Fri·Apr 28, 2023Friday·April 28, 2023

1. 01*

   NLO + parton-shower generator for Wc production in the POWHEG BOX RES

   Silvia Ferrario Ravasio🇨🇭 · Carlo Oleari🇮🇹

   We present the implementation of a next-to-leading-order plus parton-shower event generator for the hadronic production of a heavy charm quark accompanied by a leptonically-decaying $W$ boson in the POWHEG BOX RES framework. We consider both signatures, i.e. $pp\to c{\ell }^{-}{\bar{\nu }}_{\ell }$ and $pp\to \bar{c}{\ell }^{+}{\nu }_{\ell }$, and we include exactly off-shell and spin-correlation effects, as well as off-diagonal Cabibbo-Kobayashi-Maskawa contributions. We present particle-level results, obtained interfacing our code with the Herwig7.2 and Pythia8.3 shower Monte Carlo event generators, including hadronization and underlying-event effects, and compare them against the data collected by the CMS Collaboration at $\sqrt{s}=13$ TeV.

   hep-phhep-exEPJC(2023)·10 citations
2. 02*

   An observation on Feynman diagrams with axial anomalous subgraphs in dimensional regularization with an anticommuting ${\gamma }_5$

   Long Chen🇨🇳

   Through the calculation of the matrix element of the singlet axial-current operator between the vacuum and a pair of gluons in dimensional regularization with an anticommuting ${\gamma }_5$ defined in a Kreimer-scheme variant, we find that additional renormalization counter-terms proportional to the Chern-Simons current operator are needed starting from $\mathcal{O}({\alpha }_s^2)$ in QCD. This is in contrast to the well-known purely multiplicative renormalization of the singlet axial-current operator defined with a non-anticommuting ${\gamma }_5$. Consequently, without introducing compensation terms in the form of additional renormalization, the Adler-Bell-Jackiw anomaly equation does not hold automatically in the bare form in this kind of schemes. We determine the corresponding (gauge-dependent) coefficient to $\mathcal{O}({\alpha }_s^3)$ in QCD, using a variant of the original Kreimer prescription which is implemented in our computation in terms of the standard cyclic trace together with a constructively-defined ${\gamma }_5$. Owing to the factorized form of these divergences, intimately related to the axial anomaly, we further performed a check, using concrete examples, that with ${\gamma }_5$ treated in this way, the axial-current operator needs no more additional renormalization in dimensional regularization but \textit{only} for non-anomalous amplitudes in a perturbatively renormalizable theory. To be complete, we provide a few additional ingredients needed for a proposed extension of the algorithmic procedure formulated in the above analysis to potential applications to a renormalizable anomaly-free chiral gauge theory, i.e.~the electroweak theory.

   hep-phhep-thJHEP(2023)·33 citations
3. 03*

   Low energy Eta-baryon interaction

   Marcelo G. L. Nogueira-Santos🇧🇷 · Celso C. Barros Jr🇧🇷

   The $\eta$-Baryon interactions at low energies are studied in a model based in effective chiral Lagragians that take into account baryons of spin 1/2 and spin 3/2 in the intermediate states. The interacting baryons to be considered in this work are $B=N,\Lambda ,\Sigma ,\Xi$. We calculate the expected total and differential cross sections, phase-shifts and polarizations in the center-of-mass frame of reference for each reaction.

   hep-phNPA(2023)·1 citation
4. 04*

   Dynamics of axion-neutral pseudoscalar mixing

   Shuyang Cao🇺🇸 · Wenjie Huang🇺🇸 · Daniel Boyanovsky🇺🇸

   Axions mix with neutral pions after the QCD phase transition through their common coupling to the radiation bath via a Chern-Simons term, as a consequence of the $U(1)$ anomaly. The non-equilibrium effective action that describes this mixing phenomenon is obtained to second order in the coupling of neutral pions and axions to photons. We show that a misaligned axion condensate induces a neutral pion condensate after the QCD phase transition. The dynamics of the pion condensate displays long and short time scales and decays on the longer time scale exhibiting a phenomenon akin to the ``purification'' in a Kaon beam. On the intermediate time scales the macroscopic pion condensate is proportional to a condensate of the abelian Chern-Simons term induced by the axion. We argue that the coupling to the common bath also induces kinetic mixing. We obtain the axion and pion populations, and these exhibit thermalization with the bath. The mutual coupling to the bath induces long-lived axion-neutral pion coherence independent of initial conditions. The framework of the effective action and many of the consequences are more broadly general and applicable to scalar or pseudoscalar particles mixing in a medium.

   hep-phastro-ph.COhep-thPRD(2023)·3 citations
5. 05*

   Sound velocity peak and conformality in isospin QCD

   Ryuji Chiba🇯🇵 · Toru Kojo🇯🇵

   We study zero temperature equations of state (EOS) in isospin QCD within a quark-meson model which is renormalizable and hence eliminates high density artifacts in models with the ultraviolet cutoff (e.g., NJL models). The model exhibits a crossover transition of pion condensations from the Bose-Einstein-Condensation regime at low density to the Bardeen-Cooper-Schrieffer regime at high density. The EOS stiffens quickly and approaches the quark matter regime at density significantly less than the density for pions to spatially overlap. The sound velocity develops a peak in the crossover region, and then gradually relaxes to the conformal value $1/3$ from above, in contrast to the perturbative QCD results which predicts the approach from below. In the context of QCD computations, this opposite trend is in part due to the lack of gluon exchanges in our model, and also due to the non-perturbative power corrections arising from the condensates. We argue that with large power corrections the trace anomaly can be negative. In quantitative level, our EOS is consistent with the lattice results in the BEC regime but begins to get stiffer at higher density. The sound velocity peak also appears at higher density. The BCS gap in our model is $\Delta \simeq 300$ MeV in the quark matter domain, and naive application of the BCS relation for the critical temperature $T_c\simeq 0.57\Delta$ yields the estimate $T_c\simeq 170$ MeV, in good agreement with the lattice data.

   hep-phhep-thnucl-thPRD(2024)·43 citations
6. 06*

   The strong vertices of charmed mesons $D$, $D^{\ast }$ and charmonia $J/\psi$, ${\eta }_c$

   Jie Lu🇨🇳 · Guo-Liang Yu🇨🇳 · Zhi-Gang Wang🇨🇳

   In this work, the strong coupling constants of the vertices $DDJ/\psi$, $D{D}^{\ast }J/\psi$, $D^{\ast }{D}^{\ast }J/\psi$, $D{D}^{\ast }{\eta }_c$ and $D^{\ast }{D}^{\ast }{\eta }_c$ are calculated within the framework of the QCD sum rules. For each vertex, we analyze the momentum dependence of the coupling constants by considering all possible off-shell cases. In these analyses, we consider the contributions of the vacuum condensate terms $⟨\overline{q}q⟩$, $⟨\overline{q}{g}_s\sigma Gq⟩$, $⟨g_s^2{G}^2⟩$, $⟨f^3{G}^3⟩$ and $⟨\overline{q}q⟩⟨g_s^2{G}^2⟩$. Then, the momentum dependent coupling constants are fitted into analytical functions $g(Q^2)$ and are extrapolated into time-like regions. The values of strong coupling constants are obtained by using on-shell conditions of the intermediate mesons($Q^2=-m^2$). The final results are as follows, $g_{DDJ/\psi }=5.01_{-0.16}^{+0.58}$, $g_{D{D}^{\ast }J/\psi }=3.55_{-0.21}^{+0.20}$GeV${}^{-1}$, $g_{D^{\ast }{D}^{\ast }J/\psi }=5.10_{-0.43}^{+0.59}$, $g_{D{D}^{\ast }{\eta }_c}=3.68_{-0.11}^{+0.39}$ and $g_{D^{\ast }{D}^{\ast }{\eta }_c}=4.87_{-0.40}^{+0.42}$GeV${}^{-1}$.

   hep-phEPJA(2023)·11 citations
7. 07*

   Baryogenesis from sphaleron decoupling

   Muzi Hong🇯🇵 · Kohei Kamada🇯🇵 · Jun'ichi Yokoyama🇯🇵

   The electroweak sphaleron process breaks the baryon number conservation within the realms of the Standard Model of particle physics (SM). Recently, it is pointed out that its decoupling may provide the out-of-equilibrium condition required for baryogenesis. In this paper, we study such a scenario taking into account the baryon-number wash-out effect of the sphaleron itself to improve the estimate. We clarify the amount of CP violation required for this scenario to explain the observed asymmetry.

   hep-phastro-ph.COPRD(2023)·15 citations
8. 08*

   Lepton flavor physics at ${\mu }^{+}{\mu }^{+}$ colliders

   Kåre Fridell🇯🇵 · Ryuichiro Kitano🇯🇵 · Ryoto Takai🇯🇵

   We discuss sensitivities to lepton flavor violating (and conserving) interactions at future muon colliders, especially at ${\mu }^{+}{\mu }^{+}$ colliders. Compared with the searches for rare decays of $\mu$ and $\tau$, we find that the TeV-scale future colliders have better sensitivities depending on the pattern of hierarchy in the flavor mixings. As an example, we study the case with the type-II seesaw model, where the flavor mixing parameters have direct relation to the neutrino mass matrix. At a ${\mu }^{+}{\mu }^{+}$ collider, the number of events of the ${\mu }^{+}{\mu }^{+}\to {\mu }^{+}{\tau }^{+}$ process can be larger than $\mathcal{O}(100)$ with the center of mass energy $\sqrt{s}=2$ TeV, and with an integrated luminosity $\mathcal{L}=1$ ab${}^{-1}$, while satisfying bounds from rare decays of $\mu$ and $\tau$. We discuss impacts of the overall mass scale of neutrinos as well as CP violating phases to the number of expected events.

   hep-phJHEP(2023)·36 citations
9. 09*

   Resonant probing spin-0 and spin-2 dark matter mediators with fixed target experiments

   I.V.Voronchikhin🇷🇺 · D.V.Kirpichnikov🇷🇺

   We discuss the mechanism to produce electron-specific dark matter mediators of spin-0 and spin-2 in the electron fixed target experiments such as NA64 and LDMX. The secondary positrons induced by the electromagnetic shower can produce the mediators via annihilation on atomic electrons. That mechanism, for some selected kinematics, results in the enhanced sensitivity with respect to the bounds derived by the bremsstrahlunglike emission of the mediator in the specific parameter space. We derive the corresponding experimental reach of the NA64 and LDMX.

   hep-phPRD(2023)·12 citations
10. 10*

    All the matrix elements of covariant tensor currents of massless particles in the covariant formulation

    Jaehoon Jeong🇰🇷

    We present an efficient algorithm for constructing all the matrix elements of covariant tensor currents of massless particles of arbitrary spins in the covariant formulation. The construction of matrix elements can be taken simply by assembling the basic matrix elements which are derived from the basic three-point vertices. We obtain the selection rules for the decay of an off-shell massive particle into two identical massless particles which are the generalization of the Landau-Yang (LY) theorem. After showing how to identify fully the discontinuity between the matrix elements for the spacelike and lightlike momentum transfers, we derive all the matrix elements of conserved tensor currents of massless particles including high spins, from which the Weinberg and Witten (WW) theorem is automatically extracted with additional limits on the particles.

    hep-ph0 citations
11. 11*

    Analysis of the decay $Y(4500)\to D^{\ast }{\bar{D}}^{\ast }\pi$ with the light-cone QCD sum rules

    Zhi-Gang Wang🇨🇳

    In this work, we tentatively assign the $Y(4500)$ as the $[uc{]}_{\tilde{A}}[\overline{uc}{]}_V+[uc{]}_V[\overline{uc}{]}_{\tilde{A}}+[dc{]}_{\tilde{A}}[\overline{dc}{]}_V+[dc{]}_V[\overline{dc}{]}_{\tilde{A}}$ tetraquark state with the quantum numbers $J^{PC}=1^{--}$, and study the three-body strong decay $Y(4500)\to D^{\ast -}{D}^{\ast 0}{\pi }^{+}$ with the light-cone QCD sum rules. It is the first time to use the light-cone QCD sum rules to calculate the four-hadron coupling constants, the approach can be extended to study other three-body strong decays directly and diagnose the $X$, $Y$ and $Z$ states.

    hep-phNPB(2023)·13 citations
12. 12*

    Exploring the flavor structure of quarks and leptons with reinforcement learning

    Satsuki Nishimura🇯🇵 · Coh Miyao🇯🇵 · Hajime Otsuka🇯🇵

    We propose a method to explore the flavor structure of quarks and leptons with reinforcement learning. As a concrete model, we utilize a basic value-based algorithm for models with $U(1)$ flavor symmetry. By training neural networks on the $U(1)$ charges of quarks and leptons, the agent finds 21 models to be consistent with experimentally measured masses and mixing angles of quarks and leptons. In particular, an intrinsic value of normal ordering tends to be larger than that of inverted ordering, and the normal ordering is well fitted with the current experimental data in contrast to the inverted ordering. A specific value of effective mass for the neutrinoless double beta decay and a sizable leptonic CP violation induced by an angular component of flavon field are predicted by autonomous behavior of the agent. Our finding results indicate that the reinforcement learning can be a new method for understanding the flavor structure.

    hep-phcs.LGhep-thJHEP(2020)·32 citations
13. 13*

    Accounting for plasma constituent mass effects in heavy fermion energy loss calculations in hot QED and QCD

    Marc Comadran🇪🇸 · Cristina Manuel🇪🇸 · Stefano Carignano🇪🇸

    We evaluate the collisional energy loss of a energetic fermion with mass $M$ propagating through a hot QED plasma with temperature $T$, including mass corrections, that is, keeping the mass $m$ of the fermion constituents of the plasma, assuming $m\ll T\ll M$. We use the bare theory to compute the contribution of hard momentum transfer collisions, and the Braaten-Pisarski resummed theory, amended with small mass corrections, for the contribution of low momentum transfer collisions, and compute the mass corrections at leading logarithmic accuracy in the regime where the energy of the heavy fermion obeys $E\ll M^2/T$. We use dimensional regularization to regulate all possible divergences in the computation. If the fermion mass is of order of the soft scale $eT$, where $e$ is the gauge coupling constant, the mass corrections are of the same order as pure perturbative corrections, while they can be substantial for larger values of $m$. We also evaluate the impact of this correction for a QCD plasma.

    hep-phPRD(2023)·6 citations
14. 14*

    Entropy from entangled parton states and high-energy scattering behavior

    Hans Gunter Dosch🇩🇪 · Guy F. de Teramond🇨🇷 · Stanley J. Brodsky🇺🇸

    The relation between the gluon density in a hadron and entanglement entropy can shed a new light on the high energy scattering behavior of hadrons. Using the holographic light-front QCD framework the growth above the classical geometric cross section is directly related to the increase of the internal quantum entropy from the entangled parton distribution in hadrons. A rather consistent picture emerges from the scale dependence of the Pomeron from the QCD evolution of the gluon distribution function $g(x,\mu )$, the rising of the integrated cross section in photoproduction of vector mesons, the deep inelastic scattering (DIS) experiments at HERA, hadron multiplicity and quantum entropy. We also point out a possible analogy between parton entanglement entropy and the black-hole entropy of Bekenstein and Hawking.

    hep-phhep-thPLB(2024)·14 citations
15. 15*

    The trouble with the minimal renormalizable SO(10) GUT

    Kateřina Jarkovská🇨🇿 · Michal Malinský🇨🇿 · Vasja Susič🇨🇿

    We scrutinize the physical viability of the minimal non-supersymmetric $\mathrm{SO}(10)$ GUT with the scalar sector $45\oplus 126\oplus {10}_{\mathbb{C}}$, in which the unified symmetry is broken by the former two representations, and a realistic Yukawa sector is supported by the last two. Alongside the known issue of a relatively low GUT scale (and thus overly fast proton decay) encountered in minimally fine-tuned scenarios, we identify a very general problem of the model: the inability to properly accommodate a Standard-Model-like low-energy Higgs doublet in the perturbative regime.

    hep-phPRD(2023)·11 citations
16. 16*

    Extraction of the Sivers function with deep neural networks

    I. P. Fernando🇺🇸 · D. Keller🇺🇸

    Deep Neural Networks (DNNs) are a powerful and flexible tool for information extraction and modeling. In this study, we use DNNs to extract the Sivers functions by globally fitting Semi- Inclusive Deep Inelastic Scattering (SIDIS) and Drell-Yan (DY) data. To make predictions of this Transverse Momentum-dependent Distribution (TMD), we construct a minimally biased model using data from COMPASS and HERMES. The resulting Sivers function model, constructed using SIDIS data, is also used to make predictions for DY kinematics specific to the valence and sea quarks, with careful consideration given to experimental errors, data sparsity, and complexity of phase space.

    hep-phPRD(2023)·17 citations
17. 17*

    Reduction to master integrals via intersection numbers and polynomial expansions

    Gaia Fontana🇨🇭 · Tiziano Peraro🇮🇹

    Intersection numbers are rational scalar products among functions that admit suitable integral representations, such as Feynman integrals. Using these scalar products, the decomposition of Feynman integrals into a basis of linearly independent master integrals is reduced to a projection. We present a new method for computing intersection numbers that only uses rational operations and does not require any integral transformation or change of basis. We achieve this by systematically employing the polynomial series expansion, namely the expansion of functions in powers of a polynomial. We also introduce a new prescription for choosing dual integrals, de facto removing the explicit dependence on additional analytic regulators in the computation of intersection numbers. We describe a proof-of-concept implementation of the algorithm over finite fields and its application to the decomposition of Feynman integrals at one and two loops.

    hep-phhep-thJHEP(2023)·49 citations
18. 18*

    Studying the behavior of the strong interaction constant at different energy scales

    T. Obikhod🇺🇦

    The character of the behavior of the RGE constant on a certain energy interval is studied and polynomial interpolation is carried out to obtain an analytic function describing the RGE constant in QCD. A graphical description of the nature of the dependence of the beta function and the interaction constant is carried out and it is shown that a good agreement with the theoretical predictions of the asymptotic freedom is observed only in the energy region of 3800-4000 GeV.

    hep-phhep-thProceedings of the 6th International scie…·0 citations
19. 19*

    Short-range baryon-baryon potentials in constituent quark model revisited

    Takayasu Sekihara🇯🇵 · Taishi Hashiguchi🇯🇵

    We revisit the short-range baryon-baryon potentials in the flavor SU(3) sector, using the constituent quark model. We employ the color Coulomb, linear confining, and color magnetic forces between two constituent quarks, and solve the three-quark Schrödinger equation using the Gaussian expansion method to evaluate the wave functions of the octet $(N,\Lambda ,\Sigma ,\Xi )$ and decuplet $(\Delta ,{\Sigma }^{\ast },{\Xi }^{\ast },\Omega )$ baryons. We then solve the six-quark equation using the resonating group method and systematically calculate equivalent local potentials for the $S$-wave two-baryon systems which reproduce the relative wave functions of two baryons in the resonating group method. As a result, we find that the flavor antidecuplet states with total spin $J=3$, namely, $\Delta \Delta$, $\Delta {\Sigma }^{\ast }$, $\Delta {\Xi }^{\ast }$-${\Sigma }^{\ast }{\Sigma }^{\ast }$, and $\Delta \Omega$-${\Sigma }^{\ast }{\Xi }^{\ast }$ systems, have attractive potentials sufficient to generate dibaryon bound states as hadronic molecules. In addition, the $N\Omega$ system with $J=2$ in coupled channels has a strong attraction and forms a bound state. We also make a comparison with the baryon-baryon potentials from lattice QCD simulations and try to understand the behavior of the potentials from lattice QCD simulations.

    ↳ nucl-thhep-lathep-phPRC(2023)·9 citations
20. 20*

    First study of reaction ${\Xi }^{0}n\to {\Xi }^{-}p$ using ${\Xi }^0$-nucleus scattering at an electron-positron collider

    BESIII Collaboration: M. Ablikim · M. N. Achasov · P. Adlarson · R. Aliberti · A. Amoroso · M. R. An · Q. An · Y. Bai · O. Bakina · I. Balossino · Y. Ban · V. Batozskaya and 605 other authors

    Using $(1.0087\pm 0.0044)\times 10^{10}$ $J/\psi$ events collected with the BESIII detector at the BEPCII storage ring, the process ${\Xi }^{0}n\to {\Xi }^{-}p$ is studied, where the ${\Xi }^0$ baryon is produced in the process $J/\psi \to {\Xi }^0{\bar{\Xi }}^0$ and the neutron is a component of the ${}^9\mathrm{Be}$, ${}^{12}\mathrm{C}$ and ${}^{197}\mathrm{Au}$ nuclei in the beam pipe. A clear signal is observed with a statistical significance of $7.1\sigma$. The cross section of the reaction ${\Xi }^0+{}^9\mathrm{Be}\to {\Xi }^{-}+p+{}^8\mathrm{Be}$ is determined to be $\sigma ({\Xi }^0+{}^9\mathrm{Be}\to {\Xi }^{-}+p+{}^8\mathrm{Be})=(22.1\pm 5.3_{\mathrm{stat}}\pm 4.5_{\mathrm{sys}})$ mb at the ${\Xi }^0$ momentum of $0.818$ GeV/$c$, where the first uncertainty is statistical and the second is systematic. No significant $H$-dibaryon signal is observed in the ${\Xi }^{-}p$ final state. This is the first study of hyperon-nucleon interactions in electron-positron collisions and opens up a new direction for such research.

    ↳ hep-exhep-phnucl-exnucl-thPRL(2023)·42 citations
21. 21*

    A bridge between trace anomaly and deconfinement phase transition

    Bing-Kai Sheng🇨🇳 · Yong-Liang Ma🇨🇳

    Inspired by the fact that both the dilaton potential encoding the trace anomalies of QCD and the Polyakov loop potential measuring the deconfinement phase transition can be expressed in the logarithmic forms, as well as the fact that the scale symmetry is expected to be restoring and colors are deconfined in extreme conditions such as high temperatures and/or densities, we conjecture a relation between the dilaton potential and the Polyakov loop potential. Explicitly, we start from the Coleman--Weinberg type potential of a real scalar field -- a dilaton or conformal compensator -- and make an ansatz of the relation between this scalar field and the Polyakov loop to obtain the Polyakov loop potential, which can be parameterized in Lattice QCD (LQCD) in the pure glue sector. We find that the coefficients of Polyakov potential fitted from Lattice data are automatically satisfied in this ansatz, the locations of deconfinement and scale restoration are locked to each other, and the first-order phase transition can be realized. Extensions to the low-energy effective quark models are also discussed. The conjectured relation may deepen our understanding of the evolution of the universe, the mechanism of electroweak symmetry breaking, the phase diagram of QCD matter, and the properties of neutron~stars.

    ↳ nucl-thhep-lathep-phSymmetry(2024)·3 citations
22. 22*

    Composite topological solitons consisting of domain walls, strings, and monopoles in $O(N)$ models

    Minoru Eto🇯🇵 · Yu Hamada🇯🇵 · Muneto Nitta🇯🇵

    We study various composites of global solitons consisting of domain walls, strings, and monopoles in linear $O(N)$ models with $N=2$ and $3$. Spontaneous symmetry breaking (SSB) of the $O(N)$ symmetry down to $O(N-1)$ results in the vacuum manifold $S^{N-1}$, together with a perturbed scalar potential in the presence of a small explicit symmetry breaking (ESB) interaction. The $O(2)$ model is equivalent to the axion model admitting topological global (axion) strings attached by $N_{\mathrm{DW}}$ domain walls. We point out for the $N_{\mathrm{DW}}=2$ case that the topological stability of the string with two domain walls is ensured by sequential SSBs $({\mathbb{Z}}_2{)}^2\to {\mathbb{Z}}_2\to 1$, where the first SSB occurs in the vacuum leading to the topological domain wall as a mother soliton, only inside which the second SSB occurs giving rise to a subsequent kink inside the mother wall. From the bulk viewpoint, this kink is identical to a global string as a daughter soliton. This observation can be naturally extended to the $O(3)$ model, where a global monopole as a daughter soliton appears as a kink in a mother string or as a vortex on a mother domain wall, depending on ESB interactions. In the most generic case, the stability of the composite system consisting of the monopole, string, and domain wall is understood by the SSB $({\mathbb{Z}}_2{)}^3\to ({\mathbb{Z}}_2{)}^2\to {\mathbb{Z}}_2\to 1$, in which the first SSB at the vacuum gives rise to the domain wall triggering the second one, so that the daughter string appears as a domain wall inside the mother wall triggering the third SSB, which leads to a granddaughter monopole as a kink inside the daughter vortex. We demonstrate numerical simulations for the dynamical evolution of the composite solitons.

    ↳ hep-thhep-phJHEP(2023)·10 citations
23. 23*

    Perturbative Correction to the Average Expansion Rate of Spacetimes with Perfect Fluids

    Vincent Comeau🇨🇦

    This paper discusses the leading-order correction induced by cosmological perturbations on the average expansion rate of an expanding spacetime, containing one or many perfect fluids. The calculation is carried out up to the second order in the perturbations, and is kept as general as possible. In particular, no approximation such as a long-wavelength or a short-wavelength limit is invoked, and all three types of perturbations (scalar, vector, and tensor) are considered. First, the average value of the expansion rate is computed over a three-dimensional space-like surface where the total density of the fluids is constant. Then, a formula is derived relating that average value to the one over any other surface, on which a different scalar property of the fluids is constant. Moreover, the general formulas giving the correction to the average expansion rate are applied, in particular, to the case of a spacetime containing a single fluid with a constant equation of state. The sign and the effective equation of state of the corresponding back-reaction effect in the first Friedmann equation are examined.

    ↳ gr-qcastro-ph.COhep-phhep-th4 citations
24. 24*

    Multi-field inflation with large scalar fluctuations: non-Gaussianity and perturbativity

    Laura Iacconi🇬🇧 · David J. Mulryne🇬🇧

    Recently multi-field inflation models that can produce large scalar fluctuations on small scales have drawn a lot of attention, primarily because they could lead to primordial black hole production and generation of large second-order gravitational waves. In this work, we focus on models where the scalar fields responsible for inflation live on a hyperbolic field space. In this case, geometrical destabilisation and non-geodesic motion are responsible for the peak in the scalar power spectrum. We present new results for scalar non-Gaussianity and discuss its dependence on the model's parameters. On scales around the peak, we typically find that the non-Gaussianity is large and close to local in form. We validate our results by employing two different numerical techniques, utilising the transport approach, based on full cosmological perturbation theory, and the $\delta N$ formalism, based on the separate universe approximation. We discuss implications of our results for the perturbativity of the underlying theory, focusing in particular on versions of these models with potentially relevant phenomenology at interferometer scales.

    ↳ astro-ph.COgr-qchep-phhep-thJCAP(2023)·48 citations
25. 25*

    Meron configurations in easy-plane chiral magnets

    David Bachmann · Michail Lianeris · Stavros Komineas

    We demonstrate the existence and study in detail the features of chiral bimerons which are static solutions in an easy-plane magnet with the Dzyaloshinskii-Moriya (DM) interaction. These are skyrmionic textures with an integer topological charge and they present essential analogies to the meron configurations introduced in the context of quark confinement in the O(3) nonlinear sigma-model. We employ a Moebius transformation to show that, for weak chirality, bimeron configurations approach Belavin-Polyakov (BP) solutions characterized by tightly bound vortex and antivortex parts of the same size. Stronger chirality induces different vortex and antivortex sizes and also a detachment of merons, suggesting the possibility for a topological phase transition. Exploiting the fact that bimerons of opposite topological charges may exist in the same material, we demonstrate numerically a mechanism to generate meron pairs.

    ↳ cond-mat.mes-hallhep-phhep-thPRB(2023)·2 citations
26. 26*

    Scalar polarization window in gravitational-wave signals

    Hiroki Takeda🇯🇵 · Yusuke Manita🇯🇵 · Hidetoshi Omiya🇯🇵 · Takahiro Tanaka🇯🇵

    Scalar polarization modes of gravitational waves, which are often introduced in the context of the viable extension of gravity, have been actively searched. However, couplings of the scalar modes to the matter are strongly constrained by the fifth-force experiments. Thus, the amplitude of scalar polarization in the observed gravitational-wave signal must be significantly suppressed compared to that of the tensor modes. Here, we discuss the implications of the experiments in the solar system on the detectability of scalar modes in gravitational waves from compact binary coalescences, taking into account the whole processes from the generation to the observation of gravitational waves. We first claim that the energy carried by the scalar modes at the generation is, at most, that of the tensor modes from the observed phase evolution of the inspiral gravitational waves. Next, we formulate general gravitational-wave propagation and point out that the energy flux hardly changes through propagation as long as the background changes slowly compared to the wavelength of the propagating waves. Finally, we show that the possible magnitude of scalar polarization modes detected by the ground-based gravitational-wave telescopes is already severely constrained by the existing gravity tests in the solar system.

    ↳ gr-qcastro-ph.COhep-phPTEP(2023)·11 citations
27. 27*

    Matter matters in moduli fixing and modular flavor symmetries

    Victor Knapp-Perez🇺🇸 · Xiang-Gan Liu🇺🇸 · Hans Peter Nilles🇩🇪 · Saul Ramos-Sanchez🇲🇽 · Michael Ratz🇺🇸

    Modular flavor symmetries provide us with a very compelling approach to the flavor problem. It has been argued that moduli values close to some special values like $\tau =i$ or $\tau =\omega$ provide us with the best fits to data. We point out that the presence of hidden "matter" fields, needed to uplift symmetric AdS vacua, gives rise to a dynamical mechanism that leads to such values of $\tau$.

    ↳ hep-thhep-phPLB(2023)·53 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.