Mon·Sep 27, 2021Monday·September 27, 2021

1. 01*

   Multicomponent scalar dark matter at high-intensity proton beam experiments

   Amalia Betancur🇨🇴 · Andrés Castillo🇨🇴 · Guillermo Palacio🇨🇴 · Juan Suarez🇨🇴

   We study a scalar dark matter (DM) model with two DM species coupled to the Standard Model (SM) particles via a sub-GeV dark photon. In this model, we find that DM conversion occurs through the dark photon and it plays a fundamental role in setting the observed relic abundance. Furthermore, the two DM candidates can be produced at fixed-target experiments a la Beam- Dump. Detailed predictions for signal and backgrounds are obtained with the help of MadDump and NuWro Montecarlo generators. We explore the potential reach on the sensitivity of DUNE near detector and SHiP experiment, and we find that portions of the parameter space will be within reach of the two experiments

   hep-phJ.Phys.G(2022)·3 citations
2. 02*

   Constraining Time Dependent Dark Matter Signals from the Sun

   Mohammadreza Zakeri🇨🇳 · Yu-Feng Zhou🇨🇳

   Dark matter (DM) particles captured by the Sun can produce high energy electrons outside the Sun through annihilating into meta-stable mediators. The corresponding cosmic-ray electron signals observed by the space-based experiments will be time dependent due to the orbital motion of the space-based detectors. The shape of this time dependence is predictable given the orbital information of the detectors. Since the high-energy CR electron (with energy E>100 GeV) fluxes are expected to be constant in time, non-observation of such time variation can be used to place upper limits on the DM annihilation cross section. We analyze the time dependence of dark matter cosmic-ray signals in three space-based experiments: AMS-02, DAMPE and CALET. Under the assumption that no time dependent signal is observed, we derive the 95% C.L. exclusion limits on the signal strength from the current data. We map our limits onto the parameter space of the dark photon model and find that the constraints are comparable with that derived from the supernova SN1987A.

   hep-phastro-ph.HEastro-ph.SRJCAP(2022)·5 citations
3. 03*

   Revealing pion and kaon structure via generalised parton distributions

   Khepani Raya🇨🇳 · Zhu-Fang Cui🇨🇳 · Lei Chang🇨🇳 · Jose-Manuel Morgado🇪🇸 · Craig D. Roberts🇨🇳 · Jose Rodriguez-Quintero🇪🇸

   Clear windows onto emergent hadron mass (EHM) and modulations thereof by Higgs boson interactions are provided by observable measures of pion and kaon structure, many of which are accessible via generalised parton distributions (GPDs). Beginning with algebraic GPD Ansaetze, constrained entirely by hadron-scale $\pi$ and $K$ valence-parton distribution functions (DFs), in whose forms both EHM and Higgs boson influences are manifest, numerous illustrations are provided. They include the properties of electromagnetic form factors, impact parameter space GPDs, gravitational form factors and associated pressure profiles, and the character and consequences of all-orders evolution. The analyses predict that mass-squared gravitational form factors are stiffer than electromagnetic form factors; reveal that $K$ pressure profiles are tighter than $\pi$ profiles, with both mesons sustaining near-core pressures at magnitudes similar to that expected at the core of neutron stars; deliver parameter-free predictions for $\pi$ and $K$ valence, glue, and sea GPDs at the resolving scale $\zeta =2$GeV; and predict that at this scale the fraction of meson mass-squared carried by glue and sea combined matches that lodged with the valence degrees-of-freedom, with a similar statement holding for mass-squared radii.

   hep-phhep-exhep-latnucl-ex+1CPC(2022)·83 citations
4. 04*

   Signals of quark combination at hadronization in $pp$ collisions at $\sqrt{s}=200$ GeV

   Jun Song🇨🇳 · Hai-hong Li🇨🇳 · Feng-lan Shao🇨🇳

   We find signals of quark combination at hadronization from the experimental data of $p_T$ spectra of hadrons at mid-rapidity in $pp$ collisions at $\sqrt{s}=200$ GeV. The first is the constituent quark number scaling property for $p_T$ spectra of ${\Omega }^{-}$ and $\varphi$ and that for $p_T$ spectra of $p$ and ${\rho }^0$. The second is that $p_T$ spectra of $\Lambda$, ${\Xi }^{-}$, and $K^{\ast 0}$ can be self-consistently described using the spectrum of strange quarks from $\varphi$ data and that of up/down quarks from $p$ data in the equal-velocity combination mechanism. The third is that experimental data for $p_T$ spectrum of $D^{\ast +}$ are also well described using the spectrum of up/down quarks from $p$ data and that of charm quarks from perturbative QCD calculations. These results indicate a similarity between hadron production in $pp$ collisions at $\sqrt{s}=200$ GeV and that at LHC energies. We predict $p_T$ spectra of single-charm hadrons and their spectrum ratios. We suggest systematic measurements in $pp$ collisions at $\sqrt{s}=200$ GeV in future so as to better understand the property of small parton system created in $pp$ collisions at different collision energies.

   hep-phPRD(2022)·4 citations
5. 05*

   Total decay width of $H\to gg$ using the infinite-order scale-setting approach based on the intrinsic conformality

   Chu-Tian Gao🇨🇳 · Xing-Gang Wu🇨🇳 · Xu-Dong Huang🇨🇳 · Jun Zeng🇨🇳

   We make a detailed study on the properties of the total decay width of Higgs decay channel $H\to gg$ up to ${\alpha }_s^6$-order QCD corrections by using the newly suggested infinite-order scale-setting approach, which is based on the ideas of both the principle of maximum conformality and the intrinsic conformality. This approach is called as the PMC${}_{\infty }$ approach. By using the PMC${}_{\infty }$ approach, we observe that the conventional renormalization scale ambiguity in perturbative QCD calculation is eliminated and the residual scale dependence due to unknown higher-order terms can also be highly suppressed. We then obtain an accurate perturbative QCD prediction on the total decay width, e.g. $\Gamma (H\to gg){|}_{\mathrm{PM}{\mathrm{C}}_{\infty }}=336.42_{-6.92}^{+7.01}$ KeV, where the errors are squared averages of those from all the mentioned error sources.

   hep-phCPC(2022)·5 citations
6. 06*

   Energy-momentum tensor in QCD: nucleon mass decomposition and mechanical equilibrium

   Cédric Lorcé🇫🇷 · Andreas Metz🇺🇸 · Barbara Pasquini🇮🇹 · Simone Rodini🇮🇹

   We review and examine in detail recent developments regarding the question of the nucleon mass decomposition. We discuss in particular the virial theorem in quantum field theory and its implications for the nucleon mass decomposition and mechanical equilibrium. We reconsider the renormalization of the QCD energy-momentum tensor in minimal-subtraction-type schemes and the physical interpretation of its components, as well as the role played by the trace anomaly and Poincaré symmetry. We also study the concept of "quantum anomalous energy" proposed in some works as a new contribution to the nucleon mass. Examining the various arguments, we conclude that the quantum anomalous energy is not a genuine contribution to the mass sum rule, as a consequence of translation symmetry.

   hep-phnucl-thJHEP(2021)·89 citations
7. 07*

   Boosted decision trees in the era of new physics: a smuon analysis case study

   Alan S. Cornell🇿🇦 · Wesley Doorsamy🇿🇦 · Benjamin Fuks🇫🇷 · Gerhard Harmsen🇿🇦 · Lara Mason🇿🇦

   Machine learning algorithms are growing increasingly popular in particle physics analyses, where they are used for their ability to solve difficult classification and regression problems. While the tools are very powerful, they may often be under- or mis-utilised. In the following, we investigate the use of gradient boosting techniques as applicable to a generic particle physics problem. We use as an example a Beyond the Standard Model smuon collider analysis which applies to both current and future hadron colliders, and we compare our results to a traditional cut-and-count approach. In particular, we interrogate the use of metrics in imbalanced datasets which are characteristic of high energy physics problems, offering an alternative to the widely used area under the curve (auc) metric through a novel use of the F-score metric. We present an in-depth comparison of feature selection and investigation using a principal component analysis, Shapley values, and feature permutation methods in a way which we hope will be widely applicable to future particle physics analyses. Moreover, we show that a machine learning model can extend the 95% confidence level exclusions obtained in a traditional cut-and-count analysis, while potentially bypassing the need for complicated feature selections. Finally, we discuss the possibility of constructing a general machine learning model which is applicable to probe a two-dimensional mass plane.

   hep-phhep-exphysics.comp-phJHEP(2022)·40 citations
8. 08*

   Bottom-flavored inclusive emissions in the variable-flavor number scheme: A high-energy analysis

   Francesco Giovanni Celiberto🇮🇹 · Michael Fucilla🇮🇹 · Dmitry Yu. Ivanov🇷🇺 · Mohammed M.A. Mohammed🇮🇹 · Alessandro Papa🇮🇹

   We propose the inclusive semi-hard production, in proton-proton collisions, of two bottom-flavored hadrons, as well as of a single bottom-flavored hadron accompanied by a light jet, as novel channels for the manifestation of stabilization effects of the high-energy resummation under next-to-leading-order corrections. Our formalism relies on a hybrid high-energy and collinear factorization, where the BFKL resummation of leading and next-to-leading energy logarithms is used together with collinear factorization. We present results for cross sections and azimuthal correlations differential in rapidity, which are widely recognized as standard observables where to hunt for distinctive signals of the BFKL dynamics. We propose the study of double differential distributions in the transverse momenta of final-state particles as a common basis to investigate the interplay of different kinds of resummation mechanisms.

   hep-phPRD(2021)·75 citations
9. 09*

   Four-pomeron vertex

   M.A.Braun🇷🇺

   The four-pomeron vertex is studied in the perturbative QCD. Its dominating terms of the leading (zeroth and first) orders in the coupling constant and subdominant in the number of colors are constructed. The vertex consists of two terms, one with a derivative in rapidity ${\text{pd}}_y$ and the other with the BFKL interaction between pomerons. The corresponding part of the action and equations of motion are found. The iterative solution of the latter is possible only for rapidities smaller than 2 and quite large coupling constant ${\alpha }_s$, of the order or greater than unity, when the quadruple pomeron interaction is relatively small. Also iteration of the part with ${\text{pd}}_y$ is unstable in the infrared region and compels to introduce an infrared cut. The variational approach with simple trying functions allows to find the minimum of the action at ${\alpha }_s$ of the order 0.2 and rapidities up to 25. Numerical estimates for O-O collisions show that actually the influence of the quadruple pomeron interaction turns out to be rather small.

   hep-phEPJC(2021)·0 citations
10. 10*

    Conversions of propagation eigenstates of supernova neutrinos by atomic electrons

    Motohiko Kusakabe🇨🇳

    Electron number densities in stars and the Earth are inhomogeneous because of atomic electrons. The large inhomogeneities on atomic-scale tend to form at tops of respective layers of stars, and 1s electrons of O locally produce weak potentials higher than that of the high MSW resonance. Then, supernova neutrinos experience vast numbers of non-adiabatic transitions. This inhomogeneous electron potential generates finite amplitudes of all three propagation eigenstates, and wave packets effectively separate. Then, spectral differences between three flavors significantly diminishes after propagation.

    hep-phastro-ph.HEastro-ph.SR1 citation
11. 11*

    A theory vade mecum for PSI experiments

    Gilberto Colangelo🇨🇭 · Franziska Hagelstein🇨🇭 · Adrian Signer🇨🇭 · Peter Stoffer🇦🇹

    This article gives a compact introduction and overview of the theory underlying the experiments described in the rest of this review.

    hep-phhep-exnucl-thSciPost Phys.Proc.(2021)·4 citations
12. 12*

    Accelerating Monte Carlo event generation -- rejection sampling using neural network event-weight estimates

    Katharina Danziger🇩🇪 · Timo Janßen🇩🇪 · Steffen Schumann🇩🇪 · Frank Siegert🇩🇪

    The generation of unit-weight events for complex scattering processes presents a severe challenge to modern Monte Carlo event generators. Even when using sophisticated phase-space sampling techniques adapted to the underlying transition matrix elements, the efficiency for generating unit-weight events from weighted samples can become a limiting factor in practical applications. Here we present a novel two-staged unweighting procedure that makes use of a neural-network surrogate for the full event weight. The algorithm can significantly accelerate the unweighting process, while it still guarantees unbiased sampling from the correct target distribution. We apply, validate and benchmark the new approach in high-multiplicity LHC production processes, including $Z/W$+4 jets and $t\bar{t}$+3 jets, where we find speed-up factors up to ten.

    hep-phhep-exSciPost Phys.(2022)·74 citations
13. 13*

    An alternative scheme for effective range corrections in pionless EFT

    M. Ebert🇩🇪 · H.-W. Hammer🇩🇪 · A. Rusetsky🇩🇪

    We discuss an alternative scheme for including effective range corrections in pionless effective field theory. The standard approach treats range terms as perturbative insertions in the T -matrix. In a finite volume this scheme can lead to singular behavior close to the unperturbed energies. We consider an alternative scheme that resums the effective range but expands the spurious pole of the T -matrix created by this resummation. We test this alternative expansion for several model potentials and observe good convergence.

    hep-phhep-latnucl-thEPJA(2021)·16 citations
14. 14*

    Next-to-leading order QCD corrections to diphoton-plus-jet production through gluon fusion at the LHC

    Simon Badger🇮🇹 · Thomas Gehrmann🇨🇭 · Matteo Marcoli🇨🇭 · Ryan Moodie🇬🇧

    We compute the next-to-leading order (NLO) QCD corrections to the gluon-fusion subprocess of diphoton-plus-jet production at the LHC. We compute fully differential distributions by combining two-loop virtual corrections with one-loop real radiation using antenna subtraction to cancel infrared divergences. We observe significant corrections at NLO which demonstrate the importance of combining these corrections with the quark-induced diphoton-plus-jet channel at next-to-next-to-leading order (NNLO).

    hep-phPLB(2022)·51 citations
15. 15*

    Qualitative analysis of proton inelastic scattering for diquark searching

    Vladimir V. Bytev🇷🇺 · Stepan. S. Shimanskiy🇷🇺

    In this paper we discuss exclusive reactions which analysis can be used to receive direct indication of diquark existence. We make estimations of diquark scattering process measurement in inelastic proton-proton collisions. It was shown that putting special restrictions over kinematics and particles in final state of process it will be possible to enhance potential diquark contribution to scattering up to $10^4$. We put qualitative characteristics of process with diquark and ways to distinguish it from quark scattering in model-independent way.

    hep-phPhys.Atom.Nucl.(2022)·1 citation
16. 16*

    Anomalous diffusion in QCD matter

    Paul Caucal🇺🇸 · Yacine Mehtar-Tani🇺🇸

    We study the effects of quantum corrections on transverse momentum broadening of a fast parton passing through dense QCD matter. We show that, at leading logarithmic accuracy the broadening distribution tends at late times or equivalently for large system sizes $L$ to a universal distribution that only depends on a single scaling variable $k_{\perp }^2/Q_s^2$ where the typical transverse momentum scale increases with time as $\ln Q_s^2\simeq (1+2\beta )\ln L-\frac{3}{2}(1+\beta )\ln \ln L$ up to non-universal terms, with an anomalous dimension $\beta \sim \sqrt{{\alpha }_s}$. This property is analogous to geometric scaling of gluon distributions in the saturation regime and traveling waves solutions to reaction-diffusion processes. We note that since $\beta >0$ the process is super-diffusive, which is also reflected at large transverse momentum where the scaling distribution exhibits a heavy tail $k_{\perp }^{4-2\beta }$ akin to Lévy random walks.

    hep-phcond-mat.stat-mechnucl-thPRD(2022)·29 citations
17. 17*

    Determination of the rapidity evolution kernel from Drell-Yan data at low transverse momenta

    F. Hautmann🇧🇪 · I. Scimemi🇪🇸 · A. Vladimirov🇩🇪

    We report recent results on the extraction of the rapidity evolution kernel for Sudakov processes from experimental measurements of Drell-Yan (DY) transverse momentum distributions. We discuss the role of high-precision Large Hadron Collider (LHC) data, and illustrate the interplay of this analysis with transverse momentum dependent and collinear parton density functions.

    hep-phSciPost Phys.Proc.(2022)·11 citations
18. 18*

    Universal Inverse seesaw mechanism as a source of the SM fermion mass hierarchy

    A. E. Cárcamo Hernández🇨🇱 · D. T. Huong🇻🇳 · Ivan Schmidt🇨🇱

    We build a renormalizable theory where the inverse seesaw mechanism explains the pattern of SM fermion masses. To the best of our knowledge, our model corresponds to the first implementation of the inverse seesaw mechanism for the charged fermion sector. In our theory, the inverse seesaw mechanism is implemented at the tree and one-loop levels in order to generate the masses for the second and first families of the SM charged fermions, respectively. The third family of SM charged fermions obtain tree-level masses from the Higgs doublets ${\varphi }_1$ (for the top quark) and ${\varphi }_2$ (for the bottom quark and tau lepton). The masses of the active light neutrinos are generated from a two-loop level inverse seesaw mechanism. Our model successfully explains the observed SM fermion mass hierarchy, the tiny masses of the active light neutrinos, contains the necessary means for efficient leptogenesis and is in accordance with the constraints resulting from meson oscillations, as well as with the measured values of the observed dark matter relic density and of the muon and electron anomalous magnetic moments.

    hep-phEPJC(2022)·25 citations
19. 19*

    The ChPT: top-down and bottom-up

    Karol Kampf🇨🇿

    In this work, higher-derivative corrections of the non-linear sigma model of both even and odd intrinsic-parity sectors are systematically studied, focusing on ordered amplitudes of flavor scalars in massless limit. It should correspond to a theory known as Chiral perturbation theory (ChPT) without external sources and with only single-trace operators. We briefly overview its formal development and apply new S-matrix methods to its amplitude constructions. The bottom-up analysis of the tree-level amplitudes of different orders and multiplicities focuses on the formal structure of general ChPT. Possible theoretical simplifications based on the Kleiss-Kuijf and Bern-Carrasco-Johansson relations are presented. Finally, in the same context, the comparison with the so-called Z-function, which is connected with string theory, is also discussed.

    ↳ hep-thhep-phJHEP(2021)·17 citations
20. 20*

    Microphysical manifestations of viscosity and consequences for anisotropies in the very early universe

    Chandrima Ganguly🇬🇧 · Jerome Quintin🇩🇪

    It has been known that a non-perfect fluid that accounts for dissipative viscous effects can evade a highly anisotropic chaotic mixmaster approach to a singularity. Viscosity is often simply parameterised in this context, so it remains unclear whether isotropisation can really occur in physically motivated contexts. We present a few examples of microphysical manifestations of viscosity in fluids that interact either gravitationally or, for a scalar field for instance, through a self-coupling term in the potential. In each case, we derive the viscosity coefficient and comment on the applicability of the approximations involved when dealing with dissipative non-perfect fluids. Upon embedding the fluids in a cosmological context, we then show the extent to which these models allow for isotropisation of the universe in the approach to a singularity. We first do this in the context of expansion anisotropy only, i.e., in the case of a Bianchi type-I universe. We then include anisotropic 3-curvature modelled by the Bianchi type-IX metric. It is found that a self-interacting scalar field at finite temperature allows for efficient isotropisation, whether in a Bianchi type-I or type-IX spacetime, although the model is not tractable all the way to a singularity. Mixmaster chaotic behaviour, which is well known to arise in anisotropic models including anisotropic 3-curvature, is found to be suppressed in the latter case as well. We find that the only model permitting an isotropic singularity is that of a dense gas of black holes.

    ↳ gr-qcastro-ph.COhep-phhep-thPRD(2022)·26 citations
21. 21*

    Exploring the ${\Sigma }^{+}p$ interaction by measurements of the correlation function

    J. Haidenbauer🇩🇪 · U.-G. Meißner🇩🇪

    The spin-dependent components of the fundamental hyperon-nucleon interactions are largely unknown. We show that under reasonable assumptions, a measurement of the ${\Sigma }^{+}p$ correlation function in high-energy proton-proton or heavy-ion collisions combined with cross section data allows to separate the singlet and the triplet $S$-wave contributions.

    ↳ nucl-thhep-exhep-phnucl-exPLB(2022)·20 citations
22. 22*

    Viable Intermediate Inflation in the Mimetic DBI Model

    Narges Rashidi🇮🇷 · Kourosh Nozari🇮🇷

    We study the intermediate inflation in the mimetic Dirac-Born-Infeld model. By considering the scale factor as $a=a_0\exp (b{t}^{\beta })$, we show that in some ranges of the intermediate parameters $b$ and $\beta$, the model is free of the ghost and gradient instabilities. We study the scalar spectral index, tensor spectral index, and the tensor-to-scalar ratio in this model and compare the results with Planck2018 TT, TE, EE+lowE+lensing +BAO +BK14 data at $68\%$ and $95\%$ CL. In this regard, we find some constraints on the intermediate parameters that lead to the observationally viable values of the perturbation parameters. We also seek the non-gaussian features of the primordial perturbations in the equilateral configuration. By performing the numerical analysis on the nonlinearity parameter in this configuration, we show that the amplitude of the non-gaussianity in the intermediate mimetic DBI model is predicted to be in the range $-16.7<f^{equil}<-12.5$. We show that, with $0<b\le 10$ and $0.345<\beta <0.387$, we have an instabilities-free intermediate mimetic DBI model that gives the observationally viable perturbation and non-gaussianity parameters.

    ↳ astro-ph.COgr-qchep-phhep-thEPJC(2021)·2 citations
23. 23*

    Phonon emission by acoustic black holes

    Massimo Mannarelli🇮🇹 · Dario Grasso🇮🇹 · Silvia Trabucco🇮🇹 · Maria Luisa Chiofalo🇮🇹

    We present a novel interpretation of the Hawking temperature of acoustic holes, the hydrodynamic analogue of standard black holes, by connecting the geometrical properties of the horizon with the distribution function of the spontaneously generated phonons. Using covariant kinetic theory to describe the phonon gas emitted by the acoustic hole, we obtain the correct expression of the Hawking temperature by equating the entropy loss of the acoustic horizon with the entropy gain of the phonon gas. In doing this, we assume that the entropy of the acoustic hole is proportional to the area of the horizon, as in standard black holes. Since our method only depends on the geometrical properties of the acoustic horizon and on the statistical properties of the phonon gas, it is well suited to be extended to standard black holes and to out-of-equilibrium systems.

    ↳ gr-qchep-phhep-th6 citations
24. 24*

    Pseudogauge dependence of the spin polarization and of the axial vortical effect

    M. Buzzegoli🇺🇸

    The mean spin polarization vector of spin 1/2 particles in a relativistic fluid at local thermal equilibrium (LTE) in different pseudogauges (PGs), i.e., with different choices for the decomposition of orbital and spin angular momentum, is obtained. The spin polarization obtained in the canonical PG differs from the one obtained in the Belinfante PG. It is found that this difference can not be written by replacing the thermal vorticity with the spin potential in the usual polarization formula. Other PG choices affect the contribution of thermal shear to the spin polarization. Therefore, the choice of a PG affects the predictions for the polarization measured in heavy-ion collisions. In general, it is shown that the Wigner function of a noninteracting Dirac field at LTE is affected by the PG transformations. Explicit expressions of the mean axial current are also calculated and it is found that even the axial vortical effect conductivity depends on the PG.

    ↳ nucl-thhep-phPRC(2022)·51 citations
25. 25*

    Running vacuum interacting with dark matter or with running gravitational coupling. Phenomenological implications

    Joan Sola Peracaula🇪🇸

    The cosmological term, $\Lambda$, in Einstein's equations is an essential ingredient of the `concordance' $\Lambda$CDM model of cosmology. In this mini-review presentation, we assess the possibility that $\Lambda$ can be a dynamical quantity, more specifically a `running quantity' in quantum field theory in curved spacetime. A great deal of phenomenological works have shown in the last few years that this option (sometimes accompanied with a running gravitational coupling) may cure some of the tensions afflicting the $\Lambda$CDM. The `running vacuum models' (RVM's) are characterized by the vacuum energy density, ${\rho }_{\mathrm{vac}}$, being a series of (even) powers of the Hubble rate and its time derivatives. Here we describe the technical quantum field theoretical origin of the RVM structure in FLRW spacetime, which goes well-beyond the original semi-qualitative renormalization group arguments. In particular, we compute the renormalized energy-momentum tensor using the adiabatic regularization procedure and show that it leads to the RVM form. In other words, we find that the renormalized vacuum energy density, ${\rho }_{vac}(H)$ evolves as a (constant) additive term plus a leading dynamical components $\mathcal{O}(H^2)$. There are also $\mathcal{O}(H^4)$ contributions, which can be relevant for the early universe. Remarkably enough, the renormalized ${\rho }_{\mathrm{vac}}(H)$ does not exhibit dangerous terms proportional to the quartic power of the masses ($\sim m^4$) of the fields. It is well-known that these terms have been the main source of trouble since they are responsible for the extreme fine tuning and ultimately for the cosmological constant problem. In this context, the current ${\rho }_{vac}(H)$ is dominated by a constant term, as it should be, but it acquires a mild dynamical component $\sim \nu H^2$ ($|\nu |\ll 1$) which makes the RVM to mimic quintessence.

    ↳ gr-qcastro-ph.COhep-phhep-th5 citations
26. 26*

    Notes on symmetries in particle physics

    Akash Jain🇨🇦

    These are introductory notes on symmetries in quantum field theory and how they apply to particle physics. The notes cover the fundamentals of group theory, their representations, Lie groups, and Lie algebras, along with an elaborate discussion of the representations of SU(N), Lorentz, and Poincare groups and their respective algebras. We spend a lot of time on the realisation of these symmetry groups in quantum field theory, as both global and gauge symmetries, as well as their spontaneous breaking and the Higgs mechanism. In the end, we culminate all the lessons from the course to enumerate the symmetries and field content of the Standard Model of particle physics and write down the Standard Model Lagrangian. Special consideration is given to how the weak-force gauge bosons and the matter fields obtain their mass via the Higgs mechanism.

    ↳ hep-thhep-phmath-phmath.MP3 citations
27. 27*

    Cosmological Implications of Axion-Matter Couplings

    Daniel Green🇺🇸 · Yi Guo🇺🇸 · Benjamin Wallisch🇺🇸

    Axions and other light particles appear ubiquitously in physics beyond the Standard Model, with a variety of possible couplings to ordinary matter. Cosmology offers a unique probe of these particles as they can thermalize in the hot environment of the early universe for any such coupling. For sub-MeV particles, their entropy must leave a measurable cosmological signal, usually via the effective number of relativistic particles, $N_{\mathrm{eff}}$. In this paper, we will revisit the cosmological constraints on the couplings of axions and other pseudo-Nambu-Goldstone bosons to Standard Model fermions from thermalization below the electroweak scale, where these couplings are marginal and give contributions to the radiation density of $\Delta N_{\mathrm{eff}}>0.027$. We update the calculation of the production rates to eliminate unnecessary approximations and find that the cosmological bounds on these interactions are complementary to astrophysical constraints, e.g. from supernova SN 1987A. We additionally provide quantitative explanations for these bounds and their relationship.

    ↳ astro-ph.COhep-phhep-thJCAP(2022)·53 citations
28. 28*

    The Radial Action from Probe Amplitudes to All Orders

    Uri Kol🇺🇸 · Donal O'connell🇬🇧 · Ofri Telem🇺🇸

    We extract the relativistic classical radial action from scattering amplitudes, to all orders in perturbation theory, in the probe limit. Our sources include point charges and monopoles, as well as the Schwarzschild and pure-NUT gravitational backgrounds. A characteristic relativistic effect, that scattering trajectories may wind around these sources any number of times, can be recovered when all-order amplitudes are available. We show that the amplitude for scattering a probe off a pure NUT is given by the solution of a transcendental equation involving continued fractions, and explain how to solve this equation to any desired loop order.

    ↳ hep-thgr-qchep-phJHEP(2022)·68 citations
29. 29*

    Holographic approach to transport in dense QCD matter

    Carlos Hoyos🇪🇸 · Niko Jokela🇫🇮 · Matti Järvinen🇰🇷 · Javier G. Subils🇪🇸 · Javier Tarrio🇫🇮 · Aleksi Vuorinen🇫🇮

    The transport properties of dense QCD matter play a crucial role in the physics of neutron stars and their mergers, but are notoriously difficult to study with traditional quantum field theory tools. Specializing to the case of unpaired quark matter in beta equilibrium, we approach the problem through the machinery of holography, in particular the V-QCD and D3-D7 models, and derive results for the electrical and thermal conductivities and the shear and bulk viscosities. In addition we compare the bulk to shear viscosity ratio to the speed of sound and find that it violates the so-called Buchel bound. Our results differ dramatically from earlier predictions of perturbative QCD, the root causes and implications of which we analyze in detail.

    ↳ hep-thastro-ph.HEhep-phnucl-thPRD(2022)·37 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.