Fri·Jan 26, 2018Friday·January 26, 2018

1. 01*

   Fluctuations in cool quark matter and the phase diagram of Quantum Chromodynamics

   Robert D. Pisarski🇺🇸 · Vladimir V. Skokov🇺🇸 · Alexei M. Tsvelik🇺🇸

   We consider the phase diagram of hadronic matter as a function of temperature, T , and baryon chemical potential, mu. Currently the dominant paradigm is a line of first order transitions which ends at a critical endpoint. In this work we suggest that spatially inhomogenous phases are a generic feature of the hadronic phase diagram at nonzero mu and low T . Familiar examples are pion and kaon condensates. At higher densities, we argue that these condensates connect onto chiral spirals in a quarkyonic regime. Both of these phases exhibit the spontaneous breaking of a global U(1) symmetry and quasi-long range order, analogous to smectic liquid crystals. We argue that there is a continuous line of first order transitions which separate spatially inhomogenous from homogenous phases, where the latter can be either a hadronic phase or a quark-gluon plasma. While mean field theory predicts that there is a Lifshitz point along this line of first order transitions, in three spatial dimensions strong infrared fluctuations wash out any Lifshitz point. Using known results from inhomogenous polymers, we suggest that instead there is a Lifshitz regime. Non-perturbative effects are large in this regime, where the momentum dependent terms for the propagators of pions and associated modes are dominated not by terms quadratic in momenta, but quartic. Fluctuations in a Lifshitz regime may be directly relevant to the collisions of heavy ions at (relatively) low energies, sqrt(s)/A : 1 to 20 GeV.

   hep-phcond-mat.str-elPRD(2019)·46 citations
2. 02*

   From Heavy-Ion Collisions to Compact Stars: Equation of State and Relevance of the System Size

   Sylvain Mogliacci🇿🇦 · Isobel Kolbé🇿🇦 · W. A. Horowitz🇿🇦

   In this article, we start by presenting state-of-the-art methods allowing us to compute moments related to the globally conserved baryon number, by means of first principle resummed perturbative frameworks. We focus on such quantities for they convey important properties of the finite temperature and density equation of state, being particularly sensitive to changes in the degrees of freedom across the quark-hadron phase transition. We thus present various number susceptibilities along with the corresponding results as obtained by lattice quantum chromodynamics collaborations, and comment on their comparison. Next, omitting the importance of coupling corrections and considering a zero-density toy model for the sake of argument, we focus on corrections due to the small size of heavy-ion collision systems, by means of spatial compactifications. Briefly motivating the relevance of finite size effects in heavy-ion physics, in opposition to the compact star physics, we present a few preliminary thermodynamic results together with the speed of sound for certain finite size relativistic quantum systems at very high temperature.

   hep-phcond-mat.stat-mechhep-latnucl-thUniverse(2018)·3 citations
3. 03*

   Anomalous decay $f_1(1285)\to {\pi }^{+}{\pi }^{-}\gamma$ in the Nambu - Jona-Lasinio model

   A. A. Osipov🇷🇺 · M. K. Volkov🇷🇺

   Using the Nambu--Jona-Lasinio model with the $U(2)\times U(2)$ chiral symmetric effective four-quark interactions, we derive the amplitude of the radiative decay $f_1(1285)\to {\pi }^{+}{\pi }^{-}\gamma$, find the decay width $\Gamma (f_1\to {\pi }^{+}{\pi }^{-}\gamma )=346\text{mbox}keV$ and obtain the spectral di-pion effective mass distribution. It is shown that in contrast to the majority of theoretical estimates (which consider the $a_1(1260)$ meson exchange as the dominant one), the most relevant contribution to this process comes out from the ${\rho }^0$-resonance exchange related with the triangle $f_1{\rho }^0\gamma$ anomaly. The spectral function is obtained to be confronted with the future empirical data.

   hep-phPRD(2018)·5 citations
4. 04*

   Higgs bosons with large transverse momentum at the LHC

   Kirill Kudashkin🇩🇪 · Jonas M. Lindert🇬🇧 · Kirill Melnikov🇩🇪 · Christopher Wever🇩🇪

   We compute the next-to-leading order QCD corrections to the production of Higgs bosons with large transverse momentum $p_{\perp }\gg 2m_t$ at the LHC. To accomplish this, we combine the two-loop amplitudes for processes $gg\to Hg$, $qg\to Hq$ and $q\bar{q}\to Hg$, recently computed in the approximation of nearly massless top quarks, with the numerical calculation of the squared one-loop amplitudes for $gg\to Hgg$, $qg\to Hqg$ and $q\bar{q}\to Hgg$ processes. The latter computation is performed with OpenLoops. We find that the QCD corrections to the Higgs transverse momentum distribution at very high $p_{\perp }$ are large but quite similar to the QCD corrections obtained for point-like $Hgg$ coupling. Our result removes one of the largest sources of theoretical uncertainty in the description of high-$p_{\perp }$ Higgs boson production and opens a way to use the high-$p_{\perp }$ region to search for physics beyond the Standard Model.

   hep-phPLB(2018)·81 citations
5. 05*

   New physics in inclusive $B\to X_c\ell \bar{\nu }$ decay in light of $R(D^{(\ast )})$ measurements

   Saeed Kamali🇺🇸 · Ahmed Rashed🇺🇸 · Alakabha Datta🇺🇸

   In this work we study the effects of new-physics (NP) operators with different Lorentz structures on the inclusive $B\to X_c\tau \bar{\nu }$ decay and make predictions for the ratio of total decay rates $R(X_c)=\frac{\Gamma (B\to X_c\tau {\bar{\nu }}_{\tau })}{\Gamma (B\to X_c\ell {\bar{\nu }}_{\ell })}$ with $\ell =e,\mu$, the differential decay rates, $\frac{d\Gamma }{d{q}^2}$ and $\frac{d\Gamma }{d{E}_{\tau }}$, forward-backward asymmetry $A_{FB}$ and the ratio of the differential decay rates $B(q^2)=\frac{d\Gamma (B\to X_c\tau {\bar{\nu }}_{\tau })/d{q}^2}{d\Gamma (B\to X_c\ell {\bar{\nu }}_{\ell })/d{q}^2}$. In addition, we introduce some leptoquark models as explicit models of the NP operators and study their effects on the inclusive decay. We consider $\mathcal{O}({\alpha }_s)$ radiative and $1/m_b$ nonperturbative corrections to the Standard Model (SM) decay rate and ignore their small effects in the NP contributions.

   hep-phhep-exPRD(2018)·31 citations
6. 06*

   Four-loop wave function renormalization in QCD and QED

   Peter Marquard🇩🇪 · Alexander V. Smirnov🇷🇺 · Vladimir A. Smirnov🇷🇺 · Matthias Steinhauser🇩🇪

   We compute the on-shell wave function renormalization constant to four-loop order in QCD and present numerical results for all coefficients of the SU$(N_c)$ colour factors. We extract the four-loop HQET anomalous dimension of the heavy quark field and also discuss the application of our result to QED.

   hep-phPRD(2018)·38 citations
7. 07*

   A light scalar dark matter extension of the type-II two-Higgs-doublet model

   Xiao-Fang Han · Lei Wang

   We examine the type-II two-Higgs-doublet model with a light scalar dark matter ($S$) after imposing the constraints from the Higgs searches at the LHC and dark matter experiments. We first assume that both two CP-even Higgses ($h$ and $H$) are portals between the DM and SM sectors, and the CP-odd Higgs ($A$) and $H$ are heavier than 130 GeV. We find that the DM with a mass of $10\sim 50$ GeV is disfavored by the joint constraints of the 125 GeV Higgs signal data, the relic density, XENON1T (2017), PandaX-II (2017) and the Fermi-LAT. Next, we consider a special scenario in which the heavy CP-even Higgs is taken as the 125 GeV Higgs. The light CP-even Higgs is the only portal between the DM and SM sectors, and the DM mass is slightly below Higgs resonance. We find that the signal data of the 125 GeV Higgs restrict $\tan \beta$ to be in the range of $1\sim 1.5$ for $m_h<$ 62 GeV. The $gg\to A\to hZ$ and $b\bar{b}\to h\to {\tau }^{+}{\tau }^{-}$ channels at the LHC can impose lower limits and upper limits on $\tan \beta$, respectively. For appropriate values of $\tan \beta$, ${\lambda }_h$ and $m_h$, the DM with a mass of $10\sim 50$ GeV is allowed by the constraints of the Higgs searches at the LHC and dark matter experiments. For example, $\tan \beta$ is restricted to be in the range of $1.0\sim 1.5$ for 10 GeV $<m_s<$ 26 GeV, and $\frac{m_h}{2m_S}>$ 1.125 is excluded for 30 GeV $<m_S<$ 50 GeV.

   hep-phPRD(2018)·13 citations
8. 08*

   Fierz-complete NJL model study II: towards the fixed-point and phase structure of hot and dense two-flavor QCD

   Jens Braun🇩🇪 · Marc Leonhardt🇩🇪 · Martin Pospiech🇩🇪

   Nambu-Jona-Lasinio-type models are often employed as low-energy models for the theory of the strong interaction to analyze its phase structure at finite temperature and quark chemical potential. In particular at low temperature and large chemical potential, where the application of fully first-principles approaches is currently difficult at best, this class of models still plays a prominent role to guide our understanding of the dynamics of dense strong-interaction matter. In this work, we consider a Fierz-complete version of the Nambu-Jona-Lasinio model with two massless quark flavors and study its renormalization group flow and fixed-point structure at leading order of the derivative expansion of the effective action. Sum rules for the various four-quark couplings then allow us to monitor the strength of the breaking of the axial $U_{\mathrm{A}}(1)$ symmetry close to and above the phase boundary. We find that the dynamics in the ten-dimensional Fierz-complete space of four-quark couplings can only be reduced to a one-dimensional space associated with the scalar-pseudoscalar coupling in the strict large-$N_{\mathrm{c}}$ limit. Still, the interacting fixed point associated with this one-dimensional subspace appears to govern the dynamics at small quark chemical potential even beyond the large-$N_{\mathrm{c}}$ limit. At large chemical potential, corrections beyond the large-$N_{\mathrm{c}}$ limit become important and the dynamics is dominated by diquarks, favoring the formation of a chirally symmetric diquark condensate. In this regime, our study suggests that the phase boundary is shifted to higher temperatures when a Fierz-complete set of four-quark interactions is considered.

   hep-phnucl-thPRD(2018)·53 citations
9. 09*

   Testing lepton flavour universality in semileptonic ${\Lambda }_b\to {\Lambda }_c^{\ast }$ decays

   Philipp Böer🇩🇪 · Marzia Bordone🇨🇭 · Elena Graverini🇨🇭 · Patrick Owen🇨🇭 · Marcello Rotondo🇮🇹 · Danny van Dyk🇩🇪

   Lepton Flavour Universality tests with semileptonic ${\Lambda }_b\to {\Lambda }_c^{\ast }$ decays are important to corroborate the present anomalies in the similar ratios $R_{D^{(\ast )}}$, and can provide complementary constraints on possible origins of these anomalies beyond the Standard Model. In this paper we provide - for the first time - all the necessary theoretical ingredients to perform and interpret measurements of $R_{{\Lambda }_c^{\ast }}$ at the LHCb experiment. For this, we revisit the heavy-quark expansion of the relevant hadronic matrix elements, and provide their expressions to order ${\alpha }_s$ and $1/m$ accuracy. Moreover, we study the sensitivity to the form factor parameters given the projected size and purity of upcoming and future LHCb datasets of ${\Lambda }_b\to {\Lambda }_c^{\ast }\mu \bar{\nu }$ decays. We demonstrate explicitly the need to perform a simultaneous fit to both ${\Lambda }_c^{\ast }$ final states. Finally, we provide projections for the uncertainty of $R_{{\Lambda }_c^{\ast }}$ based on the form factor analysis from semimuonic decays and theoretical relations based on the heavy-quark expansion.

   hep-phhep-exJHEP(2018)·37 citations
10. 10*

    The SysCalc code: A tool to derive theoretical systematic uncertainties

    Alexis Kalogeropoulos🇺🇸 · Johan Alwall🇹🇼

    Undisputedly, derivation of theoretical systematic uncertainties is an inseparable ingredient of any robust analysis dealing with experimental data. However, it is not uncommon, even for those analyses that use state of the art methods and tools to suffer from insufficient statistics when it comes to the simulated datasets used to estimate systematic uncertainties. This practically limits the power, and sometimes the robustness of the analysis. In this paper, we present SysCalc, a code which is able to derive weights for various important theoretical systematic uncertainties, including those related to the choice of the Parton Distribution Function sets and the various scale choices. SysCalc utilizes the central sample generated events to estimate the related systematic uncertainties, thus, omitting the need for generating dedicated systematics datasets, and with only a minimal added cost in terms of computing resources. In this paper we discuss the working principles of the code accompanied by various validation plots. We also discuss the structure of the code followed by a practical guide for how to use the tool.

    hep-phhep-exphysics.comp-ph104 citations
11. 11*

    A first determination of the unpolarized quark TMDs from a global analysis

    Cristian Pisano🇮🇹 · Alessandro Bacchetta🇮🇹 · Filippo Delcarro🇮🇹 · Marco Radici🇮🇹 · Andrea Signori🇺🇸

    Transverse momentum dependent distribution and fragmentation functions of unpolarized quarks inside unpolarized protons are extracted, for the first time, through a simultaneous analysis of semi-inclusive deep-inelastic scattering, Drell-Yan and $Z$ boson hadroproduction processes. This study is performed at leading order in perturbative QCD, with energy scale evolution at the next-to-leading logarithmic accuracy. Moreover, some specific choices are made to deal with low scale evolution around 1 GeV${}^2$. Since only data in the low transverse momentum region are considered, no matching to fixed-order calculations at high transverse momentum is needed.

    hep-phPoS(2018)·5 citations
12. 12*

    Halo-independent comparison of direct detection experiments in the effective theory of dark matter-nucleon interactions

    Riccardo Catena🇸🇪 · Alejandro Ibarra🇩🇪 · Andreas Rappelt🇩🇪 · Sebastian Wild🇩🇪

    The theoretical interpretation of dark matter direct detection experiments is hindered by uncertainties of the microphysics governing the dark matter-nucleon interaction, and of the dark matter density and velocity distribution inside the Solar System. These uncertainties are especially relevant when confronting a detection claim to the null results from other experiments, since seemingly conflicting experimental results may be reconciled when relaxing the assumptions about the form of the interaction and/or the velocity distribution. We present in this paper a halo-independent method to calculate the maximum number of events in a direct detection experiment given a set of null search results, allowing for the first time the scattering to be mediated by an arbitrary combination of various interactions (concretely we consider up to 64). We illustrate this method to examine the compatibility of the dark matter interpretation of the three events detected by the silicon detectors in the CDMS-II experiment with the null results from XENON1T and PICO-60.

    hep-phastro-ph.COJCAP(2018)·23 citations
13. 13*

    NLO radiative corrections for Forward-Backward and Left-Right Asymmetries at a B-Factory

    A. Aleksejevs🇨🇦 · S. Barkanova🇨🇦 · C. Miller🇨🇦 · J. M. Roney🇨🇦 · V. Zykunov🇷🇺

    This paper presents the first calculations of the parity-violating polarization asymmetry and forward-backward asymmetry of the $e^{-}{e}^{+}\to {\mu }^{+}{\mu }^{-}(\gamma )$ process at a center-of-mass energy of 10.58 GeV with up to one-loop electroweak radiative corrections. The calculations are relevant for future precision electroweak measurements at the Belle~II experiment, which is now collecting data at the SuperKEKB $e^{-}{e}^{+}$ collider with a center-of-mass energy at the mass of the ${\rm Y}(4S)$ resonance. In this paper we take under full control the bremsstrahlung process at the conditions of Belle II/SuperKEKB, and the possibilities for a soft photon approach are discussed. The scale of the obtained relative corrections to the parity-violating and forward-backward asymmetries is significant and the scattering angle dependencies of the asymmetries is non-trivial. As an additional validation cross-check using an independent formulation, the calculated asymmetries are compared to results from the KK Monte Carlo generator.

    hep-phPRD(2020)·12 citations
14. 14*

    Extracting Particle Physics Information from Direct Detection of Dark Matter with Minimal Assumptions

    Lawrence M. Krauss🇺🇸 · Jayden L. Newstead (Arizona State University)🇺🇸

    In the absence of direct accelerator data to constrain particle models, and given existing astrophysical uncertainties associated with the phase space distribution of WIMP dark matter in our galactic halo, extracting information on fundamental particle microphysics from possible signals in underground direct detectors will be challenging. Given these challenges we explore the requirements for direct detection of dark matter experiments to extract information on fundamental particle physics interactions. In particular, using Bayesian methods, we explore the quantitative distinctions that allow differentiation between different non-relativistic effective operators, as a function of the number of detected events, for a variety of possible operators that might generate the detected distribution. Without a spinless target one cannot distinguish between spin-dependent and spin-independent interactions. In general, of order 50 events would be required to definitively determine that the fundamental dark matter scattering amplitude is momentum independent, even in the optimistic case of minimal detector backgrounds and no inelastic scattering contributions. This bound can be improved with reduced uncertainties in the dark matter velocity distribution.

    hep-phastro-ph.COastro-ph.GAhep-ex+15 citations
15. 15*

    Kinetic Mixing, Dark Photons and an Extra Dimension: I

    Thomas G. Rizzo🇺🇸

    Extra dimensions (ED) can provide a useful tool for model-building. In this paper we introduce a single, flat ED extension of the kinetic-mixing/dark photon (DP) portal for dark matter (DM) interactions with the Standard Model (SM) assuming a compactification `radius' of order $R^{-1}\sim 10-1000$ MeV and examine the resulting modifications to and augmentation of the usual DP phenomenology. In the present scenario, both the DP and DM experience the full 5-D while the SM fields are constrained to lie on a 4-D brane at the boundary of the ED. Such a setup can naturally yield the observed value of the DM relic density and explain the required rough degeneracy of the DM and DP masses needed to obtain it. Gauge symmetry breaking can occur via boundary conditions without the introduction of an additional singlet Higgs scalar thus avoiding all constraints associated with the coupling of such a field to the usual SM Higgs field in 5-D. The self-consistency of the field redefinitions that map the gauge fields into a canonical basis and thus removing the kinetic mixing terms is found to lead to a strong model building constraint on the ED setup involving a brane localized kinetic term for the 5-D gauge field on the SM brane. Multiple variations of this scenario are found to be possible which are consistent with all current experimental constraints but which predict very different phenomenologies. In this paper, after setting up the general model formalism, we discuss in detail the case of a complex scalar 5-D DM field, consistent with constraints arising from the CMB, which may or may not obtain a vacuum expectation value (vev). The resulting Kaluza-Klein (KK) towers of both the DM and DP fields are found to yield interesting and distinctive signatures.

    hep-phJHEP(2018)·43 citations
16. 16*

    Power Corrections to the Universal Heavy WIMP-Nucleon Cross Section

    Chien-Yi Chen🇨🇦 · Richard J. Hill🇺🇸 · Mikhail P. Solon🇺🇸 · Alexander M. Wijangco🇨🇦

    WIMP-nucleon scattering is analyzed at order $1/M$ in Heavy WIMP Effective Theory. The $1/M$ power corrections, where $M\gg m_W$ is the WIMP mass, distinguish between different underlying UV models with the same universal limit and their impact on direct detection rates can be enhanced relative to naive expectations due to generic amplitude-level cancellations at leading order. The necessary one- and two-loop matching calculations onto the low-energy effective theory for WIMP interactions with Standard Model quarks and gluons are performed for the case of an electroweak SU(2) triplet WIMP, considering both the cases of elementary fermions and composite scalars. The low-velocity WIMP-nucleon scattering cross section is evaluated and compared with current experimental limits and projected future sensitivities. Our results provide the most robust prediction for electroweak triplet Majorana fermion dark matter direct detection rates; for this case, a cancellation between two sources of power corrections yields a small total $1/M$ correction, and a total cross section close to the universal limit for $M\gtrsim \mathrm{few}\times 100\mathrm{GeV}$. For the SU(2) composite scalar, the $1/M$ corrections introduce dependence on underlying strong dynamics. Using a leading chiral logarithm evaluation, the total $1/M$ correction has a larger magnitude and uncertainty than in the fermionic case, with a sign that further suppresses the total cross section. These examples provide definite targets for future direct detection experiments and motivate large scale detectors capable of probing to the neutrino floor in the TeV mass regime.

    hep-phastro-ph.COPLB(2018)·24 citations
17. 17*

    The fate of $U_A(1)$ and topological features of QCD at finite temperature

    Sayantan Sharma🇺🇸

    The nature of chiral phase transition for QCD with two light quark flavors is not yet completely resolved. This is primarily because one has to understand whether or not the anomalous U(1) symmetry in the flavor sector is effectively restored along with the chiral symmetry. Since the physics near the chiral phase transition is essentially non-perturbative, we employ first principles lattice techniques to address this issue. We use overlap fermions, which have exact chiral symmetry on the lattice, to probe the anomalous U(1) symmetry violation of 2+1 flavor dynamical QCD configurations with domain wall fermions. The latter also optimally preserves chiral and flavor symmetries on the lattice. We observe that the anomalous U(1) is not effectively restored in the chiral crossover region. We perform a systematic study of the finite size and cut-off effects since the signals of U(1) violation are sensitive to it. For the same reasons we also compare our results from the continuum extrapolated results of the QCD Dirac spectrum obtained from a different lattice discretization called Highly Improved Staggered Quarks. Our studies also provide a glimpse of the microscopic topological structures of the QCD medium that are responsible for the strongly interacting nature of the quark gluon plasma phase and related to the physics of confinement and chiral symmetry breaking.

    ↳ hep-lathep-ph13 citations
18. 18*

    Density perturbations for running vacuum: a successful approach to structure formation and to the ${\sigma }_8$-tension

    Adrià Gómez-Valent🇪🇸 · Joan Solà Peracaula🇪🇸

    Recent studies suggest that dynamical dark energy (DDE) provides a better fit to the rising affluence of modern cosmological observations than the concordance model ($\Lambda$CDM) with a rigid cosmological constant, $\Lambda$. Such is the case with the running vacuum models (RVMs) and to some extent also with a simple XCDM parametrization. Apart from the cosmic microwave background (CMB) anisotropies, the most crucial datasets potentially carrying the DDE signature are: i) baryonic acoustic oscillations (BAO), and ii) direct large scale structure (LSS) formation data (i.e. the observations on $f(z){\sigma }_8(z)$ at different redshifts). As it turns out, analyses mainly focusing on CMB and with insufficient BAO+LSS input, or those just making use of gravitational weak-lensing data for the description of structure formation, generally fail to capture the DDE signature, whereas the few existing studies using a rich set of CMB+BAO+LSS data (see in particular Solà, Gómez-Valent & de Cruz Pérez 2015,2017; and Zhao et al. 2017) do converge to the remarkable conclusion that DDE might well be encoded in the current cosmological observations. Being the issue so pressing, here we explain both analytically and numerically the origin of the possible hints of DDE in the context of RVMs, which arise at a significance level of $3-4\sigma$. By performing a detailed study on the matter and vacuum perturbations within the RVMs, and comparing with the XCDM, we show why the running vacuum fully relaxes the existing ${\sigma }_8$-tension and accounts for the LSS formation data much better than the concordance model.

    ↳ astro-ph.COgr-qchep-phhep-thMNRAS(2018)·125 citations
19. 19*

    Price of Asymptotic Safety

    Andrew D. Bond🇬🇧 · Daniel F. Litim🇬🇧

    All known examples of four dimensional quantum field theories with asymptotic freedom or asymptotic safety at weak coupling involve non-abelian gauge interactions. We demonstrate that this is not a coincidence: no weakly coupled fixed points, ultraviolet or otherwise, can be reliably generated in theories lacking gauge interactions. Implications for particle physics, critical phenomena, and conformal field theory are indicated.

    ↳ hep-thhep-phPRL(2019)·47 citations
20. 20*

    Proof of the Weak Gravity Conjecture from Black Hole Entropy

    Clifford Cheung🇺🇸 · Junyu Liu🇺🇸 · Grant N. Remmen🇺🇸

    We prove that higher-dimension operators contribute positively to the entropy of a thermodynamically stable black hole at fixed mass and charge. Our results apply whenever the dominant corrections originate at tree level from quantum field theoretic dynamics. More generally, positivity of the entropy shift is equivalent to a certain inequality relating the free energies of black holes. These entropy inequalities mandate new positivity bounds on the coefficients of higher-dimension operators. One of these conditions implies that the charge-to-mass ratio of an extremal black hole asymptotes to unity from above for increasing mass. Consequently, large extremal black holes are unstable to decay to smaller extremal black holes and the weak gravity conjecture is automatically satisfied. Our findings generalize to arbitrary spacetime dimension and to the case of multiple gauge fields. The assumptions of this proof are valid across a range of scenarios, including string theory constructions with a dilaton stabilized below the string scale.

    ↳ hep-thgr-qchep-phJHEP(2018)·247 citations
21. 21*

    Constraints on the sum of the neutrino masses in dynamical dark energy models with $w(z)\ge -1$ are tighter than those obtained in $\Lambda$CDM

    Sunny Vagnozzi🇸🇪 · Suhail Dhawan🇸🇪 · Martina Gerbino🇸🇪 · Katherine Freese🇸🇪 · Ariel Goobar🇸🇪 · Olga Mena🇪🇸

    We explore cosmological constraints on the sum of the three active neutrino masses $M_{\nu }$ in the context of dynamical dark energy (DDE) models with equation of state (EoS) parametrized as a function of redshift $z$ by $w(z)=w_0+w_{a}z/(1+z)$, and satisfying $w(z)\ge -1$ for all $z$. We perform a Bayesian analysis and show that, within these models, the bounds on $M_{\nu }$ \textit{do not degrade} with respect to those obtained in the $\Lambda$CDM case; in fact the bounds are slightly tighter, despite the enlarged parameter space. We explain our results based on the observation that, for fixed choices of $w_0,w_a$ such that $w(z)\ge -1$ (but not $w=-1$ for all $z$), the upper limit on $M_{\nu }$ is tighter than the $\Lambda$CDM limit because of the well-known degeneracy between $w$ and $M_{\nu }$. The Bayesian analysis we have carried out then integrates over the possible values of $w_0$-$w_a$ such that $w(z)\ge -1$, all of which correspond to tighter limits on $M_{\nu }$ than the $\Lambda$CDM limit. We find a 95\% confidence level (C.L.) upper bound of $M_{\nu }<0.13\mathrm{eV}$. This bound can be compared with $M_{\nu }<0.16\mathrm{eV}$ at 95\%~C.L., obtained within the $\Lambda$CDM model, and $M_{\nu }<0.41\mathrm{eV}$ at 95\%~C.L., obtained in a DDE model with arbitrary EoS (which allows values of $w<-1$). Contrary to the results derived for DDE models with arbitrary EoS, we find that a dark energy component with $w(z)\ge -1$ is unable to alleviate the tension between high-redshift observables and direct measurements of the Hubble constant $H_0$. Finally, in light of the results of this analysis, we also discuss the implications for DDE models of a possible determination of the neutrino mass hierarchy by laboratory searches. (abstract abridged)

    ↳ astro-ph.COgr-qchep-phPRD(2018)·271 citations

* Reconstructed cohort: no mailing for this day survives in the archive. Papers are grouped by their submission times and arXiv's announcement cut-off, assuming announcement without delay; positions follow identifier order. Validated at ~91% exact-day agreement against the archived era.