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Showing papers in "Physical Review D in 2017"


Journal ArticleDOI
TL;DR: Fuzzy dark matter (FDM) as discussed by the authorsDM is an alternative to CDM, which is an extremely light boson having a de Broglie wavelength inside the galaxy.
Abstract: Many aspects of the large-scale structure of the Universe can be described successfully using cosmological models in which $27\ifmmode\pm\else\textpm\fi{}1%$ of the critical mass-energy density consists of cold dark matter (CDM). However, few---if any---of the predictions of CDM models have been successful on scales of $\ensuremath{\sim}10\text{ }\text{ }\mathrm{kpc}$ or less. This lack of success is usually explained by the difficulty of modeling baryonic physics (star formation, supernova and black-hole feedback, etc.). An intriguing alternative to CDM is that the dark matter is an extremely light ($m\ensuremath{\sim}{10}^{\ensuremath{-}22}\text{ }\text{ }\mathrm{eV}$) boson having a de Broglie wavelength $\ensuremath{\lambda}\ensuremath{\sim}1\text{ }\text{ }\mathrm{kpc}$, often called fuzzy dark matter (FDM). We describe the arguments from particle physics that motivate FDM, review previous work on its astrophysical signatures, and analyze several unexplored aspects of its behavior. In particular, (i) FDM halos or subhalos smaller than about $1{0}^{7}(m/{10}^{\ensuremath{-}22}\text{ }\text{ }\mathrm{eV}{)}^{\ensuremath{-}3/2}$ ${M}_{\ensuremath{\bigodot}}$ do not form, and the abundance of halos smaller than a few times $1{0}^{10}(m/{10}^{\ensuremath{-}22}\text{ }\text{ }\mathrm{eV}{)}^{\ensuremath{-}4/3}$ ${M}_{\ensuremath{\bigodot}}$ is substantially smaller in FDM than in CDM. (ii) FDM halos are comprised of a central core that is a stationary, minimum-energy solution of the Schr\"odinger-Poisson equation, sometimes called a ``soliton,'' surrounded by an envelope that resembles a CDM halo. The soliton can produce a distinct signature in the rotation curves of FDM-dominated systems. (iii) The transition between soliton and envelope is determined by a relaxation process analogous to two-body relaxation in gravitating N-body systems, which proceeds as if the halo were composed of particles with mass $\ensuremath{\sim}\ensuremath{\rho}{\ensuremath{\lambda}}^{3}$ where $\ensuremath{\rho}$ is the halo density. (iv) Relaxation may have substantial effects on the stellar disk and bulge in the inner parts of disk galaxies, but has negligible effect on disk thickening or globular cluster disruption near the solar radius. (v) Relaxation can produce FDM disks but a FDM disk in the solar neighborhood must have a half-thickness of at least $\ensuremath{\sim}300(m/{10}^{\ensuremath{-}22}\text{ }\text{ }\mathrm{eV}{)}^{\ensuremath{-}2/3}\text{ }\text{ }\mathrm{pc}$ and a midplane density less than $0.2(m/{10}^{\ensuremath{-}22}\text{ }\text{ }\mathrm{eV}{)}^{2/3}$ times the baryonic disk density. (vi) Solitonic FDM subhalos evaporate by tunneling through the tidal radius and this limits the minimum subhalo mass inside $\ensuremath{\sim}30\text{ }\text{ }\mathrm{kpc}$ of the Milky Way to a few times $1{0}^{8}(m/{10}^{\ensuremath{-}22}\text{ }\text{ }\mathrm{eV}{)}^{\ensuremath{-}3/2}$ ${M}_{\ensuremath{\bigodot}}$. (vii) If the dark matter in the Fornax dwarf galaxy is composed of CDM, most of the globular clusters observed in that galaxy should have long ago spiraled to its center, and this problem is resolved if the dark matter is FDM. (viii) FDM delays galaxy formation relative to CDM but its galaxy-formation history is consistent with current observations of high-redshift galaxies and the late reionization observed by Planck. If the dark matter is composed of FDM, most observations favor a particle mass $\ensuremath{\gtrsim}{10}^{\ensuremath{-}22}\text{ }\text{ }\mathrm{eV}$ and the most significant observational consequences occur if the mass is in the range $1--10\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}22}\text{ }\text{ }\mathrm{eV}$. There is tension with observations of the Lyman-$\ensuremath{\alpha}$ forest, which favor $m\ensuremath{\gtrsim}10--20\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}22}\text{ }\text{ }\mathrm{eV}$ and we discuss whether more sophisticated models of reionization may resolve this tension.

1,365 citations


Journal ArticleDOI
TL;DR: In this paper, the free-streaming of warm dark matter (WDM) from Lyman-α flux-power spectra was studied using hydrodynamical simulations.
Abstract: We present new measurements of the free-streaming of warm dark matter (WDM) from Lyman-α flux-power spectra. We use data from the medium resolution, intermediate redshift XQ-100 sample observed with the X-shooter spectrograph (z = 3 – 4.2) and the high-resolution, high-redshift sample used in Viel et al. (2013) obtained with the HIRES/MIKE spectrographs (z = 4.2 - 5.4). Based on further improved modelling of the dependence of the Lyman-α flux-power spectrum on the free-streaming of dark matter, cosmological parameters, as well as the thermal history of the intergalactic medium (IGM) with hydrodynamical simulations, we obtain the following limits, expressed as the equivalent mass of thermal relic WDM particles. The XQ-100 flux power spectrum alone gives a lower limit of 1.4 keV, the re-analysis of the HIRES/MIKE sample gives 4.1 keV while the combined analysis gives our best and significantly strengthened lower limit of 5.3 keV (all 2σ C.L.). The further improvement in the joint analysis is partly due to the fact that the two data sets have different degeneracies between astrophysical and cosmological parameters that are broken when the data sets are combined, and more importantly on chosen priors on the thermal evolution. These results all assume that the temperature evolution of the IGM can be modelled as a power law in redshift. Allowing for a non-smooth evolution of the temperature of the IGM with sudden temperature changes of up to 5000K reduces the lower limit for the combined analysis to 3.5 keV. A WDM with smaller thermal relic masses would require, however, a sudden temperature jump of 5000K or more in the narrow redshift interval z = 4.6 - 4.8, in disagreement with observations of the thermal history based on high-resolution resolution Lyman-α forest data and expectations for photo-heating and cooling in the low density IGM at these redshifts.

510 citations


Journal ArticleDOI
TL;DR: In this paper, the authors improved the accuracy of the effective-one-body (EOB) waveforms that were employed during the first observing run of Advanced LIGO for binaries of spinning, non-precessing black holes by calibrating them to a set of 141 numerical-relativity (NR) waveform.
Abstract: We improve the accuracy of the effective-one-body (EOB) waveforms that were employed during the first observing run of Advanced LIGO for binaries of spinning, nonprecessing black holes by calibrating them to a set of 141 numerical-relativity (NR) waveforms. The NR simulations expand the domain of calibration toward larger mass ratios and spins, as compared to the previous EOBNR model. Merger-ringdown waveforms computed in black-hole perturbation theory for Kerr spins close to extremal provide additional inputs to the calibration. For the inspiral-plunge phase, we use a Markov-chain Monte Carlo algorithm to efficiently explore the calibration space. For the merger-ringdown phase, we fit the NR signals with phenomenological formulae. After extrapolation of the calibrated model to arbitrary mass ratios and spins, the (dominant-mode) EOBNR waveforms have faithfulness—at design Advanced-LIGO sensitivity—above 99% against all the NR waveforms, including 16 additional waveforms used for validation, when maximizing only on initial phase and time. This implies a negligible loss in event rate due to modeling for these binary configurations. We find that future NR simulations at mass ratios ≳4 and double spin ≳0.8 will be crucial to resolving discrepancies between different ways of extrapolating waveform models. We also find that some of the NR simulations that already exist in such region of parameter space are too short to constrain the low-frequency portion of the models. Finally, we build a reduced-order version of the EOBNR model to speed up waveform generation by orders of magnitude, thus enabling intensive data-analysis applications during the upcoming observation runs of Advanced LIGO.

465 citations


Journal ArticleDOI
TL;DR: In this paper, the impact of primordial black holes on the CMB was analyzed, and stringent constraints on models purporting to connect dark matter to primordial Black Holes were provided.
Abstract: The LIGO observation of black hole merger has revivified interest in the idea whether primordial black holes might comprise some or all of the dark matter. The authors scrutinize the impact of primordial black holes on the CMB, analytically calculating spherical accretion onto black holes. The paper provides stringent constraints on models purporting to connect dark matter to primordial black holes.

454 citations


Journal ArticleDOI
TL;DR: In this paper, a long-lived hypermassive or supramassive neutron star is described as the merger remnant for the binary systems of GW170817, for which the initial total mass is $2.15-2.25.
Abstract: Gravitational-wave observation together with a large number of electromagnetic observations shows that the source of the latest gravitational-wave event, GW170817, detected primarily by advanced LIGO, is the merger of a binary neutron star. We attempt to interpret this observational event based on our results of numerical-relativity simulations performed so far, paying particular attention to the optical and infrared observations. We finally reach a conclusion that this event is described consistently by the presence of a long-lived hypermassive or supramassive neutron star as the merger remnant because (i) significant contamination by lanthanide elements along our line of sight to this source can be avoided by the strong neutrino irradiation from it and (ii) it could play a crucial role in producing an ejecta component of appreciable mass with fast motion in the postmerger phase. We also point out that (I) the neutron-star equation of state has to be sufficiently stiff (i.e., the maximum mass of cold spherical neutron stars, ${M}_{\mathrm{max}}$, has to be appreciably higher than $2\text{ }\text{ }{M}_{\ensuremath{\bigodot}}$) in order for a long-lived massive neutron star to be formed as the merger remnant for the binary systems of GW170817, for which the initial total mass is $\ensuremath{\gtrsim}2.73\text{ }\text{ }{M}_{\ensuremath{\bigodot}}$, and (II) the absence of optical counterparts associated with relativistic ejecta suggests a not-extremely-high value of ${M}_{\mathrm{max}}$ approximately as $2.15--2.25\text{ }\text{ }{M}_{\ensuremath{\bigodot}}$.

453 citations


Journal ArticleDOI
TL;DR: In this article, it was shown that the quantum mechanics of a real rank-3 tensor with 3-indexed tensors have a large O(n 2 )-expansion in the quartic coupling constant, which is dominated by a special class of melon diagrams.
Abstract: Certain models with rank-3 tensor degrees of freedom have been shown by Gurau and collaborators to possess a novel large $N$ limit, where ${g}^{2}{N}^{3}$ is held fixed. In this limit the perturbative expansion in the quartic coupling constant, $g$, is dominated by a special class of ``melon'' diagrams. We study ``uncolored'' models of this type, which contain a single copy of real rank-3 tensor. Its three indices are distinguishable; therefore, the models possess $O(N{)}^{3}$ symmetry with the tensor field transforming in the tri-fundamental representation. Such uncolored models also possess the large $N$ limit dominated by the melon diagrams. The quantum mechanics of a real anticommuting tensor therefore has a similar large $N$ limit to the model recently introduced by Witten as an implementation of the Sachdev-Ye-Kitaev (SYK) model which does not require disorder. Gauging the $O(N{)}^{3}$ symmetry in our quantum mechanical model removes the nonsinglet states; therefore, one can search for its well-defined gravity dual. We point out, however, that the model possesses a vast number of gauge-invariant operators involving higher powers of the tensor field, suggesting that the complete gravity dual will be intricate. We also discuss the quantum mechanics of a complex 3-index anticommuting tensor, which has $U(N{)}^{2}\ifmmode\times\else\texttimes\fi{}O(N)$ symmetry and argue that it is equivalent in the large $N$ limit to a version of SYK model with complex fermions. Finally, we discuss similar models of a commuting tensor in dimension $d$. While the quartic interaction is not positive definite, we construct the large $N$ Schwinger-Dyson equation for the two-point function and show that its solution is consistent with conformal invariance. We carry out a perturbative check of this result using the $4\ensuremath{-}\ensuremath{\epsilon}$ expansion.

438 citations


Journal ArticleDOI
TL;DR: In this paper, the authors revisited the cosmological and astrophysical constraints on the fraction of the dark matter in primordial black holes (PBHs) with an extended mass function, and showed that these constraints usually become more stringent in the extended case than the monochromatic one.
Abstract: We revisit the cosmological and astrophysical constraints on the fraction of the dark matter in primordial black holes (PBHs) with an extended mass function. We consider a variety of mass functions, all of which are described by three parameters: a characteristic mass and width and a dark matter fraction. Various observations then impose constraints on the dark matter fraction as a function of the first two parameters. We show how these constraints relate to those for a monochromatic mass function, demonstrating that they usually become more stringent in the extended case than the monochromatic one. Considering only the well-established bounds, and neglecting the ones that depend on additional astrophysical assumptions, we find that there are three mass windows, around $5\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}16}{M}_{\ensuremath{\bigodot}}$, $2\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}14}{M}_{\ensuremath{\bigodot}}$ and $25--100{M}_{\ensuremath{\bigodot}}$, where PBHs can constitute all the dark matter. However, if one includes all the bounds, PBHs can only constitute of order 10% of the dark matter.

431 citations


Journal ArticleDOI
TL;DR: In this article, the authors discuss current limits on absolute neutrino mass observables by performing a global data analysis that includes the latest results from oscillation experiments, including the latest decay bounds from the KamLAND-Zen experiment, and constraints from representative combinations of Planck measurements and other cosmological data sets.
Abstract: Within the standard three-neutrino framework, the absolute neutrino masses and their ordering (either normal, NO, or inverted, IO) are currently unknown. However, the combination of current data coming from oscillation experiments, neutrinoless double beta ($0\ensuremath{ u}\ensuremath{\beta}\ensuremath{\beta}$) decay searches, and cosmological surveys, can provide interesting constraints for such unknowns in the sub-eV mass range, down to $O({10}^{\ensuremath{-}1})\text{ }\text{ }\mathrm{eV}$ in some cases. We discuss current limits on absolute neutrino mass observables by performing a global data analysis that includes the latest results from oscillation experiments, $0\ensuremath{ u}\ensuremath{\beta}\ensuremath{\beta}$ decay bounds from the KamLAND-Zen experiment, and constraints from representative combinations of Planck measurements and other cosmological data sets. In general, NO appears to be somewhat favored with respect to IO at the level of $\ensuremath{\sim}2\ensuremath{\sigma}$, mainly by neutrino oscillation data (especially atmospheric), corroborated by cosmological data in some cases. Detailed constraints are obtained via the ${\ensuremath{\chi}}^{2}$ method, by expanding the parameter space either around separate minima in NO and IO or around the absolute minimum in any ordering. Implications for upcoming oscillation and nonoscillation neutrino experiments, including $\ensuremath{\beta}$-decay searches, are also discussed.

428 citations


Journal ArticleDOI
TL;DR: In this paper, the authors quantify the astrophysical uncertainties affecting the predictions for the number of EMRIs detectable by LISA, and find that competing astrophysical assumptions produce a variance of about three orders of magnitude in the expected intrinsic EMRI rate.
Abstract: The space-based Laser Interferometer Space Antenna (LISA) will be able to observe the gravitational-wave signals from systems comprised of a massive black hole and a stellar-mass compact object. These systems are known as extreme-mass-ratio inspirals (EMRIs) and are expected to complete ∼104–105 cycles in band, thus allowing exquisite measurements of their parameters. In this work, we attempt to quantify the astrophysical uncertainties affecting the predictions for the number of EMRIs detectable by LISA, and find that competing astrophysical assumptions produce a variance of about three orders of magnitude in the expected intrinsic EMRI rate. However, we find that irrespective of the astrophysical model, at least a few EMRIs per year should be detectable by the LISA mission, with up to a few thousands per year under the most optimistic astrophysical assumptions. We also investigate the precision with which LISA will be able to extract the parameters of these sources. We find that typical fractional statistical errors with which the intrinsic parameters (redshifted masses, massive black hole spin and orbital eccentricity) can be recovered are ∼10-6–10-4. Luminosity distance (which is required to infer true masses) is inferred to about 10% precision and sky position is localized to a few square degrees, while tests of the multipolar structure of the Kerr metric can be performed to percent-level precision or better.

410 citations


Journal ArticleDOI
TL;DR: In this paper, the authors derived the strongest bounds in the literature on the sum of the three active neutrino masses, within the assumption of a background flat CDM cosmology.
Abstract: Using some of the latest cosmological data sets publicly available, we derive the strongest bounds in the literature on the sum of the three active neutrino masses, ${M}_{\ensuremath{ u}}$, within the assumption of a background flat $\mathrm{\ensuremath{\Lambda}}\mathrm{CDM}$ cosmology. In the most conservative scheme, combining Planck cosmic microwave background temperature anisotropies and baryon acoustic oscillations (BAO) data, as well as the up-to-date constraint on the optical depth to reionization ($\ensuremath{\tau}$), the tightest 95% confidence level upper bound we find is ${M}_{\ensuremath{ u}}l0.151\text{ }\text{ }\mathrm{eV}$. The addition of Planck high-$\ensuremath{\ell}$ polarization data, which, however, might still be contaminated by systematics, further tightens the bound to ${M}_{\ensuremath{ u}}l0.118\text{ }\text{ }\mathrm{eV}$. A proper model comparison treatment shows that the two aforementioned combinations disfavor the inverted hierarchy at $\ensuremath{\sim}64%\text{ }\text{ }\text{ }\mathrm{C}.\mathrm{L}.$ and $\ensuremath{\sim}71%\text{ }\text{ }\mathrm{C}.\mathrm{L}.$, respectively. In addition, we compare the constraining power of measurements of the full-shape galaxy power spectrum versus the BAO signature, from the BOSS survey. Even though the latest BOSS full-shape measurements cover a larger volume and benefit from smaller error bars compared to previous similar measurements, the analysis method commonly adopted results in their constraining power still being less powerful than that of the extracted BAO signal. Our work uses only cosmological data; imposing the constraint ${M}_{\ensuremath{ u}}g0.06\text{ }\text{ }\mathrm{eV}$ from oscillations data would raise the quoted upper bounds by $\mathcal{O}(0.1\ensuremath{\sigma})$ and would not affect our conclusions.

402 citations


Journal ArticleDOI
TL;DR: In this paper, a supersymmetric generalization of the Sachdev-Ye-Kitaev (SYK) model is discussed, where the supercharge is given by a polynomial expression in terms of the Majorana fermions with random coefficients.
Abstract: We discuss a supersymmetric generalization of the Sachdev-Ye-Kitaev (SYK) model. These are quantum mechanical models involving $N$ Majorana fermions. The supercharge is given by a polynomial expression in terms of the Majorana fermions with random coefficients. The Hamiltonian is the square of the supercharge. The $\mathcal{N}=1$ model with a single supercharge has unbroken supersymmetry at large $N$, but nonperturbatively spontaneously broken supersymmetry in the exact theory. We analyze the model by looking at the large $N$ equation, and also by performing numerical computations for small values of $N$. We also compute the large $N$ spectrum of ``singlet'' operators, where we find a structure qualitatively similar to the ordinary SYK model. We also discuss an $\mathcal{N}=2$ version. In this case, the model preserves supersymmetry in the exact theory and we can compute a suitably weighted Witten index to count the number of ground states, which agrees with the large $N$ computation of the entropy. In both cases, we discuss the supersymmetric generalizations of the Schwarzian action which give the dominant effects at low energies.

Journal ArticleDOI
TL;DR: In this paper, the authors studied sub-GeV dark matter scattering off electrons in xenon, including the expected electron recoil spectra and annual modulation spectra, and derived improved constraints using low-energy XENON10 and XENon100 ionization-only data.
Abstract: We study in detail sub-GeV dark matter scattering off electrons in xenon, including the expected electron recoil spectra and annual modulation spectra. We derive improved constraints using low-energy XENON10 and XENON100 ionization-only data. For XENON10, in addition to including electron-recoil data corresponding to about 1--3 electrons, we include for the first time events corresponding to about 4--7 electrons. Assuming the scattering is momentum independent (${F}_{\mathrm{DM}}=1$), this strengthens a previous cross-section bound by almost an order of magnitude for dark matter masses above 50 MeV. The available XENON100 data corresponds to events with about 4--50 electrons, and leads to a constraint that is comparable to the XENON10 bound above 50 MeV for ${F}_{\mathrm{DM}}=1$. We demonstrate that a search for an annual modulation signal in upcoming xenon experiments (XENON1T, XENONnT, LZ) could substantially improve the above bounds even in the presence of large backgrounds. We also emphasize that in simple benchmark models of sub-GeV dark matter, the dark matter-electron scattering rate can be as high as one event every ten (two) seconds in the XENON1T (XENONnT or LZ) experiments, without being in conflict with any other known experimental bounds. While there are several sources of backgrounds that can produce single- or few-electron events, a large event rate can be consistent with a dark matter signal and should not be simply written off as purely a detector curiosity. This fact motivates a detailed analysis of the ionization-data (``S2'') data, taking into account the expected annual modulation spectrum of the signal rate, as well as the DM-induced electron-recoil spectra, which are another powerful discriminant between signal and background.

Journal ArticleDOI
TL;DR: In this paper, the transverse momentum balance between a jet and a reference object such as a photon, $Z$ boson, or multijet system for jets with $20 0.2 fb$^{-1}$ collected during 2015 at the LHC is derived from dijet balance measurements.
Abstract: Jet energy scale measurements and their systematic uncertainties are reported for jets measured with the ATLAS detector using proton-proton collision data with a center-of-mass energy of $\sqrt{s} = 13$ TeV, corresponding to an integrated luminosity of 3.2 fb$^{-1}$ collected during 2015 at the LHC. Jets are reconstructed from energy deposits forming topological clusters of calorimeter cells, using the anti-$k_{t}$ algorithm with radius parameter $R = 0.4$. Jets are calibrated with a series of simulation-based corrections and in situ techniques. In situ techniques exploit the transverse momentum balance between a jet and a reference object such as a photon, $Z$ boson, or multijet system for jets with $20 0.8$) is derived from dijet $p_{T}$ balance measurements. For jets of $p_{T} = 80$ GeV, the additional uncertainty for the forward jet calibration reaches its largest value of about 2% in the range $|\eta| > 3.5$ and in a narrow slice of $2.2 < |\eta| < 2.4$.

Journal ArticleDOI
TL;DR: In this article, it was shown that interacting dark energy can alleviate the current tension on the value of the Hubble constant between the cosmic microwave background anisotropies constraints obtained from the Planck satellite and the recent direct measurements reported by Riess et al. 2016.
Abstract: The answer is yes. We indeed find that interacting dark energy can alleviate the current tension on the value of the Hubble constant ${H}_{0}$ between the cosmic microwave background anisotropies constraints obtained from the Planck satellite and the recent direct measurements reported by Riess et al. 2016. The combination of these two data sets points toward a nonzero dark matter-dark energy coupling $\ensuremath{\xi}$ at more than two standard deviations, with $\ensuremath{\xi}=\ensuremath{-}0.2{6}_{\ensuremath{-}0.12}^{+0.16}$ at 95% C.L., i.e. with a moderate evidence for interacting dark energy with an odds ratio of $6\ensuremath{\mathbin:}1$ respect to a non interacting cosmological constant. However the ${H}_{0}$ tension is better solved when the equation of state of the interacting dark energy component is allowed to freely vary, with a phantomlike equation of state $w=\ensuremath{-}1.185\ifmmode\pm\else\textpm\fi{}0.064$ (at 68% C.L.), ruling out the pure cosmological constant case, $w=\ensuremath{-}1$, again at more than two standard deviations. When Planck data are combined with external datasets, as BAO, JLA Supernovae Ia luminosity distances, cosmic shear or lensing data, we find perfect consistency with the cosmological constant scenario and no compelling evidence for a dark matter-dark energy coupling.

Journal ArticleDOI
TL;DR: In this paper, the authors compute the probability distribution of orbital parameters for primordial black holes (PBHs) formed in the early Universe, accounting for tidal torquing by all other PBHs, as well as standard large-scale adiabatic perturbations.
Abstract: Primordial black holes (PBHs) have long been a candidate for the elusive dark matter (DM), and remain poorly constrained in the $\ensuremath{\sim}20--100\text{ }\text{ }{M}_{\ensuremath{\bigodot}}$ mass range PBH binaries were recently suggested as the possible source of LIGO's first detections In this paper, we thoroughly revisit existing estimates of the merger rate of PBH binaries We compute the probability distribution of orbital parameters for PBH binaries formed in the early Universe, accounting for tidal torquing by all other PBHs, as well as standard large-scale adiabatic perturbations We then check whether the orbital parameters of PBH binaries formed in the early Universe can be significantly affected between formation and merger Our analytic estimates indicate that the tidal field of halos and interactions with other PBHs, as well as dynamical friction by unbound standard DM particles, do not do significant work on nor torque PBH binaries We estimate the torque due to baryon accretion to be much weaker than previous calculations, albeit possibly large enough to significantly affect the eccentricity of typical PBH binaries We also revisit the PBH-binary merger rate resulting from gravitational capture in present-day halos, accounting for Poisson fluctuations If binaries formed in the early Universe survive to the present time, as suggested by our analytic estimates, they dominate the total PBH merger rate Moreover, this merger rate would be orders of magnitude larger than LIGO's current upper limits if PBHs make a significant fraction of the dark matter As a consequence, LIGO would constrain $\ensuremath{\sim}10--300\text{ }\text{ }{M}_{\ensuremath{\bigodot}}$ PBHs to constitute no more than $\ensuremath{\sim}1%$ of the dark matter To make this conclusion fully robust, though, numerical study of several complex astrophysical processes---such as the formation of the first PBH halos and how they may affect PBH binaries, as well as the accretion of gas onto an extremely eccentric binary---is needed

Journal ArticleDOI
TL;DR: In this article, a new set of parton distribution functions (ABMP16), the strong coupling constant αs and the quark masses mc, mb and mt were determined in a global fit to next-to-next-toleading order (NNLO) in QCD.
Abstract: We determine a new set of parton distribution functions (ABMP16), the strong coupling constant αs and the quark masses mc, mb and mt in a global fit to next-to-next-to-leading order (NNLO) in QCD. The analysis uses the MS¯ scheme for αs and all quark masses and is performed in the fixed-flavor number scheme for nf=3, 4, 5. Essential new elements of the fit are the combined data from HERA for inclusive deep-inelastic scattering (DIS), data from the fixed-target experiments NOMAD and CHORUS for neutrino-induced DIS, data from Tevatron and the LHC for the Drell-Yan process and the hadro-production of single-top and top-quark pairs. The theory predictions include new improved approximations at NNLO for the production of heavy quarks in DIS and for the hadro-production of single-top quarks. The description of higher twist effects relevant beyond the leading twist collinear factorization approximation is refined. At NNLO, we obtain the value αs(nf=5)(MZ)=0.1147±0.0008.

Journal ArticleDOI
TL;DR: In this paper, a model-independent effective Hamiltonian approach is used to determine regions of new physics parameter space that give a good description of the experimental data on rare $B$ meson decays, which is in tension with Standard Model predictions.
Abstract: We interpret the recent hints for lepton flavor universality violation in rare $B$ meson decays. Based on a model-independent effective Hamiltonian approach, we determine regions of new physics parameter space that give a good description of the experimental data on ${R}_{K}$ and ${R}_{{K}^{*}}$, which is in tension with Standard Model predictions. We suggest further measurements that can help narrowing down viable new physics explanations. We stress that the measured values of ${R}_{K}$ and ${R}_{{K}^{*}}$ are fully compatible with new physics explanations of other anomalies in rare $B$ meson decays based on the $b\ensuremath{\rightarrow}s\ensuremath{\mu}\ensuremath{\mu}$ transition. If the hints for lepton flavor universality violation are the first signs of new physics, perturbative unitarity implies new phenomena below a scale of $\ensuremath{\sim}100\text{ }\text{ }\mathrm{TeV}$.

Journal ArticleDOI
TL;DR: In this paper, the pseudoscalar-pole piece of the hadronic light-by-light contribution to the anomalous magnetic moment of the muon was calculated using a mathematical framework based on rational approximants.
Abstract: We employ a mathematical framework based on rational approximants in order to calculate the pseudoscalar-pole piece of the hadronic light-by-light contribution to the anomalous magnetic moment of the muon, ${a}_{\ensuremath{\mu}}^{\mathrm{HLbL};P}$. The method is systematic and data based, profiting from over 13 different collaborations, and able to ascribe, for the first time, a systematic uncertainty which provides for the model independence. As a result, we obtain ${a}_{\ensuremath{\mu}}^{\mathrm{HLbL};P}=94.3(5.3)\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}11}$, whose uncertainty is well below the one foreseen at future experiments measuring the $({g}_{\ensuremath{\mu}}\ensuremath{-}2)$.

Journal ArticleDOI
TL;DR: In this article, massive scalar wave functions in 4D Minkowski space that transform as 2D conformal primaries are constructed via Witten-like diagrams on a hyperbolic slicing of Minkowsky space and has a holographic flavor.
Abstract: The four-dimensional (4D) Lorentz group $SL(2,\mathbb{C})$ acts as the two-dimensional (2D) global conformal group on the celestial sphere at infinity where asymptotic 4D scattering states are specified. Consequent similarities of 4D flat space amplitudes and 2D correlators on the conformal sphere are obscured by the fact that the former are usually expressed in terms of asymptotic wave functions which transform simply under spacetime translations rather than the Lorentz $SL(2,\mathbb{C})$. In this paper we construct on-shell massive scalar wave functions in 4D Minkowski space that transform as $SL(2,\mathbb{C})$ conformal primaries. Scattering amplitudes of these wave functions are $SL(2,\mathbb{C})$ covariant by construction. For certain mass relations, we show explicitly that their three-point amplitude reduces to the known unique form of a 2D CFT primary three-point function and compute the coefficient. The computation proceeds naturally via Witten-like diagrams on a hyperbolic slicing of Minkowski space and has a holographic flavor.

Journal ArticleDOI
TL;DR: In this article, the authors studied scalar conformal primary wavefunctions on the principal continuous series of the Klein-Gordon, Maxwell, and linearized Einstein equations under the Lorentz group.
Abstract: We study solutions of the Klein-Gordon, Maxwell, and linearized Einstein equations in ${\mathbb{R}}^{1,d+1}$ that transform as $d$-dimensional conformal primaries under the Lorentz group $SO(1,d+1)$. Such solutions, called conformal primary wavefunctions, are labeled by a conformal dimension $\mathrm{\ensuremath{\Delta}}$ and a point in ${\mathbb{R}}^{d}$, rather than an on-shell ($d+2$)-dimensional momentum. We show that the continuum of scalar conformal primary wavefunctions on the principal continuous series $\mathrm{\ensuremath{\Delta}}\ensuremath{\in}\frac{d}{2}+i\mathbb{R}$ of $SO(1,d+1)$ spans a complete set of normalizable solutions to the wave equation. In the massless case, with or without spin, the transition from momentum space to conformal primary wavefunctions is implemented by a Mellin transform. As a consequence of this construction, scattering amplitudes in this basis transform covariantly under $SO(1,d+1)$ as $d$-dimensional conformal correlators.

Journal ArticleDOI
TL;DR: In this article, the shape of the acoustic gravitational wave and the velocity power spectra were explored using large-scale numerical simulations of a first order thermal phase transition in the early Universe, and the results showed that the predicted k−3 behavior, where k is the wave number, emerges clearly for detonations.
Abstract: We present results from large-scale numerical simulations of a first order thermal phase transition in the early Universe, in order to explore the shape of the acoustic gravitational wave and the velocity power spectra. We compare the results with the predictions of the recently proposed sound shell model. For the gravitational wave power spectrum, we find that the predicted k−3 behavior, where k is the wave number, emerges clearly for detonations. The power spectra from deflagrations show similar features, but exhibit a steeper high-k decay and an extra feature not accounted for in the model. There are two independent length scales: the mean bubble separation and the thickness of the sound shell around the expanding bubble of the low temperature phase. It is the sound shell thickness which sets the position of the peak of the power spectrum. The low wave number behavior of the velocity power spectrum is consistent with a causal k3, except for the thinnest sound shell, where it is steeper. We present parameters for a simple broken power law fit to the gravitational wave power spectrum for wall speeds well away from the speed of sound where this form can be usefully applied. We examine the prospects for the detection, showing that a LISA-like mission has the sensitivity to detect a gravitational wave signal from sound waves with an RMS fluid velocity of about 0.05c, produced from bubbles with a mean separation of about 10−2 of the Hubble radius. The shape of the gravitational wave power spectrum depends on the bubble wall speed, and it may be possible to estimate the wall speed, and constrain other phase transition parameters, with an accurate measurement of a stochastic gravitational wave background.

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TL;DR: In this article, the authors study the direct detection prospects for a representative set of simplified models of sub-GeV dark matter (DM), accounting for existing terrestrial, astrophysical and cosmological constraints.
Abstract: We study the direct detection prospects for a representative set of simplified models of sub-GeV dark matter (DM), accounting for existing terrestrial, astrophysical and cosmological constraints. We focus on dark matter lighter than an MeV, where these constraints are most stringent, and find three scenarios with accessible direct detection cross sections: (i) DM interacting via an ultralight kinetically mixed dark photon, (ii) a DM subcomponent interacting with nucleons or electrons through a light scalar or vector mediator, and (iii) DM coupled with nucleons via a mediator heavier than $\ensuremath{\sim}100\text{ }\text{ }\mathrm{keV}$.

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TL;DR: In this article, a stream-based analysis pipeline was proposed to detect gravitational waves from the merger of binary neutron stars, binary black holes, and neutron-star-black-hole binaries within ∼1 min of the arrival of the merger signal at Earth.
Abstract: We describe a stream-based analysis pipeline to detect gravitational waves from the merger of binary neutron stars, binary black holes, and neutron-star–black-hole binaries within ∼1 min of the arrival of the merger signal at Earth. Such low-latency detection is crucial for the prompt response by electromagnetic facilities in order to observe any fading electromagnetic counterparts that might be produced by mergers involving at least one neutron star. Even for systems expected not to produce counterparts, low-latency analysis of the data is useful for deciding when not to point telescopes, and as feedback to observatory operations. Analysts using this pipeline were the first to identify GW151226, the second gravitational-wave event ever detected. The pipeline also operates in an offline mode, in which it incorporates more refined information about data quality and employs acausal methods that are inapplicable to the online mode. The pipeline’s offline mode was used in the detection of the first two gravitational-wave events, GW150914 and GW151226, as well as the identification of a third candidate, LVT151012.

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TL;DR: In this paper, the authors construct perturbative classical solutions of the Yang-Mills equations coupled to dynamical point particles carrying color charge by applying a set of color to kinematics replacement rules first introduced by Bern, Carrasco and Johansson, which are shown to generate solutions of d-dimensional dilaton gravity.
Abstract: We construct perturbative classical solutions of the Yang-Mills equations coupled to dynamical point particles carrying color charge. By applying a set of color to kinematics replacement rules first introduced by Bern, Carrasco and Johansson, these are shown to generate solutions of d-dimensional dilaton gravity, which we also explicitly construct. Agreement between the gravity result and the gauge theory double copy implies a correspondence between non-Abelian particles and gravitating sources with dilaton charge. When the color sources are highly relativistic, dilaton exchange decouples, and the solutions we obtain match those of pure gravity. We comment on possible implications of our findings to the calculation of gravitational waveforms in astrophysical black hole collisions, directly from computationally simpler gluon radiation in Yang-Mills theory.

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TL;DR: In this article, the authors calculated the QCD equation of state using Taylor expansions that include contributions from up to sixth order in the baryon strangeness and electric charge chemical potentials.
Abstract: We calculated the QCD equation of state using Taylor expansions that include contributions from up to sixth order in the baryon strangeness and electric charge chemical potentials. Calculations have been performed with the Highly Improved Staggered Quark action in the temperature range T epsilon [135 MeV 330 MeV] using up to four different sets of lattice cutoffs corresponding to lattices of size N sigma 3x N tau with aspect ratio N sigma/N tau = 4 and N tau=6-16. The strange quark mass is tuned to its physical value and we use two strange to light quark mass ratios ms/ml = 20 and 27 which in the continuum limit correspond to a pion mass of about 160 and 140 MeV respectively. Sixth order results for Taylor expansion coefficients are used to estimate truncation errors of the fourth order expansion. We show that truncation errors are small for baryon chemical potentials less then twice the temperature (mu(B) 0.9.

Journal ArticleDOI
TL;DR: In this article, a combined fit to the decay rate of light leptons was proposed to predict the Cabibbo-Kobayashi-Maskawa matrix element of the heavy quark effective theory.
Abstract: The measured $\overline{B}\ensuremath{\rightarrow}{D}^{(*)}l\overline{\ensuremath{ u}}$ decay rates for light leptons ($l=e$, $\ensuremath{\mu}$) constrain all $\overline{B}\ensuremath{\rightarrow}{D}^{(*)}$ semileptonic form factors, by including both the leading and $\mathcal{O}({\mathrm{\ensuremath{\Lambda}}}_{\mathrm{QCD}}/{m}_{c,b})$ subleading Isgur-Wise functions in the heavy quark effective theory. We perform a novel combined fit to the $\overline{B}\ensuremath{\rightarrow}{D}^{(*)}l\overline{\ensuremath{ u}}$ decay distributions to predict the $\overline{B}\ensuremath{\rightarrow}{D}^{(*)}\ensuremath{\tau}\overline{\ensuremath{ u}}$ rates and determine the Cabibbo-Kobayashi-Maskawa matrix element $|{V}_{cb}|$. Most theoretical and experimental papers have neglected uncertainties in the predictions for form factor ratios at order ${\mathrm{\ensuremath{\Lambda}}}_{\mathrm{QCD}}/{m}_{c,b}$, which we include. We also calculate $\mathcal{O}({\mathrm{\ensuremath{\Lambda}}}_{\mathrm{QCD}}/{m}_{c,b})$ and $\mathcal{O}({\ensuremath{\alpha}}_{s})$ contributions to semileptonic $\overline{B}\ensuremath{\rightarrow}{D}^{(*)}\ensuremath{\ell}\overline{\ensuremath{ u}}$ decays for all possible $b\ensuremath{\rightarrow}c$ currents. This result has not been available for the tensor current form factors, and for two of those, which are $\mathcal{O}({\mathrm{\ensuremath{\Lambda}}}_{\mathrm{QCD}}/{m}_{c,b})$, the corrections are of the same order as approximations used in the literature. These results allow us to determine with improved precision how new physics may affect the $\overline{B}\ensuremath{\rightarrow}{D}^{(*)}\ensuremath{\tau}\overline{\ensuremath{ u}}$ rates. Our predictions can be systematically improved with more data; they need not rely on lattice QCD results, although these can be incorporated.

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TL;DR: In this article, the authors used 2-tailed Gaussian probability to assign a significance to a p-value, e.g., 0.68% and 95% correspond to 0.1% and 2.5% respectively.
Abstract: In classical general relativity (GR), an observer falling into an astrophysical black hole is not expected to experience anything dramatic as she crosses the event horizon. However, tentative resolutions to problems in quantum gravity, such as the cosmological constant problem, or the black hole information paradox, invoke significant departures from classicality in the vicinity of the horizon. It was recently pointed out that such near-horizon structures can lead to late-time echoes in the black hole merger gravitational wave signals that are otherwise indistinguishable from GR. We search for observational signatures of these echoes in the gravitational wave data released by the advanced Laser Interferometer Gravitational-Wave Observatory (LIGO), following the three black hole merger events GW150914, GW151226, and LVT151012. In particular, we look for repeating damped echoes with time delays of $8M\mathrm{log}M$ ($+\text{spin}$ corrections, in Planck units), corresponding to Planck-scale departures from GR near their respective horizons. Accounting for the ``look elsewhere'' effect due to uncertainty in the echo template, we find tentative evidence for Planck-scale structure near black hole horizons at false detection probability of 1% (corresponding to $2.5\ensuremath{\sigma}$. significance level). Future observations from interferometric detectors at higher sensitivity, along with more physical echo templates, will be able to confirm (or rule out) this finding, providing possible empirical evidence for alternatives to classical black holes, such as in ``firewall'' or ``fuzzball'' paradigms.In this paper, we use 2-tailed Gaussian probability to assign a significance to a p-value, e.g., $1\ensuremath{-}\mathrm{p}\text{-value}=68%$ and 95% correspond to $1\ensuremath{\sigma}$ and $2\ensuremath{\sigma}$, respectively.

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TL;DR: For primordial black holes (PBH) to be the dark matter in single-field inflation, the slow-roll approximation must be violated by at least $\mathcal{O}(1)$ in order to enhance the curvature power spectrum within the required number of $e$-folds between cosmic microwave background scales and PBH mass scales as mentioned in this paper.
Abstract: For primordial black holes (PBH) to be the dark matter in single-field inflation, the slow-roll approximation must be violated by at least $\mathcal{O}(1)$ in order to enhance the curvature power spectrum within the required number of $e$-folds between cosmic microwave background scales and PBH mass scales. Power spectrum predictions which rely on the inflaton remaining on the slow-roll attractor can fail dramatically leading to qualitatively incorrect conclusions in models like an inflection potential and misestimate the mass scale in a running mass model. We show that an optimized temporal evaluation of the Hubble slow-roll parameters to second order remains a good description for a wide range of PBH formation models where up to a $1{0}^{7}$ amplification of power occurs in 10 $e$-folds or more.

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TL;DR: SuperCDMS SNOLAB as discussed by the authors is a next-generation experiment aimed at directly detecting low-mass particles (with masses ≤ 10 GeV/c^2) that may constitute dark matter by using cryogenic detectors of two types (HV and iZIP) and two target materials (germanium and silicon).
Abstract: SuperCDMS SNOLAB will be a next-generation experiment aimed at directly detecting low-mass particles (with masses ≤ 10 GeV/c^2) that may constitute dark matter by using cryogenic detectors of two types (HV and iZIP) and two target materials (germanium and silicon). The experiment is being designed with an initial sensitivity to nuclear recoil cross sections ∼ 1×10^(−43) cm^2 for a dark matter particle mass of 1 GeV/c^2, and with capacity to continue exploration to both smaller masses and better sensitivities. The phonon sensitivity of the HV detectors will be sufficient to detect nuclear recoils from sub-GeV dark matter. A detailed calibration of the detector response to low-energy recoils will be needed to optimize running conditions of the HV detectors and to interpret their data for dark matter searches. Low-activity shielding, and the depth of SNOLAB, will reduce most backgrounds, but cosmogenically produced ^3H and naturally occurring ^(32)Si will be present in the detectors at some level. Even if these backgrounds are 10 times higher than expected, the science reach of the HV detectors would be over 3 orders of magnitude beyond current results for a dark matter mass of 1 GeV/c^2. The iZIP detectors are relatively insensitive to variations in detector response and backgrounds, and will provide better sensitivity for dark matter particles with masses ≳ 5 GeV/c^2. The mix of detector types (HV and iZIP), and targets (germanium and silicon), planned for the experiment, as well as flexibility in how the detectors are operated, will allow us to maximize the low-mass reach, and understand the backgrounds that the experiment will encounter. Upgrades to the experiment, perhaps with a variety of ultra-low-background cryogenic detectors, will extend dark matter sensitivity down to the “neutrino floor,” where coherent scatters of solar neutrinos become a limiting background.

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TL;DR: The vector leptoquark representation, Uμ ¼ ð3; 1; 2=3Þ, was recently identified as an exceptional single-parameter model to address experimental hints on lepton flavor universality violation in semileptonic B-meson decays, both in neutral (b → sμμ) and charged (b→ cτν) current processes.
Abstract: The vector leptoquark representation, Uμ ¼ ð3; 1; 2=3Þ, was recently identified as an exceptional single mediator model to address experimental hints on lepton flavor universality violation in semileptonic B-meson decays, both in neutral (b → sμμ) and charged (b → cτν) current processes. Nonetheless, it is well known that massive vectors crave an ultraviolet (UV) completion. We present the first full-fledged UV complete and calculable gauge model which incorporates this scenario while remaining in agreement with all other indirect flavor and electroweak precision measurements, as well as, direct searches at high-pT . The model is based on a new non-Abelian gauge group spontaneously broken at the TeV scale, and a specific flavor structure suppressing flavour violation in ΔF ¼ 2 processes while inducing sizeable semileptonic transitions