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On the stability of string-hole gas
No full textFocusing on a string-hole gas within the pre-big bang scenario, we study the stability of its solutions in the phase space.We firstly extend the analysis present in the literature relaxing the ideal-gas properties of the string-hole gas, taking into account a (bulk-) viscosity term. Then we consider the case of a theory described by a complete O(d,d)-invariant action up to all orders inα'-corrections (the Hohm-Zwiebach action), studying the stability of the string-hole gas solution with or without the introduction of the viscosity term.Furthermore, the bulk viscosity is also considered for two different first order α'-corrected actions: the Gasperini-Maggiore-Veneziano-action and theMeissner-action.The results obtained show how the viscosity can help to stabilize the string-hole gas solution, obtaining constraints on the equation of state of the gas
Super heavy dark matter from inflationary Schwinger production
No full textWe consider a simple setup with a dark sector containing dark electrons charged under an Abelian U(1)D gauge symmetry. We show that, if the massless dark photon associated to the U(1)D is produced during inflation in such a way as to form a classical dark electric field, then dark electron-positron pairs are also produced close to the end of inflation via the Schwinger effect even if they are very massive. For large enough dark electric force, dark electrons with masses larger than the Hubble scale can be produced which are nonrelativistic at production and throughout their cosmic evolution. They can account for the dark matter abundance today for masses in the range ∼100 GeV to 1017 GeV and up to 6 orders of magnitude larger than the Hubble scale at the end of inflation where purely gravitational production is exponentially suppressed. We examine the regime where the dark electrons do not thermalize with the dark photons throughout their cosmic history and assume negligible kinetic mixing with the visible U(1) so they remain decoupled from the Standard Model thermal bath as well. Thus, the final dark matter relic abundance is determined only by the initial inflationary Schwinger production and redshifting after reheating
Structure of single -hypernuclei with Gogny-type -nucleon forces
No full textWe study the structure of single -hypernuclei using the Hartree–Fock–Bogoliubov method. Finite range Gogny-type forces are used to describe the nucleon–nucleon and -nucleon interactions. Three different -nucleon Gogny forces are built. The unknown parameters of these forces are obtained by fitting the experimental binding energies of the 1s single-particle state in various hypernuclei using the "Simulated Annealing Method". These forces are then used to calculate the binding energies of the other (1p, 1d, 1f, 1g) single-particle states in the different hypernuclei. The predicted values are found to be in good agreement with the experimental data for the three forces constructed. In addition, we calculate also the root-mean-square radii of ground state orbital, as well as several global properties of the hypernuclei considered such as their ground-state Hartree–Fock–Bogoliubov energy, their pairing energy and their quadrupole moment
Renormalisation group running effects in in the Standard Model Effective Field Theory
No full textWe study the effects of renormalisation group running of the Wilson coefficients in Standard Model Effective Field Theory, using the process as a showcase. We consider both strong and top Yukawa running effects, since the latter can be relevant in presence of large Wilson coefficients. We study the difference between the use of a dynamical and fixed renormalisation scale by exploring different scenarios for the higher-dimensional operators at the high energy scale of new physics, assumed to be at the TeV scale
Consistent truncation of eleven-dimensional supergravity on S× S
No full textEleven-dimensional supergravity on S × S is conjectured to be dual to the M-theory matrix model. We prove that the dynamics of a subset of fluctuations around this background is consistently described by D = 2 SO(9) gauged maximal supergravity. We provide the full non-linear uplift formulæ for all bosonic fields. We also present a further truncation to the SO(3)×SO(6) invariant sector and discuss its relation to the BMN matrix model at finite temperature. The construction relies on the framework of generalised Scherk-Schwarz reductions, established for E exceptional field theory in a companion paper. As a by-product, we severely constrain the most general gauge deformations in D = 2 admitting an uplift to higher dimensions
Isospin diffusion from <math><mrow><mmultiscripts><mi>Ca</mi><mprescripts/><none/><mrow><mn>40</mn><mo>,</mo><mn>48</mn></mrow></mmultiscripts><mo>+</mo><mmultiscripts><mi>Ca</mi><mprescripts/><none/><mrow><mn>40</mn><mo>,</mo><mn>48</mn></mrow></mmultiscripts></mrow></math> experimental data at Fermi energies: Direct comparisons with transport model calculations
No full textThis article presents an investigation of isospin equilibration in cross-bombarding Ca40,48+Ca40,48 reactions at 35 MeV/nucleon, by comparing experimental data with filtered transport model calculations. Isospin diffusion is studied using the evolution of the isospin transport ratio with centrality. The asymmetry parameter δ=(N−Z)/A of the quasiprojectile (QP) residue is used as isospin-sensitive observable, while a recent method for impact parameter reconstruction is used for centrality sorting. A benchmark of global observables is proposed to assess the relevance of the antisymmetrized molecular dynamics (amd) model, coupled to gemini++, in the study of dissipative collisions. Our results demonstrate the importance of considering cluster formation to reproduce observables used for isospin transport and centrality studies. Within the amd model, we prove the applicability of the impact parameter reconstruction method, enabling a direct comparison to the experimental data for the investigation of isospin diffusion. For both, we evidence a tendency to isospin equilibration with an impact parameter decreasing from 9 to 3 fm, while the full equilibration is not reached. A weak sensitivity to the stiffness of the equation of state employed in the model is also observed, with a better reproduction of the experimental trend for the neutron-rich reactions
Phenomenology of superheavy decaying dark matter from string theory
No full textWe study the phenomenology of superheavy decaying dark matter with mass around 10 GeV which can arise in the low-energy limit of string compactifications. Generic features of string theory setups (such as high scale supersymmetry breaking and epochs of early matter domination driven by string moduli) can accommodate superheavy dark matter with the correct relic abundance. In addition, stringy instantons induce tiny R-parity violating couplings which make dark matter unstable with a lifetime well above the age of the Universe. Adopting a model-independent approach, we compute the flux and spectrum of high-energy gamma rays and neutrinos from three-body decays of superheavy dark matter and constrain its mass-lifetime plane with current observations and future experiments. We show that these bounds have only a mild dependence on the exact nature of neutralino dark matter and its decay channels. Applying these constraints to an explicit string model sets an upper bound of (0.1) on the string coupling, ensuring that the effective field theory is in the perturbative regime
The spindle index from localization
No full textWe present a new supersymmetric index for three-dimensional gauge theories defined on , where is a spindle, with twist or anti-twist for the R-symmetry background gauge field. We start examining general supersymmetric backgrounds of Euclidean new minimal supergravity admitting two Killing spinors of opposite R-charges. We then focus on and demostrate how to realise twist and anti-twist. We compute the supersymmetric partition functions on such backgrounds via localization and show that these are captured by a general formula, depending on the type of twist, which unifies and generalises the superconformal and topologically twisted indices
Causal influence versus signaling for interacting quantum channels
No full textA causal relation between quantum agents, say Alice and Bob, is necessarily mediated by an interaction. Modeling the latter as a reversible quantum channel, an intervention of Alice can have causal influence on Bob's system, modifying correlations between Alice and Bob's systems. Causal influence between quantum systems necessarily allows for signaling. Here we prove a mismatch between causal influence and signaling via direct computation of the two quantities for the Cnot gate. Finally we show a continuity theorem for causal effects of unitary channels: a channel has small causal influence if it allows for small signaling
Sommerfeld enhancement at NLO and the dark matter unitarity bound
No full textWe reexamine the consequences of perturbative unitarity on dark matter freeze-out when both Sommerfeld enhancement and bound state formation affect dark matter annihilations. At leading order the annihilation cross section is infrared dominated and the connection between the unitarity bound and the upper bound on the dark matter mass depends only on how the different partial waves are populated. We compute how this picture is modified at next-to-leading order with the goal of assigning a reliable theory uncertainty to the freeze-out predictions. We explicitly compute next-to-leading order corrections in a simple model with Abelian gauge interactions and provide an estimate of the theoretical uncertainty for the thermal masses of heavy electroweak n-plets. Along the way, we clarify the regularization and matching procedure necessary to deal with singular potentials in quantum mechanics with a calculable, relativistic UV completion