Thu·Jul 13, 2017Thursday·July 13, 2017

1. 01*

   Vacuum Stability in the Early Universe and the Backreaction of Classical Gravity

   Tommi Markkanen🇬🇧

   In the case of a metastable electroweak vacuum the quantum corrected effective potential plays a crucial role in the potential instability of the Standard Model. In the Early Universe, in particular during inflation and reheating, this instability can be triggered leading to catastrophic vacuum decay. We discuss how the large spacetime curvature of the Early Universe can be incorporated in the calculation and in many cases significantly modify the flat space prediction. The two key new elements are the unavoidable generation of the non-minimal coupling between the Higgs field and the scalar curvature of gravity and a curvature induced contribution to the running of the constants. For the minimal set up of the Standard Model and a decoupled inflation sector we show how a metastable vacuum can lead to very tight bounds for the non-minimal coupling. We also discuss a novel and very much related dark matter generation mechanism.

   hep-phastro-ph.COgr-qcPhil.Trans.Roy.Soc.Lond.A(2018)·7 citations
2. 02*

   $ZZ\gamma$ production in the NLO QCD+EW accuracy at the LHC

   Wang Yong🇨🇳 · Zhang Ren-You🇨🇳 · Ma Wen-Gan🇨🇳 · Li Xiao-Zhou🇨🇳 · Wang Shao-Ming🇨🇳 · Bi Huan-Yu🇨🇳

   In this paper we present the first study of the impact of the $\mathcal{O}(\alpha )$ EW correction to the $pp\to ZZ\gamma +X$ process at the CERN Large Hadron Collider (LHC). The subsequent $Z$-boson leptonic decays are considered at the leading order using the MadSpin method, which takes into account the spin-correlation and off-shell effects from the $Z$-boson decays. We provide numerical results of the integrated cross section and the kinematic distributions for this process. In coping with final-state photon-jet separation in the QCD real emission and photon-induced processes, we adopt both the Frixione isolated-photon plus jets algorithm and the phenomenological quark-to-photon fragmentation function method for comparison. We find that the next-to-leading order (NLO) EW correction to the $ZZ\gamma$ production can be sizeable and amounts to about $-7\%$ of the integrated cross section, and provides a non$-$negligible contribution to the kinematic distributions, particularly in the high energy region. We conclude that the NLO EW correction should be included in precision theoretical predictions in order to match future experimental accuracy.

   hep-phJ.Phys.G(2017)·7 citations
3. 03*

   An approach to the instanton effect in B system

   Noriaki Kitazawa🇯🇵 · Yuki Sakai🇯🇵

   We discuss the constraint on the size of QCD instanton effects in low-energy effective theory. Among various instanton effects in meson mass spectrum and dynamics, we concentrate on the instanton-induced masses of light quarks. The famous instanton-induced six-quark interaction, so-called 't Hooft vertex, could give non-perturbative quantum corrections to light quark masses. Many works have already been achieved to constrain the mass corrections in light meson system, or the system of pi, K, eta and eta', and now we know for a fact that the instanton-induced mass of up-quark is too small to realize the solution of the strong CP problem by vanishing current mass of up-quark. In this work we give a constraint on the instanton-induced mass correction to light quarks from the mass spectrum of heavy mesons, B+, B0, Bs and their anti-particles. To accomplish this, the complete second order chiral symmetry breaking terms are identified in heavy meson effective theory. We find that the strength of the constraint from heavy meson masses is at the same level of that from light mesons, and it would be made even stronger by more precise data from future B factories and lattice calculations.

   hep-phInt.J.Mod.Phys.A(2018)·1 citation
4. 04*

   Possible hadronic molecules composed of the doubly charmed baryon and nucleon

   Lu Meng🇨🇳 · Ning Li🇩🇪 · Shi-lin Zhu🇨🇳

   We perform a systematical investigation of the possible deuteron-like bound states with configuration ${\Xi }_{cc}N(\bar{N})$, where $N(\bar{N})$ denotes the nucleon (anti-nucleon), in the framework of the one-boson-exchange-potential model. In the spin-triplet sector we take into account both the ${}^3{S}_1$ and ${}^3{D}_1$ channels due to non-vanishing tensor force. There exist several candidates of the loosely bound molecular states for the ${\Xi }_{cc}N$ and ${\Xi }_{cc}\bar{N}$ systems, which lie below the threshold of ${\Lambda }_c{\Lambda }_c$ or ${\Lambda }_c{\bar{\Lambda }}_c$. We also investigate the possible loosely bound states with configurations ${\Lambda }_{c}N(\bar{N})$ and ${\Sigma }_{c}N(\bar{N})$. These molecular candidates may be searched for at Belle II and LHC in the near future.

   hep-phhep-exnucl-thEPJA(2018)·40 citations
5. 05*

   Vacuum Magnetic Birefringence Experiment as a probe of Dark Sector

   Xing Fan🇺🇸 · Shusei Kamioka🇯🇵 · Kimiko Yamashita🇯🇵 · Shoji Asai🇯🇵 · Akio Sugamoto🇯🇵

   Vacuum magnetic birefringence (VMB) is a nonlinear electromagnetic effect predicted by QED. In addition to the effect from QED, the effect also has a possibility to probe the dark sector. The effect predicted by QED is parity conservative, but the effect from the dark sector can induce parity violation. To pursue this possibility, we calculated the effect from the dark sector with the generalized Heisenberg-Euler effective Lagrangian that is applicable to parity-violating theories. Various dark sector models exist, among which the contribution of the dark sector neutrinos to the VMB experiment is examined. The contribution comes from the mixing of photon with the dark sector Z boson and violates parity, thus inducing a parity-violating electromagnetic interaction. If the polarization vector is denoted by $ϵ({\theta }_i)$ when its direction is rotated by an angle ${\theta }_i$ from the direction of the applied magnetic field, the change of the polarization from $ϵ(45^{\circ })$ to $ϵ(-45^{\circ })$ and vice versa are examined. The contribution from the dark sector modifies the magnitude of the polarization change, so it can be detected by measuring the magnitude precisely. In addition to the change in the magnitude, the dark sector also induces parity-violating effects. We also propose a new scheme to measure the effect of parity violation directly. By measuring the change of polarization from $ϵ(0^{\circ })$ to $ϵ(90^{\circ })$, and vice versa, with a ring Fabry-Pérot resonator, one can search for the effect directly. The signal that appears in this scheme is evidence of parity violation from beyond standard model theories.

   hep-phhep-exhep-thPTEP(2018)·4 citations
6. 06*

   Chiral Magnetic Effect in the Dirac-Heisenberg-Wigner formalism

   Dániel Berényi🇭🇺 · Péter Lévai🇭🇺

   In this paper the emergence of the Chiral Magnetic Effect (CME) and the related anomalous current is investigated using the real time Dirac-Heisenberg-Wigner formalism. This method is widely used for describing strong field physics and QED vacuum tunneling phenomena as well as pair production in heavy-ion collisions. We extend earlier investigations of the CME in constant flux tube configuration by considering time dependent fields. In this model we can follow the formation of axial charge separation, formation of axial current and then the emergence of the anomalous electric current. Qualitative results are shown for special field configurations that help to interpret the predictions of CME related effects in heavy-ion collisions at the RHIC Beam Energy Scan program.

   hep-phPLB(2018)·4 citations
7. 07*

   Unified Model of Chaotic Inflation and Dynamical Supersymmetry Breaking

   Keisuke Harigaya🇺🇸 · Kai Schmitz🇩🇪

   The large hierarchy between the Planck scale and the weak scale can be explained by the dynamical breaking of supersymmetry in strongly coupled gauge theories. Similarly, the hierarchy between the Planck scale and the energy scale of inflation may also originate from strong dynamics, which dynamically generate the inflaton potential. We present a model of the hidden sector which unifies these two ideas, i.e., in which the scales of inflation and supersymmetry breaking are provided by the dynamics of the same gauge group. The resultant inflation model is chaotic inflation with a fractional power-law potential in accord with the upper bound on the tensor-to-scalar ratio. The supersymmetry breaking scale can be much smaller than the inflation scale, so that the solution to the large hierarchy problem of the weak scale remains intact. As an intrinsic feature of our model, we find that the sgoldstino, which might disturb the inflationary dynamics, is automatically stabilized during inflation by dynamically generated corrections in the strongly coupled sector. This renders our model a field-theoretical realization of what is sometimes referred to as sgoldstino-less inflation.

   hep-phastro-ph.COhep-thPLB(2017)·10 citations
8. 08*

   Neutrino mass ordering and \mu-\tau reflection symmetry breaking

   Zhi-zhong Xing🇨🇳 · Jing-yu Zhu🇨🇳

   If the neutrino mass spectrum turns out to be m^{}_3 < m^{}_1 < m^{}_2, one may choose to relabel it as m^{\prime}_1 < m^{\prime}_2 < m^{\prime}_3 such that all the masses of fundamental fermions with the same electrical charges are in order. In this case the columns of the 3\times 3 lepton flavor mixing matrix U should be reordered accordingly, and the resulting pattern U^\prime may involve one or two large mixing angles in the standard parametrization or its variations. Since the Majorana neutrino mass matrix keeps unchanged in such a mass relabeling, a possible \mu-\tau reflection symmetry is respected in this connection and its breaking effects are model-independently constrained at the 3\sigma level by using current experimental data.

   hep-phhep-exCPC(2017)·30 citations
9. 09*

   Charmless $B_c\to VV$ decays in the QCD factorization approach

   Qin Chang🇨🇳 · Na Wang🇨🇳 · Junfeng Sun🇨🇳 · Lin Han🇨🇳

   In this paper, we studied the charmless $B_c\to VV$ ($V$ denotes the light ground $\mathrm{SU}(3)$ vector meson) decays within the framework of QCD factorization. In the evaluation, two different schemes for regulating the end-point divergence are adopted. One (scheme I) is to use parameterization model, which is usually employed in the QCD factorization approach; the other (scheme II) is based on the infrared finite gluon propagator of Cornwall prescription. It is found that, in the annihilation amplitudes, the end-point divergence appears only in the power-suppressed corrections related to the twist-3 distribution amplitudes of $V$-meson. The strength of annihilation amplitudes evaluated in scheme II is generally larger than the one in scheme I. Numerically, in the decay modes considered in this paper, the CKM-favored $B_c\to {\rho }^{-}\omega ,K^{\ast -}{K}^{\ast 0}$ decays have the relatively large branching fractions, $\sim \mathcal{O}(10^{-7})$, and hence are likely to be the first observed by the future experiments. In addition, all of the decay modes are dominated by the longitudinal polarization state; numerically, $f_L(B_c\to VV)\gtrsim 99\%$.

   hep-phJ.Phys.G(2017)·3 citations
10. 10*

    Thermal properties of the exotic $X(3872)$ state via QCD sum rule

    E. Veli Veliev🇹🇷 · S. Günaydin🇹🇷 · H. Sundu🇹🇷

    In this work we investigate the $X(3872)$ meson with quantum numbers $J^{PC}=1^{++}$ in the framework of the thermal QCD sum rules method. We use a diquark-antidiquark current with the corresponding quantum numbers and calculate the two-point correlation function including contributions of non-perturbative condensates up to six dimensions. Analysis of the obtained thermal sum rule allows us to study contributions of a medium to the mass and coupling constant of the $X(3872)$ resonance. Our numerical calculations demonstrate that the mass and the meson-current coupling constant are insensitive to the variation of temperature up to $T=110\sim MeV$ , however after this point; they start to fall by increasing the temperature. At deconfinement temperature, the meson-current coupling constants attain roughly to $34\%$ of the vacuum value.

    hep-phhep-exhep-lat2 citations
11. 11*

    Probing medium-induced jet splitting and energy loss in heavy-ion collisions

    Ning-Bo Chang🇨🇳 · Shanshan Cao🇺🇸 · Guang-You Qin🇨🇳

    The nuclear modification of jet splitting in relativistic heavy-ion collisions at RHIC and the LHC energies is studied based on the higher twist formalism. Assuming coherent energy loss for the two splitted subjets, a non-monotonic jet energy dependence is found for the nuclear modification of jet splitting function: strongest modification at intermediate jet energies whereas weaker modification for larger or smaller jet energies. Combined with the smaller size and lower density of the QGP medium at RHIC than at the LHC, this explains the CMS-STAR groomed jet puzzle -- strong nuclear modification of the momentum sharing $z_g$ distribution at the LHC whereas no obvious modification of the $z_g$ distribution at RHIC. In contrast, the observed nuclear modification pattern of the groomed jet $z_g$ distribution cannot be explained solely by independent energy loss of the two subjets. Our result may be tested in future measurements of groomed jets with lower jet energies at the LHC and larger jet energies at RHIC, for different angular separations between the two subjets.

    hep-phnucl-thPLB(2018)·73 citations
12. 12*

    Magnetized color superconducting quark matter under compact star conditions: Phase structure within the SU(2)f NJL model

    M. Coppola🇦🇷 · P. Allen🇦🇷 · A. G. Grunfeld🇦🇷 · N. N. Scoccola🇦🇷

    The properties of magnetized color superconducting cold dense quark matter under compact star conditions are investigated using a $SU(2{)}_f$ Nambu Jona-Lasinio (NJL)-type model in which the divergences are treated using a magnetic field independent regularization scheme in order to avoid unphysical oscillations. We study the phase diagram for several model parametrizations. The features of each phase are analyzed through the behavior of the chiral and superconducting condensates together with the different particle densities for increasing chemical potential or magnetic field. While confirming previous results derived for the zero magnetic field or isospin symmetric matter case, we show how the phases are modified in the presence of $\beta$-equilibrium as well as color and electric charge neutrality conditions.

    hep-phPRD(2017)·20 citations
13. 13*

    Exotic Doubly Charmed Ds0*(2317)D and Ds1*(2460)D* Molecules

    Mario Sanchez Sanchez🇫🇷 · Li-Sheng Geng🇨🇳 · Jun-Xu Lu🇨🇳 · Tetsuo Hyodo🇯🇵 · Manuel Pavon Valderrama🇨🇳

    The $D_{s0}^{\ast }(2317)D$ and $D_{s1}^{\ast }(2460)D^{\ast }$ heavy meson systems can exchange a kaon that is emitted in S-wave owing to the opposite intrinsic parity of the $D_{s0}^{\ast }$($D_{s1}^{\ast }$) and $D$($D^{\ast }$) mesons. As a consequence of the mass difference of the $D_{s0}^{\ast }$($D_{s1}^{\ast }$) and $D$($D^{\ast }$) mesons, the range of the kaon exchange potential will be significantly longer than expected, corresponding to an effective mass of about $200\mathrm{MeV}$. The potential will be very strong: the strength of the interaction is proportional to $(m_{D_{s0}}-m_D{)}^2/f_{\pi }^2$ and $(m_{D_{s1}}-m_{D^{\ast }}{)}^2/f_{\pi }^2$. This combination of range and strength almost guarantees the existence of $D_{s0}^{\ast }(2317)D$ and $D_{s1}^{\ast }(2460)D^{\ast }$ bound states with $J^P=0^{-}$ and $J^P=0^{-},2^{-}$ respectively. Concrete calculations indicate a binding energy of $5-15\mathrm{MeV}$ independently of $J^P$. The $D_{s0}^{\ast }(2317)D$ and $D_{s1}^{\ast }(2460)D^{\ast }$ molecules have manifestly exotic flavour quantum numbers: $C=2$, $S=1$ and $I=1/2$. We expect the existence of bottom counterparts composed of the $B{B}_{s0}$ and $B^{\ast }{B}_{s1}^{\ast }$ mesons, which will be more bound and have a richer spectrum that might include a shallow P-wave state and an excited S-wave state.

    hep-phhep-exhep-latnucl-thPRD(2018)·40 citations
14. 14*

    Collapsed Dark Matter Structures

    Matthew R. Buckley🇺🇸 · Anthony DiFranzo🇺🇸

    The distributions of dark matter and baryons in the Universe are known to be very different: the dark matter resides in extended halos, while a significant fraction of the baryons have radiated away much of their initial energy and fallen deep into the potential wells. This difference in morphology leads to the widely held conclusion that dark matter cannot cool and collapse on any scale. We revisit this assumption, and show that a simple model where dark matter is charged under a "dark electromagnetism" can allow dark matter to form gravitationally collapsed objects with characteristic mass scales much smaller than that of a Milky Way-type galaxy. Though the majority of the dark matter in spiral galaxies would remain in the halo, such a model opens the possibility that galaxies and their associated dark matter play host to a significant number of collapsed substructures. The observational signatures of such structures are not well explored, but potentially interesting.

    hep-phastro-ph.COPRL(2018)·85 citations
15. 15*

    Exploring extra dimensions through inflationary tensor modes

    Sang Hui Im🇩🇪 · Hans Peter Nilles🇩🇪 · Andreas Trautner🇩🇪

    Predictions of inflationary schemes can be influenced by the presence of extra dimensions. This could be of particular relevance for the spectrum of gravitational waves in models where the extra dimensions provide a brane-world solution to the hierarchy problem. Apart from models of large as well as exponentially warped extra dimensions, we analyze the size of tensor modes in the Linear Dilaton scheme recently revived in the discussion of the "clockwork mechanism". The results are model dependent, significantly enhanced tensor modes on one side and a suppression on the other. In some cases we are led to a scheme of "remote inflation", where the expansion is driven by energies at a hidden brane. In all cases where tensor modes are enhanced, the requirement of perturbativity of gravity leads to a stringent upper limit on the allowed Hubble rate during inflation.

    hep-phastro-ph.COgr-qchep-thJHEP(2018)·27 citations
16. 16*

    Impact of Resonance on Thermal Targets for Invisible Dark Photon Searches

    Jonathan L. Feng🇺🇸 · Jordan Smolinsky🇺🇸

    Dark photons in the MeV to GeV mass range are important targets for experimental searches. We consider the case where dark photons $A^{\prime }$ decay invisibly to hidden dark matter $X$ through $A^{\prime }\to XX$. For generic masses, proposed accelerator searches are projected to probe the thermal target region of parameter space, where the $X$ particles annihilate through $XX\to A^{\prime }\to \text{SM}$ in the early universe and freeze out with the correct relic density. However, if $m_{A^{\prime }}\approx 2m_X$, dark matter annihilation is resonantly enhanced, shifting the thermal target region to weaker couplings. For $\sim 10\%$ degeneracies, we find that the annihilation cross section is generically enhanced by four (two) orders of magnitude for scalar (pseudo-Dirac) dark matter. For such moderate degeneracies, the thermal target region drops to weak couplings beyond the reach of all proposed accelerator experiments in the scalar case and becomes extremely challenging in the pseudo-Dirac case. Proposed direct detection experiments can probe moderate degeneracies in the scalar case. For greater degeneracies, the effect of the resonance can be even more significant, and both scalar and pseudo-Dirac cases are beyond the reach of all proposed accelerator and direct detection experiments. For scalar dark matter, we find an absolute minimum that sets the ultimate experimental sensitivity required to probe the entire thermal target parameter space, but for pseudo-Dirac fermions, we find no such thermal target floor.

    hep-phastro-ph.COhep-exPRD(2017)·88 citations
17. 17*

    Note on gauge and gravitational anomalies of discrete $Z_N$ symmetries

    Pritibhajan Byakti🇮🇳 · Diptimoy Ghosh🇮🇱 · Tarun Sharma🇿🇦

    In this note, we discuss the consistency conditions which a discrete $Z_N$ symmetry should satisfy in order that it is not violated by gauge and gravitational instantons. As examples, we enlist all the $Z_N$ $\mathcal{R}$-symmetries as well as non-$\mathcal{R}$ $Z_N$ symmetries (N=2,3,4) in the minimally supersymmetric standard model (MSSM) that are free from gauge and gravitational anomalies. We show that there exists non-anomalous discrete symmetries that forbid Baryon number violation up to dimension 6 level (in superspace). We also observe that there exists no non-anomalous $Z_3$ $\mathcal{R}$-symmetry in the MSSM. Furthermore, we point out that in a theory with one Majorana spin 3/2 gravitino, a large class of $Z_4$ $\mathcal{R}$-symmetries are violated in the presence of Eguchi-Hanson (EH) gravitational instanton. This is also in general true for higher $Z_N$ $\mathcal{R}$-symmetries. We also notice that in 4 dimensional $\mathcal{N}=1$ supergravity, the global $U(1)$ $\mathcal{R}$-symmetry is always violated by the EH instanton irrespective of the matter content of the theory.

    hep-phhep-thJHEP(2018)·7 citations
18. 18*

    A superfield constraint for N=2 --> N=0 breaking

    E. Dudas🇫🇷 · S. Ferrara🇨🇭 · A. Sagnotti🇮🇹

    We identify a cubic holomorphic constraint that subtends the total breaking of N=2 supersymmetry in a vector multiplet and exhibit its microscopic origin. The new constraint leaves behind, at low energies, a vector and the two goldstini, in a non-linear Lagrangian that generalizes the N=2 Volkov-Akulov model.

    ↳ hep-thhep-phJHEP(2017)·22 citations
19. 19*

    Massive Black Holes from Dissipative Dark Matter

    Guido D'Amico🇨🇭 · Paolo Panci🇨🇭 · Alessandro Lupi🇫🇷 · Stefano Bovino🇩🇪 · Joseph Silk🇫🇷

    We show that a subdominant component of dissipative dark matter resembling the Standard Model can form many intermediate-mass black hole seeds during the first structure formation epoch. We also observe that, in the presence of this matter sector, the black holes will grow at a much faster rate with respect to the ordinary case. These facts can explain the observed abundance of supermassive black holes feeding high-redshift quasars. The scenario will have interesting observational consequences for dark substructures and gravitational wave production.

    ↳ astro-ph.COastro-ph.GAhep-phMNRAS(2018)·65 citations
20. 20*

    Inflation in a closed universe

    Bharat Ratra🇺🇸

    To derive a power spectrum for energy density inhomogeneities in a closed universe, we study a spatially-closed inflation-modified hot big bang model whose evolutionary history is divided into three epochs: an early slowly-rolling scalar field inflation epoch and the usual radiation and non-relativistic matter epochs. (For our purposes it is not necessary to consider a final dark energy dominated epoch.) We derive general solutions of the relativistic linear perturbation equations in each epoch. The constants of integration in the inflation epoch solutions are determined from de Sitter invariant quantum-mechanical initial conditions in the Lorentzian section of the inflating closed de Sitter space derived from Hawking's prescription that the quantum state of the universe only include field configurations that are regular on the Euclidean (de Sitter) sphere section. The constants of integration in the radiation and matter epoch solutions are determined from joining conditions derived by requiring that the linear perturbation equations remain nonsingular at the transitions between epochs. The matter epoch power spectrum of gauge-invariant energy density inhomogeneities is not a power law, and depends on spatial wavenumber in the way expected for a generalization to the closed model of the standard flat-space scale-invariant power spectrum. The power spectrum we derive appears to differ from a number of other closed inflation model power spectra derived assuming different (presumably non de Sitter invariant) initial conditions.

    ↳ astro-ph.COgr-qchep-phhep-thPRD(2017)·63 citations
21. 21*

    Planck 2015 constraints on the non-flat $\Lambda$CDM inflation model

    Junpei Ooba🇯🇵 · Bharat Ratra🇺🇸 · Naoshi Sugiyama🇯🇵

    We study Planck 2015 cosmic microwave background (CMB) anisotropy data using the energy density inhomogeneity power spectrum generated by quantum fluctuations during an early epoch of inflation in the non-flat $\Lambda$CDM model. Unlike earlier analyses of non-flat models, which assumed an inconsistent power-law power spectrum of energy density inhomogeneities, we find that the Planck 2015 data alone, and also in conjunction with baryon acoustic oscillation measurements, are reasonably well fit by a closed $\Lambda$CDM model in which spatial curvature contributes a few percent of the current cosmological energy density budget. In this model, the measured Hubble constant and non-relativistic matter density parameter are in good agreement with values determined using most other data. Depending on parameter values, the closed $\Lambda$CDM model has reduced power, relative to the tilted, spatially-flat $\Lambda$CDM case, and can partially alleviate the low multipole CMB temperature anisotropy deficit and can help partially reconcile the CMB anisotropy and weak lensing ${\sigma }_8$ constraints, at the expense of somewhat worsening the fit to higher multipole CMB temperature anisotropy data. Our results are interesting but tentative; a more thorough analysis is needed to properly gauge their significance.

    ↳ astro-ph.COgr-qchep-phhep-thApJ(2018)·113 citations
22. 22*

    Spins of primordial black holes formed in the matter-dominated phase of the Universe

    Tomohiro Harada🇯🇵 · Chul-Moon Yoo🇯🇵 · Kazunori Kohri🇯🇵 · Ken-Ichi Nakao🇯🇵

    Angular momentum plays very important roles in the formation of PBHs in the matter-dominated phase if it lasts sufficiently long. In fact, most collapsing masses are bounced back due to centrifugal force, since angular momentum significantly grows before collapse. As a consequence, most of the formed PBHs are rapidly rotating near the extreme value $a_{\ast }=1$, where $a_{\ast }$ is the nondimensional Kerr parameter at their formation. The smaller the density fluctuation ${\sigma }_H$ at horizon entry is, the stronger the tendency towards the extreme rotation. Combining the effect of angular momentum with that of anisotropy, we estimate the black hole production rate. We find that the production rate suffers from suppression dominantly due to angular momentum for a smaller value of ${\sigma }_H$, while due to anisotrpopy for a larger value of ${\sigma }_H$. We argue that matter domination significantly enhances the production of PBHs despite the suppression. If the matter-dominated phase does not last so long, the effect of the finite duration significantly suppresses PBH formation and weakens the tendency towards large spins. (abridged)

    ↳ gr-qcastro-ph.COastro-ph.HEhep-ph+1PRD(2017)·221 citations
23. 23*

    Collisionless shocks in self-interacting dark matter

    Matti Heikinheimo🇫🇮 · Martti Raidal🇪🇪 · Christian Spethmann🇪🇪 · Hardi Veermae🇪🇪

    Self-interacting dark matter has been proposed as a solution to small scale problems in cosmological structure formation, and hints of dark matter self scattering have been observed in mergers of galaxy clusters. One of the simplest models for self-interacting dark matter is a particle that is charged under dark electromagnetism, a new gauge interaction analogous to the usual electromagnetic force, but operating on the dark matter particle instead of the visible particles. In this case, the collisional behaviour of dark matter is primarily due to the formation of collisionless shocks, that should affect the distribution of DM in merging galaxy clusters. We evaluate the time and length scales of shock formation in cluster mergers, and discuss the implications for modelling charged dark matter in cosmological simulations.

    ↳ astro-ph.COhep-phphysics.plasm-phPlasma Phys.Control.Fusion(2018)·7 citations
24. 24*

    Tracking our Universe to de Sitter by a Horndeski scalar

    Cristiano Germani🇪🇸 · Prado Martin-Moruno🇪🇸

    Assuming both that our Universe is evolving into a de Sitter space and a vanishing cosmological constant, leaves only the option that the observed acceleration is provided by a "kinetic" energy of a scalar field. From an effective field theory point of view, the absence of Ostrogradsky instabilities restricts the choice to shift-symmetric Horndeski theories. Within these theories, we find the conditions for the existence of a de Sitter critical point in a universe filled by matter, radiation and a Horndeski scalar. Moreover, we show that this point is a universal attractor and we provide the tracking trajectory. Therefore, if a de Sitter fixed point exists within these models, our Universe will eventually evolve into a de Sitter space. As an example, we have discussed the case of the combined Galileon-Slotheon system, in which the Galileon is kinetically non-minimal coupled to the Einstein tensor. Interestingly, we have also found that the tracker trajectory of this system does not follow previous literature assumptions.

    ↳ gr-qcastro-ph.COhep-phhep-thPhys.Dark Univ.(2017)·14 citations
25. 25*

    TMDs of Spin-one Targets: Formalism and Covariant Calculations

    Yu Ninomiya🇯🇵 · Wolfgang Bentz🇯🇵 · Ian C. Cloët🇺🇸

    We present a covariant formulation and model calculations of transverse momentum-dependent quark distribution functions (TMDs) for spin-one hadrons. Emphasis is placed on a description of these 3-dimensional distribution functions which is independent of any constraints on the spin quantization axis. We apply our covariant spin description to all nine leading-twist time-reversal even $\rho$ meson TMDs in the framework provided by the Nambu--Jona-Lasinio model, incorporating important aspects of quark confinement via the infrared cut-off in the proper-time regularization scheme. In particular, the behavior of the 3-dimensional TMDs in a tensor polarized spin-one hadron are illustrated. Sum rules and positivity constraints are discussed in detail. Results of particular interest include the finding that the tensor polarized TMDs -- associated with spin-one hadrons -- are very sensitive to quark orbital angular momentum, and that the TMDs associated with the quark operator ${\gamma }^{+}{\mathbf{\gamma }}_T{\gamma }_5$ would vanish were it not for dynamical chiral symmetry breaking. In addition, we find that 44% of the $\rho$ meson's spin is carried by the orbital angular momentum of the quarks, and that the magnitude of the tensor polarized quark distribution function is about 30% of the unpolarized quark distribution. A qualitative comparison between our results for the tensor structure of a quark-antiquark bound state is made to previous experimental and theoretical results for the two-nucleon (deuteron) bound state.

    ↳ nucl-thhep-phPRC(2017)·51 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.