, depending on the additional degrees of freedom. They should thus be studied accordingly
QCD-based charge symmetry breaking interaction and the Okamoto-Nolen-Schiffer anomaly
No full textAn approach is proposed to link the charge symmetry breaking (CSB) nuclear interaction and the low-energy constants in quantum chromodynamics (QCD) by matching the CSB effect in nuclear matter. The resulting CSB interaction is applied to study the Okamoto-Nolen-Schiffer anomaly, still lacking a satisfactory microscopic understanding, on the energy differences of mirror nuclei by taking F17-O17, O15-N15, Sc41-Ca41, and Ca39-K39 as typical examples. The magnitude and sign of the QCD-based CSB interactions are found to resolve the anomaly successfully within theoretical uncertainties
Measurement of <math display="inline"><mi>C</mi><mi>P</mi></math> Violation in <math display="inline"><mrow><msup><mrow><mi>B</mi></mrow><mrow><mn>0</mn></mrow></msup><mo stretchy="false">→</mo><mi>ψ</mi><mo stretchy="false">(</mo><mo stretchy="false">→</mo><msup><mrow><mo>ℓ</mo></mrow><mrow><mo>+</mo></mrow></msup><msup><mrow><mo>ℓ</mo></mrow><mrow><mo>-</mo></mrow></msup><mo stretchy="false">)</mo><msubsup><mrow><mi>K</mi></mrow><mrow><mi>S</mi></mrow><mrow><mn>0</mn></mrow></msubsup><mo stretchy="false">(</mo><mo stretchy="false">→</mo><msup><mrow><mi>π</mi></mrow><mrow><mo>+</mo></mrow></msup><msup><mrow><mi>π</mi></mrow><mrow><mo>-</mo></mrow></msup><mo stretchy="false">)</mo></mrow></math> Decays
No full textA measurement of time-dependent CP violation in the decays of B0 and B¯0 mesons to the final states J/ψ(→μ+μ-)KS0, ψ(2S)(→μ+μ-)KS0 and J/ψ(→e+e-)KS0 with KS0→π+π- is presented. The data correspond to an integrated luminosity of 6 fb-1 collected at a center-of-mass energy of s=13 TeV with the LHCb detector. The CP-violation parameters are measured to be SψKS0=0.717±0.013(stat)±0.008(syst) and CψKS0=0.008±0.012(stat)±0.003(syst). This measurement of SψKS0 represents the most precise single measurement of the CKM angle β to date and is more precise than the current world average. In addition, measurements of the CP-violation parameters of the individual channels are reported and a combination with the LHCb Run 1 measurements is performed
The cosmic dance - Tracing Supermassive black holes in cosmological simulations
Get PDF<p>Talk at a conference.</p>
Gravity with torsion as deformed BF theory
No full textWe study a family of (possibly non topological) deformations of BF theory for the Lie algebra obtained by quadratic extension of by an orthogonal module. The resulting theory, called quadratically extended General Relativity (qeGR), is shown to be classically equivalent to certain models of gravity with dynamical torsion. The classical equivalence is shown to promote to a stronger notion of equivalence within the Batalin–Vilkovisky formalism. In particular, both Palatini–Cartan gravity and a deformation thereof by a dynamical torsion term, called (quadratic) generalised Holst theory, are recovered from the standard Batalin–Vilkovisky formulation of qeGR by elimination of generalised auxiliary fields
Gravitational waves from supermassive black hole binaries in light of the NANOGrav 15-year data
No full textThe NANOGrav and other pulsar timing arrays (PTAs) have recently announced evidence for nHz gravitational waves (GWs) that may originate from supermassive black hole (SMBH) binaries. The spectral index of the GW signal differs from that predicted for binary evolution by GW emission alone, and we show that environmental effects such as dynamical friction with gas, stars, and dark matter improve the consistency of the SMBH binary model with the PTA data. We comment on the possible implications of environmental effects for PTA observations of fluctuations in the GW frequency spectrum and measurements of GWs at higher frequencies
Algebras and their covariant representations in quantum gravity
No full textWe study a physically motivated representation of an algebra of operators in gravitational and non gravitational theories called the covariant representation of an algebra. This is a representation where the symmetries of the operator algebra are implemented unitarily on the Hilbert space. We emphasize the very close similarity of this representation to the crossed product of an algebra. In fact, as an example of (and sometimes identified with) a covariance algebra, the crossed product of an algebra is in one to one correspondence with the covariant representation of the algebra. This will in turn illuminate physically what the crossed product algebra is in the context of quantum gravity
Effects of renormalon scheme and perturbative scale choices on determinations of the strong coupling from <math display="inline"><mrow><msup><mrow><mi>e</mi></mrow><mrow><mo>+</mo></mrow></msup><msup><mrow><mi>e</mi></mrow><mrow><mo>-</mo></mrow></msup></mrow></math> event shapes
No full textWe study the role of renormalon cancellation schemes and perturbative scale choices in extractions of the strong coupling constant αs(mZ) and the leading nonperturbative shift parameter Ω1 from resummed predictions of the e+e- event shape thrust. We calculate the thrust distribution to NL3L′ resummed accuracy in soft-collinear effective theory (SCET) matched to the fixed-order O(αs2) prediction, and perform a new high-statistics computation of the O(αs3) matching in EERAD3, although we do not include the latter in our final αs fits due to some observed systematics that require further investigation. We are primarily interested in testing the phenomenological impact sourced from varying amongst three renormalon cancellation schemes and two sets of perturbative scale profile choices. We then perform a global fit to available data spanning center-of-mass energies between 35–207 GeV in each scenario. Relevant subsets of our results are consistent with prior SCET-based extractions of αs(mZ), but we are also led to a number of novel observations. Notably, we find that the combined effect of altering the renormalon cancellation scheme and profile parameters can lead to few-percent-level impacts on the extracted values in the αs-Ω1 plane, indicating a potentially important systematic theory uncertainty that should be accounted for. We also observe that fits performed over windows dominated by dijet events are typically of a higher quality than those that extend into the far tails of the distributions, possibly motivating future fits focused more heavily in this region. Finally, we discuss how different estimates of the three-loop soft matching coefficient cS˜3 can also lead to measurable changes in the fitted {αs,Ω1} values
What is the source of the PTA GW signal?
No full textThe most conservative interpretation of the nHz stochastic gravitational wave background (SGWB) discovered by NANOGrav and other pulsar timing array (PTA) collaborations is astrophysical, namely that it originates from supermassive black hole (SMBH) binaries. However, alternative cosmological models have been proposed, including cosmic strings, phase transitions, domain walls, primordial fluctuations, and "audible" axions. We perform a multimodel analysis (MMA) to compare how well these different hypotheses fit the NANOGrav data, both in isolation and in combination with SMBH binaries, and address the questions: Which interpretations fit the data best, and which are disfavored? We also discuss experimental signatures that can help discriminate between different sources of the PTA GW signal, including fluctuations in the signal strength between frequency bins, individual sources, and how the PTA signal extends to higher frequencies
Renormalizing Love: tidal effects at the third post-Newtonian order
No full textWe present the conservative effective two-body Hamiltonian at the third order in the post-Newtonian expansion with gravitoelectric quadrupolar dynamical tidal-interactions. Our derivation of the effective two-body Lagrangian is based on the diagrammatic effective field theory approach and it involves Feynman integrals up to three loops, which are evaluated within the dimensional regularization scheme. The elimination of the divergent terms occurring in the effective Lagrangian requires the addition of counterterms to ensure finite observables, thereby introducing a renormalization group flow to the post-adiabatic Love number. As a limiting case of the renormalized dynamical effective Hamiltonian, we also derive the effective Hamiltonian for adiabatic tides, and, in this regime, calculate the binding energy for a circular orbit, and the scattering angle in a hyperbolic scattering