HEP Phenomenology·hep-ph

Thu·Nov 19, 2020Thursday·November 19, 2020

27 papers—18 primary·9 cross-listed·reconstructed*

01*
Multiplicity distributions in the low x regime in a simple model
G. R. Germano🇧🇷 · F.S. Navarra🇧🇷
In this work we introduce small changes in the model proposed by E. Levin and D. Kharzeev for multiplicity distributions of particles produced in proton-proton collisions. We compare the predictions of the model with the available experimental data from the LHC. We also consider the most recent version of the model proposed by E. Gotsman and E. Levin. These two versions of the model give a good description of the measured multiplicity distributions in the central pseudo-rapidity region ( $∣ η ∣ < 0.5$ ). The agreement with data is not so good when we consider the particles measured over a wider pseudo-rapidity interval ( $∣ η ∣ < 2.4$ ). Interestingly, the agreement becomes better when one selects events with higher transverse momentum ( $p_{T} > 500$ MeV).
hep-ph7 citations
02*
Gamma-ray and Synchrotron Radiation from Dark Matter annihilations in Ultra-faint Dwarf Galaxies
Pooja Bhattacharjee🇮🇳 · Debajyoti Choudhury🇮🇳 · Kasinath Das🇮🇳 · Dilip Kumar Ghosh🇮🇳 · Pratik Majumdar🇮🇳
The very large (100-1000) mass-to-light ratio applicable to the ultra-faint dwarf galaxies (UFDs) implies a high concentration of dark matter, thus rendering them ideal theatres for indirect signatures of dark matter. In this paper, we consider 14 recently discovered UFDs and study the electromagnetic radiation emanating from them over a wide range, from gamma ray down to radio frequencies. We analyze the Fermi-LAT data on high energy gamma rays and radio fluxes at the GMRT and VLA to obtain upper limits on annihilation cross section $⟨ σ v ⟩$ in a model independent way. We further discuss the sensitivity of the Square Kilometer Array radio telescope in probing the synchrotron radiation from the aforementioned UFDs. We also investigate the dependences of the said upper limits on the uncertainties in the determination of various astrophysical parameters.
hep-phastro-ph.GAastro-ph.HEJCAP(2021)·8 citations
03*
Xenon1T excess from electron recoils of non-relativistic Dark Matter
Dario Buttazzo🇮🇹 · Paolo Panci🇮🇹 · Daniele Teresi🇮🇹 · Robert Ziegler🇩🇪
We show that electron recoils induced by non-relativistic Dark Matter interactions can fit well the recently reported Xenon1T excess, if they are mediated by a light pseudo-scalar in the MeV range. This is due to the favorable momentum-dependence of the resulting scattering rate, which partially compensates the unfavorable kinematics that tends to strongly suppress keV electron recoils. We study the phenomenology of the mediator and identify the allowed parameter space of the Xenon1T excess which is compatible with all experimental limits. We also find that the anomalous magnetic moments $(g - 2)_{μ, e}$ of muons and electrons can be simultaneously explained in this scenario, at the prize of a fine-tuning in the couplings of the order of a few percent.
hep-phastro-ph.COPLB(2021)·34 citations
04*
Baryonic and Leptonic GeV Dark Matter
Bartosz Fornal🇺🇸 · Alec Hewitt🇺🇸 · Yue Zhao🇺🇸
We perform a systematic analysis of models with GeV-scale dark matter coupled to baryons and leptons. Such theories provide a natural framework to explain the matter-antimatter asymmetry of the universe. We find that only a few baryonic dark matter models are free from tree-level proton decay without explicitly imposing baryon number conservation. We enumerate those cases and provide a brief overview of their phenomenology. We then focus on a leptonic dark matter model for a more detailed discussion of the baryon asymmetry generation via leptogenesis, the symmetry restoration in the dark sector and the expected dark matter annihilation signals in indirect detection experiments.
hep-phPLB(2021)·10 citations
05*
Global View of Axion Stars with (Nearly) Planck-Scale Decay Constants
Joshua Eby🇮🇱 · Lauren Street🇺🇸 · Peter Suranyi🇺🇸 · L.C.R. Wijewardhana🇺🇸
We show that axion stars formed from axions with nearly Planck-scale decay constants $f$ are unstable to decay, and are unlikely to have phenomenological consequences. More generally, we show how results at smaller $f$ cannot be naively extrapolated to $f = O (M_{P})$ as, contrary to conventional wisdom, gravity and special relativity can both become relevant in the same regime. We clarify the rate of decay by reviewing and extending previous work on oscillons and axion stars, which imply a fast decay rate even for so-called dilute states at large $f$ .
hep-phastro-ph.COPRD(2021)·14 citations
06*
2HDM singlet portal to dark matter
M. E. Cabrera🇬🇹 · J. A. Casas🇪🇸 · A. Delgado🇺🇸 · S. Robles🇦🇺
Higgs portal models are the most minimal way to explain the relic abundance of the Universe. They add just a singlet that only couples to the Higgs through a single parameter that controls both the dark matter relic abundance and the direct detection cross-section. Unfortunately this scenario, either with scalar or fermionic dark matter, is almost ruled out by the latter. In this paper we analyze the Higgs-portal idea with fermionic dark matter in the context of a 2HDM. By disentangling the couplings responsible for the correct relic density from those that control the direct detection cross section we are able to open the parameter space and find wide regions consistent with both the observed relic density and all the current bounds.
hep-phastro-ph.COJHEP(2021)·10 citations
07*
Landscape of Modular Symmetric Flavor Models
Keiya Ishiguro🇯🇵 · Tatsuo Kobayashi🇯🇵 · Hajime Otsuka🇯🇵
We study the moduli stabilization from the viewpoint of modular flavor symmetries. We systematically analyze stabilized moduli values in possible configurations of flux compactifications, investigating probabilities of moduli values and showing which moduli values are favorable from our moduli stabilization. Then, we examine their implications on modular symmetric flavor models. It is found that distributions of complex structure modulus $τ$ determining the flavor structure are clustered at a fixed point with the residual $Z_{3}$ symmetry in the $S L (2, Z)$ fundamental region. Also, they are clustered at other specific points such as intersecting points between $∣ τ ∣^{2} = k /2$ and $Re τ = 0, \pm 1/4, \pm 1/2$ , although their probabilities are less than the $Z_{3}$ fixed point. In general, CP-breaking vacua in the complex structure modulus are statistically disfavored in the string landscape. Among CP-breaking vacua, the values $Re τ = \pm 1/4$ are most favorable in particular when the axio-dilaton $S$ is stabilized at $Re S = \pm 1/4$ . That shows a strong correlation between CP phases originated from string moduli.
hep-phhep-thJHEP(2021)·98 citations
08*
$Z_{cs} (3985)^{-}$ : a strange hidden-charm tetraquark resonance or not?
Rui Chen🇨🇳 · Qi Huang🇨🇳
Inspired by the newly $Z_{cs} (3985)^{-}$ reported by the BESIII Collaboration in the $K^{+}$ recoil-mass spectrum of the of $e^{+} e^{-} \to (D^{* 0} D_{s}^{-} / D^{0} D_{s}^{*-}) K^{+}$ processes, we perform a dynamical study on the $D^{(*) 0} D_{s}^{*-}$ interactions by adopting a one-boson-exchange model and considering the coupled channel effect. After producing the phase shifts for all the discussed channels, our results exclude the newly $Z_{cs} (3985)^{-}$ as a $D^{* 0} D_{s}^{-} / D^{0} D_{s}^{*-} / D^{* 0} D_{s}^{*-}$ resonance with $I (J^{P}) = 1/2 (1^{+}, 0^{-}, 1^{-}, 2^{-})$ .
hep-phPRD(2021)·51 citations
09*
The nature of charged charmonium-like states $Z_{c} (3900)$ and its strange partner $Z_{cs} (3982)$
Meng-Chuan Du🇨🇳 · Qian Wang🇨🇳 · Qiang Zhao🇨🇳
The observation of $Z_{cs} (3985)$ by BESIII in the $D_{s}^{*-} D^{0}$ and $D_{s}^{-} D^{* 0}$ channel adds important dynamic information for a coherent understanding of both $Z_{c} (3900)$ and $Z_{c} (4020)$ , as well as their strange partners $Z_{cs} (3985)$ and $Z_{cs} (4120)$ , on the basis of heavy quark spin symmetry. With an overall short-ranged contact potential in SU(3) flavor symmetry we show that the pole structures can be extracted from the experimental data. Meanwhile, we show the key role played by the $S$ -wave open thresholds in $e^{+} e^{-}$ annihilations which are correlated with the production of these $Z$ states in a hadronic molecule picture. Implications of their scalar heavy quark spin partners $W_{c 0, 1, 2}$ and $W_{cs 0, 1, 2}$ are also gained.
hep-phhep-ex43 citations
10*
Photoproduction of strange hidden-charm and hidden-bottom states
Xu Cao🇨🇳 · Jian-Ping Dai🇨🇳 · Zhi Yang🇨🇳
Recently BESIII collaboration discovered a charged strange hidden-charm state $Z_{cs}$ (3985) in the $D_{s}^{-} D^{* 0} + D_{s}^{*-} D^{0}$ spectrum. A higher $Z_{cs}^{'}$ state coupling to $D ˉ_{s}^{*-} D^{* 0}$ is expected by SU(3)-flavor symmetry, and their bottom partners are anticipated by heavy quark flavor symmetry. Here we study the photoproduction of these exotic states and investigate carefully the background from Pomeron exchange. Our results indicate that the maximal photoproduction cross section of strange partner is around 1 $\sim$ 2 orders of magnitude smaller than that of the corresponding non-strange states. The possibility of searching for them in future electron-ion colliders (EIC) is briefly discussed.
hep-phEPJC(2021)·30 citations
11*
Probing the anomalous positron fraction origin with fully leptonic decaying gravitino dark matter candidates
Johannes Buchner🇨🇱 · Edson Carquin🇨🇱 · Marco A. Díaz🇨🇱 · Germán A. Gómez-Vargas🇨🇱 · Boris Panes🇨🇱 · Nicolás Viaux🇨🇱
The flux of electron and positron cosmic rays measured by the space-based experiments PAMELA, AMS-02, CALET, DAMPE and Fermi-LAT shows an unexpected behaviour at high energies, in comparison with expectations from standard astrophysical sources. In particular, AMS-02 observations provide compelling evidence for a new source of positrons and electrons whose origin is still unknown. Plausible scenarios include either the contribution of dark matter or unresolved astrophysical sources, such as nearby pulsars. It has been shown that explanations based mostly on dark matter, tend to overproduce gamma-rays, entering in conflict with measurements of the extra-galactic gamma-ray background (EGB). Although this situation seems to be quite generic, it ultimately depends on the properties of the dark matter candidate. In this work we revisit a model in which the gravitino is a dark matter candidate decaying to SM particles through R-parity violating couplings. We show that decay channels allowed by trilinear couplings produce more electrons and positrons and fewer photons in comparison to channels allowed by bilinear couplings. Indeed, when considering AMS-02 data alone we find that the trilinear model is compatible with EGB constraints. However, this result may change when DAMPE or CALET measurements of the sum of electrons and positrons fluxes are considered instead of AMS-02 data. Therefore, in order to evaluate this model further, discrepancies between the data collected by these experiments need to be clarified
hep-ph1 citation
12*
Wash-In Leptogenesis
Valerie Domcke🇨🇭 · Kohei Kamada🇯🇵 · Kyohei Mukaida🇩🇪 · Kai Schmitz🇨🇭 · Masaki Yamada🇯🇵
We present a leptogenesis mechanism based on the standard type-I seesaw model that successfully operates at right-handed-neutrino masses as low as a few 100 TeV. This mechanism, which we dub "wash-in leptogenesis", does not require any CP violation in the neutrino sector and can be implemented even in the regime of strong wash-out. The key idea behind wash-in leptogenesis is to generalize standard freeze-out leptogenesis to a nonminimal cosmological background in which the chemical potentials of all particles not in chemical equilibrium at the temperature of leptogenesis are allowed to take arbitrary values. This sets the stage for building a plethora of new baryogenesis models where chemical potentials generated at high temperatures are reprocessed to generate a nonvanishing B-L asymmetry at low temperatures. As concrete examples, we discuss wash-in leptogenesis after axion inflation and in the context of grand unification.
hep-phastro-ph.COhep-thPRL(2021)·69 citations
13*
Explanation of the newly obseaved $Z_{cs}^{-} (3985)$ as a $D_{s}^{(*) -} D^{(*) 0}$ molecular state
Zhi-Feng Sun🇨🇳 · Chu-Wen Xiao🇨🇳
Inspired by the newly observed $Z_{cs}^{-} (3985)$ by BESIII collaboration, we study the structure of this particle in the picture of $D_{s}^{(*) -} D^{(*) 0}$ molecular state. Firstly we systematically construct the Lagrangians which describing the interaction of charmed mesons, taking into account the chiral and hidden local symmetries. With the obtained effective potentials from the Lagrangians constructed, we solve the coupled channel Bethe-Salpeter equation with the on-shell approximation. On the third Reimann sheet, a pole position of around $3982.34 - i 0.53$ MeV is obtained, which can be associated to the $Z_{cs}^{-} (3985)$ and explained as a loose bound state of $D_{s}^{*} D ˉ^{*}$ .
hep-ph42 citations
14*
UV Completed Composite Higgs model with heavy composite partners
Zi-Yu Dong🇨🇳 · Cong-Sen Guan🇨🇳 · Teng Ma🇮🇱 · Jing Shu🇨🇳 · Xiao Xue🇨🇳
We study electroweak symmetry breaking in minimal composite Higgs models $S U (4) / S p (4)$ with purely fermionic UV completions based on a confining Hypercolor gauge group and find that the extra Higgs potential from the underlying preon mass can destruct the correlation between the mass of Higgs and composite partners. Thus the composite partners can be very heavy for successful electroweak symmetry breaking without enhancing the separation between the new physical scale and Higgs VEV. So this kind of model can be easily realized by ordinary strong dynamics theories without artificial assumptions and more likely consistent with lattice simulations. The UV completion of partial compositeness predicts a light singlet Goldstone boson which interacts with QCD and electroweak gauge bosons through Wess-Zumino-Witten terms. It can be produced through gluon fusion at LHC and decay into gauge boson pairs. We briefly discuss its phenomenology and derive its bounds from LHC searches.
hep-phhep-thPRD(2021)·18 citations
15*
Light Dark Matter from Inflaton Decay
Takeo Moroi🇯🇵 · Wen Yin🇯🇵
We propose a simple mechanism of light dark matter (DM) production from the decay of the oscillating inflaton condensation. If the reheating temperature after inflation is higher than the inflaton mass, which is of the same order of the momentum of the DM at the time of the production, the DM momentum can be suppressed compared to the temperature of the thermal plasma if the interaction of the DM is weak enough. Consequently, the DM can be cold enough to avoid the observational constraints on the warm DM, like the Lyman- $α$ bound even if the DM mass is small. We study the bosonic and fermionic DM production from the inflaton decay, taking into account the effect of the stimulated emission and Pauli blocking, respectively. In both cases, the DM can be cold and abundant enough to be a viable candidate of the DM. We also apply our mechanism to the production of isocurvature-problem-free axion DM and Dirac sea DM of right-handed neutrino consistent the seesaw relation for the active neutrino masses.
hep-phastro-ph.COgr-qcJHEP(2021)·69 citations
16*
Dark Matter Detection With Bound Nuclear Targets: The Poisson Phonon Tail
Yonatan Kahn🇺🇸 · Gordan Krnjaic🇺🇸 · Bashi Mandava🇺🇸
Dark matter (DM) scattering with nuclei in solid-state systems may produce elastic nuclear recoil at high energies and single-phonon excitation at low energies. When the dark matter momentum is comparable to the momentum spread of nuclei bound in a lattice, $q_{0} = 2 m_{N} ω_{0}$ where $m_{N}$ is the mass of the nucleus and $ω_{0}$ is the optical phonon energy, an intermediate scattering regime characterized by multi-phonon excitations emerges. We study a greatly simplified model of a single nucleus in a harmonic potential and show that, while the mean energy deposited for a given momentum transfer $q$ is equal to the elastic value $q^{2} / (2 m_{N})$ , the phonon occupation number follows a Poisson distribution and thus the energy spread is $Δ E = q ω_{0} / (2 m_{N})$ . This observation suggests that low-threshold calorimetric detectors may have significantly increased sensitivity to sub-GeV DM compared to the expectation from elastic scattering, even when the energy threshold is above the single-phonon energy, by exploiting the tail of the Poisson distribution for phonons above the elastic energy. We use a simple model of electronic excitations to argue that this multi-phonon signal will also accompany ionization signals induced from DM-electron scattering or the Migdal effect. In well-motivated models where DM couples to a heavy, kinetically-mixed dark photon, we show that these signals can probe experimental milestones for cosmological DM production via thermal freeze-out, including the thermal target for Majorana fermion DM.
hep-phastro-ph.COhep-exPRL(2021)·39 citations
17*
Theoretical and experimental status of rare charm decays
Hector Gisbert🇩🇪 · Marcel Golz🇩🇪 · Dominik Stefan Mitzel🇨🇭
Rare charm decays offer the unique possibility to explore flavour-changing neutral-currents in the up-sector within the Standard Model and beyond. Due to the lack of effective methods to reliably describe its low energy dynamics, rare charm decays have been considered as less promising for long. However, this lack does not exclude the possibility to perform promising searches for New Physics per se, but a different philosophy of work is required. Exact or approximate symmetries of the Standard Model allow to construct clean null-test observables, yielding an excellent road to the discovery of New Physics, complementing the existing studies in the down-sector. In this review, we summarize the theoretical and experimental status of rare charm $∣Δ c ∣ = ∣Δ u ∣ = 1$ transitions, as well as opportunities for current and future experiments such as LHCb, Belle II, BES III, the FCC-ee and proposed tau-charm factories. We also use the most recent experimental results to report updated limits on lepton-flavour conserving and lepton-flavour violating Wilson coefficients.
hep-phhep-exMod.Phys.Lett.A(2021)·49 citations
18*
Color-Dipole Picture versus Hard Pomeron in Deep Inelastic Scattering
Dieter Schildknecht🇩🇪
For photon virtualities of $Q^{2} \gsim 20 GeV^{2}$ , the results of the (hard Pomeron) fit in the tensor-Pomeron model in terms of the variables $Q^{2}$ and the virtual-photon-proton energy squared, $W^{2}$ , provide empirical evidence for the validity of the Color Dipole Picture (CDP). Consistency of the CDP with the perturbative QCD (pQCD) improved parton model implies the prediction of $C_{2} = ϵ_{0} ≅ 0.30$ for the exponent $C_{2}$ of the energy-squared dependence in agreement with the results of the fits. For $Q^{2} \lsim 20 G e V^{2}$ , the CDP yields a parameter-free smooth transition from $Q^{2} \gsim 20 GeV^{2}$ to $Q^{2} = 0$ photoproduction, in distinction from the tensor-Pomeron model that relies on the additional parameter quantifying the intercept of the soft-Pomeron trajectory.
hep-phPRD(2021)·7 citations
19*
A paradigm of warm quintessential inflation and production of relic gravity waves
Mayukh R. Gangopadhyay🇮🇳 · Shynaray Myrzakul🇰🇿 · Mohammad Sami🇰🇿 · Mohit K. Sharma🇮🇳
We consider the framework of quintessential inflation in the warm background which is caused by the dissipation of the scalar field energy density into relativistic degrees of freedom. The dissipation process has important consequences for the evolution both at the levels of background as well as perturbation and allows us to easily satisfy the observational constraints.~Our numerical analysis confirms that the model conforms to observational constraints even if the field-radiation coupling strength is weak. In the warm background, we investigate the post inflationary evolution of relic gravity waves produced during inflation whose amplitude is constrained by the Big Bang Nucleosynthesis constraint. Further, we investigate the effect of coupling on the amplitude of gravity waves and obtain the allowed phase space between the model parameters. The mechanism of quintessential inflation gives rise to the blue spectrum of gravitational wave background at high frequencies. We discuss the perspectives of detection of the signal of relic gravity waves by future proposed missions. Improvements of their sensitivities in the high-frequency regime, in the future, might allow us to probe the blue tilt of the spectrum caused by the presence of a kinetic regime in the underlying framework of inflation.
↳ astro-ph.COgr-qchep-phPRD(2021)·30 citations
20*
Constraints on Lightly Ionizing Particles from CDMSlite
SuperCDMS Collaboration: I. Alkhatib🇨🇦 · D.W.P. Amaral🇬🇧 · T. Aralis🇺🇸 · T. Aramaki🇺🇸 · I.J. Arnquist🇺🇸 · I. Ataee Langroudy🇺🇸 · E. Azadbakht🇺🇸 · S. Banik🇮🇳 · D. Barker🇺🇸 · C. Bathurst🇺🇸 · D.A. Bauer🇺🇸 · L.V.S. Bezerra🇨🇦 and 105 other authors
The Cryogenic Dark Matter Search low ionization threshold experiment (CDMSlite) achieved efficient detection of very small recoil energies in its germanium target, resulting in sensitivity to Lightly Ionizing Particles (LIPs) in a previously unexplored region of charge, mass, and velocity parameter space. We report first direct-detection limits calculated using the optimum interval method on the vertical intensity of cosmogenically-produced LIPs with an electric charge smaller than $e / (3 \times 1 0^{5}$ ), as well as the strongest limits for charge $\leq e /160$ , with a minimum vertical intensity of $1.36 \times 1 0^{- 7}$ \,cm $^{- 2}$ s $^{- 1}$ sr $^{- 1}$ at charge $e /160$ . These results apply over a wide range of LIP masses (5\,MeV/ $c^{2}$ to 100\,TeV/ $c^{2}$ ) and cover a wide range of $β γ$ values (0.1 -- $1 0^{6}$ ), thus excluding non-relativistic LIPs with $β γ$ as small as 0.1 for the first time.
↳ hep-exastro-ph.COastro-ph.HEhep-ph+1PRL(2021)·21 citations
21*
The theory of cosmic-ray scattering on pre-existing MHD modes meets data
Ottavio Fornieri🇮🇹 · Daniele Gaggero🇪🇸 · Silvio Sergio Cerri🇺🇸 · Pedro De la Torre Luque🇮🇹 · Stefano Gabici🇫🇷
We present a comprehensive study about the phenomenological implications of the theory describing Galactic cosmic-ray scattering onto magnetosonic and Alfvénic fluctuations in the $GeV - PeV$ domain. We compute a set of diffusion coefficients from first principles, for different values of the Alfvénic Mach number and other relevant parameters associated to both the Galactic halo and the extended disk, taking into account the different damping mechanisms of turbulent fluctuations acting in these environments. We confirm that the scattering rate associated to Alfvénic turbulence is highly suppressed if the anisotropy of the cascade is taken into account. On the other hand, we highlight that magnetosonic modes play a dominant role in Galactic confinement of cosmic rays up to $PeV$ energies. We implement the diffusion coefficients in the numerical framework of the {\tt DRAGON} code, and simulate the equilibrium spectrum of different primary and secondary cosmic-ray species. We show that, for reasonable choices of the parameters under consideration, all primary and secondary fluxes at high energy (above a rigidity of $≃ 200 GV$ ) are correctly reproduced within our framework, in both normalization and slope.
↳ astro-ph.HEhep-phphysics.plasm-phMNRAS(2021)·46 citations
22*
Chemical freeze-out of light nuclei in high energy nuclear collisions and resolution of the hyper-triton chemical freeze-out puzzle
K. A. Bugaev🇺🇦 · O. V. Vitiuk🇺🇦 · B. E. Grinyuk🇺🇦 · N. S. Yakovenko🇺🇦 · E. S. Zherebtsova🇷🇺 · V. V. Sagun🇺🇦 · O. I. Ivanytskyi🇺🇦 · D. O. Savchenko🇺🇦 · L. V. Bravina🇳🇴 · D. B. Blaschke🇵🇱 · G. R. Farrar🇺🇸 · S. Kabana🇨🇱 and 5 other authors
We present a summary of the recent results obtained with the novel hadron resonance gas model with the multicomponent hard-core repulsion which is extended to describe the mixtures of hadrons and light (anti-, hyper-)nuclei. A very accurate description is obtained for the hadronic and the light nuclei data measured by STAR at the collision energy $s_{N N} = 200$ GeV and by ALICE at $s_{N N} = 2.76$ TeV. The most striking result discussed here is that for the most probable chemical freeze-out scenario for the STAR energy the found parameters allow us to reproduce the values of the experimental ratios $S_{3}$ and $S_{3}$ without fitting.
↳ nucl-thhep-phJ.Phys.Conf.Ser.(2020)·0 citations
23*
Cosmology of the string derived flipped $S U (5)$
Ignatios Antoniadis🇫🇷 · Dimitri V. Nanopoulos🇺🇸 · John Rizos🇬🇷
We study the cosmology of a string derived supersymmetric flipped $S U (5)$ model in the context of free-fermionic heterotic constructions that allow full calculability of the effective supergravity in perturbation theory around the fermionic vacuum where all string moduli have fixed values. The model has 3 generations of chiral families and a Higgs sector leading to particle phenomenology consistent with low energy data, that has been extensively studied in the past. Here, we show that it can also accommodate a novel successful cosmology, based on the no-scale effective supergravity derived from string theory as well as an appropriate induced superpotential suppressed by five powers of the string scale. It utilises two gauge singlet chiral superfields present in the low energy spectrum: the inflaton $y$ , identified as the superpartner of a state mixed with R-handed neutrinos, and the goldstino $z$ with a superpotential of the form $W_{I} = M_{I} z (y - λ y^{2})$ (in supergravity units) where $λ$ is a dimensionless $O (1)$ parameter and $M_{I}$ the mass scale of inflation generated at 5th order by the breaking of an anomalous $U (1)_{A}$ gauge symmetry, characteristic of heterotic string chiral vacua. The resulting scalar potential leads to Starobinsky type inflation. Our results can be easily generalised to a large class of models with similar properties.
↳ hep-thastro-ph.COgr-qchep-phJCAP(2021)·21 citations
24*
Zilch Vortical Effect for Fermions
Artem Alexandrov🇷🇺 · Pavel Mitkin🇷🇺
We consider the notion of zilch current that was recently discussed in the literature as an alternative helicity measure for photons. Developing this idea, we suggest the generalization of the zilch for the systems of fermions. We start with the definition of the photonic zilch current in chiral kinetic theory framework and work out field-theoretical definition of the fermionic zilch using the Wigner function formalism. This object has similar properties to the photonic zilch and is conserved in the non-interacting theory. We also show that, in full analogy with a case of photons, the fermionic zilch acquires a non-trivial contribution due to the medium rotation - zilch vortical effect (ZVE) for fermions. Combined with a previously studied ZVE for photons, these results form a wider set of chiral effects parameterized by the spin of the particles and the spin of the current. We briefly discuss the origin of the ZVE, its possible relation to the anomalies in the underlying microscopic theory and possible application for studying the spin polarization in chiral media.
↳ hep-thhep-phnucl-thJHEP(2021)·5 citations
25*
On the interplay between magnetic field and anisotropy in holographic QCD
Umut Gürsoy🇳🇱 · Matti Järvinen🇰🇷 · Govert Nijs🇺🇸 · Juan F. Pedraza🇬🇧
We investigate the combined effects of anisotropy and a magnetic field in strongly interacting gauge theories by the gauge/gravity correspondence. Our main motivation is the quark-gluon plasma produced in off-central heavy-ion collisions which exhibits large anisotropy in pressure gradients as well as large external magnetic fields. We explore two different configurations, with the anisotropy either parallel or perpendicular to the magnetic field, focusing on the competition and interplay between the two. A detailed study of the RG flow in the ground state reveals a rich structure where depending on which of the two, anisotropy or magnetic field, is stronger, intermediate geometries with approximate AdS $_{4} \times R$ and AdS $_{3} \times R^{2}$ factors arise. This competition is also manifest in the phase structure at finite temperature, specifically in the dependence of the chiral transition temperature on anisotropy and magnetic field, from which we infer the presence of inverse magnetic and anisotropic catalyses of the chiral condensate. Finally, we consider other salient observables in the theory, including the quark-antiquark potential, shear viscosity, entanglement entropy and the butterfly velocity. We demonstrate that they serve as good probes of the theory, in particular, distinguishing between the effects of the magnetic field and anisotropy in the ground and plasma states. We also find that the butterfly velocity, which codifies how fast information propagates in the plasma, exhibits a rich structure as a function of temperature, anisotropy and magnetic field, exceeding the conformal value in certain regimes.
↳ hep-thgr-qchep-phJHEP(2021)·50 citations
26*
Wavefunctions in dS/CFT revisited: principal series and double-trace deformations
Hiroshi Isono🇹🇭 · Hoiki Madison Liu🇯🇵 · Toshifumi Noumi🇯🇵
We study wavefunctions of heavy scalars on de Sitter spacetime and their implications to dS/CFT correspondence. In contrast to light fields in the complementary series, heavy fields in the principal series oscillate outside the cosmological horizon. As a consequence, the quadratic term in the wavefunction does not follow a simple scaling and so it is hard to identify it with a conformal two-point function. In this paper, we demonstrate that it should be interpreted as a two-point function on a cyclic RG flow which is obtained by double-trace deformations of the dual CFT. This is analogous to the situation in nonrelativistic AdS/CFT with a bulk scalar whose mass squared is below the Breitenlohner-Freedman (BF) bound. We also provide a new dS/CFT dictionary relating de Sitter two-point functions and conformal two-point functions in the would-be dual CFT.
↳ hep-thgr-qchep-phJHEP(2021)·21 citations
27*
Rollercoaster Cosmology
Guido D'Amico🇮🇹 · Nemanja Kaloper🇺🇸
(Abridged) Does inflation have to happen all in one go? The answer is a resounding no! All cosmological problems can be solved by a sequence of short bursts of cosmic acceleration, interrupted by short epochs of decelerated expansion. The spectrum of perturbations will still match the CMB and LSS if the earliest stage of the last $O (50) - O (60)$ efolds is at least $O (15)$ efolds long. Other stages can be considerably shorter. But as long as they add up to $O (50) - O (60)$ efolds and the stages of decelerated expansion in between them are shorter and also overall last less, the ensuing cosmology will pass muster. The presence of the interruptions resets the efold clock of each accelerating stage, and changes its value at the CMB pivot point. This change opens up the theory space, loosening the bounds. In particular some models that seem excluded at $N = 60$ fit very well as shorter stages with $N = 30$ . Interesting predictions are that both the scalar and tensor spectra of perturbations are rapidly modified at short wavelengths. These features could be tested with future CMB spectroscopy searches and with short wavelength primordial gravity probes. The spatial curvature in these models can be larger than the largest wavelength scalar perturbations, because $Ω_{k}$ evolves differently than the scalar perturbations $\frac{δ ρ}{ρ} ∣_{S}$ . Finally, with many short stages of accelerated expansion, the abundance of reheating products from previous accelerated stages does not get completely wiped out. This implies that the universe may contain additional populations of particles, more rare than the visible ones, or even primordial black holes, created during a late decelerated epoch before last reheating, which may be dark matter.
↳ hep-thastro-ph.COgr-qchep-phJCAP(2021)·37 citations

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