Search

We explore the effect of neutron lifetime and its uncertainty on standard big-bang nucleosynthesis (BBN). BBN describes the cosmic production of the light nuclides $^1{\rm H}$, ${\rm D}$, $^3{\rm H}$+$^3{\rm He}$, $^4{\rm He}$, and $^7{\rm Li}$+$^7{\rm Be}$ in the first minutes of cosmic time. The neutron mean life $\tau_n$ has two roles in modern BBN calculations: (1) it normalizes the matrix element for weak $n \leftrightarrow p$ interconversions, and (2) it sets the rate of free neutron decay after the weak interactions freeze out. We review the history of the interplay between $\tau_n$ measurements and BBN, and present a study of the sensitivity of the light element abundances to the modern neutron lifetime measurements. We find that $\tau_n$ uncertainties dominate the predicted $^4{\rm He}$ error budget, but these theory errors remain smaller than the uncertainties in $^4{\rm He}$ observations, even with the dispersion in recent neutron lifetime measurements. For the other light-element predictions, $\tau_n$ contributes negligibly to their error budget. Turning the problem around, we combine present BBN and cosmic microwave background (CMB) determinations of the cosmic baryon density to $\textit{predict}$ a "cosmologically preferred" mean life of $\tau_{n}({\rm BBN+CMB}) = 870 \pm 16 \ \rm sec$, which is consistent with experimental mean life determinations. We go on to show that if future astronomical and cosmological helium observations can reach an uncertainty of $\sigma_{\rm obs}(Y_p) = 0.001$ in the $^4{\rm He}$ mass fraction $Y_p$, this could begin to discriminate between the mean life determinations., Comment: 27 pages, 11 figures

We revisit the calculation of the electron, neutron, and proton electric dipole moments (EDMs) in the constrained minimal supersymmetric standard model (CMSSM). The relatively large mass of the Higgs boson, $m_H \simeq 125$ GeV coupled with the (as yet) lack of discovery of any supersymmetric particle at the LHC, has pushed the supersymmetry breaking scale to several TeV or higher. Though one might expect this decoupling to have relaxed completely any bounds on the two CP violating phases in the CMSSM ($\theta_\mu$ and $\theta_A$), the impressive experimental improvements in the limits on the EDMs (particularly the electron EDM) still allow us to set constraints of order $(0.01 - 0.1)\pi$ on $\theta_A$ and $(0.001 - 0.1)\pi$ on $\theta_\mu$. We also discuss the impact of future improvements in the experimental limits on supersymmetric models., Comment: 34 pages, 8 figures

We show that a minimal scenario, utilizing only the graviton as an intermediate messenger between the inflaton, the dark sector and the Standard Model (SM), is able to generate $simultaneously$ the observed relic density of dark matter (DM), the baryon asymmetry through leptogenesis, as well as a sufficiently hot thermal bath after inflation. We assume an inflaton potential of the form $V(\phi)\propto \phi^k$ about the minimum at the end of inflation. The possibility of reheating via minimal gravitational interactions has been excluded by constraints on dark radiation for excessive gravitational waves produced from inflation. We thus extend the minimal model in several ways: i) we consider non-minimal gravitational couplings--this points to the parameter range of DM masses $M_{N_1} \simeq 2-10 $ PeV, and right-handed neutrino masses $M_{N_2} \simeq (5-20) \times 10^{11}$ GeV, and $T_\text{rh} \lesssim 3 \times 10^5$ GeV (for $k \le 20$); ii) we propose an explanation for the PeV excess observed by IceCube when the DM has a direct but small Yukawa coupling to the SM; and iii) we also propose a novel scenario, where the gravitational production of DM is a two-step process, first through the production of two scalars, which then decay to fermionic DM final states. In this case, the absence of a helicity suppression enhances the production of DM and baryon asymmetry, and allows a great range for the parameters including a dark matter mass below an MeV where dark matter warmness can be observable by cosmic 21-cm lines, even when gravitational interactions are responsible for reheating. We also show that detectable primordial gravitational wave signals provide the opportunity to probe this scenario for $T_\text{rh}\lesssim 5\times 10^6$ GeV in future experiments, such as BBO, DECIGO, CE and ET., Comment: 38 pages, 11 figures, 3 tables, Gravitational wave analysis added, version accepted for publication in JHEP

We consider the prospects for the direct detection of dark matter in pure gravity meditation (PGM) models of supersymmetry breaking. Minimal PGM models require only two parameters, the gravitino mass, $m_{3/2}$, which sets the UV mass for all scalar masses, and $\tan\beta$. Gaugino masses are generated through anomaly mediation. Typically the lightest supersymmetric state (the dark matter candidate) is a wino. Here, we consider a one-parameter extension of the minimal model by allowing the Higgs soft masses to deviate from universality. For simplicity, we take these to be equal and use the $\mu$-term as a surrogate. We also consider non-universal stop masses. When $|\mu| \sim 1$ TeV, the Higgsino is a viable dark matter candidate when the gravitino mass is of order $\sim 1$ PeV and $\tan\beta \simeq 2$. We calculate the spin-dependent and spin-independent cross sections for dark matter scattering on protons. For spin-independent scattering, existing experimental limits place constraints on the PGM parameter space. Much of the currently allowed parameter space lies above the irreducible neutrino background. Thus, future direct detection experiments will be able to probe much of the remaining PGM parameter space., Comment: 20 pages, 18 figures

We analyze nucleon decay modes in a no-scale supersymmetric flipped SU(5) GUT model, and contrast them with the predictions for proton decays via dimension-6 operators in a standard unflipped supersymmetric SU(5) GUT model. We find that these GUT models make very different predictions for the ratios $\Gamma(p \to \pi^0 \mu^+)/\Gamma(p \to \pi^0 e^+)$, $\Gamma(p \to \pi^+ \bar{\nu})/\Gamma(p \to \pi^0 e^+)$, $\Gamma(p \to K^0 e^+)/\Gamma(p \to \pi^0 e^+)$ and $\Gamma(p \to K^0 \mu^+)/\Gamma(p \to \pi^0 \mu^+)$, and that predictions for the ratios $\Gamma(p \to \pi^0 \mu^+)/\Gamma(p \to \pi^0 e^+)$ and $\Gamma(p \to \pi^+ \bar{\nu})/\Gamma(p \to \pi^0 e^+)$ also differ in variants of the flipped SU(5) model with normal- or inverse-ordered light neutrino masses. Upcoming large neutrino experiments may have interesting opportunities to explore both GUT and flavour physics in proton and neutron decays., Comment: 25 pages, 4 figures

We consider the production of matter and radiation during reheating after inflation, restricting our attention solely to gravitational interactions. Processes considered are the exchange of a graviton, $h_{\mu \nu}$, involved in the scattering of the inflaton or particles in the newly created radiation bath. In particular, we consider the gravitational production of dark matter (scalar or fermionic) from the thermal bath as well as from scattering of the inflaton condensate. We also consider the gravitational production of radiation from inflaton scattering. In the latter case, we also derive a lower bound on the maximal temperature of order of $10^{12}$ GeV for a typical $\alpha-$attractor scenario from $\phi \phi \rightarrow h_{\mu \nu} \rightarrow$ Standard Model fields (dominated by the production of Higgs bosons). This lower gravitational bound becomes the effective maximal temperature for reheating temperatures, $T_{\rm{RH}} \lesssim 10^9$ GeV. The processes we consider are all minimal in the sense that they are present in any non-minimal extension of the Standard Model theory based on Einstein gravity and can not be neglected. We compare each of these processes to determine their relative importance in the production of both radiation and dark matter., Comment: 15 pages, 4 figures, 2 tables; v2: fixed the Lagrangian and production rates

We consider the effects of non-minimal couplings to curvature of the form $\xi_S S^2 R$, for three types of scalars: the Higgs boson, the inflaton, and a scalar dark matter candidate. We compute the abundance of dark matter produced by these non-minimal couplings to gravity and compare to similar results with minimal couplings. We also compute the contribution to the radiation bath during reheating. The main effect is a potential augmentation of the maximum temperature during reheating. A model independent limit of $\mathcal{O}(10^{12})$ GeV is obtained. For couplings $\xi_S \gtrsim \mathcal{O}(1)$, these dominate over minimal gravitational interactions., Comment: 14 pages, 8 figures

Recent BICEP/Keck data on the cosmic microwave background, in combination with previous WMAP and Planck data, impose strong new constraints on the tilt in the scalar perturbation spectrum, $n_s$, as well as the tensor-to-scalar ratio, $r$. These constrain the number of e-folds of inflation, $N_*$, the magnitude of the inflaton coupling to matter, $y$, and the reheating temperature, $T_{\rm reh}$, which we evaluate in attractor models of inflation as formulated in no-scale supergravity. The 68% C.L. region of $(n_s, r)$ favours large values of $N_*, y$ and $T_{\rm reh}$ that are constrained by the production of gravitinos and supersymmetric dark matter., v1: 9 pages, 2 figures. v2: 10 pages, 3 figures, added discussion of constraints of 2112.07961. v3: matches published version

We consider the production of dark matter during the process of reheating after inflation. The relic density of dark matter from freeze-in depends on both the energy density and energy distribution of the inflaton scattering or decay products composing the radiation bath. We compare the perturbative and non-perturbative calculations of the energy density in radiation. We also consider the (likely) possibility that the final state scalar products are unstable. Assuming either thermal or non-thermal energy distribution functions, we compare the resulting relic density based on these different approaches. We show that the present-day cold dark matter density can be obtained through freeze-in from preheating for a large range of dark matter masses., Comment: 39 pages, 13 figures

We re-examine the extremely metal-poor (XMP) dwarf galaxy AGC 198691 using a high quality spectrum obtained by the LBT's MODS instrument. Previous spectral observations obtained from KOSMOS on the Mayall 4-m and the Blue Channel spectrograph on the MMT 6.5-m telescope did not allow for the determination of sulfur, argon, or helium abundances. We report an updated and full chemical abundance analysis for AGC 198691, including confirmation of the extremely low "direct" oxygen abundance with a value of 12 + log(O/H) = 7.06 $\pm$ 0.03. AGC 198691's low metallicity potentially makes it a high value target for helping determine the primordial helium abundance ($Y_p$). Though complicated by a Na I night sky line partially overlaying the He I $\lambda$5876 emission line, the LBT/MODS spectrum proved adequate for determining AGC 198691's helium abundance. We employ the recently expanded and improved model of Aver et al. (2021), incorporating higher Balmer and Paschen lines, augmented by the observation of the infrared helium emission line He I $\lambda$10830 obtained by Hsyu et al. (2020). Applying our full model produced a reliable helium abundance determination, consistent with the expectation for its metallicity. Although this is the lowest metallicity object with a detailed helium abundance, unfortunately, due to its faintness (EW(H$\beta$) $, Comment: 10 pages, 2 figures

The lack of evidence for low-scale supersymmetry suggests that the scale of supersymmetry breaking may be higher than originally anticipated. However, there remain many motivations for supersymmetry including gauge coupling unification and a stable dark matter candidate. Models like pure gravity mediation (PGM) evade LHC searches while still providing a good dark matter candidate and gauge coupling unification. Here, we study the effects of PGM if the input boundary conditions for soft supersymmetry breaking masses are pushed beyond the unification scale and higher dimensional operators are included. The added running beyond the unification scale opens up the parameter space by relaxing the constraints on $\tan\beta$. If higher dimensional operators involving the SU(5) adjoint Higgs are included, the mass of the heavy gauge bosons of SU(5) can be suppressed leading to proton decay, $p\to \pi^0 e^+$, that is within reach of future experiments. Higher dimensional operators involving the supersymmetry breaking field can generate additional contributions to the A- and B-terms of order $m_{3/2}$. The threshold effects involving these A- and B-terms significantly impact the masses of the gauginos and can lead to a bino LSP. In some regions of parameter space the bino can be degenerate with the wino or gluino and give an acceptable dark matter relic density., Comment: 37 pages, 27 figures

We explore a missing-partner model based on the minimal SU(5) gauge group with $\bf{75}$, $\bf{50}$ and $\bf{\overline{50}}$ Higgs representations, assuming a super-GUT CMSSM scenario in which soft supersymmetry-breaking parameters are universal at some high scale $M_{\rm in}$ above the GUT scale $M_{\rm GUT}$. We identify regions of parameter space that are consistent with the cosmological dark matter density, the measured Higgs mass and the experimental lower limit on $\tau(p \to K^+ \nu)$. These constraints can be satisfied simultaneously along stop coannihilation strips in the super-GUT CMSSM with $\tan \beta \sim 3.5 - 5$ where the input gaugino mass $m_{1/2} \sim 15 - 25$~TeV, corresponding after strong renormalization by the large GUT Higgs representations between $M_{\rm in}$ and $M_{\rm GUT}$ to $m_{\rm LSP}, m_{\tilde t_1} \sim 2.5 - 5$~TeV and $m_{\tilde g} \sim 13 - 20$~TeV, with the light-flavor squarks significantly heavier. We find that $\tau(p \to K^+ \nu) \lesssim 3 \times 10^{34}$~yrs throughout the allowed range of parameter space, within the range of the next generation of searches with the JUNO, DUNE and Hyper-Kamiokande experiments., Comment: 30 pages, 13 figures

We consider the direct $s$-channel gravitational production of dark matter during the reheating process. Independent of the identity of the dark matter candidate or its non-gravitational interactions, the gravitational process is always present and provides a minimal production mechanism. During reheating, a thermal bath is quickly generated with a maximum temperature $T_{\rm max}$, and the temperature decreases as the inflaton continues to decay until the energy densities of radiation and inflaton oscillations are equal, at $T_{\rm RH}$. During these oscillations, $s$-channel gravitational production of dark matter occurs. We show that the abundance of dark matter (fermionic or scalar) depends primarily on the combination $T_{\rm max}^4/T_{\rm RH} M_P^3$. We find that a sufficient density of dark matter can be produced over a wide range of dark matter masses: from a GeV to a ZeV., 6 pages, 4 figures; several improvements, version published in Physical Review D

We analyze in detail the perturbative decay of the inflaton oscillating about a generic form of its potential $V(\phi) = \phi^k$, taking into account the effects of non-instantaneous reheating. We show that evolution of the temperature as a function of the cosmological scale factor depends on the spin statistics of the final state decay products when $k > 2$. We also include the inflaton-induced mass of the final states leading to either kinematic suppression or enhancement if the final states are fermionic or bosonic respectively. We compute the maximum temperature reached after inflation, the subsequent evolution of the temperature and the final reheat temperature. We apply our results to the computation of the dark matter abundance through thermal scattering during reheating. We also provide an example based on supersymmetry for the coupling of the inflaton to matter., Comment: 40 pages, 17 figures

We explore the possible values of the $\mu \to e \gamma$ branching ratio, $\text{BR}(\mu\rightarrow e\gamma)$, and the electron dipole moment (eEDM), $d_e$, in no-scale SU(5) super-GUT models with the boundary conditions that soft supersymmetry-breaking matter scalar masses vanish at some high input scale, $M_{\rm in}$, above the GUT scale, $M_{\rm GUT}$. We take into account the constraints from the cosmological cold dark matter density, $\Omega_{CDM} h^2$, the Higgs mass, $M_h$, and the experimental lower limit on the lifetime for $p \to K^+ \bar \nu$, the dominant proton decay mode in these super-GUT models. Reconciling this limit with $\Omega_{CDM} h^2$ and $M_h$ requires the Higgs field responsible for the charge-2/3 quark masses to be twisted, and possibly also that responsible for the charge-1/3 and charged-lepton masses, with model-dependent soft supersymmetry-breaking masses. We consider six possible models for the super-GUT initial conditions, and two possible choices for quark flavor mixing, contrasting their predictions for proton decay with versions of the models in which mixing effects are neglected. We find that $\tau\left(p\rightarrow K^+ \bar{\nu}\right)$ may be accessible to the upcoming Hyper-Kamiokande experiment, whereas all the models predict $\text{BR}(\mu\rightarrow e\gamma)$ and $d_e$ below the current and prospective future experimental sensitivities or both flavor choices, when the dark matter density, Higgs mass and current proton decay constraints are taken into account. However, there are limited regions with one of the flavor choices in two of the models where $\mu \to e$ conversion on a heavy nucleus may be observable in the future. Our results indicate that there is no supersymmetric flavor problem in the class of no-scale models we consider., Comment: 45 pages, 38 figures

We couple a sterile neutrino sector to a spin-3/2 particle and show that with a Planck reduced coupling, we can obtain a sufficiently long lifetime making the spin-3/2 particle a good dark matter candidate. We show that this dark matter candidate can be produced during inflationary reheating through the scattering of Standard Model particles. The relic abundance as determined by Planck and other experimental measurements is attained for reasonable values of the reheating temperature $T_{\rm RH} \gtrsim 10^{8}$ GeV. We consider two possible gauge invariant couplings to the extended Standard Model. We find a large range of masses are possible which respect the experimental limits on its decay rate. We expect smoking-gun signals in the form of a monochromatic photon with a possible monochromatic neutrino, which can be probed in the near future in IceCube and other indirect detection experiments., Comment: 20 pages, 13 figures. v3: matches published version

After reviewing the motivations for cosmological inflation formulated in the formalism of supersymmetry, we argue that the appropriate framework is that of no-scale supergravity. We then show how to construct within this framework inflationary models whose predictions for the tilt in the spectrum of scalar perturbations, $n_s$, and the ratio, $r$, of tensor and scalar perturbations coincide with those of the $R + R^2$ model of inflation proposed by Starobinsky. A more detailed study of no-scale supergravity reveals a structure that is closely related to that of $R^2$ modifications of the minimal Einstein-Hilbert action for general relativity, opening avenues for constructing no-scale de Sitter and anti-de Sitter models by combining pairs of Minkowski models, as well as generalizations of the original no-scale Starobinsky models of inflation. We then discuss the phenomenology of no-scale models of inflation, including inflaton decay and reheating, and then the construction of explicit scenarios based on SU(5), SO(10) and string-motivated flipped SU(5)$\times$U(1) GUT models. The latter provides a possible model of almost everything below the Planck scale, including neutrino masses and oscillations, the cosmological baryon asymmetry and cold dark matter, as well as $n_s$ and $r$., 84 pages, 21 figures, invited review submitted to IJMPD

We propose a model where a long-lived pseudoscalar EeV particle can be produced with sufficient abundance so as to account for the cold dark matter density, despite having a Planck mass suppressed coupling to the thermal bath. Connecting this state to a hidden sterile neutrino sector through derivative couplings, induced by higher dimensional operators, allows one to account for light neutrino masses while having a lifetime that can be much larger than the age of the Universe. Moreover, the same derivative coupling accounts for the production of dark matter in the very first instant of the reheating. Given the sensitivity of the IceCube and ANITA collaborations, we study the possible signatures of such a model in the form of Ultra-High-Energy Cosmic Rays in the neutrino sector, and show that such signals could be detected in the near future., Comment: 13 pages, 5 figures. Typo corrected

We have recently proposed attractor models for modulus fixing, inflation, supersymmetry breaking and dark energy based on no-scale supergravity. In this paper we develop phenomenological and cosmological aspects of these no-scale attractor models that underpin their physical applications. We consider models in which inflation is driven by a modulus field ($T$-type) with supersymmetry broken by a Polonyi field, or a matter field ($\phi$-type) with supersymmetry broken by the modulus field. We derive the possible patterns of soft supersymmetry-breaking terms, which depend in $T$-type models whether the Polonyi and/or matter fields are twisted or not, and in $\phi$-type models on whether the inflaton and/or other matter fields are twisted or not. In $\phi$-type models, we are able to directly relate the scale of supersymmetry breaking to the inflaton mass. We also discuss cosmological constraints from entropy considerations and the density of dark matter on the mechanism for stabilizing the modulus field via higher-order terms in the no-scale K\"ahler potential., Comment: 41 pages, 2 figures, published version

We perform a systematic analysis of dark matter production during post-inflationary reheating. Following the period of exponential expansion, the inflaton begins a period of damped oscillations as it decays. These oscillations and the evolution of temperature of the thermalized decay products depend on the shape of the inflaton potential $V(\Phi)$. We consider potentials of the form $\Phi^k$. Standard matter-dominated oscillations occur for $k=2$. In general, the production of dark matter may depend on either (or both) the maximum temperature after inflation, or the reheating temperature, where the latter is defined when the Universe becomes radiation dominated. We show that dark matter production is sensitive to the inflaton potential and depends heavily on the maximum temperature when $k>2$. We also consider the production of dark matter with masses larger than the reheating temperature., Comment: 15 pages, 5 figures

We propose a non-oscillatory no-scale supergravity model of inflation (NO-NO inflation) in which the inflaton does not oscillate at the end of the inflationary era. Instead, the Universe is then dominated by the inflaton kinetic energy density (kination). During the transition from inflation to kination, the Universe preheats instantly through a coupling to Higgs-like fields. These rapidly annihilate and scatter into ultra-relativistic matter particles, which subsequently dominate the energy density, and reheating occurs at a temperature far above that of Big Bang Nucleosynthesis. After the electroweak transition, the inflaton enters a tracking phase as in some models of quintessential inflation. The model predictions for cosmic microwave background observables are consistent with Planck 2018 data, and the density of gravitational waves is below the upper bound from Big Bang Nucleosynthesis. We also find that the density of supersymmetric cold dark matter produced by gravitino decay is consistent with Planck 2018 data over the expected range of supersymmetric particle masses., Comment: 16 pages, 7 figures, accepted for publication in JCAP

Currently, the primordial helium abundance is best estimated through spectroscopic observations of H II regions in metal-poor galaxies. However these determinations are limited by several systematic uncertainties which ultimately limit our ability to accurately ascertain the primordial abundance. In this study, we improve the methodologies for solving for the reddening, the emission contributions from collisional excitation of the H I atoms, the effects underlying absorption in the H I and He I emission lines, and the treatment of the blended H I and He I emission at $\lambda$3889 with the aim of lowering the systematic uncertainties in helium abundance determinations. To apply these methods, we have obtained observations of the He I $\lambda$10830 emission line in the brightest H II region in the extremely metal-poor (3$\%$ Z$_{\odot}$) galaxy Leo P with the LUCI1 instrument on the LBT. We combine this measurement with previous MODS/LBT observations to derive an improved helium abundance. In doing so, our present analysis results in a decrease in the uncertainty in the helium abundance of Leo P by approximately 70%. This result is combined with data from other observations to estimate the primordial helium mass fraction, Y$_{p}$ $=$ 0.2453 $\pm$ 0.0034., Comment: 30 pages, 3 figures

No-scale supergravity provides a successful framework for Starobinsky-like inflation models. Two classes of models can be distinguished depending on the identification of the inflaton with the volume modulus, $T$ (C-models), or a matter-like field, $\phi$ (WZ-models). When supersymmetry is broken, the inflationary potential may be perturbed, placing restrictions on the form and scale of the supersymmetry breaking sector. We consider both types of inflationary models in the context of high-scale supersymmetry. We further distinguish between models in which the gravitino mass is below and above the inflationary scale. We examine the mass spectra of the inflationary sector. We also consider in detail mechanisms for leptogenesis for each model when a right-handed neutrino sector, used in the seesaw mechanism to generate neutrino masses, is employed. In the case of C-models, reheating occurs via inflaton decay to two Higgs bosons. However, there is a direct decay channel to the lightest right-handed neutrino which leads to non-thermal leptogenesis. In the case of WZ-models, in order to achieve reheating, we associate the matter-like inflaton with one of the right-handed sneutrinos whose decay to the lightest right handed neutrino simultaneously reheats the Universe and generates the baryon asymmetry through leptogenesis., Comment: 39 pages, 9 figures

Axion cold dark matter from standard misalignment typically requires a decay constant $f_a~\gtrsim~10^{11}$ GeV. Kinetic misalignment and parametric resonance easily allow lower values of $f_a$ when the radial Peccei-Quinn (PQ) symmetry breaking field takes large initial values. Here, we consider the effects of inflation on kinetic misalignment and parametric resonance. We assume that the initial PQ field value is determined by quantum fluctuations, and is set by the Hubble parameter during inflation, $H_I$, and the PQ field mass. PQ field oscillations begin before or after the completion of reheating after inflation at a temperature $T_R$. We determine the range of $f_a$ and the inflationary parameters $(H_I, T_R)$ consistent with axion dark matter for a quartic potential for the PQ field. We find that $4\times 10^8$ GeV $< f_a < 10^{11}$ GeV can consistently produce axion dark matter. A significant portion of the allowed parameter space predicts rare kaon decays, $K_L \rightarrow (��^0 + \rm{missing \; energy})$, and/or suppression of structure formation on small scales., 40 pages, 6 figures

Encouraged by the advent of a new generation of underground detectors---JUNO, DUNE and Hyper-Kamiokande---that are projected to improve significantly on the present sensitivities to various baryon decay modes, we revisit baryon decay in the minimal supersymmetric SU(5) GUT. We discuss the phenomenological uncertainties associated with hadronic matrix elements and the value of the strong coupling $\alpha_s$---which are the most important---the weak mixing angle $\theta_W$, quark masses including one-loop renormalization effects, quark mixing and novel GUT phases that are not visible in electroweak interaction processes. We apply our analysis to a variety of CMSSM, super- and sub-GUT scenarios in which soft supersymmetry-breaking parameters are assumed to be universal at, above and below the GUT scale, respectively. In many cases, we find that the next generation of underground detectors should be able to probe models with sparticle masses that are ${\cal O}(10)$~TeV, beyond the reach of the LHC., Comment: 53 pages, 17 figures

We develop a string-inspired model for particle cosmology, based on a flipped SU(5)$\times$U(1) gauge group formulated in a no-scale supergravity framework. The model realizes Starobinsky-like inflation, which we assume to be followed by strong reheating, with the GUT symmetry being broken subsequently by a light `flaton' field whose decay generates a second stage of reheating. We discuss the production of gravitinos and the non-thermal contribution made by their decays to the density of cold dark matter, which is assumed to be provided by the lightest neutralino. We also discuss the masses of light and heavy neutrinos and leptogenesis. As discussed previously [1], a key r\^ole is played by a superpotential coupling between the inflaton, matter and GUT Higgs fields, called $\lambda_6$. We scan over possible values of $\lambda_6$, exploring the correlations between the possible values of observables. We emphasize that the release of entropy during the GUT transition allows large regions of supersymmetry-breaking parameter space that would otherwise lead to severe overdensity of dark matter. Furthermore, we find that the Big Bang nucleosynthesis lower limit on the reheating temperature of $\sim 1$ MeV restricts the supersymmetry-breaking scale to a range ${\cal O}(10)$ TeV that is consistent with the absence of supersymmetric particles at the LHC., Comment: 33 pages, 13 figures

We show the uniqueness of superpotentials leading to Minkowski vacua of single-field no-scale supergravity models, and the construction of dS/AdS solutions using pairs of these single-field Minkowski superpotentials. We then extend the construction to two- and multifield no-scale supergravity models, providing also a geometrical interpretation. We also consider scenarios with additional twisted or untwisted moduli fields, and discuss how inflationary models can be constructed in this framework., Comment: 31 pages, 8 figures

We present a minimal SU(2,1)/SU(2) x U(1) no-scale model that incorporates in an economical way modulus fixing, Starobinsky-like inflation, an adjustable scale for supersymmetry breaking and the possibility of a small cosmological constant, a.k.a. dark energy., Comment: 6 pages, 1 figure, v2: discussion on phase transitions updated, matches the published version

Measurements of the cosmic microwave background (CMB) favour models of inflation with a small tensor-to-scalar ratio r, as predicted by the Starobinsky R + R^2 model. It has been shown previously that various models based on no-scale supergravity with different forms of superpotential make predictions similar to those of the Starobinsky model. In this paper we present a unified and general treatment of Starobinsky avatars of no-scale supergravity, using the underlying non-compact SU(2,1)/SU(2) x U(1) symmetry to demonstrate equivalences between different models, exhibiting 6 specific equivalence classes., 21 pages, 6 figures; details on stabilization added, version published in JHEP

We discuss the parameter spaces of supersymmetry (SUSY) scenarios taking into account the improved Higgs-mass prediction provided by FeynHiggs 2.14.1. Among other improvements, this prediction incorporates three-loop renormalization-group effects and two-loop threshold corrections, and can accommodate three separate mass scales: m_{\tilde q} (for squarks), m_{\tilde g} (for gluinos) and m_{\tilde\chi} (for electroweakinos). Furthermore, it contains an improved treatment of the DRbar scalar top parameters avoiding problems with the conversion to on-shell parameters, that yields more accurate results for large SUSY-breaking scales. We first consider the CMSSM, in which the soft SUSY-breaking parameters m_0 and m_{1/2} are universal at the GUT scale, and then sub-GUT models in which universality is imposed at some lower scale. In both cases, we consider the constraints from the Higgs-boson mass M_h in the bulk of the (m_0, m_{1/2}) plane and also along stop coannihilation strips where sparticle masses may extend into the multi-TeV range. We then consider the minimal anomaly-mediated SUSY-breaking (mAMSB) scenario, in which large sparticle masses are generic. In all these scenarios the substantial improvements between the calculations of M_h in FeynHiggs 2.14.1 and FeynHiggs 2.10.0, which was used in an earlier study, change significantly the preferred portions of the models' parameter spaces. Finally, we consider the pMSSM11, in which sparticle masses may be significantly smaller and we find only small changes in the preferred regions of parameter space., Comment: 35 pages, 12 figues

We compare dark matter production from the thermal bath in the early universe with its direct production through the decay of the inflaton. We show that even if dark matter does not possess a direct coupling with the inflaton, Standard Model loop processes may be sufficient to generate the correct relic abundance., 12 pages, 8 figures

We assess the status of big-bang nucleosynthesis (BBN) in light of the final Planck data release and other recent developments, and in anticipation of future measurements. Planck data fix the cosmic baryon density to 0.9% precision, and determine the helium abundance and effective number of neutrinos with precision approaching that of astronomical and BBN determinations respectively. In addition, new high-redshift measurements give D/H to better precision than theoretical predictions, and new Li/H data reconfirm the lithium problem. We present new ${}^{7}{\rm Be}(n,p){}^{7}{\rm Li}$ rates using new neutron capture measurements; we have also examined the effect of proposed changes in the $d(p,\gamma){}^{3}{\rm He}$ rates. Using these results we perform a series of likelihood analyses. We assess BBN/CMB consistency, with attention to how our results depend on the choice of Planck data, as well as how the results depend on the choice of non-BBN, non-Planck data sets. Most importantly the lithium problem remains, and indeed is more acute given the very tight D/H observational constraints; new neutron capture data reveals systematics that somewhat increases uncertainty and thus slightly reduces but does not essentially change the problem. We confirm that $d(p,\gamma){}^{3}{\rm He}$ theoretical rates brings D/H out of agreement and slightly increases 7Li; new experimental data are needed at BBN energies. Setting the lithium problem aside, we find the effective number of neutrino species at BBN is $N_\nu = 2.86 \pm 0.15$. Future CMB Stage-4 measurements promise substantial improvements in BBN parameters: helium abundance determinations will be competitive with the best astronomical determinations, and $N_{\rm eff}$ will approach sensitivities capable of detecting the effects of Standard Model neutrino heating of the primordial plasma. (Abridged), Comment: 63 pages, 22 figures. Comments welcome

No-scale supergravity is the appropriate general framework for low-energy effective field theories derived from string theory. The simplest no-scale K\"ahler potential with a single chiral field corresponds to a compactification to flat Minkowski space with a single volume modulus, but generalizations to single-field no-scale models with de Sitter vacua are also known. In this paper we generalize these de Sitter constructions to two- and multi-field models of the types occurring in string compactifications with more than one relevant modulus. We discuss the conditions for stability of the de Sitter solutions and holomorphy of the superpotential, and give examples whose superpotential contains only integer powers of the chiral fields., Comment: 22 pages, 7 figures

Gauge coupling unification and the stability of the Higgs vacuum are among two of the cherished features of low-energy supersymmetric models. Putting aside questions of naturalness, supersymmetry might only be realised in nature at very high energy scales. If this is the case, the preservation of gauge coupling unification and the stability of the Higgs vacuum would certainly require new physics, but it need not necessarily be at weak scale energies. New physics near the unification scale could in principle ensure Grand Unification, while new physics below $\mu \sim 10^{10}$ GeV could ensure the stability of the Higgs vacuum. Surprisingly however, we find that in the context of a supersymmetric SO(10) Grand Unified Theory, gauge coupling unification and the Higgs vacuum stability, when taken in conjunction with existing phenomenological constraints, require the presence of $\mathcal{O}$(TeV)-scale physics. This weak-scale physics takes the form of a complex scalar SU(2)$_L$ triplet with zero hypercharge, originating from the $\mathbf{210}$ of SO(10)., Comment: 30 pages, 20 figures

We revisit the uncertainties in the calculation of spin-independent scattering matrix elements for the scattering of WIMP dark matter particles on nuclear matter. In addition to discussing the uncertainties due to limitations in our knowledge of the nucleonic matrix elements of the light quark scalar densities < N |{\bar u} u, {\bar d} d, {\bar s} s| N>, we also discuss the importances of heavy quark scalar densities < N |{\bar c} c, {\bar b} b, {\bar t} t| N >, and comment on uncertainties in quark mass ratios. We analyze estimates of the light-quark densities made over the past decade using lattice calculations and/or phenomenological inputs. We find an uncertainty in the combination < N |{\bar u} u + {\bar d} d | N > that is larger than has been assumed in some phenomenological analyses, and a range of < N |{\bar s} s| N > that is smaller but compatible with earlier estimates. We also analyze the importance of the {\cal O}(��_s^3) calculations of the heavy-quark matrix elements that are now available, which provide an important refinement of the calculation of the spin-independent scattering cross section. We use for illustration a benchmark CMSSM point in the focus-point region that is compatible with the limits from LHC and other searches., 25 pages, 17 figures

Stop coannihilation may bring the relic density of heavy supersymmetric dark matter particles into the range allowed by cosmology. The efficiency of this process is enhanced by stop-antistop annihilations into the longitudinal (Goldstone) modes of the $W$ and $Z$ bosons, as well as by Sommerfeld enhancement of stop annihilations and the effects of bound states. Since the couplings of the stops to the Goldstone modes are proportional to the trilinear soft supersymmetry-breaking $A$-terms, these annihilations are enhanced when the $A$-terms are large. However, the Higgs mass may be reduced below the measured value if the $A$-terms are too large. Unfortunately, the interpretation of this constraint on the stop coannihilation strip is clouded by differences between the available Higgs mass calculators. For our study, we use as our default calculator FeynHiggs 2.13.0, the most recent publicly available version of this code. Exploring the CMSSM parameter space, we find that along the stop coannihilation strip the masses of the stops are severely split by the large $A$-terms. This suppresses the Higgs mass drastically for $��$ and $A_0 > 0$, whilst the extent of the stop coannihilation strip is limited for $A_0 < 0$ and either sign of $��$. However, in sub-GUT models, reduced renormalization-group running mitigates the effect of the large $A$-terms, allowing larger LSP masses to be consistent with the Higgs mass calculation. We give examples where the dark matter particle mass may reach $\gtrsim 8$ TeV., 26 pages, 28 figures

The abundance of magnesium in the interstellar medium is a powerful probe of star formation processes over cosmological timescales. Magnesium has three stable isotopes, 24Mg, 25Mg, 26Mg, which can be produced both in massive and intermediate-mass (IM) stars with masses between 2 and 8 M_\odot. In this work, we use constraints on the cosmic star formation rate density (SFRD) and explore the role and mass range of intermediate mass stars using the observed isotopic ratios. We compare several models of stellar nucleosynthesis with metallicity-dependent yields and also consider the effect of rotation on the yields massive stars and its consequences on the evolution of the Mg isotopes. We use a cosmic evolution model updated with new observational SFRD data and new reionization constraints coming from 2018 Planck collaboration determinations. We find that the main contribution of 24Mg comes from massive stars whereas 25Mg and 26Mg come from intermediate mass stars. To fit the observational data on magnesium isotopic ratios, an additional intermediate mass SFRD component is preferred. Moreover, the agreement between model and data is further improved when the range of IM masses is narrowed towards higher masses (5-8 M_\odot). While some rotation also improves the fit to data, we can exclude the case where all stars have high rotational velocities due to an over-production of 26Mg., Comment: 12 pages, 17 figures

No-scale supergravity and the flipped SU(5)$\times$U(1) gauge group provide an ambitious prototype string-inspired scenario for physics below the string scale, which can accommodate the Starobinsky-like inflation favoured by observation when the inflaton is associated with one of the singlet fields associated with neutrino mass generation. During inflation, the vacuum remains in the unbroken GUT phase, and GUT symmetry breaking occurs later when a field with a flat direction (the flaton) acquires a vacuum expectation value. Inflaton decay and the reheating process depend crucially on GUT symmetry breaking, as decay channels open and close, depending on the value of the flaton vacuum expectation value. Here, we consider the simultaneous cosmological evolution of both the inflaton and flaton fields after inflation. We distinguish weak, moderate and strong reheating regimes, and calculate in each case the entropy produced as all fields settle to their global minima. These three reheating scenarios differ in the value of a Yukawa coupling that introduces mass mixing between the singlets and the ${\bf 10}$s of SU(5). The dynamics of the GUT transition has an important impact on the production of gravitinos, and we also discuss the pattern of neutrino masses we expect in each of the three cases. Finally, we use recent CMB limits on neutrino masses to constrain the reheating models, finding that neutrino masses and the cosmological baryon asymmetry can both be explained if the reheating is strong., Comment: 49 pages, 21 figures

The European physical journal / C 78(3), 256 (2018). doi:10.1140/epjc/s10052-018-5697-0, We use MasterCode to perform a frequentist analysis of the constraints on a phenomenological MSSM model with 11 parameters, the pMSSM$_{11}$, including constraints from ∼36/fb of LHC data at 13 TeV and PICO, XENON$_1$T and PandaX-II searches for dark matter scattering, as well as previous accelerator and astrophysical measurements, presenting fits both with and without the (g−2)$_μ$ constraint. The pMSSM$_{11}$ is specified by the following parameters: 3 gaugino masses M$_{1,2,3}$, a common mass for the first-and second-generation squarks $m_{\tilde{q}}$ and a distinct third-generation squark mass $m_{\tilde{q}}3$, a common mass for the first-and second-generation sleptons $m_{\tilde{ℓ}}$ and a distinct third-generation slepton mass $m_{\tilde{τ}}$, a common trilinear mixing parameter A, the Higgs mixing parameter μ, the pseudoscalar Higgs mass $M_A$ and tanβ. In the fit including (g−2)$_μ$, a Bino-like $\tilde{χ}^{0}_1$ is preferred, whereas a Higgsino-like $\tilde{χ}^{0}_1$ is mildly favoured when the (g−2)$_μ$ constraint is dropped. We identify the mechanisms that operate in different regions of the pMSSM${11}$ parameter space to bring the relic density of the lightest neutralino, $\tilde{χ}^{0}_1$, into the range indicated by cosmological data. In the fit including (g−2)$_μ$, coannihilations with $\tilde{χ}^{0}_2$ and the Wino-like $\tilde{χ}^{±}_1$ or with nearly-degenerate first- and second-generation sleptons are active, whereas coannihilations with the $\tilde{χ}^{0}_2$ and the Higgsino-like $\tilde{χ}^{±}_1$ or with first- and second-generation squarks may be important when the (g−2)$_μ$ constraint is dropped. In the two cases, we present $χ^2$ functions in two-dimensional mass planes as well as their one-dimensional profile projections and best-fit spectra. Prospects remain for discovering strongly-interacting sparticles at the LHC, in both the scenarios with and without the (g−2)$_μ$ constraint, as well as for discovering electroweakly-interacting sparticles at a future linear $e^{+}e^−$ collider such as the ILC or CLIC., Published by Springer, Berlin

We consider the effects of R-parity violation due to the inclusion of a bilinear $\mu^\prime L H_u$ superpotential term in high scale supersymmetric models with an EeV scale gravitino as dark matter. Although the typical phenomenological limits on this coupling (e.g. due to lepton number violation and the preservation of the baryon asymmetry) are relaxed when the supersymmetric mass spectrum is assumed to be heavy (in excess of the inflationary scale of $3 \times 10^{13}$ GeV), the requirement that the gravitino be sufficiently long-lived so as to account for the observed dark matter density, leads to a relatively strong bound on $\mu^\prime \lesssim 20$ GeV. The dominant decay channels for the longitudinal component of the gravitino are $Z \nu, W^\pm l^\mp$, and $h\nu$. To avoid an excess neutrino signal in IceCube, our limit on $\mu'$ is then strengthened to $\mu' \lesssim 50$ keV. When the bound is saturated, we find that there is a potentially detectable flux of mono-chromatic neutrinos with EeV energies., Comment: 27 pages, 4 figures

We generalize models invoking a spin-2 particle as a mediator between the dark sector and the Standard Model. We show that a massive spin-2 messenger can efficiently play the role of a portal between the two sectors. The dark matter is then produced via a freeze-in mechanism during the reheating epoch. In a large part of the parameter space, production through the exchange of a massive spin-2 mediator dominates over processes involving a graviton with Planck suppressed couplings. We perform a systematic analysis of such models for different values of the spin-2 mass relative to the maximum and the final temperature attained at reheating., Comment: 10 pages, 3 figures

Recent observations in the total luminosity density have led to significant progress in establishing the star formation rate (SFR) at high redshift. Concurrently observed gamma-ray burst rates have also been used to extract the SFR at high redshift. The SFR in turn can be used to make a host of predictions concerning the ionization history of the Universe, the chemical abundances, and supernova rates. We compare the predictions made using a hierarchical model of cosmic chemical evolution based on three recently proposed SFRs: two based on extracting the SFR from the observed gamma-ray burst rate at high redshift, and one based on the observed galaxy luminosity function at high redshift. Using the WMAP/Planck data on the optical depth and epoch of reionization, we find that only the SFR inferred from gamma-ray burst data at high redshift suffices to allow a single mode (in the initial mass function) of star formation which extends from z = 0 to redshifts > 10. For the case of the more conservative SFR based on the observed galaxy luminosity function, the reionization history of the Universe requires a bimodal IMF which includes at least a coeval high (or intermediate) mass mode of star formation at high redshift (z> 10). Therefore, we also consider here a more general bimodal case which includes an early-forming high mass mode as a fourth model to test the chemical history of the Universe. We compute the abundances of several trace elements, as well as the expected supernova rates, the stellar mass density and the specific SFR, sSFR, as a function of redshift for each of the four models considered. We conclude that observational constraints on the global metallicity and optical depth at high redshift favor unseen faint but active star forming galaxies as pointed out in many recent studies., 29 pages, 18 figures

We show that $R^2$ gravity coupled conformally to scalar fields is equivalent to the real bosonic sector of SU(N,1)/SU(N)$\times$U(1) no-scale supergravity, where the conformal factor can be identified with the K\"ahler potential, and we review the construction of Starobinsky-like models of inflation within this framework., Comment: 15 pages, version accepted for publication

We describe a likelihood analysis using MasterCode of variants of the MSSM in which the soft supersymmetry-breaking parameters are assumed to have universal values at some scale M below the supersymmetric grand unification scale M, as can occur in mirage mediation and other models. In addition to M, such ‘sub-GUT’ models have the 4 parameters of the CMSSM, namely a common gaugino mass m, a common soft supersymmetry-breaking scalar mass m, a common trilinear mixing parameter A and the ratio of MSSM Higgs vevs tan β, assuming that the Higgs mixing parameter μ> 0. We take into account constraints on strongly- and electroweakly-interacting sparticles from ∼ 36 /fb of LHC data at 13 TeV and the LUX and 2017 PICO, XENON1T and PandaX-II searches for dark matter scattering, in addition to the previous LHC and dark matter constraints as well as full sets of flavour and electroweak constraints. We find a preference for M∼ 10 to 109GeV, with M∼ M disfavoured by Δ χ∼ 3 due to the BR (Bs,d → μ+μ−) constraint. The lower limits on strongly-interacting sparticles are largely determined by LHC searches, and similar to those in the CMSSM. We find a preference for the LSP to be a Bino or Higgsino with mχ~10∼1TeV, with annihilation via heavy Higgs bosons H / A and stop coannihilation, or chargino coannihilation, bringing the cold dark matter density into the cosmological range. We find that spin-independent dark matter scattering is likely to be within reach of the planned LUX-Zeplin and XENONnT experiments. We probe the impact of the (g- 2) constraint, finding similar results whether or not it is included., The work of E. B. and G. W. is supported in part by the Collaborative Research Center SFB676 of the DFG, “Particles, Strings and the early Universe”. The work of M. B. and D. M. S. is supported by the European Research Council via Grant BSMFLEET 639068. The work of J. C. C. is supported by CNPq (Brazil). The work of M. J. D. is supported in part by the Australia Research Council. The work of J. E. is supported in part by STFC (UK) via the research Grant ST/L000326/1 and in part via the Estonian Research Council via a Mobilitas Pluss grant, and the work of H. F. is also supported in part by STFC (UK). The work of S. H. is supported in part by the MEINCOP Spain under contract FPA2016-78022-P, in part by the Spanish Agencia Estatal de Investigación (AEI) and the EU Fondo Europeo de Desarrollo Regional (FEDER) through the project FPA2016-78645-P, in part by the AEI through the Grant IFT Centro de Excelencia Severo Ochoa SEV-2016-0597, and by the Spanish MICINN Consolider-Ingenio 2010 Program under Grant MultiDark CSD2009-00064. The work of M. L. and I. S. F. is supported by XuntaGal. The work of K.A.O. is supported in part by DOE Grant de-sc0011842 at the University of Minnesota. K. S. thanks the TU Munich for hospitality during the final stages of this work and has been partially supported by the DFG cluster of excellence EXC 153 “Origin and Structure of the Universe, by the Collaborative Research Center SFB1258. The work of K. S. is also partially supported by the National Science Centre, Poland, under research Grants DEC-2014/15/B/ST2/02157, DEC-2015/18/M/ST2/00054 and DEC-2015/19/D/ST2/03136. The work of G. W. is also supported in part by the European Commission through the “HiggsTools” Initial Training Network PITN-GA-2012-316704. Funded by SCOAP3

In the first stages of inflationary reheating, the temperature of the radiation produced by inflaton decays is typically higher than the commonly defined reheating temperature $T_{RH} \sim (\Gamma_\phi M_P)^{1/2}$ where $\Gamma_\phi$ is the inflaton decay rate. We consider the effect of particle production at temperatures at or near the maximum temperature attained during reheating. We show that the impact of this early production on the final particle abundance depends strongly on the temperature dependence of the production cross section. For $\langle \sigma v \rangle \sim T^n/M^{n+2}$, and for $n < 6$, any particle produced at $T_{\rm max}$ is diluted by the later generation of entropy near $T_{RH}$. This applies to cases such as gravitino production in low scale supersymmetric models ($n=0$) or NETDM models of dark matter ($n=2$). However, for $n\ge6$ the net abundance of particles produced during reheating is enhanced by over an order of magnitude, dominating over the dilution effect. This applies, for instance to gravitino production in high scale supersymmetry models where $n=6$., Comment: 16 pages, 5 figures

We embed a flipped ${\rm SU}(5) \times {\rm U}(1)$ GUT model in a no-scale supergravity framework, and discuss its predictions for cosmic microwave background observables, which are similar to those of the Starobinsky model of inflation. Measurements of the tilt in the spectrum of scalar perturbations in the cosmic microwave background, $n_s$, constrain significantly the model parameters. We also discuss the model's predictions for neutrino masses, and pay particular attention to the behaviours of scalar fields during and after inflation, reheating and the GUT phase transition. We argue in favor of strong reheating in order to avoid excessive entropy production which could dilute the generated baryon asymmetry., 51 pages, 13 figures

We have presented previously a general treatment of Starobinsky-like inflation in no-scale supergravity where the tensor-to-scalar ratio $r = 3(1 - n_s)^2$, and $n_s$ is the tilt of the scalar perturbations. In particular, we have shown how this scenario can be unified with modulus fixing, supersymmetry breaking and a small cosmological constant. In this paper we extend these constructions to inflationary models based on generalized no-scale structures. In particular, we consider alternative values of the curvature parameter, $\alpha < 1$, as may occur if not all the complex K\"ahler moduli contribute to driving inflation, as well as $\alpha > 1$, as may occur if complex structure moduli also contribute to driving inflation. In all cases, we combine these $\alpha$-Starobinsky inflation models with supersymmetry breaking and a present-day cosmological constant, allowing for additional contributions to the vacuum energy from stages of gauge symmetry breaking., Comment: 32 pages, 4 figures

The European physical journal / C 77(2), 104(2017). doi:10.1140/epjc/s10052-017-4639-6, We perform a likelihood analysis of the constraints from accelerator experiments and astrophysical observations on supersymmetric (SUSY) models with SU(5) boundary conditions on soft SUSY-breaking parameters at the GUT scale. The parameter space of the models studied has seven parameters: a universal gaugino mass m$_{1/2}$, distinct masses for the scalar partners of matter fermions in five- and ten-dimensional representations of SU(5), m$_5$ and m$_{10}$, and for the 5 and $\bar{5}$ Higgs representations m$_{{H}_{u}}$ and m$_{{H}_{d}}$ , a universal trilinear soft SUSY-breaking parameter A$_0$, and the ratio of Higgs vevs tanβ. In addition to previous constraints from direct sparticle searches, low-energy and flavour observables, we incorporate constraints based on preliminary results from 13 TeV LHC searches for jets + $E\!\!\!/_T$events and long-lived particles, as well as the latest PandaX-II and LUX searches for direct Dark Matter detection. In addition to previously identified mechanisms for bringing the supersymmetric relic density into the range allowed by cosmology, we identify a novel $\tilde{u}_{R}/\tilde{c}_{R} − \tilde{χ}^{0}_1$ coannihilation mechanism that appears in the supersymmetric SU(5) GUT model and discuss the role of $\tilde{\nu}_\tau$ coannihilation. We find complementarity between the prospects for direct Dark Matter detection and SUSY searches at the LHC., Published by Springer, Berlin

In this article, we study the renormalization group equations of the Next-to-Minimal Supersymmetric Standard Model, and investigate universality conditions on the soft supersymmetry-breaking parameters at the Grand Unification scale. We demonstrate that the inclusion of right-handed neutrino superfields can have a substantial effect on the running of the soft terms (greatly contributing to driving the singlet Higgs mass- squared parameter negative), which makes it considerably easier to satisfy the conditions for radiative electroweak symmetry-breaking. The new fields also lead to larger values of the Standard Model Higgs mass, thus making it easier to reproduce the measured value. We investigate the phenomenology of this constrained scenario, and focus on two viable benchmark points, which feature a neutral lightest supersymmetric particle (either the lightest neutralino or the right-handed sneutrino). We show that all bounds from colliders and low-energy observables can be fulfilled in wide areas of the parameter space. However, the relic density in these regions is generally too high requiring some form of late entropy production to dilute the density of the lightest supersymmetric particle., Comment: 21 pages, 4 figures

Stellar core collapse events are expected to produce gravitational waves via several mechanisms, most of which are not yet fully understood due to the current limitations in the numerical simulations of these events. In this paper, we begin with an empirical functional form that fits the gravitational-wave spectra from existing simulations of stellar core collapse and integrate over all collapse events in the universe to estimate the resulting stochastic gravitational-wave background. We then use a Gaussian functional form to separately fit and model a low-frequency peak in the core-collapse strain spectra, which likely occurs due to prompt convection. We systematically study the parameter space of both models, as well as the combined case, and investigate their detectability by upcoming gravitational-wave detectors, such as Advanced LIGO and Einstein Telescope. Assuming realistic formation rates for progenitors of core-collapse supernovae, our results indicate that both models are 2--4 orders of magnitude below the expected sensitivity of Advanced LIGO, and 1--2 orders of magnitude below that of the Einstein Telescope., 13 pages, 11 figures