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All sourcesNASA NTRSDOE OSTI
DOE OSTI2014

Self-unitarization of New Higgs Inflation and compatibility with Planck and BICEP2 data

In this paper we show that the Germani-Kehagias model of Higgs inflation (or New Higgs Inflation), where the Higgs boson is kinetically non-minimally coupled to the Einstein tensor is in perfect compatibility with the latest Planck and BICEP2 data. Moreover, we show that the tension between the Planck and BICEP2 data can be relieved within the New Higgs inflation scenario by a negative running of the spectral index. Regarding the unitarity of the model, we argue that it is unitary throughout the evolution of the Universe. Weak couplings in the Higgs-Higgs and Higgs-graviton sectors are provided by a large background dependent cut-off scale during inflation. In the same regime, the W and Z gauge bosons acquire a very large mass, thus decouple. On the other hand, if they are also non-minimally coupled to the Higgs boson, their effective masses can be enormously reduced. In this case, the W and Z bosons are no longer decoupled. After inflation, the New Higgs model is well approximated by a quartic Galileon with a renormalizable potential. We argue that this can unitarily create the right conditions for inflation to eventually start.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2015

Hill crossing during preheating after hilltop inflation

In ''hilltop inflation'', inflation takes place when the inflaton field slowly rolls from close to a maximum of its potential (i.e. the ''hilltop'') towards its minimum. When the inflaton potential is associated with a phase transition, possible topological defects produced during this phase transition, such as domain walls, are efficiently diluted during inflation. It is typically assumed that they also do not reform after inflation, i.e. that the inflaton field stays on its side of the ''hill'', finally performing damped oscillations around the minimum of the potential. In this paper we study the linear and the non-linear phases of preheating after hilltop inflation. We find that the fluctuations of the inflaton field during the tachyonic oscillation phase grow strong enough to allow the inflaton field to form regions in position space where it crosses ''over the top of the hill'' towards the ''wrong vacuum''. We investigate the formation and behaviour of these overshooting regions using lattice simulations: rather than durable domain walls, these regions form oscillon-like structures (i.e. localized bubbles that oscillate between the two vacua) which should be included in a careful study of preheating in hilltop inflation.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2015

WIMP dark matter and unitarity-conserving inflation via a gauge singlet scalar

A gauge singlet scalar with non-minimal coupling to gravity can drive inflation and later freeze out to become cold dark matter. We explore this idea by revisiting inflation in the singlet direction (S-inflation) and Higgs Portal Dark Matter in light of the Higgs discovery, limits from LUX and observations by Planck. We show that large regions of parameter space remain viable, so that successful inflation is possible and the dark matter relic abundance can be reproduced. Moreover, the scalar singlet can stabilise the electroweak vacuum and at the same time overcome the problem of unitarity-violation during inflation encountered by Higgs Inflation, provided the singlet is a real scalar. The 2-σ Planck upper bound on n{sub s} imposes that the singlet mass is below 2 TeV, so that almost the entire allowed parameter range can be probed by XENON1T.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2016

Higgs inflation, reheating and gravitino production in no-scale Supersymmetric GUTs

We extend our previous study of supersymmetric Higgs inflation in the context of no-scale supergravity and grand unification, to include models based on the flipped SU(5) and the Pati-Salam group. Like the previous SU(5) GUT model, these yield a class of inflation models whose inflation predictions interpolate between those of the quadratic chaotic inflation and Starobinsky-like inflation, while avoiding tension with proton decay limits. We further analyse the reheating process in these models, and derive the number of e-folds, which is independent of the reheating temperature. We derive the corresponding predictions for the scalar tilt and the tensor-to-scalar ratio in cosmic microwave background perturbations, as well as discussing the gravitino production following inflation.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2021

Realistic inflation in no-scale U(1) R symmetric flipped SU(5)

We have realized non-minimal Higgs inflation and standard hybrid inflation in the supersymmetric flipped SU(5) model with U(1) R symmetry using the no-scale form of the Kähler potential. In non-minimal Higgs inflation the waterfall Higgs field plays the role of inflaton, and in standard hybrid inflation the gauge singlet field S is employed as an inflaton. The predictions of both models are in good agreement with the Planck 2018 data. For numerical calculations we have fixed the gauge symmetry breaking scale, M, around 2 × 10 16 GeV. In both models the inflaton field values are constrained below m P . The tensor to scalar ratio r in non-minimal inflation is of the order of 10 -3 and for standard hybrid inflation r is tiny, of order 10 -15 –10 -4 . The scalar spectral index in both cases lie within the Planck 1-σ bounds, and the running of the scalar spectral index lies in the range, -dn s /d ln k ~ 6 × 10 -4 for non-minimal model and 10 -9 –10 -3 for the standard hybrid model. A realistic scenario of reheating and non-thermal leptogenesis is employed with reheat temperature T r ~ 10 9 GeV for non-minimal model and 10 6 –10 10 GeV for standard hybrid model. The R-symmetry plays a vital role in forbidding rapid proton decay, but at the same time it also suppresses terms responsible for generating right handed neutrino masses. A realistic scenario of right handed neutrino masses is obtained by considering effective R symmetry breaking at the nonrenormalizable level with adequate suppression of rapid proton decay.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2021

Lattice simulations of inflation

The scalar field theory of cosmological inflation constitutes nowadays one of the preferred scenarios for the physics of the early universe. In this paper we aim at studying the inflationary universe making use of a numerical lattice simulation. Various lattice codes have been written in the last decades and have been extensively used for understating the reheating phase of the universe, but they have never been used to study the inflationary phase itself far from the end of inflation (i.e. about 50 e-folds before the end of inflation). In this paper we use a lattice simulation to reproduce the well-known results of some simple models of single-field inflation, particularly for the scalar field perturbation. The main model that we consider is the standard slow-roll inflation with an harmonic potential for the inflaton field. We explore the technical aspects that need to be accounted for in order to reproduce with precision the nearly scale invariant power spectrum of inflaton perturbations. We also consider the case of a step potential, and show that the simulation is able to correctly reproduce the oscillatory features in the power spectrum of this model. Even if a lattice simulation is not needed in these cases, that are well within the regime of validity of linear perturbation theory, this sets the basis to future work on using lattice simulations to study more complicated models of inflation.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2025

Cosmological perturbations from a new approach to inflation

In a previous paper, we proposed a new approach to the beginning of inflation—a lingering universe [Melcher et al. Phys. Rev. D 110, 063517 (2024).]—that is a quasistatic phase prior to inflation. The Universe begins in a lingering state with a nearly vanishing Hubble parameter. This calls into question the absolute age of the Universe, as the Hubble time can be nearly infinite. It also provides promise for addressing the initial singularity of inflation and issues with quantum field theory in de Sitter spacetime. Such models arise in classical cosmologies with nonvanishing spatial curvature (inspired by PLANCK 2018 data) and independently by models that arise in string cosmology. Here, in this paper, we consider the importance of cosmological perturbations for the stability of the lingering phase and how this influences cosmological observations. Our goal is to establish observables in this new paradigm for the origin of inflation, which is in contrast to eternal inflation and cyclic cosmologies. We also address questions of stability and the transition to inflation.

cosmology↗
NASA NTRS2019

Inflatable Technology: Using Flexible Materials to Make Large Structures

Space structures are one of the most critical components for any spacecraft, as they must provide the maximum amount of livable volume with the minimum amount of mass. Deployable structures can be used to gain additional space that would not normally fit under a launch vehicle shroud. This expansion capability allows it to be packed in a small launch volume for launch, and deploy into its fully open volume once in space. Inflatable, deployable structures in particular, have been investigated by NASA since the early 1950’s and used in a number of spaceflight applications. Inflatable satellites, booms, and antennas can be used in low-Earth orbit applications. Inflatable heatshields, decelerators, and airbags can be used for entry, descent and landing applications. Inflatable habitats, airlocks, and space stations can be used for in-space living spaces and surface exploration missions. Inflatable blimps and rovers can be used for advanced missions to other worlds. These applications are just a few of the possible uses for inflatable structures that will continued to be studied as we look to expand our presence throughout the solar system.

structures↗
DOE OSTI2016

Primordial gravitational waves for universality classes of pseudoscalar inflation

Current bounds from the polarization of the CMB predict the scale-invariant gravitational wave (GW) background of inflation to be out of reach for upcoming GW interferometers. This prospect dramatically changes if the inflaton is a pseudoscalar, in which case its generic coupling to any abelian gauge field provides a new source of GWs, directly related to the dynamics of inflation. This opens up new ways of probing the scalar potential responsible for cosmic inflation. Dividing inflation models into universality classes, we analyze the possible observational signatures. One of the most promising scenarios is Starobinsky inflation, which may lead to observational signatures both in direct GW detection as well as in upcoming CMB detectors. In this case, the complementarity between the CMB and direct GW detection, as well as the possibility of a multi-frequency analysis with upcoming ground and space based GW interferometers, may provide a first clue to the microphysics of inflation.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2016

On the thermodynamic origin of the initial radiation energy density in warm inflation

In warm inflation scenarios, radiation always exists, so that the radiation energy density is also assumed to be finite when inflation starts. To find out the origin of the non-vanishing initial radiation energy density, we revisit thermodynamic analysis for a warm inflation model and then derive an effective Stefan-Boltzmann law which is commensurate with the temperature-dependent effective potential by taking into account the non-vanishing trace of the total energy-momentum tensors. The effective Stefan-Boltzmann law shows that the zero energy density for radiation at the Grand Unification epoch increases until the inflation starts and it becomes eventually finite at the initial stage of warm inflation. By using the above effective Stefan-Boltzmann law, we also study the cosmological scalar perturbation, and obtain the sufficient radiation energy density in order for GUT baryogenesis at the end of inflation.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2017

CMB spectral distortion constraints on thermal inflation

Thermal inflation is a second epoch of exponential expansion at typical energy scales V {sup 1/4} ∼ 10{sup 6} {sup ∼} {sup 8} GeV. If the usual primordial inflation is followed by thermal inflation, the primordial power spectrum is only modestly redshifted on large scales, but strongly suppressed on scales smaller than the horizon size at the beginning of thermal inflation, k > k {sub b} = a {sub b} H {sub b}. We calculate the spectral distortion of the cosmic microwave background generated by the dissipation of acoustic waves in this context. For k {sub b} || 10{sup 3} Mpc{sup −1}, thermal inflation results in a large suppression of the μ-distortion amplitude, predicting that it falls well below the standard value of μ ≅ 2× 10{sup −8}. Thus, future spectral distortion experiments, similar to PIXIE, can place new limits on the thermal inflation scenario, constraining k {sub b} ∼> 10{sup 3} Mpc{sup −1} if μ ≅ 2× 10{sup −8} were found.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2017

Inflection-point inflation in a hyper-charge oriented U ( 1 ) X model

Inflection-point inflation is an interesting possibility to realize a successful slow-roll inflation when inflation is driven by a single scalar field with its value during inflation below the Planck mass (ΦI≲M Pl ). In order for a renormalization group (RG) improved effective λΦ 4 potential to develop an inflection-point, the running quartic coupling λ(Φ) must exhibit a minimum with an almost vanishing value in its RG evolution, namely λ(Φ I )≃0 and β λ (ΦI)≃0, where β λ is the beta-function of the quartic coupling. Here in this paper, we consider the inflection-point inflation in the context of the minimal gauged U(1) X extended Standard Model (SM), which is a generalization of the minimal U(1) B$-$L model, and is constructed as a linear combination of the SM U(1) Y and U(1) B$-$L gauge symmetries. We identify the U(1) X Higgs field with the inflaton field. For a successful inflection-point inflation to be consistent with the current cosmological observations, the mass ratios among the U(1) X gauge boson, the right-handed neutrinos and the U(1) X Higgs boson are fixed. Focusing on the case that the extra U(1) X gauge symmetry is mostly aligned along the SM U(1) Y direction, we investigate a consistency between the inflationary predictions and the latest LHC Run-2 results on the search for a narrow resonance with the di-lepton final state.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2017

Thermal inflation with flaton chemical potential

Thermal inflation driven by a scalar field called a “flaton” is a possible scenario to solve the cosmological moduli problem. Here we study a model of thermal inflation with a flaton chemical potential. In the presence of the chemical potential, a negative mass squared of the flaton—which is necessary to terminate thermal inflation—is naturally induced. We identify the allowed parameter region for the chemical potential (μ) and the flaton self-coupling constant to solve the cosmological moduli problem and satisfy theoretical consistencies. In general, the chemical potential is a free parameter and it can be taken to be much larger than the typical scale of soft supersymmetry-breaking parameters of O(1) TeV. For μ≳10 8 GeV, we find that the reheating temperature after thermal inflation can be high enough for the thermal leptogenesis scenario to be operative. This is in sharp contrast to the standard thermal inflation scenario, in which the reheating temperature is quite low and a special mechanism is necessary for generating a sufficient amount of baryon asymmetry in the Universe after thermal inflation.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2017

A Measurement of Radius Inflation in the Pleiades and Its Relation to Rotation and Lithium Depletion

Precise measurements of eclipsing binary parameters and statistical studies of young clusters have suggested that some magnetically active low-mass dwarfs possess radii inflated by ∼5%–15% relative to theoretical expectations. If true, this effect should be pronounced in young open clusters, due to the rapid rotation and strong magnetic activity of their most extreme members. We explore this possibility by determining empirical radii for 83 members of the nearby Pleiades open cluster, using spectral energy distribution fitting to establish F{sub bol} with a typical accuracy of ≈3% together with color and spectro-photometric indices to determine T{sub eff}. We find several Pleiades members with radii inflated above radius-T{sub eff} models from state-of-the-art calculations, and apparent dispersions in radii for the K-dwarfs of the cluster. Moreover, we demonstrate that this putative radius inflation correlates strongly with rotation rate, consistent with inflation of young stars by magnetic activity and/or starspots. We argue that this signal is not a consequence of starspot-induced color anomalies, binarity, or depth effects in the cluster, employing Gaia DR1 distances as a check. Finally, we consider the lithium abundances of these stars, demonstrating a triple correlation between rotation rate, radius inflation, and enhanced lithium abundance. Our result—already significant to ∼99.99% confidence—provides strong support for a magnetic origin of the inflated radii and lithium dispersion observed in young, low-mass stars.

79 ASTRONOMY AND ASTROPHYSICS↗
NASA NTRS2000

Preventing Damaging Pressure Gradients at the Walls of an Inflatable Space System

An inflatable structural system to deploy a space system such as a solar shield, an antenna or another similar instrument, requires a stiffening element after it is extended by the inflated gas pressure. The stiffening element has to be packaged in a folded configuration before the deployment. It must be relatively small, lightweight, non-damaging to the inflated system, and be able to become stiff in a short time. One stiffening method is to use a flexible material inserted in the deployable system, which, upon a temperature curing, can become stiff and is capable to support the entire structure. There are two conditions during the space operations when the inflated volume could be damaged: during the transonic region of the launch phase and when the curing of the rigidizing element occurs. In both cases, an excess of pressure within the volume containing the rigid element could burst the walls of the low-pressure gas inflated portion of the system. This paper investigates those two conditions and indicates the vents, which will prevent those damaging overpressures. Vent openings at the non-inflated volumes have been calculated for the conditions existing during the launch. Those vents allow the initially folded volume to exhaust the trapped atmospheric gas at approximately the same rate as the ambient pressure drops. That will prevent pressure gradients across the container walls which otherwise could be as high as 14.7 psi. The other condition occurring during the curing of the stiffening element has been investigated. This has required the testing of the element to obtain the gas generation during the curing and the transformation from a pliable material to a rigid one. The tested material is a composite graphite/epoxy weave. The outgassing of the uncured sample at 121C was carried with the Cahn Microbalance and with other outgassing facilities including the micro-CVCM ASTM E-595 facility. The tests provided the mass of gas evolved during the test. That data, including the chemical nature of the evolved gas, provided the data for the calculation of the pressure produced within the volume. The evaluation of the areas of the vents that would prevent excessive pressures and provide a rapid release of the gas away from contamination sensitive surfaces has been carried out. The pressure decay with time has been indicated.

Scialdone, John J.↗
NASA NTRS2000

Preventing Damaging Pressure Gradients at the Walls of an Inflatable Space System

An inflatable structural system to deploy a space system such as a solar shield, an antenna or another similar instrument requires a stiffening element after it is extended by the inflated gas pressure. The stiffening element has to be packaged in folded configuration before the deployment. It must be relatively small, lightweight, non-damaging to the inflated system and be able to become stiff in a short time. One stiffening method is to use a flexible material inserted in the deployable system, which, upon a temperature curing, can become stiff and is capable of supporting the entire structure. There are two conditions during the space operations when the inflated volume could be damaged: during the transonic region of the launch phase and when the curing of the rigidizing element occurs. In both cases, an excess of pressure within the volume containing the rigid element could burst the walls of the low-pressure gas inflated portion of the system. This paper investigates those two conditions and indicates the vents, which will prevent those damaging overpressures. Vent openings at the non-inflated volumes have been calculated for the conditions existing during the launch. Those vents allow the initially folded volume to exhaust the trapped atmospheric gas at approximately the same rate as the ambient pressure drops. That will prevent pressure gradients across the container walls which otherwise could be as high as 14.7 psi. The other condition occurring during the curing of the stiffening element has been investigated. This has required the testing of the element to obtain the gas generation during the curing and the transformation from a pliable material to a rigid on The tested material is a composite graphite/epoxy weave. The outgassing of the uncured sample at 121 deg Celcius was carried with the Cahn Microbalance and with other outgassing facilities including the micro-CVCM ASTM E-595 facility. The test provided the mass of gas evolved during the test. That data, including the chemical nature of the evolved gas, provided the data for the calculation of the pressure produced within the volume. The evaluation of the areas of the vents that would prevent excessive pressures and provide a rapid release of the gas away from contamination sensitive surfaces has be carried out. The pressure decay with time has been indicated.

Scialdone, John J.↗
NASA NTRS2001

Dynamic Characterization of an Inflatable Concentrator for Solar Thermal Propulsion

An inflatable structural system that is a technology demonstrator for solar thermal propulsion and other applications is characterized for structural dynamic behavior both experimentally and computationally. The inflatable structure is a pressurized assembly developed for use in orbit to support a Fresnel lens or inflatable lenticular element for focusing sunlight into a solar thermal rocket engine. When the engine temperature reaches a pre-set level, the propellant is injected into the engine, absorbs heat from an exchanger, and is expanded through the nozzle to produce thrust. The inflatable structure is a passively adaptive system in that a regulator and relief valve are utilized to maintain pressure within design limits during the full range of orbital conditions. Modeling and test activities are complicated by the fact that the polyimide film material used for construction of the inflatable is nonlinear, with modulus varying as a function of frequency, temperature, and level of excitation. Modal vibration testing and finite element modeling are described in detail in this paper. The test database is used for validation and modification of the model. This work is highly significant because of the current interest in inflatable structures for space application, and because of the difficulty in accurately modeling such systems.

Leigh, Larry↗
NASA NTRS2005

Development of Inflatable Entry Systems Technologies

Achieving the objectives of NASA s Vision for Space Exploration will require the development of new technologies, which will in turn require higher fidelity modeling and analysis techniques, and innovative testing capabilities. Development of entry systems technologies can be especially difficult due to the lack of facilities and resources available to test these new technologies in mission relevant environments. This paper discusses the technology development process to bring inflatable aeroshell technology from Technology Readiness Level 2 (TRL-2) to TRL-7. This paper focuses mainly on two projects: Inflatable Reentry Vehicle Experiment (IRVE), and Inflatable Aeroshell and Thermal Protection System Development (IATD). The objectives of IRVE are to conduct an inflatable aeroshell flight test that demonstrates exoatmospheric deployment and inflation, reentry survivability and stability, and predictable drag performance. IATD will continue the development of the technology by conducting exploration specific trade studies and feeding forward those results into three more flight tests. Through an examination of these projects, and other potential projects, this paper discusses some of the risks, issues, and unexpected benefits associated with the development of inflatable entry systems technology.

Player, Charles J.↗