Fri·Sep 8, 2017Friday·September 8, 2017

1. 01*

   On the direct detection of multi-component dark matter: sensitivity studies and parameter estimation

   Juan Herrero-Garcia🇦🇺 · Andre Scaffidi🇦🇺 · Martin White🇦🇺 · Anthony G. Williams🇦🇺

   We study the case of multi-component dark matter, in particular how direct detection signals are modified in the presence of several stable weakly-interacting-massive particles. Assuming a positive signal in a future direct detection experiment, stemming from two dark matter components, we study the region in parameter space where it is possible to distinguish a one from a two-component dark matter spectrum. First, we leave as free parameters the two dark matter masses and show that the two hypotheses can be significantly discriminated for a range of dark matter masses with their splitting being the critical factor. We then investigate how including the effects of different interaction strengths, local densities or velocity dispersions for the two components modifies these conclusions. We also consider the case of isospin-violating couplings. In all scenarios, we show results for various types of nuclei both for elastic spin-independent and spin-dependent interactions. Finally, assuming that the two-component hypothesis is confirmed, we quantify the accuracy with which the parameters can be extracted and discuss the different degeneracies that occur. This includes studying the case in which only a single experiment observes a signal, and also the scenario of having two signals from two different experiments, in which case the ratios of the couplings to neutrons and protons may also be extracted.

   hep-phastro-ph.HEJCAP(2017)·51 citations
2. 02*

   Searching for Leptoquarks at IceCube and the LHC

   Ujjal Kumar Dey🇮🇳 · Deepak Kar🇿🇦 · Manimala Mitra🇮🇳 · Michael Spannowsky🇬🇧 · Aaron C. Vincent🇬🇧

   In the light of recent experimental results from IceCube, LHC searches for scalar leptoquark, and the flavor anomalies $R_K$ and $R_{K^{\ast }}$, we analyze two scalar leptoquark models with hypercharge $Y=1/6$ and $Y=7/6$. We consider the 53 high-energy starting events from IceCube and perform a statistical analysis, taking into account both the Standard Model and leptoquark contribution together. The lighter leptoquark states that are in agreement with IceCube are strongly constrained from LHC di-lepton+dijet search. Heavier leptoquarks in the TeV mass range are in agreement both with IceCube and LHC. We furthermore show that leptoquark which explains the $B$-physics anomalies and does not have any coupling with the third generation of quarks and leptons, can be strongly constrained.

   hep-phPRD(2018)·67 citations
3. 03*

   Counting the number of Feynman Graphs in QCD

   T. Kaneko🇯🇵

   Information about the number of Feynman graphs for a given physical process in a given field theory is especially useful for confirming the result of a Feynman graph generator used in an automatic system of perturbative calculations. A method of counting the number of Feynman graphs with weight of symmetry factor was established based on zero-dimensional field theory, and was used in scalar theories and QED. In this article this method is generalized to more complicated models by direct calculation of generating functions on a symbolic calculating system. This method is applied to QCD with and without counter terms, where many higher order are being calculated automatically.

   hep-phComput.Phys.Commun.(2018)·3 citations
4. 04*

   Observation of the isospin breaking decay ${\rm Y}(10860)\to {\rm Y}(1S)f_0(980)\to {\rm Y}(1S)\eta {\pi }^0$ with the Belle II detector

   N.N. Achasov🇷🇺 · G.N. Shestakov🇷🇺

   Using the Belle data on the decay ${\rm Y}(10860)\to {\rm Y}(1S)f_0(980)\to {\rm Y}(1S){\pi }^{+}{\pi }^{-}$, we estimate the fraction of the process ${\rm Y}(10860)\to {\rm Y}(1S)f_0(980)\to {\rm Y}(1S)\eta {\pi }^0$, caused by the mixing of $a_0^0(980)$ and $f_0(980)$ resonances that breaks the isotopic invariance due to the $K^{+}$ and $K^0$ meson mass difference. With an instantaneous luminosity of $8\times 10^{35}$ cm${}^2\cdot$\,s${}^{-1}$ at the SuperKEKB collider, one can collect with the Belle II detector about a hundred ${\rm Y}(10860)\to {\rm Y}(1S)\eta {\pi }^0$ events in the narrow region of the $\eta {\pi }^0$ invariant mass near the $K\bar{K}$ thresholds in a time roughly spent on the present Belle experiment.

   hep-phhep-exnucl-thPRD(2017)·7 citations
5. 05*

   Light Pseudoscalar Mesons: an Inverse Instantaneous Bethe-Salpeter Glimpse

   Wolfgang Lucha🇦🇹 · Franz F. Schoberl🇦🇹

   Achieving self-consistent simultaneous interpretations of pions and kaons as bound states of quark and antiquark and as the (almost) massless boson states related, according to Goldstone's theorem, to the dynamical (and explicit) breakdown of the chiral symmetries of QCD still represents a major challenge. Applying inversion techniques to conveniently simplified versions of the homogeneous Bethe-Salpeter equation, governing bound states in quantum field theory, enables us to get along a straightforward route a qualitative idea of how the underlying effective interaction might look like.

   hep-phnucl-thPoS(2017)·1 citation
6. 06*

   Decay Constants of the Heavy-Light Mesons $D^{(\ast )}$ and $B^{(\ast )}$: Isospin Breaking

   Wolfgang Lucha🇦🇹 · Dmitri Melikhov🇦🇹 · Silvano Simula🇮🇹

   QCD sum rules are analytic predictions of hadron observables from quantum chromodynamics. In the so-called local-duality limit of their Borel-transformed form, all nonperturbative contributions are encompassed by just a single quantity, an effective threshold beyond which, by assumption, all hadronic contributions are reliably described by perturbative QCD. Reconstructing its quark-mass dependence enables us to investigate the differences of the leptonic decay constants of heavy-light mesons effectuated by the tiny isospin-violating discrepancy of the masses of up and down quarks. By and large, our findings enjoy excellent agreement with the outcomes of earlier studies, the only exception being a lattice-QCD prediction for the $B$ mesons, where we find dramatic disagreement.

   hep-phhep-latnucl-thPoS(2017)·4 citations
7. 07*

   Exotic states and their properties from large-$N_{\mathrm{c}}$ QCD

   Wolfgang Lucha🇦🇹 · Dmitri Melikhov🇦🇹 · Hagop Sazdjian🇫🇷

   The analysis of two-ordinary-meson scattering amplitudes in the limit of a large number $N_{\mathrm{c}}$ of the colour degrees of freedom of quantum chromodynamics, with suitably decreasing strong coupling and all quarks transforming according to the gauge group's fundamental representation, enables us to establish a set of rigorous consistency conditions for the emergence of a tetraquark (i.e., a bound state of two quarks and two antiquarks) as a pole in these amplitudes. For genuinely flavour-exotic tetraquarks, these constraints require the existence of two tetraquark states distinguishable by their preferred couplings to two ordinary mesons, whereas, for cryptoexotic tetraquarks, our constraints may be satisfied by a single tetraquark state, which then, however, may mix with ordinary mesons. For elucidation of the tetraquark features, the consideration of the subleading contributions proves to be mandatory: for both variants of tetraquarks, their decay widths fall off like $1/N_{\mathrm{c}}^2$ for large $N_{\mathrm{c}}.$

   hep-phPoS(2017)·11 citations
8. 08*

   Towards the minimal seesaw model via CP violation of neutrinos

   Yusuke Shimizu🇯🇵 · Kenta Takagi🇯🇵 · Morimitsu Tanimoto🇯🇵

   We study the minimal seesaw model, where two right-handed Majorana neutrinos are introduced, focusing on the CP violating phase. In addition, we take the trimaximal mixing pattern for the neutrino flavor where the charged lepton mass matrix is diagonal. Thanks to this symmetric framework, the $3\times 2$ Dirac neutrino mass matrix is given in terms of a few parameters. Numerical studies reveal that the observation of the CP violating phase can determine the flavor structure of the Dirac neutrino mass matrix in the minimal seesaw model. In particular, new minimal Dirac neutrino mass matrices are proposed in the case of $\mathrm{T}{\mathrm{M}}_1$, which is derived by the additional 2-3 family mixing to the tri-bimaximal mixing basis in the normal hierarchy of neutrino masses. Our analyses include the Littlest seesaw model by King {\it et al.}, which is one of the specific one in our results. Furthermore, it is remarked that our $3\times 2$ Dirac neutrino mass matrix is reproduced by introducing gauge singlet flavons with the specific alignments of the VEV's. These alignments suggest the residual symmetry of $S_4$ group.

   hep-phJHEP(2017)·31 citations
9. 09*

   Towards next-to-next-to-leading-log accuracy for the width difference in the $B_s-{\bar{B}}_s$ system: fermionic contributions to order $(m_c/m_b{)}^0$ and $(m_c/m_b{)}^1$

   H. M. Asatrian🇦🇲 · Artyom Hovhannisyan🇦🇲 · Ulrich Nierste🇩🇪 · Arsen Yeghiazaryan🇦🇲

   We calculate a class of three-loop Feynman diagrams which contribute to the next-to-next-to-leading logarithmic approximation for the width difference $\Delta {\Gamma }_s$ in the $B_s-{\bar{B}}_s$ system. The considered diagrams contain a closed fermion loop in a gluon propagator and constitute the order ${\alpha }_s^2{N}_f$, where $N_f$ is the number of light quarks. Our results entail a considerable correction in that order, if $\Delta {\Gamma }_s$ is expressed in terms of the pole mass of the bottom quark. If the $\overline{MS}$ scheme is used instead, the correction is much smaller. As a result, we find a decrease of the scheme dependence. Our result also indicates that the usually quoted value of the NLO renormalization scale dependence underestimates the perturbative error.

   hep-phJHEP(2017)·41 citations
10. 10*

    The $f_0(1790)$ and $a_0(1950)$ Resonances as Excited $\bar{q}q$ States in the Extended Linear Sigma Model

    Denis Parganlija🇦🇹 · Francesco Giacosa🇩🇪

    A decade ago, BES Collaboration reported the discovery of a new scalar isosinglet resonance denoted as $f_0(1790)$. The finding was subsequently confirmed by LHCb. Recently, the existence of the corresponding isotriplet state -- the $a_0(1950)$ resonance -- has been claimed by BABAR. We investigate whether these resonances can be described as excited $\bar{q}q$ states. To this end, a comprehensive Lagrangian containing ground-state $\bar{q}q$ mesons as well as their first excitations is constructed in accordance with symmetries of the strong interaction. Both $f_0(1790)$ and $a_0(1950)$ emerge as compatible with $\bar{q}q$ excitations; however, tension appears to arise between the simultaneous interpretation of $f_0(1790)$/$a_0(1950)$ and pseudoscalar mesons $\eta (1295)$, $\pi (1300)$, $\eta (1440)$ and $K(1460)$ as excited $\bar{q}q$ states.

    hep-phActa Phys.Polon.Supp.(2017)·0 citations
11. 11*

    Heavy quark production in $k_t$ factorization approach at LHC energies

    Yu.M. Shabelski🇷🇺 · A.G. Shuvaev🇷🇺 · I.V. Surnin🇷🇺

    A new version of the $k_T$ factorization approach is formulated for the high energy heavy quark production. The results are in reasonable agreement with the experimental data at LHC energies.

    hep-phInt.J.Mod.Phys.A(2017)·7 citations
12. 12*

    $P_5^{\prime }$ Anomaly for Top: $t{Z}^{\prime }$ Production at LHC

    George W.-S. Hou🇦🇺

    The $P_5^{\prime }$ anomaly uncovered by the LHCb experiment in $B\to K^{\ast }\mu \mu$ angular observables has motivated a possible $Z^{\prime }$ boson that couples to left-handed $b\to s$ transitions, where a model would be gauged $L_{\mu }-L_{\tau }$ symmetry, but direct search for such a $Z^{\prime }$ is not promising. Less constrained is an analogous $Z^{\prime }$ coupling to right-handed $t\to c$ transitions. Motivated by this, we study $cg\to t{Z}^{\prime }$ associated production at LHC, both for a generic model, and in $L_{\mu }-L_{\tau }$ with a vector-like U quark. We also study $c\bar{c}\to Z^{\prime }$ production that exists within the model. Both processes can be probed already with LHC Run 2 data, all the way up to the HL-LHC with discovery potential.

    hep-ph1 citation
13. 13*

    Uncertainties of the $B\to D$ transition form factor from the $D$-Meson Leading-Twist Distribution Amplitude

    Yi Zhang🇨🇳 · Tao Zhong🇨🇳 · Xing-Gang Wu🇨🇳 · Ke Li🇨🇳 · Hai-Bing Fu🇨🇳 · Tao Huang🇨🇳

    The $B\to D$ transition form factor (TFF) $f_{+}^{B\to D}(q^2)$ is determined mainly by the $D$-meson leading-twist distribution amplitude (DA) , ${\varphi }_{2;D}$, if the proper chiral current correlation function is adopted within the light-cone QCD sum rules. It is therefore significant to make a comprehensive study of DA ${\varphi }_{2;D}$ and its impact on $f_{+}^{B\to D}(q^2)$. In this paper, we calculate the moments of ${\varphi }_{2;D}$ with the QCD sum rules under the framework of the background field theory. New sum rules for the leading-twist DA moments ${⟨{\xi }^n⟩}_D$ up to fourth order and up to dimension-six condensates are presented. At the scale $\mu =2\mathrm{GeV}$, the values of the first four moments are: ${⟨{\xi }^1⟩}_D=-0.418_{-0.022}^{+0.021}$, ${⟨{\xi }^2⟩}_D=0.289_{-0.022}^{+0.023}$, ${⟨{\xi }^3⟩}_D=-0.178\pm 0.010$ and ${⟨{\xi }^4⟩}_D=0.142_{-0.012}^{+0.013}$. Basing on the values of ${⟨{\xi }^n⟩}_D(n=1,2,3,4)$, a better model of ${\varphi }_{2;D}$ is constructed. Applying this model for the TFF $f_{+}^{B\to D}(q^2)$ under the light cone sum rules, we obtain $f_{+}^{B\to D}(0)=0.673_{-0.041}^{+0.038}$ and $f_{+}^{B\to D}(q_{\max }^2)=1.124_{-0.058}^{+0.053}$. The uncertainty of $f_{+}^{B\to D}(q^2)$ from ${\varphi }_{2;D}$ is estimated and we find its impact should be taken into account, especially in low and central energy region. The branching ratio $\mathcal{B}(B\to Dl{\bar{\nu }}_l)$ is calculated, which is consistent with experimental data.

    hep-phEPJC(2018)·22 citations
14. 14*

    The neutral Higgs self-couplings in the (h)MSSM

    G. Chalons🇫🇷 · A. Djouadi🇫🇷 · J. Quevillon🇬🇧

    We consider the Minimal Supersymmetric extension of the Standard Model in the regime where the supersymmetric breaking scale is extermely large. In this MSSM, not only the Higgs masses will be affected by large radiative corrections, the dominant part of which is provided by the third generation quark/squark sector, but also the various self-couplings among the Higgs states. In this note, assuming that squarks are extremely heavy, we evaluate the next-to-leading order radiative corrections to the two neutral CP-even Higgs self-couplings ${\lambda }_{Hhh}$ and ${\lambda }_{hhh}$ and to the partial decay width $\Gamma (H\to hh)$ that are most relevant at the LHC. The calculation is performed using an effective field theory approach that resums the large logarithmic squark contributions and allows to keep under control the perturbative expansion. Since the direct loop vertex corrections are generally missing in this effective approach, we have properly renormalised the effective theory to take them into account. Finally, we perform a comparison of the results in this effective MSSM with those obtained in a much simpler way in the so-called hMSSM approach in which the mass value for the lightest Higgs boson $M_h=125$ GeV is used as an input. We show that the hMSSM provides a reasonably good approximation of the corrected self-couplings and $H\to hh$ decay rate and, hence, it can be used also in these cases.

    hep-phPLB(2018)·17 citations
15. 15*

    Conformal Window 2.0: The Large $N_f$ Safe Story

    Oleg Antipin🇭🇷 · Francesco Sannino🇩🇰

    We extend the phase diagram of SU(N) gauge-fermion theories as function of number of flavours and colours to the region in which asymptotic freedom is lost. We argue, using large $N_f$ results, for the existence of an ultraviolet interacting fixed point at sufficiently large number of flavours opening up to a second ultraviolet conformal window in the number of flavours vs colours phase diagram. We first review the state-of-the-art for the large $N_f$ beta function and then estimate the lower boundary of the ultraviolet window. The theories belonging to this new region are examples of safe non-abelian quantum electro dynamics, termed here {\it safe QCD}. Therefore, according to Wilson, they are fundamental. An important critical quantity is the fermion mass anomalous dimension at the ultraviolet fixed point that we determine at leading order in $1/N_f$. We discover that its value is comfortably below the bootstrap bound. We also investigate the abelian case and find that at the potential ultraviolet fixed point the related fermion mass anomalous dimension has a singular behaviour suggesting that a more careful investigation of its ultimate fate is needed.

    hep-phhep-lathep-thPRD(2018)·64 citations
16. 16*

    Six Higgs Doublets Model for Dark Matter

    Mohammad Alakhras · Nidal Chamoun🇸🇾 · Xue-Lei Chen🇨🇳 · Chao-Shang Huang🇨🇳 · Chun Liu🇨🇳

    We consider an extension of the Higgs sector in the standard model (SM) with six Higgs doublets. The gauge couplings are unified without supersymmetry in this model. The lightest of the extra Higgs particles, being stabilized by a discrete symmetry imposed from the outset, presents a plausible candidate for dark matter. For a specific acceptable benchmark point, we show that the model is viable regarding the constraints of relic density, direct detection and invisible Higgs decay. We comment on the mean free path of the dark matter candidate.

    hep-phPRD(2017)·3 citations
17. 17*

    Collisional and thermal dissociation of $J/\psi$ and ${\rm Y}$ states at the LHC

    Samuel Aronson🇺🇸 · Evan Borras🇺🇸 · Brunel Odegard🇺🇸 · Rishi Sharma🇮🇳 · Ivan Vitev🇺🇸

    We present new results for the suppression of high transverse momentum charmonium [$J/\psi ,\psi (2S)$] and bottomonium [${\rm Y}(1S),{\rm Y}(2S),{\rm Y}(3S)$] states in Pb+Pb collisions at the Large Hadron Collider. Our theoretical formalism combines the collisional dissociation of quarkonia, as they propagate in the quark-gluon plasma, with the thermal wavefunction effects due to the screening of the $Q\bar{Q}$ attractive potential in the medium. We find that a good description of the relative suppression of the ground and higher excited quarkonium states, transverse momentum and centrality distributions is achieved, when comparison to measurements at a center-of-mass energy of 2.76 TeV is performed. Theoretical predictions for the highest Pb+Pb center-of-mass energy of 5.02 TeV at the LHC, where new experimental results are being finalized, are also presented.

    hep-phnucl-thPLB(2018)·62 citations
18. 18*

    Born Again Universe

    Peter W. Graham🇺🇸 · David E. Kaplan🇺🇸 · Surjeet Rajendran🇺🇸

    We present a class of nonsingular, bouncing cosmologies that evade singularity theorems through the use of vorticity in compact extra dimensions. The vorticity combats the focusing of geodesics during the contracting phase. The construction requires fluids that violate the null energy condition (NEC) in the compact dimensions, where they can be provided by known stable NEC violating sources such as Casimir energy. The four dimensional effective theory contains an NEC violating fluid of Kaluza-Klein excitations of the higher dimensional metric. These spacetime metrics could potentially allow dynamical relaxation to solve the cosmological constant problem. These ideas can also be used to support traversable Lorentzian wormholes.

    ↳ hep-thastro-ph.COhep-phPRD(2018)·32 citations
19. 19*

    High cumulants of conserved charges and their statistical uncertainties

    Li-Zhu Chen🇨🇳 · Ye-Yin Zhao🇨🇳 · Xue Pan🇨🇳 · Zhi-Ming Li🇨🇳 · Yuan-Fang Wu🇨🇳

    We study the influence of measured high cumulants of conserved charges on their associated statistical uncertainties in relativistic heavy-ion collisions. With a given number of events, the measured cumulants randomly fluctuate with an approximately normal distribution, while the estimated statistical uncertainties are found to be correlated with corresponding values of the obtained cumulants. Generally, with a given number of events, the larger the cumulants we measure, the larger the statistical uncertainties that are estimated. The error-weighted averaged cumulants are dependent on statistics. Despite this effect, however, it is found that the three sigma rule of thumb is still applicable when the statistics are above one million.

    ↳ nucl-thhep-phCPC(2017)·3 citations
20. 20*

    Viscous Self Interacting Dark Matter and Cosmic Acceleration

    Abhishek Atreya🇮🇳 · Jitesh R. Bhatt🇮🇳 · Arvind Mishra🇮🇳

    Self interacting dark matter (SIDM) provides us with a consistent solution to certain astrophysical observations in conflict with collision-less cold DM paradigm. In this work we estimate the shear viscosity $(\eta )$ and bulk viscosity $(\zeta )$ of SIDM, within kinetic theory formalism, for galactic and cluster size SIDM halos. To that extent we make use of the recent constraints on SIDM crossections for the dwarf galaxies, LSB galaxies and clusters. We also estimate the change in solution of Einstein's equation due to these viscous effects and find that $\sigma /m$ constraints on SIDM from astrophysical data provide us with sufficient viscosity to account for the observed cosmic acceleration at present epoch, without the need of any additional dark energy component. Using the estimates of dark matter density for galactic and cluster size halo we find that the mean free path of dark matter $\sim$ few Mpc. Thus the smallest scale at which the viscous effect start playing the role is cluster scale. Astrophysical data for dwarf, LSB galaxies and clusters also seems to suggest the same. The entire analysis is independent of any specific particle physics motivated model for SIDM.

    ↳ astro-ph.COhep-phhep-thJCAP(2018)·26 citations
21. 21*

    Search for Bosonic Super-WIMP Interactions with the XENON100 Experiment

    XENON collaboration: E. Aprile🇺🇸 · J. Aalbers🇳🇱 · F. Agostini🇮🇹 · M. Alfonsi🇩🇪 · L. Althueser🇩🇪 · F. D. Amaro🇵🇹 · M. Anthony🇺🇸 · F. Arneodo🇦🇪 · P. Barrow🇨🇭 · L. Baudis🇨🇭 · B. Bauermeister🇸🇪 · M. L. Benabderrahmane🇦🇪 and 109 other authors

    We present results of searches for vector and pseudo-scalar bosonic super-WIMPs, which are dark matter candidates with masses at the keV-scale, with the XENON100 experiment. XENON100 is a dual-phase xenon time projection chamber operated at the Laboratori Nazionali del Gran Sasso. A profile likelihood analysis of data with an exposure of 224.6 live days $\times$ 34\,kg showed no evidence for a signal above the expected background. We thus obtain new and stringent upper limits in the $(8-125)$\,keV/c${}^2$ mass range, excluding couplings to electrons with coupling constants of $g_{ae}>3\times 10^{-13}$ for pseudo-scalar and ${\alpha }^{\prime }/\alpha >2\times 10^{-28}$ for vector super-WIMPs, respectively. These limits are derived under the assumption that super-WIMPs constitute all of the dark matter in our galaxy.

    ↳ astro-ph.COhep-exhep-phPRD(2017)·33 citations
22. 22*

    Dark matter searches at the LHC

    Tae Min Hong🇺🇸

    We present a summary of the current status of searches for dark matter at the LHC from the ATLAS and CMS experiments. For various assumptions in the simplified parameter space, the LHC exclusions is complementary to direct detection results. Mono-object analyses in search of dark matter and various analyses searching for dark matter mediators are presented.

    ↳ hep-exhep-ph8 citations
23. 23*

    Constraining the dark energy models with H(z) data: an approach independent of $H_0$

    Fotios Anagnostopoulos🇬🇷 · Spyros Basilakos🇬🇷

    We study the performance of the latest $H(z)$ data in constraining the cosmological parameters of different cosmological models, including that of Chevalier-Polarski-Linder $w_0{w}_1$ parametrization. First, we introduce a statistical procedure in which the chi-square estimator is not affected by the value of the Hubble constant. As a result, we find that the $H(z)$ data do not rule out the possibility of either non-flat models or dynamical dark energy cosmological models. However, we verify that the time varying equation of state parameter $w(z)$ is not constrained by the current expansion data. Combining the $H(z)$ and the Type Ia supernova data we find that the $H(z)$/SNIa overall statistical analysis provides a substantial improvement of the cosmological constraints with respect to those of the $H(z)$ analysis. Moreover, the $w_0-w_1$ parameter space provided by the $H(z)$/SNIa joint analysis is in a very good agreement with that of Planck 2015, which confirms that the present analysis with the $H(z)$ and SNIa probes correctly reveals the expansion of the Universe as found by the team of Planck. Finally, we generate sets of Monte Carlo realizations in order to quantify the ability of the $H(z)$ data to provide strong constraints on the dark energy model parameters. The Monte Carlo approach shows significant improvement of the constraints, when increasing the sample to 100 $H(z)$ measurements. Such a goal can be achieved in the future, especially in the light of the next generation of surveys.

    ↳ astro-ph.COgr-qchep-phPRD(2018)·43 citations
24. 24*

    Brane world models with bulk perfect fluid and broken 4D Poincare invariance

    Ozgur Akarsu🇹🇷 · Alexey Chopovsky🇺🇦 · Maxim Eingorn🇺🇸 · Seyed Hossein Fakhr🇺🇦 · Alexander Zhuk🇹🇷

    We consider 5D brane world models with broken global 4D Poincar\a'{e} invariance (4D part of the spacetime metric is not conformal to the Minkowski spacetime). The bulk is filled with the negative cosmological constant and may contain a perfect fluid. In the case of empty bulk (the perfect fluid is absent), it is shown that one brane solution always has either a physical or a coordinate singularity in the bulk. We cut off these singularities in the case of compact two brane model and obtain regular exact solutions for both 4D Poincar\a'{e} broken and restored invariance. When the perfect fluid is present in the bulk, we get the master equation for the metric coefficients in the case of arbitrary bulk perfect fluid equation of state (EoS) parameters. In two particular cases of EoS, we obtain the analytic solutions for thin and thick branes. First one generalizes the well known Randall-Sundrum model with one brane to the case of the bulk anisotropic perfect fluid. In the second solution, the 4D Poincar\a'{e} invariance is restored. Here, the spacetime goes asymptotically to the anti-de Sitter one far from the thick brane.

    ↳ gr-qcastro-ph.COhep-phhep-thPRD(2018)·1 citation
25. 25*

    Entanglement Entropy and Decoupling in the Universe

    Yuichiro Nakai🇺🇸 · Noburo Shiba🇺🇸 · Masaki Yamada🇺🇸

    In the expanding universe, two interacting fields are no longer in thermal contact when the interaction rate becomes smaller than the Hubble expansion rate. After decoupling, two subsystems are usually treated separately in accordance with equilibrium thermodynamics and the thermodynamic entropy gives a fiducial quantity conserved in each subsystem. In this paper, we discuss a correction to this paradigm from quantum entanglement of two coupled fields. The thermodynamic entropy is generalized to the entanglement entropy. We formulate a perturbation theory to derive the entanglement entropy and present Feynman rules in diagrammatic calculations. For specific models to illustrate our formulation, an interacting scalar-scalar system, quantum electrodynamics, and the Yukawa theory are considered. We calculate the entanglement entropy in these models and find a quantum correction to the thermodynamic entropy. The correction is revealed to be important in circumstances of instantaneous decoupling.

    ↳ hep-thastro-ph.COhep-phPRD(2017)·10 citations
26. 26*

    A Note on the WGC, Effective Field Theory and Clockwork within String Theory

    Luis E. Ibanez🇪🇸 · Miguel Montero🇳🇱

    It has been recently argued that Higgsing of theories with $U(1{)}^n$ gauge interactions consistent with the Weak Gravity Conjecture (WGC) may lead to effective field theories parametrically violating WGC constraints. The minimal examples typically involve Higgs scalars with a large charge with respect to a $U(1)$ (e.g. charges $(Z,1)$ in $U(1{)}^2$ with $Z\gg 1$). This type of Higgs multiplets play also a key role in clockwork $U(1)$ theories. We study these issues in the context of heterotic string theory and find that, while indeed there is no new physics at the standard magnetic WGC scale $\Lambda \sim g_{IR}{M}_P$, the string scale is just slightly above, at a scale $\sim \sqrt{k_{IR}}\Lambda$. Here $k_{IR}$ is the level of the IR $U(1)$ worldsheet current. We show that, unlike the standard magnetic cutoff, this bound is insensitive to subsequent Higgsing. One may argue that this constraint gives rise to no bound at the effective field theory level since $k_0$ is model dependent and in general unknown. However there is an additional constraint to be taken into account, which is that the Higgsing scalars with large charge $Z$ should be part of the string massless spectrum, which becomes an upper bound $k_{IR}\le k_0^2$, where $k_0$ is the level of the UV currents. Thus, for fixed $k_0$, $Z$ cannot be made parametrically large. The upper bound on the charges $Z$ leads to limitations on the size and structure of hierarchies in an iterated $U(1)$ clockwork mechanism.

    ↳ hep-thhep-phJHEP(2018)·41 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.