On the predictiveness of single-field inflationary models
NASA Astrophysics Data System (ADS)
Burgess, C. P.; Patil, Subodh P.; Trott, Michael
2014-06-01
We re-examine the predictiveness of single-field inflationary models and discuss how an unknown UV completion can complicate determining inflationary model parameters from observations, even from precision measurements. Besides the usual naturalness issues associated with having a shallow inflationary potential, we describe another issue for inflation, namely, unknown UV physics modifies the running of Standard Model (SM) parameters and thereby introduces uncertainty into the potential inflationary predictions. We illustrate this point using the minimal Higgs Inflationary scenario, which is arguably the most predictive single-field model on the market, because its predictions for A S , r and n s are made using only one new free parameter beyond those measured in particle physics experiments, and run up to the inflationary regime. We find that this issue can already have observable effects. At the same time, this UV-parameter dependence in the Renormalization Group allows Higgs Inflation to occur (in principle) for a slightly larger range of Higgs masses. We comment on the origin of the various UV scales that arise at large field values for the SM Higgs, clarifying cut off scale arguments by further developing the formalism of a non-linear realization of SU L (2) × U(1) in curved space. We discuss the interesting fact that, outside of Higgs Inflation, the effect of a non-minimal coupling to gravity, even in the SM, results in a non-linear EFT for the Higgs sector. Finally, we briefly comment on post BICEP2 attempts to modify the Higgs Inflation scenario.
Primordial non-Gaussianities in single field inflationary models with non-trivial initial states
Bahrami, Sina; Flanagan, Éanna É. E-mail: eef3@cornell.edu
2014-10-01
We compute the non-Gaussianities that arise in single field, slow roll inflationary models arising from arbitrary homogeneous initial states, as well as subleading contributions to the power spectrum. Non Bunch-Davies vacuum initial states can arise if the transition to the single field, slow roll inflation phase occurs only shortly before observable modes left the horizon. They can also arise from new physics at high energies that has been integrated out. Our general result for the bispectrum exhibits several features that were previously seen in special cases.
Inflationary signatures of single-field models beyond slow-roll
Ribeiro, Raquel H.
2012-05-01
If the expansion of the early Universe was not close to de Sitter, the statistical imprints of the primordial density perturbation on the cosmic microwave background can be quite different from those derived in slow-roll inflation. In this paper we study the inflationary signatures of all single-field models which are free of ghost-like instabilities. We allow for a rapid change of the Hubble parameter and the speed of sound of scalar fluctuations, in a way that is compatible with a nearly scale-invariant spectrum of perturbations, as supported by current cosmological observations. Our results rely on the scale-invariant approximation, which is different from the standard slow-roll approximation. We obtain the propagator of scalar fluctuations and compute the bispectrum, keeping next-order corrections proportional to the deviation of the spectral index from unity. These theories offer an explicit example where the shape and scale-dependences of the bispectrum are highly non-trivial whenever slow-roll is not a good approximation.
Reheating phase diagram for single-field slow-roll inflationary models
NASA Astrophysics Data System (ADS)
Cai, Rong-Gen; Guo, Zong-Kuan; Wang, Shao-Jiang
2015-09-01
We investigate the influence on the inflationary predictions from the reheating processes characterized by the e -folding number Nreh and the effective equation-of-state parameter wreh during the reheating phase. For the first time, reheating processes can be constrained in the Nreh-wreh plane from Planck 2015. We find that for Higgs inflation with a nonminimal coupling to gravity, the predictions are insensitive to the reheating phase for current CMB measurements. We also find that the spontaneously broken SUSY inflation and axion monodromy inflation with ϕ2 /3 potential, which with instantaneous reheating lie outside or at the edge of the 95% confidence region in the ns-r plane from Planck 2015 TT, TE, EE +lowP , can well fit the data with the help of reheating processes. Future CMB experiments would put strong constraints on reheating processes.
Reconstructing inflationary paradigm within Effective Field Theory framework
NASA Astrophysics Data System (ADS)
Choudhury, Sayantan
2016-03-01
In this paper my prime objective is to analyse the constraints on a sub-Planckian excursion of a single inflaton field within Effective Field Theory framework in a model independent fashion. For a generic single field inflationary potential, using the various parameterization of the primordial power spectrum I have derived the most general expression for the field excursion in terms of various inflationary observables, applying the observational constraints obtained from recent Planck 2015 and Planck 2015 + BICEP2/Keck Array data. By explicit computation I have reconstructed the structural form of the inflationary potential by constraining the Taylor expansion co-efficients appearing in the generic expansion of the potential within the Effective Field Theory. Next I have explicitly derived, a set of higher order inflationary consistency relationships, which would help us to break the degeneracy between various class of inflationary models by differentiating them. I also provided two simple examples of Effective Theory of inflation- inflection-point model and saddle-point model to check the compatibility of the prescribed methodology in the light of Planck 2015 and Planck 2015 + BICEP2/Keck Array data. Finally, I have also checked the validity of the prescription by estimating the cosmological parameters and fitting the theoretical CMB TT, TE and EE angular power spectra with the observed data within the multipole range 2 < l < 2500.
Can CMB data constrain the inflationary field range?
Garcia-Bellido, Juan
2014-09-01
We study to what extent the spectral index n{sub s} and the tensor-to-scalar ratio r determine the field excursion Δφ during inflation. We analyse the possible degeneracy of Δ φ by comparing three broad classes of inflationary models, with different dependence on the number of e-foldings N, to benchmark models of chaotic inflation with monomial potentials. The classes discussed cover a large set of inflationary single field models. We find that the field range is not uniquely determined for any value of (n{sub s}, r); one can have the same predictions as chaotic inflation and a very different Δ φ. Intriguingly, we find that the field range cannot exceed an upper bound that appears in different classes of models. Finally, Δ φ can even become sub-Planckian, but this requires to go beyond the single-field slow-roll paradigm.
Constraining brane inflationary magnetic field from cosmoparticle physics after Planck
NASA Astrophysics Data System (ADS)
Choudhury, Sayantan
2015-10-01
In this article, I have studied the cosmological and particle physics constraints on a generic class of large field (|Δ ϕ| > M p ) and small field (|Δ ϕ| < M p ) models of brane inflationary magnetic field from: (1) tensor-to-scalar ratio ( r), (2) reheating, (3) leptogenesis and (4) baryogenesis in case of Randall-Sundrum single braneworld gravity (RSII) framework. I also establish a direct connection between the magnetic field at the present epoch ( B 0) and primordial gravity waves ( r), which give a precise estimate of non-vanishing CP asymmetry ( ɛ CP) in leptogenesis and baryon asymmetry ( η B ) in baryogenesis scenario respectively. Further assuming the conformal invariance to be restored after inflation in the framework of RSII, I have explicitly shown that the requirement of the sub-dominant feature of large scale coherent magnetic field after inflation gives two fold non-trivial characteristic constraints- on equation of state parameter ( w) and the corresponding energy scale during reheating ( ρ rh 1/4 ) epoch. Hence giving the proposal for avoiding the contribution of back-reaction from the magnetic field I have established a bound on the generic reheating characteristic parameter ( R rh ) and its rescaled version ( R sc ), to achieve large scale magnetic field within the prescribed setup and further apply the CMB constraints as obtained from recently observed Planck 2015 data and Planck+BICEP2+Keck Array joint constraints. Using all these derived results I have shown that it is possible to put further stringent constraints on various classes of large and small field inflationary models to break the degeneracy between various cosmological parameters within the framework of RSII. Finally, I have studied the consequences from two specific models of brane inflation-monomial and hilltop, after applying the constraints obtained from inflation and primordial magnetic field.
Inflationary solutions in the nonminimally coupled scalar field theory
NASA Astrophysics Data System (ADS)
Koh, Seoktae; Kim, Sang Pyo; Song, Doo Jong
2005-08-01
We study analytically and numerically the inflationary solutions for various type scalar potentials in the nonminimally coupled scalar field theory. The Hamilton-Jacobi equation is used to deal with nonlinear evolutions of inhomogeneous spacetimes and the long-wavelength approximation is employed to find the homogeneous solutions during an inflation period. The constraints that lead to a sufficient number of e-folds, a necessary condition for inflation, are found for the nonminimal coupling constant and initial conditions of the scalar field for inflation potentials. In particular, we numerically find an inflationary solution in the new inflation model of a nonminimal scalar field.
Primordial magnetic fields from the post-inflationary universe
Kobayashi, Takeshi
2014-05-01
We explore cosmological magnetogenesis in the post-inflationary universe, when the inflaton oscillates around its potential minimum and the universe is effectively dominated by cold matter. During this epoch prior to reheating, large-scale magnetic fields can be significantly produced by the cosmological background. By considering magnetogenesis both during and after inflation, we demonstrate that magnetic fields stronger than 10{sup −15} G can be generated on Mpc scales without having strong couplings in the theory, or producing too large electric fields that would dominate the universe.
Effective field theory of dark matter from membrane inflationary paradigm
NASA Astrophysics Data System (ADS)
Choudhury, Sayantan; Dasgupta, Arnab
2016-09-01
In this article, we have studied the cosmological and particle physics constraints on dark matter relic abundance from effective field theory of inflation from tensor-to-scalar ratio (r), in case of Randall-Sundrum single membrane (RSII) paradigm. Using semi-analytical approach we establish a direct connection between the dark matter relic abundance (ΩDMh2) and primordial gravity waves (r), which establishes a precise connection between inflation and generation of dark matter within the framework of effective field theory in RSII membrane. Further assuming the UV completeness of the effective field theory perfectly holds good in the prescribed framework, we have explicitly shown that the membrane tension, σ ≤ O(10-9) Mp4, bulk mass scale M5 ≤ O(0.04 - 0.05) Mp, and cosmological constant Λ˜5 ≥ - O(10-15) Mp5, in RSII membrane plays the most significant role to establish the connection between dark matter and inflation, using which we have studied the features of various mediator mass scale suppressed effective field theory "relevant operators" induced from the localized s, t and u channel interactions in RSII membrane. Taking a completely model independent approach, we have studied an exhaustive list of tree-level Feynman diagrams for dark matter annihilation within the prescribed setup and to check the consistency of the obtained results, further we apply the constraints as obtained from recently observed Planck 2015 data and Planck + BICEP2 + Keck Array joint data sets. Using all of these derived results we have shown that to satisfy the bound on, ΩDMh2 = 0.1199 ± 0.0027, as from Planck 2015 data, it is possible to put further stringent constraint on r within, 0.01 ≤ r ≤ 0.12, for thermally averaged annihilation cross-section of dark matter, < σv > ≈ O(10-28 - 10-27) cm3 / s, which are very useful to constrain various membrane inflationary models.
The behavior of the Higgs field in the new inflationary universe
NASA Technical Reports Server (NTRS)
Guth, Alan H.; Pi, So-Young
1986-01-01
Answers are provided to questions about the standard model of the new inflationary universe (NIU) which have raised concerns about the model's validity. A baby toy problem which consists of the study of a single particle moving in one dimension under the influence of a potential with the form of an upside-down harmonic oscillator is studied, showing that the quantum mechanical wave function at large times is accurately described by classical physics. Then, an exactly soluble toy model for the behavior of the Higgs field in the NIU is described which should provide a reasonable approximation to the behavior of the Higgs field in the NIU. The dynamics of the toy model is described, and calculative results are reviewed which, the authors claim, provide strong evidence that the basic features of the standard picture are correct.
On SUSY restoration in single-superfield inflationary models of supergravity
NASA Astrophysics Data System (ADS)
Ketov, Sergei V.; Terada, Takahiro
2016-08-01
We study the conditions of restoring supersymmetry (SUSY) after inflation in the supergravity-based cosmological models with a single chiral superfield and a quartic stabilization term in the Kähler potential. Some new, explicit, and viable inflationary models satisfying those conditions are found. The inflaton's scalar superpartner is dynamically stabilized during and after inflation. We also demonstrate a possibility of having small and adjustable SUSY breaking with a tiny cosmological constant.
NASA Astrophysics Data System (ADS)
Ijjas, Anna; Steinhardt, Paul J.; Loeb, Abraham
2014-09-01
Classic inflation, the theory described in textbooks, is based on the idea that, beginning from typical initial conditions and assuming a simple inflaton potential with a minimum of fine-tuning, inflation can create exponentially large volumes of space that are generically homogeneous, isotropic and flat, with nearly scale-invariant spectra of density and gravitational wave fluctuations that are adiabatic, Gaussian and have generic predictable properties. In a recent paper, we showed that, in addition to having certain conceptual problems known for decades, classic inflation is for the first time also disfavored by data, specifically the most recent data from WMAP, ACT and Planck2013. Guth, Kaiser and Nomura and Linde have each recently published critiques of our paper, but, as made clear here, we all agree about one thing: the problematic state of classic inflation. Instead, they describe an alternative inflationary paradigm that revises the assumptions and goals of inflation, and perhaps of science generally. Assuming simple inflaton potentials with a single phase of inflation is “not at all realistic”, whereas highly complex potentials with many parameters, tunings, and fields are “very plausible according to recent ideas in high-energy physics” [GKN10-11]. The complex potentials inevitably lead to multiple stages of inflation and a multiverse in which anything can happen [GKN7]. The validity of the postmodern inflationary paradigm cannot be judged on whether it works for typical initial conditions since we do not know what those conditions are [GKN13]. Even if the initial conditions are determined some day they will not affect the validity of inflation; rather, the (yet unknown) measure will then be adjusted such that the observed properties of the universe are likely to emerge from those (yet unknown) initial conditions [GKN14]. The volume measure is rejected in favor of complex measures that are to be (re-)adjusted (a posteriori) to ensure that the
LRS Bianchi Type-II Inflationary Universe with Massless Scalar Field and Time Varying Λ
NASA Astrophysics Data System (ADS)
Raj, Bali; Swati
2012-08-01
The locally rotationally symmetric (LRS) Bianchi type-II inflationary cosmological model is investigated for massless scalar field with flat potential and time varying Λ. To obtain the deterministic solution, it is assumed that scale factor is a(t)~eHt as we considered previously for Bianchi type-I spacetime and Λ~a-2 as considered by Chen and Wu, where H is the Hubble constant and effective potential V(phi)=const; phi Higg's field. It is shown that such a time varying Λ leads to no conflict with existing observations. However, it does change the predictions of standard cosmology in the matter-dominated phase and alleviates some problems in reconciling observations with the inflationary scenario. The model represents anisotropic spacetime in general. However, the model isotropizes for large values of t and β = 3H2, where β is constant. The physical and geometrical aspects of the model in the context of an inflationary scenario is also discussed.
Inflationary cosmology: First 30+ years
NASA Astrophysics Data System (ADS)
Sato, Katsuhiko; Yokoyama, Jun'ichi
2015-08-01
Starting with an account of historical developments in Japan and Russia, we review inflationary cosmology and its basic predictions in a pedagogical manner. We also introduce the generalized G-inflation model, in terms of which all the known single-field inflation models may be described. This formalism allows us to analyze and compare the many inflationary models that have been proposed simultaneously and within a common framework. Finally, current observational constraints on inflation are reviewed, with particular emphasis on the sensitivity of the inferred constraints to the choice of datasets used.
Sensitivity of Inflationary Predictions to Pre-inflationary Phases
NASA Astrophysics Data System (ADS)
Bahrami, Sina; Flanagan, Eanna; LaboratoryHigh Energy Physics Team
2015-04-01
How sensitive are the predictions of inflation to pre-inflationary conditions when the number of efolds of inflation is not too large? In an attempt to address this question, we consider a simple model where the inflationary era is preceded by an era dominated by a radiation fluid that is coupled to the inflaton only gravitationally. We show that there is a natural generalized Bunch-Davies vacuum state for perturbations to the coupled inflaton-gravity-fluid system at early times. With this choice of initial state the model predicts interesting deviations from the standard power spectrum of single field slow-roll inflation. However, the deviations are too small to be observable in near future observations.
Sensitivity of inflationary predictions to pre-inflationary phases
NASA Astrophysics Data System (ADS)
Bahrami, Sina; Flanagan, Éanna É.
2016-01-01
How sensitive are the predictions of inflation to pre-inflationary conditions when the number of efolds of inflation is not too large? In an attempt to address this question, we consider a simple model where the inflationary era is preceded by an era dominated by a radiation fluid, which is coupled to the inflaton only gravitationally and which extends back to the Planck era. We show that there is a natural generalized Bunch-Davies vacuum state for perturbations to the coupled inflaton-gravity-fluid system at early times. With this choice of initial state the model predicts interesting deviations from the standard power spectrum of single field slow-roll inflation at large scales. However, the deviations are too small to be observable in near future CMB observations.
Phenomenological Classification of Inflationary Potentials
NASA Astrophysics Data System (ADS)
Mack, Katie; Efstathiou, George
2004-11-01
We investigate the Lyth relationship between the tensor-scalar ratio, r, and the variation of the inflaton field, Δφ, over the course of inflation. We compute r and Δφ for 106 single-field inflationary models generated using the the Monte Carlo reconstruction method of Easther and Kinney. Despite a large scatter, our results show that the Lyth relation provides a useful classification of inflationary models since a detectable value of the tenser-scalar ratio necessarily requires an inflaton field variation of the order of the Planck mass. Inflationary models that satisfy current observational constraints on the scalar spectral index and its first derivative satisfy a much tighter relation between r and Δφ. For example, all models with r >~ 0.01 (roughly the limit at which lensing of E-modes produces a B-mode signal comparable to those generated by inflation), require a field variation Δφ >~ 1.5mPl. Such a large variation probably requires that the underlying theory of inflation possesses a shift symmetry φ --> φ + constant.
Non-local scalar fields inflationary mechanism in light of Planck 2013
NASA Astrophysics Data System (ADS)
Sheikhahmadi, Haidar; Ghorbani, Soheyla; Saaidi, Khaled
2015-06-01
A generalization of the canonical and non-canonical theory of inflation is introduced in which the kinetic energy term in action is written as non-local term. The inflationary universe within the framework of considering this non-locality will be studied. To investigate the effects of non-locality on the inflationary parameters we consider two well known models of the inflationary scenario including chaotic and exponential inflation proposals. For such scenarios some important parameters include slow roll parameters, scalar and tensor power spectra, spectral indices, the tensor-to-scalar ratio and so on for both mentioned models, chaotic and exponential inflationary scenarios, will be calculated. Also the Hamilton-Jacobi formalism, as an easiest way to study the effect of perturbation based on e-folding number N, to investigate inflationary attractors will be used. The free theoretical parameters of this model will be compared with observations by means of Planck 2013, WMAP9+ eCMB+ BAO+ H 0 data sets in addition to BICEP2 data surveying. It will be shown that our theoretical results are in acceptable range in comparison to observations. For instance the tensor-to-scalar ratio for exponential potential, by considering BICEP2 is in best agreement in comparison with chaotic inflation.
Inflationary paradigm in trouble after Planck2013
NASA Astrophysics Data System (ADS)
Ijjas, Anna; Steinhardt, Paul J.; Loeb, Abraham
2013-06-01
Recent results from the Planck satellite combined with earlier observations from WMAP, ACT, SPT and other experiments eliminate a wide spectrum of more complex inflationary models and favor models with a single scalar field, as reported by the Planck Collaboration. More important, though, is that all the simplest inflaton models are disfavored statistically relative to those with plateau-like potentials. We discuss how a restriction to plateau-like models has three independent serious drawbacks: it exacerbates both the initial conditions problem and the multiverse-unpredictability problem and it creates a new difficulty that we call the inflationary "unlikeliness problem." Finally, we comment on problems reconciling inflation with a standard model Higgs, as suggested by recent LHC results. In sum, we find that recent experimental data disfavors all the best-motivated inflationary scenarios and introduces new, serious difficulties that cut to the core of the inflationary paradigm. Forthcoming searches for B-modes, non-Gaussianity and new particles should be decisive.
Cosmological constraints on general, single field inflation
NASA Astrophysics Data System (ADS)
Agarwal, Nishant; Bean, Rachel
2009-01-01
Inflation is now an accepted paradigm in standard cosmology, with its predictions consistent with observations of the cosmic microwave background. It lacks, however, a firm physical theory, with many possible theoretical origins beyond the simplest, canonical, slow-roll inflation, including Dirac-Born-Infeld inflation and k-inflation. We discuss how a hierarchy of Hubble flow parameters, extended to include the evolution of the inflationary sound speed, can be applied to compare a general, single field inflationary action with cosmological observational data. We show that it is important to calculate the precise scalar and tensor primordial power spectra by integrating the full flow and perturbation equations, since values of observables can deviate appreciably from those obtained using typical second-order Taylor expanded approximations in flow parameters. As part of this, we find that a commonly applied approximation for the tensor-to-scalar ratio, r≈16csγ, becomes poor (deviating by as much as 50%) as cs deviates from 1 and hence the Taylor expansion including next-to-leading order contribution terms involving cs is required. By integrating the full flow equations, we use a Monte-Carlo-Markov-Chain approach to impose constraints on the parameter space of general single field inflation, and reconstruct the properties of such an underlying theory in light of recent cosmic microwave background and large-scale structure observations.
Topics in inflationary cosmologies
Mahajan, S.
1986-04-01
Several aspects of inflationary cosmologies are discussed. An introduction to the standard hot big bang cosmological model is reviewed, and some of the problems associated with it are presented. A short review of the proposals for solving the cosmological conundrums of the big bang model is presented. Old and the new inflationary scenarios are discussed and shown to be unacceptable. Some alternative scenarios especially those using supersymmetry are reviewed briefly. A study is given of inflationary models where the same set of fields that breaks supersymmetry is also responsible for inflation. In these models, the scale of supersymmetry breaking is related to the slope of the potential near the origin and can thus be kept low. It is found that a supersymmetry breaking scale of the order of the weak breaking scale. The cosmology obtained from the simplest of such models is discussed in detail and it is shown that there are no particular problems except a low reheating temperature and a violation of the thermal constraint. A possible solution to the thermal constraint problem is given by introducing a second field, and the role played by this second field in the scenario is discussed. An alternative mechanism for the generation of baryon number within the framework of supergravity inflationary models is studied using the gravitational couplings of the heavy fields with the hidden sector (the sector which breaks supersymmetry). This mechanism is applied to two specific models - one with and one without supersymmetry breaking. The baryon to entropy ratio is found to be dependent on parameters which are model dependent. Finally, the effect of direct coupling between the two sectors on results is related, 88 refs., 6 figs.
Exact Approach to Inflationary Universe Models
NASA Astrophysics Data System (ADS)
del Campo, Sergio
In this chapter we introduce a study of inflationary universe models that are characterized by a single scalar inflation field . The study of these models is based on two dynamical equations: one corresponding to the Klein-Gordon equation for the inflaton field and the other to a generalized Friedmann equation. After describing the kinematics and dynamics of the models under the Hamilton-Jacobi scheme, we determine in some detail scalar density perturbations and relic gravitational waves. We also introduce the study of inflation under the hierarchy of the slow-roll parameters together with the flow equations. We apply this approach to the modified Friedmann equation that we call the Friedmann-Chern-Simons equation, characterized by F(H) = H^2- α H4, and the brane-world inflationary models expressed by the modified Friedmann equation.
Enhanced Inflationary Trispectrum from a Non-Vacuum Initial State
NASA Astrophysics Data System (ADS)
Agullo, I.; Navarro-Salas, J.; Parker, L.
2015-01-01
We work out the primordial inflationary trispectrum for curvature perturbations in models with standard kinetic terms, when the initial quantum state is not necessarily the Bunch-Davies vacuum state. The presence of initial perturbations enhances the trispectrum amplitude for squeezed configurations, in parallel to the bispectrum enhancement. For those squeezed configurations the trispectrum acquires the so-called local form, with a scale dependent amplitude that can get values larger than the prediction of the so-called Maldacena consistency relation. The enhancement factor could be as large as 106, and could reach the sensitivity of forthcoming observations, even for single-field inflationary models.
Gauge invariant backreaction in general single field models of inflation
NASA Astrophysics Data System (ADS)
Marozzi, G.; Vacca, G. P.
2013-07-01
In a general single field inflationary model, we consider the effects of long wavelength scalar fluctuations on the effective expansion rate and equation of state seen by a class of free-falling observers, using a physical gauge invariant formulation. In a previous work we showed that for a free massive inflaton no backreaction is observed within some constraints. In this paper we extend the validity of our previous results to the case of an arbitrary self-interacting inflation potential, working to second order in cosmological perturbation theory and to all order in slow-roll approximation. For these general inflationary models, we also show the equivalence of the free-falling observers to the ones comoving with the inflaton field.
K-inflationary power spectra at second order
Martin, Jérôme; Vennin, Vincent; Ringeval, Christophe E-mail: christophe.ringeval@uclouvain.be
2013-06-01
Within the class of inflationary models, k-inflation represents the most general single field framework that can be associated with an effective quadratic action for the curvature perturbations and a varying speed of sound. The incoming flow of high-precision cosmological data, such as those from the Planck satellite and small scale Cosmic Microwave Background (CMB) experiments, calls for greater accuracy in the inflationary predictions. In this work, we calculate for the first time the next-to-next-to-leading order scalar and tensor primordial power spectra in k-inflation needed in order to obtain robust constraints on the inflationary theory. The method used is the uniform approximation together with a second order expansion in the Hubble and sound flow functions. Our result is checked in various limits in which it reduces to already known situations.
Curvaton reheating in a logamediate inflationary model
Campo, Sergio del; Herrera, Ramon; Saavedra, Joel; Campuzano, Cuauhtemoc; Rojas, Efrain
2009-12-15
In a logamediate inflationary universe model we introduce the curvaton field in order to bring this inflationary model to an end. In this approach we determine the reheating temperature. We also outline some interesting constraints on the parameters that describe our models. Thus, we give the parameter space in this scenario.
Rangarajan, Raghavan; Nanopoulos, D. V.
2001-09-15
In this paper we explore the possibility of creating the baryon asymmetry of the universe during inflation and reheating due to the decay of a field associated with the inflaton. CP violation is attained by assuming that this field is complex with a phase that varies as the inflaton evolves. We consider chaotic and natural inflation scenarios. In the former case, the complex decaying field is the inflaton itself and, in the latter case, the phase of the complex field is the inflaton. We calculate the asymmetry produced using the Bogolyubov formalism that relates annihilation and creation operators at late time to the annihilation and creation operators at early time.
NASA Astrophysics Data System (ADS)
Lyth, D. H.
The author has revisited inflationary axion cosmology. The treatment involves fewer assumptions than in the past, and he arrives at a scenario specified by the values of three parameters fa/N, Nθ¯, and Nσθ (√2fa is the vacuum value of the modulus of the Peccei-Quinn field, θ and σθ are the mean and rms dispersion of its phase θ just before the axion mass switches on, and N is the number of distinct vacuum values of θ once the mass has turned on). The following conclusions are presented: first, axionic domain walls can be cosmologically interesting only if fa/N is within an order of magnitude of its extreme astrophysical lower bound 2×108GeV. Second, the axion density perturbation can be either Gaussian or of the χ2type, but the latter case is likely only if fa/N ≤ 1010GeV. Third, at least in the absence of walls the axion density perturbation can probably not become big enough to be the cause of the observed structure, though the non-Gaussian case requires further investigation. Finally, the author makes the additional assumption that interactions of the Peccei-Quinn field do not alter the effective value of fa, while relevant scales leave the horizon during inflation. This leads to the strong bound on the inflationary energy density.
Spinor-unit field representation of electromagnetism applied to a model inflationary cosmology
NASA Astrophysics Data System (ADS)
Nash, Patrick L.
2012-09-01
The new spinor-unit field representation of the electromagnetism (Nash in J Math Phys 51:042501-1-042501-27, 2010) (with quark and lepton sources) is integrated via minimal coupling with standard Einstein gravitation, to formulate a Lagrangian model of the very early universe. A completely new solution to the coupled Einstein-Maxwell equations, with sources, is derived. These equations are generalized somewhat, but not in a way that violates any physical principles. The solution of the coupled Euler-Lagrange field equations yields a scale factor a( t) (comoving coordinates) that initially exponentially increases N e-folds from a(0) ≈ 0 to a 1 = a(0) e N ( N = 60 is illustrated), then exponentially decreases, then exponentially increases to a 1, and so on almost periodically. (Oscillatory cosmological models are not knew, and have been derived from string theory and loop quantum gravity.) It is not known if the scale factor escapes this periodic trap. This model is noteworthy in several respects: 1. All fundamental fields other than gravity are realized by spinor fields. 2. A plausible connection between the unit field u and the generalization of the photon wave function with a form of Dark Energy is described, and a simple natural scenario is outlined that allocates a fraction of the total energy of the Universe to this form of Dark Energy. 3. A solution of an analog of the pure Einstein-Maxwell equations is found using an approach that is in marked contrast with the method followed to obtain a solution of the well known Friedmann model of a radiation-dominated universe.
Constraints on single-field inflation
NASA Astrophysics Data System (ADS)
Pirtskhalava, David; Santoni, Luca; Trincherini, Enrico
2016-06-01
Many alternatives to canonical slow-roll inflation have been proposed over the years, one of the main motivations being to have a model, capable of generating observable values of non-Gaussianity. In this work, we (re-)explore the physical implications of a great majority of such models within a single, effective field theory framework (including novel models with large non-Gaussianity discussed for the first time below). The constraints we apply—both theoretical and experimental—are found to be rather robust, determined to a great extent by just three parameters: the coefficients of the quadratic EFT operators (δN)2 and δNδE, and the slow-roll parameter ε. This allows to significantly limit the majority of single-field alternatives to canonical slow-roll inflation. While the existing data still leaves some room for most of the considered models, the situation would change dramatically if the current upper limit on the tensor-to-scalar ratio decreased down to r < 10‑2. Apart from inflationary models driven by plateau-like potentials, the single-field model that would have a chance of surviving this bound is the recently proposed slow-roll inflation with weakly-broken galileon symmetry. In contrast to canonical slow-roll inflation, the latter model can support r < 10‑2 even if driven by a convex potential, as well as generate observable values for the amplitude of non-Gaussianity.
Inflationary buildup of a vector field condensate and its cosmological consequences
Sanchez, Juan C. Bueno; Dimopoulos, Konstantinos E-mail: k.dimopoulos1@lancaster.ac.uk
2014-01-01
Light vector fields during inflation obtain a superhorizon perturbation spectrum when their conformal invariance is appropriately broken. Such perturbations, by means of some suitable mechanism (e.g. the vector curvaton mechanism), can contribute to the curvatue perturbation in the Universe and produce characteristic signals, such as statistical anisotropy, on the microwave sky, most recently surveyed by the Planck satellite mission. The magnitude of such characteristic features crucially depends on the magnitude of the vector condensate generated during inflation. However, in the vast majority of the literature the expectation value of this condensate has so-far been taken as a free parameter, lacking a definite prediction or a physically motivated estimate. In this paper, we study the stochastic evolution of the vector condensate and obtain an estimate for its magnitude. Our study is mainly focused in the supergravity inspired case when the kinetic function and mass of the vector boson is time-varying during inflation, but other cases are also explored such as a parity violating axial theory or a non-minimal coupling between the vector field and gravity. As an example, we apply our findings in the context of the vector curvaton mechanism and contrast our results with current observations.
Recovering the inflationary potential
Turner, Michael S.
1993-08-06
A procedure is developed for the recovery of the inflationary potential owl the interval that affects astrophysical scales. The amplitudes of the scalar and tensor metric perturbations and their power-spectrum indices, which can in principle be inferred from large-angle CBR anisotropy experiments and other cosmological data, determine the value of the inflationary potential and its first two derivatives. From these, the inflationary potential can be reconstructed in a Taylor series and the consistency of the inflationary hypothesis tested. A number of examples are presented, and the effect of observational uncertainties is discussed.
The best inflationary models after Planck
Martin, Jérôme; Vennin, Vincent; Ringeval, Christophe; Trotta, Roberto E-mail: christophe.ringeval@uclouvain.be E-mail: vennin@iap.fr
2014-03-01
We compute the Bayesian evidence and complexity of 193 slow-roll single-field models of inflation using the Planck 2013 Cosmic Microwave Background data, with the aim of establishing which models are favoured from a Bayesian perspective. Our calculations employ a new numerical pipeline interfacing an inflationary effective likelihood with the slow-roll library ASPIC and the nested sampling algorithm MultiNest. The models considered represent a complete and systematic scan of the entire landscape of inflationary scenarios proposed so far. Our analysis singles out the most probable models (from an Occam's razor point of view) that are compatible with Planck data, while ruling out with very strong evidence 34% of the models considered. We identify 26% of the models that are favoured by the Bayesian evidence, corresponding to 15 different potential shapes. If the Bayesian complexity is included in the analysis, only 9% of the models are preferred, corresponding to only 9 different potential shapes. These shapes are all of the plateau type.
Toward the inflationary paradigm: Lectures on inflationary cosmology
Turner, M.S.
1987-02-01
Guth's inflationary Universe scenario has revolutionized our thinking about the very early Universe. The inflationary scenario offers the possibility of explaining a handful of very fundamental cosmological facts - the homogeneity, isotropy, and flatness of the Universe, the origin of density inhomogeneities and the origin of the baryon asymmetry, while at the same time avoiding the monopole problem. It is based upon microphysical events which occurred early (t less than or equal to 10/sup -34/ sec) in the history of the Universe, but well after the planck epoc (t greater than or equal to 10/sup -43/ sec). While Guth's original model was fundamentally flawed, the variant based on the slow-rollover transition proposed by Linde, and Albrecht and Steinhardt (dubbed 'new inflation') appears viable. Although old inflation and the earliest models of new inflation were based upon first order phase transitions associated with spontaneous-symmetry breaking (SSB), it now appears that the inflationary transition is a much more generic phenomenon, being associated with the evolution of a weakly-coupled scalar field which for some reason or other was initially displaced from the minimum of its potential. Models now exist which are based on a wide variety of microphysics: SSB, SUSY/SUGR, compactification of extra dimensions, R/sup 2/ gravity, induced gravity, and some random, weakly-coupled scalar field. While there are several models which successfully implement the inflation, none is particularly compelling and all seem somewhat ad hoc. The common distasteful feature of all the successful models is the necessity of a small dimensionless number in the model - usually in the form of a dimensionless coupling of order 10/sup -15/. All inflationary scenarios rely upon the assumption that vacuum energy was once dynamically very significant, whereas today there exists every evidence that it is not. 133 refs., 17 figs.
From instantons to inflationary universe.
NASA Astrophysics Data System (ADS)
Khalatnikov, I. M.; Schiller, P.
1993-01-01
The present paper is based on a theory which includes gravity and a complex scalar field. In such a theory it is possible to analyze the evolution from instantons in the classically forbidden (Euclidean) region in minisuperspace to the inflationary universe in the classically allowed (Minkowski) region. The characteristics for the Hamilton-Jacobi equation, which define the action in the quasiclassical approximation, are described by four first-order differential equations. This four-dimensional dynamical system was integrated numerically. In the closed Euclidean region two types of instantons were found. It is shown that the instantons correspond to extremal trajectories. The existence of two types of instantons gives rise to different possibilities for tunneling from Euclidean region to Minkowski region and for creation of inflationary universes.
From instanton to inflationary universe
NASA Astrophysics Data System (ADS)
Khalatnikov, I. M.; Schiller, P.
1993-03-01
The present paper is based on a theory which includes gravity and a complex scalar field [I.M. Khalatnikov and A. Mezhlumian, Phys. Lett. A 169 (1992) 308]. It is shown that in such a theory we can proceed the evolution from instantons in the classically forbidden (euclidean) region in minisuperspace to the inflationary universe in the classically allowed (Minkowski) region. The characteristics for the Hamilton-Jacobi equation, which define the action in the quasiclassical approximation, are described by four differential equations of first order. This four-dimensional dynamical system was integrated numerically. In the euclidean compact region we found two types of instantons. It is shown that the instantons correspond to extremal trajectories. The existence of two types of instantons gives different possibilities for tunneling from euclidean to Minkowski regions and for creation of inflationary universes.
Red density perturbations and inflationary gravitational waves
Pagano, Luca; Melchiorri, Alessandro; Cooray, Asantha; Kamionkowski, Marc E-mail: acooray@uci.edu E-mail: kamion@tapir.caltech.edu
2008-04-15
We study the implications of recent indications from the Wilkinson Microwave Anisotropy Probe (WMAP) and other cosmological data for a red spectrum of primordial density perturbations for the detection of inflationary gravitational waves (IGWs) with forthcoming cosmic microwave background experiments. We consider a variety of single-field power-law, chaotic, spontaneous symmetry-breaking and Coleman-Weinberg inflationary potentials which are expected to provide a sizable tensor component and quantify the expected tensor-to-scalar ratio given existing constraints from WMAP on the tensor-to-scalar ratio and the power spectrum tilt. We discuss the ability of the near-future Planck satellite to detect the IGW background in the framework of those models. We find that the proposed satellite missions of the Cosmic Vision and Inflation Probe programs will be able to detect IGWs from all the models we have surveyed at better than 5{sigma} confidence level. We also provide an example of what is required if the IGW background is to remain undetected even by these latter experiments.
Excitation of photons by inflationary gravitons
NASA Astrophysics Data System (ADS)
Wang, C. L.; Woodard, R. P.
2015-06-01
We use a recent result for the graviton contribution to the one-loop vacuum polarization to solve the effective field equations for dynamical photons on a de Sitter background. Our results show that the electric field experiences a secular enhancement proportional to the number of inflationary e -foldings. We discuss the minimum effect this establishes for primordial inflation to seed cosmic magnetic fields.
Simple inflationary quintessential model
NASA Astrophysics Data System (ADS)
de Haro, Jaume; Amorós, Jaume; Pan, Supriya
2016-04-01
In the framework of a flat Friedmann-Lemaître-Robertson-Walker geometry, we present a non-geodesically past complete model of our Universe without the big bang singularity at finite cosmic time, describing its evolution starting from its early inflationary era up to the present accelerating phase. We found that a hydrodynamical fluid with nonlinear equation of state could result in such scenario, which after the end of this inflationary stage, suffers a sudden phase transition and enters into the stiff matter dominated era, and the Universe becomes reheated due to a huge amount of particle production. Finally, it asymptotically enters into the de Sitter phase concluding the present accelerated expansion. Using the reconstruction technique, we also show that this background provides an extremely simple inflationary quintessential potential whose inflationary part is given by the well-known 1-dimensional Higgs potential, i.e., a double well inflationary potential, and the quintessential one by an exponential potential that leads to a deflationary regime after this inflation, and it can depict the current cosmic acceleration at late times. Moreover the Higgs potential leads to a power spectrum of the cosmological perturbations which fit well with the latest Planck estimations. Further, we compared our viable potential with some known inflationary quintessential potential, which shows that our quintessential model, that is, the Higgs potential combined with the exponential one, is an improved version of them because it contains an analytic solution that allows us to perform all analytic calculations. Finally, we have shown that the introduction of a nonzero cosmological constant simplifies the potential considerably with an analytic behavior of the background which again permits us to evaluate all the quantities analytically.
Critical constraint on inflationary magnetogenesis
Fujita, Tomohiro; Yokoyama, Shuichiro E-mail: shu@icrr.u-tokyo.ac.jp
2014-03-01
Recently, there are several reports that the cosmic magnetic fields on Mpc scale in void region is larger than ∼ 10{sup −15}G with an uncertainty of a few orders from the current blazar observations. On the other hand, in inflationary magnetogenesis models, additional primordial curvature perturbations are inevitably produced from iso-curvature perturbations due to generated electromagnetic fields. We explore such induced curvature perturbations in a model independent way and obtained a severe upper bound for the energy scale of inflation from the observed cosmic magnetic fields and the observed amplitude of the curvature perturbation , as ρ{sub inf}{sup 1/4} < 300MeV × (B{sub obs}/10{sup −15}G){sup −1} where B{sub obs} is the strength of the magnetic field at present. Therefore, without a dedicated low energy inflation model or an additional amplification of magnetic fields after inflation, inflationary magnetogenesis on Mpc scale is generally incompatible with CMB observations.
Transport equations for the inflationary trispectrum
Anderson, Gemma J.; Seery, David; Mulryne, David J. E-mail: D.Mulryne@qmul.ac.uk
2012-10-01
We use transport techniques to calculate the trispectrum produced in multiple-field inflationary models with canonical kinetic terms. Our method allows the time evolution of the local trispectrum parameters, τ{sub NL} and g{sub NL}, to be tracked throughout the inflationary phase. We illustrate our approach using examples. We give a simplified method to calculate the superhorizon part of the relation between field fluctuations on spatially flat hypersurfaces and the curvature perturbation on uniform density slices, ζ, and obtain its third-order part for the first time. We clarify how the 'backwards' formalism of Yokoyama et al. relates to our analysis and other recent work. We supply explicit formulae which enable each inflationary observable to be computed in any canonical model of interest, using a suitable first-order ODE solver.
Causality, initial conditions, and inflationary magnetogenesis
NASA Astrophysics Data System (ADS)
Tsagas, Christos G.
2016-05-01
The post-inflationary evolution of inflation-produced magnetic fields, conventional or not, can change dramatically when two fundamental issues are accounted for. The first is causality, which demands that local physical processes can never affect superhorizon perturbations. The second is the nature of the transition from inflation to reheating and then to the radiation era, which determine the initial conditions at the start of these epochs. Causality implies that inflationary magnetic fields do not freeze into the matter until they have re-entered the causal horizon. The nature of the cosmological transitions and the associated initial conditions, on the other hand, determine the large-scale magnetic evolution after inflation. Put together, the two can slow down the adiabatic magnetic decay on superhorizon scales throughout the Universe's post-inflationary evolution and thus lead to considerably stronger residual magnetic fields. This is "good news" for both the conventional and the nonconventional scenarios of cosmic magnetogenesis. Mechanisms operating outside standard electromagnetism, in particular, do not need to enhance their fields too much during inflation in order to produce seeds that can feed the galactic dynamo today. In fact, even conventionally produced inflationary magnetic fields might be able to sustain the dynamo.
PLANCK and WMAP constraints on generalised Hubble flow inflationary trajectories
Contaldi, Carlo R.; Horner, Jonathan S. E-mail: j.horner11@imperial.ac.uk
2014-08-01
We use the Hamilton-Jacobi formalism to constrain the space of possible single field, inflationary Hubble flow trajectories when compared to the WMAP and PLANK satellites Cosmic Microwave Background (CMB) results. This method yields posteriors on the space of Hubble Slow Roll (HSR) parameters that uniquely determine the history of the Hubble parameter during the inflating epoch. The trajectories are used to numerically determine the observable primordial power spectrum and bispectra that can then be compared to observations. Our analysis is used to infer the most likely shape of the inflaton potential V(φ) and also yields a prediction for, B, the dimensionless amplitude of the non-Gaussian bispectrum.
Adding helicity to inflationary magnetogenesis
Caprini, Chiara; Sorbo, Lorenzo E-mail: sorbo@physics.umass.edu
2014-10-01
The most studied mechanism of inflationary magnetogenesis relies on the time-dependence of the coefficient of the gauge kinetic term F{sub μν} F{sup μν}. Unfortunately, only extremely finely tuned versions of the model can consistently generate the cosmological magnetic fields required by observations. We propose a generalization of this model, where also the pseudoscalar invariant F{sub μν} F-tilde {sup μν} is multiplied by a time dependent function. The new parity violating term allows more freedom in tuning the amplitude of the field at the end of inflation. Moreover, it leads to a helical magnetic field that is amplified at large scales by magnetohydrodynamical processes during the radiation dominated epoch. As a consequence, our model can satisfy the observational lower bounds on fields in the intergalactic medium, while providing a seed for the galactic dynamo, if inflation occurs at an energy scale ranging from 10{sup 5} to 10{sup 10} GeV. Such energy scale is well below that suggested by the recent BICEP2 result, if the latter is due to primordial tensor modes. However, the gauge field is a source of tensors during inflation and generates a spectrum of gravitational waves that can give a sizable tensor to scalar ratio r=O(0.2) even if inflation occurs at low energies. This system therefore evades the Lyth bound. For smaller values of r, lower values of the inflationary energy scale are required. The model predicts fully helical cosmological magnetic fields and a chiral spectrum of primordial gravitational waves.
Observational Signatures and Non-Gaussianities ofGeneral Single Field Inflation
Chen, Xingang; Huang, Min-xin; Kachru, Shamit; Shiu, Gary
2006-05-05
We perform a general study of primordial scalar non-Gaussianities in single field inflationary models. We consider models where the inflaton Lagrangian is an arbitrary function of the scalar field and its first derivative, and the sound speed is arbitrary. We find that under reasonable assumptions, the non-Gaussianity is completely determined by 5 parameters. In special limits of the parameter space, one finds distinctive ''shapes'' of the non-Gaussianity. In models with a small sound speed, several of these shapes would become potentially observable in the near future. Different limits of our formulae recover various previously known results.
Single-field inflation constraints from CMB and SDSS data
Finelli, Fabio; Leach, Samuel M.; Lesgourgues, Julien E-mail: hamann@phys.au.dk E-mail: julien.lesgourgues@cern.ch
2010-04-01
We present constraints on canonical single-field inflation derived from WMAP five year, ACBAR, QUAD, BICEP data combined with the halo power spectrum from SDSS LRG7. Models with a non-scale-invariant spectrum and a red tilt n{sub S} < 1 are now preferred over the Harrison-Zel'dovich model (n{sub S} = 1, tensor-to-scalar ratio r = 0) at high significance. Assuming no running of the spectral indices, we derive constraints on the parameters (n{sub S}, r) and compare our results with the predictions of simple inflationary models. The marginalised credible intervals read n{sub S} = 0.962{sup +0.028}{sub −0.026} and r < 0.17 (95% confidence level). With respect to previous analyses, the portion of the 68% c.l. contours compatible with potentials which are concave in the observable region becomes even smaller, but the quadratic potential model remains inside the 95% c.l. contours. We demonstrate that these results are robust to changes in the datasets considered and in the theoretical assumptions made. We then consider a non-vanishing running of the spectral indices by employing different methods, non-parametric but approximate, or parametric but exact. With our combination of CMB and LSS data, running models are preferred over power-law models only by a Δχ{sup 2} ≅ 5.8, allowing inflationary stages producing a sizable negative running −0.063{sup +0.061}{sub −0.049} and larger tensor-scalar ratio r < 0.33 at the 95% c.l. This requires large values of the third derivative of the inflaton potential within the observable range. We derive bounds on this derivative under the assumption that the inflaton potential can be approximated as a third order polynomial within the observable range.
Single-field inflation constraints from CMB and SDSS data
NASA Astrophysics Data System (ADS)
Finelli, Fabio; Hamann, Jan; Leach, Samuel M.; Lesgourgues, Julien
2010-04-01
We present constraints on canonical single-field inflation derived from WMAP five year, ACBAR, QUAD, BICEP data combined with the halo power spectrum from SDSS LRG7. Models with a non-scale-invariant spectrum and a red tilt nS < 1 are now preferred over the Harrison-Zel'dovich model (nS = 1, tensor-to-scalar ratio r = 0) at high significance. Assuming no running of the spectral indices, we derive constraints on the parameters (nS, r) and compare our results with the predictions of simple inflationary models. The marginalised credible intervals read nS = 0.962+0.028-0.026 and r < 0.17 (95% confidence level). With respect to previous analyses, the portion of the 68% c.l. contours compatible with potentials which are concave in the observable region becomes even smaller, but the quadratic potential model remains inside the 95% c.l. contours. We demonstrate that these results are robust to changes in the datasets considered and in the theoretical assumptions made. We then consider a non-vanishing running of the spectral indices by employing different methods, non-parametric but approximate, or parametric but exact. With our combination of CMB and LSS data, running models are preferred over power-law models only by a Δχ2 simeq 5.8, allowing inflationary stages producing a sizable negative running -0.063+0.061-0.049 and larger tensor-scalar ratio r < 0.33 at the 95% c.l. This requires large values of the third derivative of the inflaton potential within the observable range. We derive bounds on this derivative under the assumption that the inflaton potential can be approximated as a third order polynomial within the observable range.
Quantum inflationary minisuperspace cosmological models
Kim Sangpyo.
1991-01-01
The Wheeler-DeWitt equations for the Friedmann-Robertson-Walker cosmology conformally and minimally coupled to scalar fields with power-lay potential are expanded in the eigenstates of the scalar field parts. The gravitational parts become a diagonal matrix-valued differential equation for a conformal scalar field, and a coupled matrix-valued differential equation for a minimally coupled scalar field. The Cauchy initial value problem is defined with respect to the intrinsic timelike coordinate, and the wavefunctions incorporating initial data are constructed using the product integral formulation. The packetlike wavefunctions around classical turning points are shown possible in the product integral formulation, and the returning wavepackets near the returning point of the classical Friedmann-Robertson-Walker cosmology are constructed. The wavefunctions to the Wheeler-DeWitt equation minimally coupled to the scaler field are constructed by two differential methods, the master equation and the enlarged matrix equation. The spectrum for the wavefunctions regular at the infinite size of universe is found, and these are interpreted as the Hawking-Page spectrum of wormholes connecting two asymptotically Euclidean regions. The quantum Friedmann-Robertson-Walker cosmology is extended to the minimal scalar field with the inflationary potential having a first order phase transition. The Wheeler-DeWitt equation is expanded in the eigenstates of the scalar field, and the gravitational part becomes a coupled matrix-valued differential equation.
The new inflationary universe, 1984
NASA Technical Reports Server (NTRS)
Guth, Alan H.
1986-01-01
The present status of the new inflationary theory in cosmology is discussed. The standard scenario of the very early universe, the problems of this scenario, and the basics of the new inflationary theory are reviewed. The ways in which this theory solves the problems connected with the standard scenario are described.
Probing the primordial power spectra with inflationary priors
Kawasaki, Masahiro; Sekiguchi, Toyokazu E-mail: sekiguti@icrr.u-tokyo.ac.jp
2010-02-01
We investigate constraints on power spectra of the primordial curvature and tensor perturbations with priors based on single-field slow-roll inflation models. The Hubble slow-roll parameters are included in cosmological parameters and the primordial power spectra are generated using the inflationary flow equations. Using data from recent observations of CMB and several measurements of geometrical distances in the late Universe, we perform Bayesian parameter estimation and model selection for models that have separate priors on the slow-roll parameters. The same analysis is also performed adopting the standard parameterization of the primordial power spectra. We confirmed that the scale-invariant Harrison-Zel'dovich spectrum is disfavored with more significance than previous studies. While current observations appear to be optimally modeled with some simple models of single-field slow-roll inflation, data is not enough constraining to distinguish these models.
Inflationary potentials in DBI models
Bessada, Dennis; Kinney, William H.; Tzirakis, Konstantinos E-mail: whkinney@buffalo.edu
2009-09-01
We study DBI inflation based upon a general model characterized by a power-law flow parameter ε(φ) ∝ φ{sup α} and speed of sound c{sub s}(φ) ∝ φ{sup β}, where α and β are constants. We show that in the slow-roll limit this general model gives rise to distinct inflationary classes according to the relation between α and β and to the time evolution of the inflaton field, each one corresponding to a specific potential; in particular, we find that the well-known canonical polynomial (large- and small-field), hybrid and exponential potentials also arise in this non-canonical model. We find that these non-canonical classes have the same physical features as their canonical analogs, except for the fact that the inflaton field evolves with varying speed of sound; also, we show that a broad class of canonical and D-brane inflation models are particular cases of this general non-canonical model. Next, we compare the predictions of large-field polynomial models with the current observational data, showing that models with low speed of sound have red-tilted scalar spectrum with low tensor-to-scalar ratio, in good agreement with the observed values. These models also show a correlation between large non-gaussianity with low tensor amplitudes, which is a distinct signature of DBI inflation with large-field polynomial potentials.
Coupling the inflationary sector to matter
NASA Astrophysics Data System (ADS)
Kallosh, Renata; Linde, Andrei; Wrase, Timm
2016-04-01
We describe the coupling of matter fields to an inflationary sector of supergravity, the inflaton Φ and a stabilizer S, in models where the Kähler potential has a flat inflaton direction. Such models include, in particular, advanced versions of the hyperbolic α-attractor models with a flat inflaton direction Kähler potential, providing a good fit to the observational data. If the superpotential is at least quadratic in the matter fields U i , with restricted couplings to the inflaton sector, we prove that under certain conditions: i) The presence of the matter fields does not affect a successful inflationary evolution. ii) There are no tachyons in the matter sector during and after inflation. iii) The matter masses squared are higher than 3 H 2 during inflation. The simplest class of theories satisfying all required conditions is provided by models with a flat direction Kähler potential, and with the inflaton Φ and a stabilizer S belonging to a hidden sector, so that matter fields have no direct coupling to the inflationary sector in the Kähler potential and in the superpotential.
Closed inflationary universe in patch cosmology
Campo, Sergio del Herrera, Ramon Saavedra, Joel Labrana, Pedro
2009-09-15
In this paper, we study closed inflationary universe models using the Gauss-Bonnet Brane. We determine and characterize the existence of a universe with {omega}>1, with an appropriate period of inflation. We have found that this model is less restrictive in comparison with the standard approach where a scalar field is considered. We use recent astronomical observations to constrain the parameters appearing in the model.
Statistical anisotropy in the inflationary universe
Shtanov, Yuri; Pyatkovska, Hanna
2009-07-15
During cosmological inflation, quasiclassical perturbations are permanently generated on super-Hubble spatial scales, their power spectrum being determined by the fundamental principles of quantum field theory. By the end of inflation, they serve as primeval seeds for structure formation in the universe. At early stages of inflation, such perturbations break homogeneity and isotropy of the inflationary background. In the present paper, we perturbatively take into account this quasiclassical background inhomogeneity of the inflationary universe while considering the evolution of small-scale (sub-Hubble) quantum modes. As a result, the power spectrum of primordial perturbations develops statistical anisotropy, which can subsequently manifest itself in the large-scale structure and cosmic microwave background. The statistically anisotropic contribution to the primordial power spectrum is predicted to have almost scale-invariant form dominated by a quadrupole. Theoretical expectation of the magnitude of this anisotropy depends on the assumptions about the physics in the trans-Planckian region of wave numbers.
Einstein Inflationary Probe (EIP)
NASA Technical Reports Server (NTRS)
Hinshaw, Gary
2004-01-01
I will discuss plans to develop a concept for the Einstein Inflation Probe: a mission to detect gravity waves from inflation via the unique signature they impart to the cosmic microwave background (CMB) polarization. A sensitive CMB polarization satellite may be the only way to probe physics at the grand-unified theory (GUT) scale, exceeding by 12 orders of magnitude the energies studied at the Large Hadron Collider. A detection of gravity waves would represent a remarkable confirmation of the inflationary paradigm and set the energy scale at which inflation occurred when the universe was a fraction of a second old. Even a strong upper limit to the gravity wave amplitude would be significant, ruling out many common models of inflation, and pointing to inflation occurring at much lower energy, if at all. Measuring gravity waves via the CMB polarization will be challenging. We will undertake a comprehensive study to identify the critical scientific requirements for the mission and their derived instrumental performance requirements. At the core of the study will be an assessment of what is scientifically and experimentally optimal within the scope and purpose of the Einstein Inflation Probe.
Observing inflationary reheating.
Martin, Jérôme; Ringeval, Christophe; Vennin, Vincent
2015-02-27
Reheating is the epoch which connects inflation to the subsequent hot big-bang phase. Conceptually very important, this era is, however, observationally poorly known. We show that the current Planck satellite measurements of the cosmic microwave background (CMB) anisotropies constrain the kinematic properties of the reheating era for most of the inflationary models. This result is obtained by deriving the marginalized posterior distributions of the reheating parameter for about 200 models of slow-roll inflation. Weighted by the statistical evidence of each model to explain the data, we show that the Planck 2013 measurements induce an average reduction of the posterior-to-prior volume by 40%. Making some additional assumptions on reheating, such as specifying a mean equation of state parameter, or focusing the analysis on peculiar scenarios, can enhance or reduce this constraint. Our study also indicates that the Bayesian evidence of a model can substantially be affected by the reheating properties. The precision of the current CMB data is therefore such that estimating the observational performance of a model now requires incorporating information about its reheating history. PMID:25768752
Observing Inflationary Reheating
NASA Astrophysics Data System (ADS)
Martin, Jérôme; Ringeval, Christophe; Vennin, Vincent
2015-02-01
Reheating is the epoch which connects inflation to the subsequent hot big-bang phase. Conceptually very important, this era is, however, observationally poorly known. We show that the current Planck satellite measurements of the cosmic microwave background (CMB) anisotropies constrain the kinematic properties of the reheating era for most of the inflationary models. This result is obtained by deriving the marginalized posterior distributions of the reheating parameter for about 200 models of slow-roll inflation. Weighted by the statistical evidence of each model to explain the data, we show that the Planck 2013 measurements induce an average reduction of the posterior-to-prior volume by 40%. Making some additional assumptions on reheating, such as specifying a mean equation of state parameter, or focusing the analysis on peculiar scenarios, can enhance or reduce this constraint. Our study also indicates that the Bayesian evidence of a model can substantially be affected by the reheating properties. The precision of the current CMB data is therefore such that estimating the observational performance of a model now requires incorporating information about its reheating history.
Signs of analyticity in single-field inflation
NASA Astrophysics Data System (ADS)
Baumann, Daniel; Green, Daniel; Lee, Hayden; Porto, Rafael A.
2016-01-01
The analyticity of response functions and scattering amplitudes implies powerful relations between low-energy observables and the underlying short-distance dynamics. These "IR/UV" relations are rooted in basic physical principles, such as causality and unitarity. In this paper, we seek similar connections in inflation, relating cosmological observations to the physics responsible for the accelerated expansion. We assume that the inflationary theory is Lorentz invariant at short distances, but allow for nonrelativistic interactions and a nontrivial speed of propagation at low energies. Focusing on forward scattering, we derive a "sum rule" which equates a combination of low-energy parameters to an integral which is sensitive to the high-energy behavior of the theory. While for relativistic amplitudes unitarity is sufficient to prove positivity of the sum rule, this is not guaranteed in the nonrelativistic case. We discuss the conditions under which positivity still applies, and show that they are satisfied by all known UV completions of single-field inflation. In that case, we obtain a consistency condition for primordial non-Gaussianity, which constrains the size and the sign of the equilateral four-point function in terms of the amplitude of the three-point function. The resulting bound rules out about half of the parameter space that is still allowed by current observations. Finding a violation of our consistency condition would point toward less conventional theories of inflation, or violations of basic physical principles.
Non-gaussian signatures of general inflationary trajectories
Horner, Jonathan S.; Contaldi, Carlo R. E-mail: c.contaldi@imperial.ac.uk
2014-09-01
We carry out a numerical calculation of the bispectrum in generalised trajectories of canonical, single-field inflation. The trajectories are generated in the Hamilton-Jacobi (HJ) formalism based on Hubble Slow Roll (HSR) parameters. The calculation allows generally shape and scale dependent bispectra, or dimensionless f{sub NL}, in the out-of-slow-roll regime. The distributions of f{sub NL} for various shapes and HSR proposals are shown as an example of how this procedure can be used within the context of Monte Carlo exploration of inflationary trajectories. We also show how allowing out-of-slow-roll behaviour can lead to a bispectrum that is relatively large for equilateral shapes.
Higgs vacuum stability and inflationary dynamics after BICEP2 and PLANCK dust polarisation data
NASA Astrophysics Data System (ADS)
Bhattacharya, Kaushik; Chakrabortty, Joydeep; Das, Suratna; Mondal, Tanmoy
2014-12-01
If the recent detection of B-mode polarization of the Cosmic Microwave Background by BICEP2 observations, withstand the test of time after the release of recent PLANCK dust polarisation data, then it would surprisingly put the inflationary scale near Grand Unification scale if one considers single-field inflationary models. On the other hand, Large Hadron Collider has observed the elusive Higgs particle whose presently observed mass can lead to electroweak vacuum instability at high scale (~ Script O(1010) GeV). In this article, we seek for a simple particle physics model which can simultaneously keep the vacuum of the theory stable and yield high-scale inflation successfully. To serve our purpose, we extend the Standard Model of particle physics with a U(1)B-L gauged symmetry which spontaneously breaks down just above the inflationary scale. Such a scenario provides a constrained parameter space where both the issues of vacuum stability and high-scale inflation can be successfully accommodated. The threshold effect on the Higgs quartic coupling due to the presence of the heavy inflaton field plays an important role in keeping the electroweak vacuum stable. Furthermore, this scenario is also capable of reheating the universe at the end of inflation. Though the issues of Dark Matter and Dark Energy, which dominate the late-time evolution of our universe, cannot be addressed within this framework, this model successfully describes the early universe dynamics according to the Big Bang model.
Higgs vacuum stability and inflationary dynamics after BICEP2 and PLANCK dust polarisation data
Bhattacharya, Kaushik; Chakrabortty, Joydeep; Das, Suratna; Mondal, Tanmoy E-mail: joydeep@iitk.ac.in E-mail: tanmoym@prl.res.in
2014-12-01
If the recent detection of B-mode polarization of the Cosmic Microwave Background by BICEP2 observations, withstand the test of time after the release of recent PLANCK dust polarisation data, then it would surprisingly put the inflationary scale near Grand Unification scale if one considers single-field inflationary models. On the other hand, Large Hadron Collider has observed the elusive Higgs particle whose presently observed mass can lead to electroweak vacuum instability at high scale (∼ O(10{sup 10}) GeV). In this article, we seek for a simple particle physics model which can simultaneously keep the vacuum of the theory stable and yield high-scale inflation successfully. To serve our purpose, we extend the Standard Model of particle physics with a U(1){sub B-L} gauged symmetry which spontaneously breaks down just above the inflationary scale. Such a scenario provides a constrained parameter space where both the issues of vacuum stability and high-scale inflation can be successfully accommodated. The threshold effect on the Higgs quartic coupling due to the presence of the heavy inflaton field plays an important role in keeping the electroweak vacuum stable. Furthermore, this scenario is also capable of reheating the universe at the end of inflation. Though the issues of Dark Matter and Dark Energy, which dominate the late-time evolution of our universe, cannot be addressed within this framework, this model successfully describes the early universe dynamics according to the Big Bang model.
WMAP normalization of inflationary cosmologies
Liddle, Andrew R.; Parkinson, David; Mukherjee, Pia; Leach, Samuel M.
2006-10-15
We use the three-year WMAP observations to determine the normalization of the matter power spectrum in inflationary cosmologies. In this context, the quantity of interest is not the normalization marginalized over all parameters, but rather the normalization as a function of the inflationary parameters n{sub S} and r with marginalization over the remaining cosmological parameters. We compute this normalization and provide an accurate fitting function. The statistical uncertainty in the normalization is 3%, roughly half that achieved by COBE. We use the k-l relation for the standard cosmological model to identify the pivot scale for the WMAP normalization. We also quote the inflationary energy scale corresponding to the WMAP normalization.
Inflationary reheating classes via spectral methods
NASA Astrophysics Data System (ADS)
Bassett, Bruce A.
1998-07-01
Inflationary reheating is almost completely controlled by the Floquet indices, μk. Using spectral theory, we demonstrate that the stability bands (where μk=0) of the Mathieu and Lamé equations are destroyed even in Minkowski spacetime, leaving a fractal Cantor set or a measure zero set of stable modes in the cases, where the inflaton evolves in an almost-periodic or stochastic manner, respectively. These two types of potential model the expected multi-field and quantum back reaction effects during reheating.
CMB cold spot from inflationary feature scattering
NASA Astrophysics Data System (ADS)
Wang, Yi; Ma, Yin-Zhe
2016-05-01
We propose a "feature-scattering" mechanism to explain the cosmic microwave background cold spot seen from WMAP and Planck maps. If there are hidden features in the potential of multi-field inflation, the inflationary trajectory can be scattered by such features. The scattering is controlled by the amount of isocurvature fluctuations, and thus can be considered as a mechanism to convert isocurvature fluctuations into curvature fluctuations. This mechanism predicts localized cold spots (instead of hot ones) on the CMB. In addition, it may also bridge a connection between the cold spot and a dip on the CMB power spectrum at ℓ ∼ 20.
Chaotic Inflationary Scenario in Bianchi Type i Spacetime
NASA Astrophysics Data System (ADS)
Bali, Raj
2012-03-01
Chaotic inflationary model of the early universe proposed by Linde7 is investigated in the frame work of Bianchi type I spacetime. To determine inflationary scenario, we assume that scale factor R3 = ABC ˜ e3Ht, V(φ ) = (1)/(2)m2φ ^2+(λ )/(n)φ ^n, λ being a constant, m the mass, V(ϕ) the potential energy density. It is shown that chaotic model leads to an inflationary phase which also helps in isotropization process. The Higg's field (ϕ) is initially large but decreases due to lapse of time in both cases. The assumption R3 = ABC e3Ht does not lead to FRW model immediately but for large values of t, it reduces to FRW model since shear σ = 0 in FRW model and shear σ ≠ 0 in Bianchi type I model. The physical aspects of the model are also discussed.
Pre-inflationary clues from String Theory?
Kitazawa, N.; Sagnotti, A. E-mail: sagnotti@sns.it
2014-04-01
''Brane supersymmetry breaking'' occurs in String Theory when the only available combinations of D-branes and orientifolds are not mutually BPS and yet do not introduce tree-level tachyon instabilities. It is characterized by the emergence of a steep exponential potential, and thus by the absence of maximally symmetric vacua. The corresponding low-energy supergravity admits intriguing spatially-flat cosmological solutions where a scalar field is forced to climb up toward the steep potential after an initial singularity, and additional milder terms can inject an inflationary phase during the ensuing descent. We show that, in the resulting power spectra of scalar perturbations, an infrared suppression is typically followed by a pre-inflationary peak that reflects the end of the climbing phase and can lie well apart from the approximately scale invariant profile. A first look at WMAP9 raw data shows that, while the χ{sup 2} fits for the low-ℓ CMB angular power spectrum are clearly compatible with an almost scale invariant behavior, they display nonetheless an eye-catching preference for this type of setting within a perturbative string regime.
A scenario for inflationary magnetogenesis without strong coupling problem
Tasinato, Gianmassimo
2015-03-23
Cosmological magnetic fields pervade the entire universe, from small to large scales. Since they apparently extend into the intergalactic medium, it is tantalizing to believe that they have a primordial origin, possibly being produced during inflation. However, finding consistent scenarios for inflationary magnetogenesis is a challenging theoretical problem. The requirements to avoid an excessive production of electromagnetic energy, and to avoid entering a strong coupling regime characterized by large values for the electromagnetic coupling constant, typically allow one to generate only a tiny amplitude of magnetic field during inflation. We propose a scenario for building gauge-invariant models of inflationary magnetogenesis potentially free from these issues. The idea is to derivatively couple a dynamical scalar, not necessarily the inflaton, to fermionic and electromagnetic fields during the inflationary era. Such couplings give additional freedom to control the time-dependence of the electromagnetic coupling constant during inflation. This fact allows us to find conditions to avoid the strong coupling problems that affect many of the existing models of magnetogenesis. We do not need to rely on a particular inflationary set-up for developing our scenario, that might be applied to different realizations of inflation. On the other hand, specific requirements have to be imposed on the dynamics of the scalar derivatively coupled to fermions and electromagnetism, that we are able to satisfy in an explicit realization of our proposal.
Revisiting cosmic no-hair theorem for inflationary settings
NASA Astrophysics Data System (ADS)
Maleknejad, A.; Sheikh-Jabbari, M. M.
2012-06-01
In this work we revisit Wald’s cosmic no-hair theorem [R. M. Wald, Phys. Rev. DPRVDAQ0556-2821 28, 2118 (1983).10.1103/PhysRevD.28.2118] in the context of accelerating Bianchi cosmologies for a generic cosmic fluid with nonvanishing anisotropic stress tensor and when the fluid energy-momentum tensor is of the form of a cosmological constant term plus a piece which does not respect strong or dominant energy conditions. Such a fluid is the one appearing in inflationary models. We show that for such a system anisotropy may grow, in contrast to the cosmic no-hair conjecture. In particular, for a generic inflationary model we show that there is an upper bound on the growth of anisotropy. For slow-roll inflationary models, our analysis can be refined further and the upper bound is found to be of the order of slow-roll parameters. We examine our general discussions and our extension of Wald’s theorem for three classes of slow-roll inflationary models, generic multiscalar field driven models, anisotropic models involving U(1) gauge fields and the gauge-flation scenario.
NASA Astrophysics Data System (ADS)
Popa, L. A.; Mandolesi, N.; Caramete, A.; Burigana, C.
2009-12-01
We make a more general determination of the inflationary observables in the standard four-dimensional (4D) and five-dimensional (5D) single-field inflationary scenarios by the exact reconstruction of the dynamics of the inflation potential during the observable inflation with a minimal number of assumptions: the computation does not assume the slow-roll approximation and is valid in all regimes if the field is monotonically rolling down its potential. We address higher order effects in the standard and braneworld single-field inflation scenarios by fitting the Hubbble expansion rate and subsequently the inflationary potential directly to WMAP5+SN+BAO and Planck-like simulated data sets. Making use of the Hamilton-Jacobi formalism developed for the 5D single-field inflation model, we compute the scale dependence of the amplitudes of the scalar and tensor perturbations by integrating the exact mode equation. The solutions in 4D and 5D inflation scenarios differ through the dynamics of the background scalar field and the number of e-folds assumed to be compatible with the observational window of inflation. We analyze the implications of the theoretical uncertainty in the determination of the reheating temperature after inflation on the observable predictions of inflation and evaluate its impact on the degeneracy of the standard inflation consistency relation. We find that the detection of tensor perturbations and the theoretical uncertainties in the inflationary observable represents a significant challenge for the future Planck cosmic microwave background measurements: distinguishing between the observational signatures of the standard and braneworld single-field inflation scenarios. This work has been done in the frame of Planck Core Team activities.
Popa, L. A.; Caramete, A.; Mandolesi, N.; Burigana, C.
2009-12-01
We make a more general determination of the inflationary observables in the standard four-dimensional (4D) and five-dimensional (5D) single-field inflationary scenarios by the exact reconstruction of the dynamics of the inflation potential during the observable inflation with a minimal number of assumptions: the computation does not assume the slow-roll approximation and is valid in all regimes if the field is monotonically rolling down its potential. We address higher order effects in the standard and braneworld single-field inflation scenarios by fitting the Hubbble expansion rate and subsequently the inflationary potential directly to WMAP5+SN+BAO and Planck-like simulated data sets. Making use of the Hamilton-Jacobi formalism developed for the 5D single-field inflation model, we compute the scale dependence of the amplitudes of the scalar and tensor perturbations by integrating the exact mode equation. The solutions in 4D and 5D inflation scenarios differ through the dynamics of the background scalar field and the number of e-folds assumed to be compatible with the observational window of inflation. We analyze the implications of the theoretical uncertainty in the determination of the reheating temperature after inflation on the observable predictions of inflation and evaluate its impact on the degeneracy of the standard inflation consistency relation. We find that the detection of tensor perturbations and the theoretical uncertainties in the inflationary observable represents a significant challenge for the future Planck cosmic microwave background measurements: distinguishing between the observational signatures of the standard and braneworld single-field inflation scenarios. This work has been done in the frame of Planck Core Team activities.
Modified Chaplygin gas inspired inflationary model in braneworld scenario
NASA Astrophysics Data System (ADS)
Jawad, Abdul; Rani, Shamaila; Mohsaneen, Sidra
2016-05-01
We investigate the modified Chaplygin gas inspired inflationary regime in the brane-world framework in the presence of standard and tachyon scalar fields. We consider the intermediate inflationary scenario and construct the slow-roll parameters, e-folding numbers, spectral index, scalar and tensor power spectra, tensor to scalar ratio for both scalar field models. We develop the ns - N and r - N planes and concluded that ns˜eq96^{+0.5}_{-0.5} and r≤0.0016 for N˜eq60^{+5}_{-5} in both cases of scalar field models as well as for all values of m. These constraints are consistent with observational data such as WMAP7, WMAP9 and Planck data.
Inflationary perturbation theory is geometrical optics in phase space
NASA Astrophysics Data System (ADS)
Seery, David; Mulryne, David J.; Frazer, Jonathan; Ribeiro, Raquel H.
2012-09-01
A pressing problem in comparing inflationary models with observation is the accurate calculation of correlation functions. One approach is to evolve them using ordinary differential equations ("transport equations"), analogous to the Schwinger-Dyson hierarchy of in-out quantum field theory. We extend this approach to the complete set of momentum space correlation functions. A formal solution can be obtained using raytracing techniques adapted from geometrical optics. We reformulate inflationary perturbation theory in this language, and show that raytracing reproduces the familiar "δN" Taylor expansion. Our method produces ordinary differential equations which allow the Taylor coefficients to be computed efficiently. We use raytracing methods to express the gauge transformation between field fluctuations and the curvature perturbation, ζ, in geometrical terms. Using these results we give a compact expression for the nonlinear gauge-transform part of fNL in terms of the principal curvatures of uniform energy-density hypersurfaces in field space.
Inflationary perturbation theory is geometrical optics in phase space
Seery, David; Frazer, Jonathan; Mulryne, David J.; Ribeiro, Raquel H. E-mail: D.Mulryne@qmul.ac.uk E-mail: R.Ribeiro@damtp.cam.ac.uk
2012-09-01
A pressing problem in comparing inflationary models with observation is the accurate calculation of correlation functions. One approach is to evolve them using ordinary differential equations ({sup t}ransport equations{sup )}, analogous to the Schwinger-Dyson hierarchy of in-out quantum field theory. We extend this approach to the complete set of momentum space correlation functions. A formal solution can be obtained using raytracing techniques adapted from geometrical optics. We reformulate inflationary perturbation theory in this language, and show that raytracing reproduces the familiar 'δN' Taylor expansion. Our method produces ordinary differential equations which allow the Taylor coefficients to be computed efficiently. We use raytracing methods to express the gauge transformation between field fluctuations and the curvature perturbation, ζ, in geometrical terms. Using these results we give a compact expression for the nonlinear gauge-transform part of f{sub NL} in terms of the principal curvatures of uniform energy-density hypersurfaces in field space.
Relaxing the limits on inflationary magnetogenesis
NASA Astrophysics Data System (ADS)
Tsagas, Christos G.
2015-11-01
Inflation has long been considered the best way to produce primordial large-scale magnetic fields. To achieve fields strong enough to seed the galactic dynamo, most of the mechanisms operate outside conventional electromagnetic theory. The latter is typically restored after the end of the de Sitter phase. Breaking away from standard electromagnetism can lead to substantially stronger magnetic fields by the end of inflation, thus compensating for their subsequent adiabatic depletion. We argue that the drastic magnetic enhancement during the de Sitter era may no longer be necessary because, contrary to the widespread perception, superhorizon-sized magnetic fields decay at a slower pace after inflation. The principle behind this claim is causality, which confines the postinflationary electric currents inside the horizon. Without the currents there can be no magnetic-flux freezing on super-Hubble lengths. There, the magnetic decay rate slows down, thus making it much easier to produce primordial fields of astrophysical interest. To quantify this qualitative statement, one can start from the current galactic-dynamo requirements and "reverse engineer" the magnetic strengths needed at the end of inflation in order to produce astrophysically relevant residual seeds today. Our numerical estimates suggest that, depending on the magnetic scale, mechanisms of inflationary magnetogenesis generating fields stronger than 1017 G by the end of the de Sitter phase could successfully seed the galactic dynamo at present.
Power-law and intermediate inflationary models in f( T)-gravity
NASA Astrophysics Data System (ADS)
Rezazadeh, K.; Abdolmaleki, A.; Karami, K.
2016-01-01
We study inflation in the framework of f( T)-gravity in the presence of a canonical scalar field. After reviewing the basic equations governing the background cosmology in f( T)-gravity, we turn to study the cosmological perturbations and obtain the evolutionary equations for the scalar and tensor perturbations. Solving those equations, we find the power spectra for the scalar and tensor perturbations. Then, we consider a power-law f( T) function and investigate the inflationary models with the power-law and intermediate scale factors. We see that in contrast with the standard inflationary scenario based on the Einstein gravity, the power-law and intermediate inflationary models in f( T)-gravity can be compatible with the observational results of Planck 2015 at 68% CL. We find that in our f( T) setting, the potentials responsible for the both power-law and intermediate inflationary models have the power-law form V( ϕ) ∝ ϕ m but the power m is different for them. Therefore, we can refine some of power-law inflationary potentials in the framework of f( T)-gravity while they are disfavored by the observational data in the standard inflationary scenario. Interestingly enough, is that the self-interacting quartic potential V( ϕ) ∝ ϕ 4 which has special reheating properties, can be consistent with the Planck 2015 data in our f( T) scenario while it is ruled out in the standard inflationary scenario.
A Jacobian elliptic single-field inflation
NASA Astrophysics Data System (ADS)
Villanueva, J. R.; Gallo, Emanuel
2015-06-01
In the scenario of single-field inflation, this field is described in terms of Jacobian elliptic functions. This approach provides, when constrained to particular cases, analytic solutions already known in the past, generalizing them to a bigger family of analytical solutions. The emergent cosmology is analyzed using the Hamilton-Jacobi approach and then the main results are contrasted with the recent measurements obtained from the Planck 2015 data.
Inflationary magnetogenesis without the strong coupling problem
Ferreira, Ricardo J.Z.; Jain, Rajeev Kumar; Sloth, Martin S. E-mail: jain@cp3.dias.sdu.dk
2013-10-01
The simplest gauge invariant models of inflationary magnetogenesis are known to suffer from the problems of either large backreaction or strong coupling, which make it difficult to self-consistently achieve cosmic magnetic fields from inflation with a field strength larger than 10{sup −32}G today on the Mpc scale. Such a strength is insufficient to act as seed for the galactic dynamo effect, which requires a magnetic field larger than 10{sup −20}G. In this paper we analyze simple extensions of the minimal model, which avoid both the strong coupling and back reaction problems, in order to generate sufficiently large magnetic fields on the Mpc scale today. First we study the possibility that the coupling function which breaks the conformal invariance of electromagnetism is non-monotonic with sharp features. Subsequently, we consider the effect of lowering the energy scale of inflation jointly with a scenario of prolonged reheating where the universe is dominated by a stiff fluid for a short period after inflation. In the latter case, a systematic study shows upper bounds for the magnetic field strength today on the Mpc scale of 10{sup −13}G for low scale inflation and 10{sup −25}G for high scale inflation, thus improving on the previous result by 7-19 orders of magnitude. These results are consistent with the strong coupling and backreaction constraints.
Probing Inflationary Cosmology: The Atacama B-Mode Search (ABS)
NASA Astrophysics Data System (ADS)
Essinger-Hileman, Thomas
Observations of the Cosmic Microwave Background (CMB) have provided compelling evidence for the Standard Model of Cosmology and have led to the most precise estimates of cosmological parameters to date. Through its sensitivity to gravitational waves, the CMB provides a glimpse into the state of the universe just 10-35 seconds after the Big Bang and of physics on grand-unification-theory (GUT) energy scales around 1016 GeV, some 13 orders of magnitude above the energies achievable by current terrestrial particle accelerators. A gravitational-wave background (GWB) in the early universe would leave a unique, odd-parity pattern of polarization in the CMB called B modes, the magnitude of which is characterized by the tensor-to-scalar ratio, r. A GWB is generically predicted to exist by inflationary theories, and the current generation of CMB polarization experiments will probe the interesting parameter space of r < 0.05 corresponding to single-field inflationary models at GUT scales. I detail the design and construction of the Atacama B-Mode Search (ABS), which aims to measure the polarization of the CMB at degree angular scales where the primordial B-mode signal is expected to peak. ABS is a 145-GHz polarimeter that will operate from a high-altitude site in the Atacama Desert of Chile, consisting of a 60-cm crossed-Dragone telescope with cryogenic primary and secondary reflectors; an array of 240 feedhorn-coupled, transition-edge-sensor, bolometric polarimeters; and, a continuously-rotating, warm, sapphire half-wave plate (HWP) that will provide modulation of the incoming polarization of light. In this thesis, I describe the optical, mechanical, and cryogenic design of the receiver, including the reflector design, focal-plane layout, HWP design, and free-space lowpass filters. I describe physical-optics modeling of the reflector and feedhorn to validate the optical design. A matrix model that allows the calculation of the Mueller matrix of the anti
Linde, Andrei
2015-05-05
I describe a simple class of α-attractors, generalizing the single-field GL model of inflation in supergravity. The new class of models is defined for 0<α≲1, providing a good match to the present cosmological data. I also present a generalized version of these models which can describe not only inflation but also dark energy and supersymmetry breaking.
Loop Quantum Cosmology: holonomy corrections to inflationary models
Artymowski, Michal; Lalak, Zygmunt; Szulc, Lukasz
2009-01-15
In the recent years the quantization methods of Loop Quantum Gravity have been successfully applied to the homogeneous and isotropic Friedmann-Robertson-Walker space-times. The resulting theory, called Loop Quantum Cosmology (LQC), resolves the Big Bang singularity by replacing it with the Big Bounce. We argue that the LQC holonomy corrections generate also certain corrections to field theoretical inflationary scenarios. These corrections imply that in the LQC the effective sonic horizon becomes infinite at some point after the bounce and that the scale of the inflationary potential implied by the COBE normalisation increases. The evolution of scalar fields immediately after the Bounce becomes modified in an interesting way. We point out that one can use COBE normalisation to establish an upper bound on the quantum of length of LQG. LQC corrections other than the holonomy one are assumed to be subdominant.
The reconstruction of inflationary potentials
NASA Astrophysics Data System (ADS)
Lin, Jianmang; Gao, Qing; Gong, Yungui
2016-07-01
The observational data on the anisotropy of the cosmic microwave background constraints the scalar spectral tilt ns and the tensor to scalar ratio r which depend on the first and second derivatives of the inflaton potential. The information can be used to reconstruct the inflaton potential in the polynomial form up to some orders. However, for some classes of potentials, ns and r behave as ns(N) and r(N) universally in terms of the number of e-folds N. The universal behaviour of ns(N) can be used to reconstruct a class of inflaton potentials. By parametrizing one of the parameters ns(N), ɛ(N) and φ(N), and fitting the parameters in the models to the observational data, we obtain the constraints on the parameters and reconstruct the classes of the inflationary models which include the chaotic inflation, T-model, hilltop inflation, s-dual inflation, natural inflation and R2 inflation.
Inflationary back-reaction effects from Relativistic Quantum Geometry
NASA Astrophysics Data System (ADS)
Bellini, Mauricio
2016-03-01
We study the dynamics of scalar metric fluctuations in a non-perturbative variational formalism recently introduced, by which the dynamics of a geometrical scalar field θ, describes the quantum geometrical effects on a Weylian-like manifold with respect to a background Riemannian space-time. In this letter we have examined an example in the framework of inflationary cosmology. The resulting spectral predictions are in very good agreement with observations and other models of inflation.
Inflationary potentials from the exact renormalisation group
NASA Astrophysics Data System (ADS)
Grozdanov, Sašo; Kraljić, David; Svanes, Eirik Eik
2016-08-01
We show that an inflationary slow-roll potential can be derived as an IR limit of the non-perturbative exact renormalisation group equation for a scalar field within the mean-field approximation. The result follows without having to specify a Lagrangian in the UV, which we take to be somewhere below the Planck scale to avoid discussing quantum gravity effects. We assume that the theory contains a scalar mode with suppressed coupling to other fields, and that higher derivative couplings are suppressed. In this framework the exact RG equation becomes a one-dimensional Schrödinger equation, which we solve. The effective IR potential is then dominated by the eigen-states of the RG Hamiltonian with the highest eigenvalues. We find that these potentials can generically give rise to slow-roll inflation, which is fully consistent with recent observations. As an example of how the proposed renormalisation group procedure works, we perform an explicit calculation in the ϕ4 theory in an appendix.
The BICEP2 data and a single Higgs-like interacting scalar field
NASA Astrophysics Data System (ADS)
Verma, Murli Manohar; Pathak, Shankar Dayal
2014-08-01
It is proposed that the recently announced BICEP2 value of tensor-to-scalar ratio r 0.2 can be explained as containing an extra contribution from the recent acceleration of the universe. In fact this contribution, being robust, recent and of much longer duration (by a large order of magnitude) may dominate the contribution from the inflationary origin. In a possible scenario, matter (dark or baryonic) and radiation etc. can emerge from a single Higgs-like tachyonic scalar field in the universe through a physical mechanism not yet fully known to us. The components interact among themselves to achieve the thermodynamical equilibrium in the evolution of the universe. The field potential for the present acceleration of the universe would give a boost to the amplitude of the tensor fluctuations of gravity waves generated by the early inflation and the net effects may be higher than the earlier Planck bounds. In the process, the dark energy, as a cosmological constant decays into creation of dark matter. The diagnostics for the three-component, spatially homogeneous tachyonic scalar field are discussed in detail. The components of the field with perturbed equation of state (EoS) are taken to interact mutually and the conservation of energy for individual components gets violated. We study mainly the Om(x) diagnostics with the observed set of H(z) values at various redshifts, and the dimensionless statefinders for these interacting components. This analysis provides a strong case for the interacting dark energy in our model.
Surprising phenomena in a rich new class of inflationary models
Vaudrevange, Pascal M.; Podolsky, Dmitry I.; Starkman, Glenn D. E-mail: podolsky@phys.cwru.edu
2010-04-01
We report on a new class of fast-roll inflationary models. In a huge part of its parameter space, inflationary perturbations exhibit quite unusual phenomena such as scalar and tensor modes freezing out at widely different times, as well as scalar modes reentering the horizon during inflation. One specific point in parameter space is characterized by extraordinary behavior of the scalar perturbations. Freeze-out of scalar perturbations as well as particle production at horizon crossing are absent. Also the behavior of the perturbations around this quasi-de Sitter background is dual to a quantum field theory in flat space-time. Finally, the form of the primordial power spectrum is determined by the interaction between different modes of scalar perturbations.
Initial conditions for anisotropic extended-type inflationary universes
del Campo, S. )
1992-05-15
Recently, extended-type inflationary universe models have been proposed as an appealing approach for solving most of the cosmological puzzles'' that, in contrast with previous models, do not require a fine-tuning'' for the microphysical parameters present in the effective potential. These scenarios rest on a Brans-Dicke-type theory, where a nonminimal coupling of the form {ital f}({ital cphi}){ital R} is assumed, and it may or may not include a potential for the Brans-Dicke field. In its classical description, different extended inflationary universe scenarios are described, where anisotropy is taken into account. By using the Hartle-Hawking and the Vilenkin boundary conditions for the wave function of the Universe, the probability distributions for the initial states of these extended models in the case of a small anisotropy are determined and discussed.
Galilean creation of the inflationary universe
Kobayashi, Tsutomu; Yamaguchi, Masahide; Yokoyama, Jun’ichi
2015-07-13
It has been pointed out that the null energy condition can be violated stably in some non-canonical scalar-field theories. This allows us to consider the Galilean Genesis scenario in which the universe starts expanding from Minkowski spacetime and hence is free from the initial singularity. We use this scenario to study the early-time completion of inflation, pushing forward the recent idea of Pirtskhalava et al. We present a generic form of the Lagrangian governing the background and perturbation dynamics in the Genesis phase, the subsequent inflationary phase, and the graceful exit from inflation, as opposed to employing the effective field theory approach. Our Lagrangian belongs to a more general class of scalar-tensor theories than the Horndeski theory and Gleyzes-Langlois-Piazza-Vernizzi generalization, but still has the same number of the propagating degrees of freedom, and thus can avoid Ostrogradski instabilities. We investigate the generation and evolution of primordial perturbations in this scenario and show that one can indeed construct a stable model of inflation preceded by (generalized) Galilean Genesis.
Path integral for inflationary perturbations
NASA Astrophysics Data System (ADS)
Prokopec, Tomislav; Rigopoulos, Gerasimos
2010-07-01
The quantum theory of cosmological perturbations in single-field inflation is formulated in terms of a path integral. Starting from a canonical formulation, we show how the free propagators can be obtained from the well-known gauge-invariant quadratic action for scalar and tensor perturbations, and determine the interactions to arbitrary order. This approach does not require the explicit solution of the energy and momentum constraints, a novel feature which simplifies the determination of the interaction vertices. The constraints and the necessary imposition of gauge conditions is reflected in the appearance of various commuting and anticommuting auxiliary fields in the action. These auxiliary fields are not propagating physical degrees of freedom but need to be included in internal lines and loops in a diagrammatic expansion. To illustrate the formalism we discuss the tree-level three-point and four-point functions of the inflaton perturbations, reproducing the results already obtained by the methods used in the current literature. Loop calculations are left for future work.
Electric field breakdown in single molecule junctions.
Li, Haixing; Su, Timothy A; Zhang, Vivian; Steigerwald, Michael L; Nuckolls, Colin; Venkataraman, Latha
2015-04-22
Here we study the stability and rupture of molecular junctions under high voltage bias at the single molecule/single bond level using the scanning tunneling microscope-based break-junction technique. We synthesize carbon-, silicon-, and germanium-based molecular wires terminated by aurophilic linker groups and study how the molecular backbone and linker group affect the probability of voltage-induced junction rupture. First, we find that junctions formed with covalent S-Au bonds are robust under high voltage and their rupture does not demonstrate bias dependence within our bias range. In contrast, junctions formed through donor-acceptor bonds rupture more frequently, and their rupture probability demonstrates a strong bias dependence. Moreover, we find that the junction rupture probability increases significantly above ∼1 V in junctions formed from methylthiol-terminated disilanes and digermanes, indicating a voltage-induced rupture of individual Si-Si and Ge-Ge bonds. Finally, we compare the rupture probabilities of the thiol-terminated silane derivatives containing Si-Si, Si-C, and Si-O bonds and find that Si-C backbones have higher probabilities of sustaining the highest voltage. These results establish a new method for studying electric field breakdown phenomena at the single molecule level. PMID:25675085
Anatomy of bispectra in general single-field inflation — Modal expansions
Battefeld, Thorsten; Grieb, Jan E-mail: jgrieb@astro.physik.uni-goettingen.de
2011-12-01
We discuss bispectra of single-field inflationary models described by general Lorentz invariant Lagrangians that are at most first order in field derivatives, including the fast-roll models investigated by Noller and Magueijo. Based on a factor analysis, we identify the least correlated basic contributions to the general shape and show quantitatively which templates provide a good approximation. We compute how relative contributions of basic shapes to the total bispectrum scale as slow roll is relaxed. To enable future comparison with CMB observations, we provide a modal expansion of these non-separable bispectra in Fourier space, employing the formalism by Fergusson et al. Convergence is rapid, usually better than ninety-five percent with less than thirty modes, due to the smoothness of these primordial shapes. Truncated polynomial modal expansions have restrictions, which we highlight using an example with slow convergence. The particular shape originates from particle production during inflation (common in trapped inflation) and entails both localized and oscillatory features. We show that this shape can be recovered efficiently using a Fourier basis and outline the prospect of future model parameter extraction and N-body simulations based on modal techniques.
Inflationary magnetogenesis with broken local U(1) symmetry
NASA Astrophysics Data System (ADS)
Domènech, Guillem; Lin, Chunshan; Sasaki, Misao
2016-07-01
We point out that a successful inflationary magnetogenesis could be realised if we break the local U(1) gauge symmetry during inflation. The effective electric charge is fixed as a fundamental constant, which allows us to obtain an almost scale-invariant magnetic spectrum avoiding both the strong coupling and back reaction problems. We examine the corrections to the primordial curvature perturbation due to these stochastic electromagnetic fields and find that, at both linear and non-linear orders, the contributions from the electromagnetic field are negligible compared to those created from vacuum fluctuations. Finally, the U(1) gauge symmetry is restored at the end of inflation.
NASA Astrophysics Data System (ADS)
Choudhury, Sayantan
2015-05-01
In this paper my prime objective is to explain the generation of large tensor-to-scalar ratio from the single field sub-Planckian inflationary paradigm within Randall-Sundrum (RS) single braneworld scenario in a model independent fashion. By explicit computation I have shown that the effective field theory prescription of brane inflation within RS single brane setup is consistent with sub-Planckian excursion of the inflaton field, which will further generate large value of tensor-to-scalar ratio, provided the energy density for inflaton degrees of freedom is high enough compared to the brane tension in high energy regime. Finally, I have mentioned the stringent theoretical constraint on positive brane tension, cut-off of the quantum gravity scale and bulk cosmological constant to get sub-Planckian field excursion along with large tensor-to-scalar ratio as recently observed by BICEP2 or at least generates the tensor-to-scalar ratio consistent with the upper bound of Planck (2013 and 2015) data and Planck+BICEP2+Keck Array joint constraint.
Inflationary quasiscale-invariant attractors
NASA Astrophysics Data System (ADS)
Rinaldi, Massimiliano; Vanzo, Luciano; Zerbini, Sergio; Venturi, Giovanni
2016-01-01
In a series of recent papers Kallosh, Linde, and collaborators provide a unified description of single-field inflation with several types of potentials ranging from power law to supergravity, in terms of just one parameter α . These so-called α attractors predict a spectral index ns and a tensor-to-scalar ratio r , which are fully compatible with the latest Planck data. The only common feature of all α attractors is a noncanonical kinetic term with a pole, and a potential analytic around the pole. In this paper, starting from the same Einstein frame with a noncanonical scalar kinetic energy, we explore the case of nonanalytic potentials. We find the functional form that corresponds to quasiscale-invariant gravitational models in the Jordan frame characterized by a universal relation between r and ns that fits the observational data but is clearly distinct from the one of the α attractors. It is known that the breaking of the exact classical scale invariance in the Jordan frame can be attributed to one-loop corrections. Therefore we conclude that there exists a class of nonanalytic potentials in the noncanonical Einstein frame that is physically equivalent to a class of models in the Jordan frame, with scale invariance softly broken by one-loop quantum corrections.
Warm inflationary model in loop quantum cosmology
Herrera, Ramon
2010-06-15
A warm inflationary universe model in loop quantum cosmology is studied. In general we discuss the condition of inflation in this framework. By using a chaotic potential, V({phi}){proportional_to}{phi}{sup 2}, we develop a model where the dissipation coefficient {Gamma}={Gamma}{sub 0}=constant. We use recent astronomical observations for constraining the parameters appearing in our model.
Decoding the bispectrum of single-field inflation
Ribeiro, Raquel H.; Seery, David E-mail: D.Seery@sussex.ac.uk
2011-10-01
Galileon fields arise naturally from the decoupling limit of massive gravities, and possess special self-interactions which are protected by a spacetime generalization of Galilean symmetry. We briefly revisit the inflationary phenomenology of Galileon theories. Working from recent computations of the fluctuation Lagrangian to cubic order in the most general model with second-order equations of motion, we show that a distinct shape is present but with suppressed amplitude. A similar shape has been found in other higher-derivative models. It may be visible in a theory tuned to suppress the leading-order shapes, or if the overall bispectrum has large amplitude. Using a partial-wave expansion of the bispectrum, we suggest a possible origin for the frequent appearance of this shape. It follows that models with very disparate microphysics can produce very similar bispectra. We argue that it may be more profitable to distinguish these models by searching for relations between the amplitudes of these common shapes. We illustrate this method using the examples of DBI and k-inflation.
Validation of inflationary noninvasive blood pressure monitoring in the emergency room
Kikuchi, Yoshiharu; Usuda, Takashi; Hori, Shingo
2015-01-01
Objective The aim of this study was to compare the values of a noninvasive blood pressure (NIBP) measurement during cuff inflation (inflationary NIBP) and deflationary NIBP measurements and to verify whether inflationary NIBP is equivalent to conventional deflationary NIBP and is acceptable for clinical use in the emergency room (ER). Materials and methods A total of 2981 NIBP data points were collected from 175 patients (age, 56.5±22.2 years; range, 7–92 years) who had been treated in the resuscitation area of the ER at Keio University Hospital. The data points were obtained using two alternate algorithms with a standard monitor (BSM-6000). One algorithm consisted of continuous inflationary and deflationary measurements in a single cycle (dual algorithm, 1502 data points); this algorithm was used to verify the success rate and the precision of the data. The second algorithm (1479 data points) consisted of only conventional deflationary measurements and was used to verify the duration of the measurement cycle. Results The success rate of the inflationary NIBP (completed using only the inflationary method) was 69.0%. Failures in the inflationary measurements were caused by arrhythmia and/or body motions. The mean difference and SD of the systolic pressure and the diastolic pressure between inflationary NIBP and deflationary NIBP were −0.6±8.8 and 3.5±7.5 mmHg, respectively. The confidence intervals were −0.6 (95% confidence interval=−1.1 to −0.1) and 3.5 (95% confidence interval=3.0 to 4.0) mmHg. The coefficients of correlation were 0.96 and 0.93. Inflationary NIBP was capable of determining the NIBP more quickly compared with deflationary NIBP (average of 15.9 vs. 34.2 s; P<0.05). Conclusion Inflationary NIBP measurements have a reasonable accuracy and a sufficient rapidity, compared with deflationary NIBP measurements, in ER patients. PMID:26241294
About the isocurvature tension between axion and high scale inflationary models
NASA Astrophysics Data System (ADS)
Estevez, M.; Santillán, O.
2016-07-01
The present work suggests that the isocurvature tension between axion and high energy inflationary scenarios may be avoided by considering a double field inflationary model involving the hidden Peccei-Quinn Higgs and the Standard Model one. Some terms in the lagrangian we propose explicitly violate the Peccei-Quinn symmetry but, at the present era, their effect is completely negligible. The resulting mechanism allows for a large value for the axion constant, of the order f_a˜ M_p, thus the axion isocurvature fluctuations are suppressed even when the scale of inflation H_{inf} is very high, of the order of H_{inf}˜ M_{gut}. This numerical value is typical in Higgs inflationary models. An analysis about topological defect formation in this scenario is also performed, and it is suggested that, under certain assumptions, their effect is not catastrophic from the cosmological point of view.
Effects of viscous pressure on warm inflationary generalized cosmic Chaplygin gas model
Sharif, M.; Saleem, Rabia E-mail: rabiasaleem1988@yahoo.com
2014-12-01
This paper is devoted to study the effects of bulk viscous pressure on an inflationary generalized cosmic Chaplygin gas model using FRW background. The matter contents of the universe are assumed to be inflaton and imperfect fluid. We evaluate inflaton fields, potentials and entropy density for variable as well as constant dissipation and bulk viscous coefficients in weak as well as high dissipative regimes during intermediate era. In order to discuss inflationary perturbations, we evaluate entropy density, scalar (tensor) power spectra, their corresponding spectral indices, tensor-scalar ratio and running of spectral index in terms of inflaton which are constrained using recent Planck, WMAP7 and Bicep2 probes.
Cosmic inflation in a landscape of heavy-fields
Céspedes, Sebastián; Palma, Gonzalo A. E-mail: gpalmaquilod@ing.uchile.cl
2013-10-01
Heavy isocurvature fields may have a strong influence on the low energy dynamics of curvature perturbations during inflation, as long as the inflationary trajectory becomes non-geodesic in the multi-field target space (the landscape). If fields orthogonal to the inflationary trajectory are sufficiently heavy, one expects a reliable effective field theory describing the low energy dynamics of curvature perturbations, with self-interactions determined by the shape of the inflationary trajectory. Previous work analyzing the role of heavy-fields during inflation have mostly focused in the effects on curvature perturbations due to a single heavy-field. In this article we extend the results of these works by studying models of inflation in which curvature perturbations interact with two heavy-fields. We show that the second heavy-field (orthogonal to both tangent and normal directions of the inflationary trajectory) may significantly affect the evolution of curvature modes. We compute the effective field theory for the low energy curvature perturbations obtained by integrating out the two heavy-fields and show that the presence of the second heavy-field implies the existence of additional self-interactions not accounted for in the single heavy-field case. We conclude that future observations will be able to constrain the number of heavy fields interacting with curvature perturbations.
Density perturbations and the cosmological constant from inflationary landscapes
Feldstein, Brian; Hall, Lawrence J.; Watari, Taizan
2005-12-15
An anthropic understanding of the cosmological constant requires that the vacuum energy at late time scans from one patch of the universe to another. If the vacuum energy during inflation also scans, the various patches of the universe acquire exponentially differing volumes. In a generic landscape with slow-roll inflation, we find that this gives a steeply varying probability distribution for the normalization of the primordial density perturbations, resulting in an exponentially small fraction of observers measuring the Cosmic Background Explorer value of 10{sup -5}. Inflationary landscapes should avoid this ''{sigma} problem,'' and we explore features that can allow them to do that. One possibility is that, prior to slow-roll inflation, the probability distribution for vacua is extremely sharply peaked, selecting essentially a single anthropically allowed vacuum. Such a selection could occur in theories of eternal inflation. A second possibility is that the inflationary landscape has a special property: although scanning leads to patches with volumes that differ exponentially, the value of the density perturbation does not vary under this scanning. This second case is preferred over the first, partly because a flat inflaton potential can result from anthropic selection, and partly because the anthropic selection of a small cosmological constant is more successful.
Saez, D.
1987-03-15
In this work the metric is coupled with a scalar field phi in a simple way. Although this coupling becomes problematic because the energy density of phi appears to be unbounded from below, it is displayed as a very simple coupling leading to a nonsingular cosmological model with an early antigravity regime. A basic study of the inflationary period and various suggestions are presented.
Initial directional singularity in inflationary models
NASA Astrophysics Data System (ADS)
Fernández-Jambrina, L.
2016-07-01
In Haro, Amorós, and Pan [Phys. Rev. D 93, 084018 (2016)] a new cosmological model is proposed with no big bang singularity in the past, though past geodesically incomplete. This model starts with an inflationary era, follows with a stiff matter dominated period and evolves to accelerated expansion in an asymptotically de Sitter regime in a realistic fashion. The big bang singularity is replaced by a directional singularity. This singularity cannot be reached by comoving observers, since it would take them an infinite proper time lapse to go back to it. On the contrary, observers with nonzero linear momentum have the singularity at finite proper time in their past, though arbitrarily large. Hence, the time lapse from the initial singularity can be as long as desired, even infinity, depending on the linear momentum of the observer. This conclusion applies to similar inflationary models. Due to the interest of these models, we address here the properties of such singularities.
On the initial condition of inflationary fluctuations
NASA Astrophysics Data System (ADS)
Jiang, Hongliang; Wang, Yi; Zhou, Siyi
2016-04-01
It is usually assumed that the inflationary fluctuations start from the Bunch-Davies (BD) vacuum and the iε prescription is used when interactions are calculated. We show that those assumptions can be verified explicitly by calculating the loop corrections to the inflationary two-point and three-point correlation functions. Those loop corrections can be resummed to exponential factors, which suppress non-BD coefficients and behave as the iε factor for the case of the BD initial condition. A new technique of loop chain diagram resummation is developed for this purpose. For the non-BD initial conditions which is setup at finite time and has not fully decayed, explicit correction to the two-point and three-point correlation functions are calculated. Especially, non-Gaussianity in the folded limit is regularized due to the interactions.
Inflation after COBE: Lectures on inflationary cosmology
Turner, M.S. . Enrico Fermi Inst. Fermi National Accelerator Lab., Batavia, IL )
1992-01-01
In these lectures I review the standard hot big-bang cosmology, emphasizing its successes, its shortcomings, and its major challenge-a detailed understanding of the formation of structure in the Universe. I then discuss the motivations for and the fundamentals of inflationary cosmology, particularly emphasizing the quantum origin of metric (density and gravity-wave) perturbations. Inflation addresses the shortcomings of the standard cosmology and provides the initial data'' for structure formation. I conclude by addressing the implications of inflation for structure formation, evaluating the various cold dark matter models in the light of the recent detection of temperature anisotropies in the cosmic background radiation by COBE. In the near term, the study of structure formation offers a powerful probe of inflation, as well as specific inflationary models.
Inflation after COBE: Lectures on inflationary cosmology
Turner, M.S. |
1992-12-31
In these lectures I review the standard hot big-bang cosmology, emphasizing its successes, its shortcomings, and its major challenge-a detailed understanding of the formation of structure in the Universe. I then discuss the motivations for and the fundamentals of inflationary cosmology, particularly emphasizing the quantum origin of metric (density and gravity-wave) perturbations. Inflation addresses the shortcomings of the standard cosmology and provides the ``initial data`` for structure formation. I conclude by addressing the implications of inflation for structure formation, evaluating the various cold dark matter models in the light of the recent detection of temperature anisotropies in the cosmic background radiation by COBE. In the near term, the study of structure formation offers a powerful probe of inflation, as well as specific inflationary models.
Inflationary tensor perturbations after BICEP2.
Caligiuri, Jerod; Kosowsky, Arthur
2014-05-16
The measurement of B-mode polarization of the cosmic microwave background at large angular scales by the BICEP experiment suggests a stochastic gravitational wave background from early-Universe inflation with a surprisingly large amplitude. The power spectrum of these tensor perturbations can be probed both with further measurements of the microwave background polarization at smaller scales and also directly via interferometry in space. We show that sufficiently sensitive high-resolution B-mode measurements will ultimately have the ability to test the inflationary consistency relation between the amplitude and spectrum of the tensor perturbations, confirming their inflationary origin. Additionally, a precise B-mode measurement of the tensor spectrum will predict the tensor amplitude on solar system scales to 20% accuracy for an exact power-law tensor spectrum, so a direct detection will then measure the running of the tensor spectral index to high precision. PMID:24877926
Inflationary magnetogenesis and non-local actions: the conformal anomaly
NASA Astrophysics Data System (ADS)
Kamal El-Menoufi, Basem
2016-02-01
We discuss the possibility of successful magnetogenesis during inflation by employing the one-loop effective action of massless QED. The action is strictly non-local and results from the long distance fluctuations of massless charged particles present at the inflationary scale. Most importantly, it encodes the conformal anomaly of QED which is crucial to avoid the vacuum preservation in classical electromagnetism. In particular, we find a blue spectrum for the magnetic field with spectral index nB simeq 2 - αe where αe depends on both the number of e-folds during inflation as well as the coefficient of the one-loop beta function. In particular, the sign of the beta function has important bearing on the final result. A low reheating temperature is required for the present day magnetic field to be consistent with the lower bound inferred on the field in the intergalactic medium.
Fermionic influence on inflationary fluctuations
NASA Astrophysics Data System (ADS)
Boyanovsky, Daniel
2016-04-01
Motivated by apparent persistent large scale anomalies in the cosmic microwave background we study the influence of fermionic degrees of freedom on the dynamics of inflaton fluctuations as a possible source of violations of (nearly) scale invariance on cosmological scales. We obtain the nonequilibrium effective action of an inflaton-like scalar field with Yukawa interactions (YD ,M) to light fermionic degrees of freedom both for Dirac and Majorana fields in de Sitter space-time. The effective action leads to Langevin equations of motion for the fluctuations of the inflaton-like field, with self-energy corrections and a stochastic Gaussian noise. We solve the Langevin equation in the super-Hubble limit implementing a dynamical renormalization group resummation. For a nearly massless inflaton its power spectrum of super-Hubble fluctuations is enhanced, P (k ;η )=(H/2 π )2eγt[-k η ] with γt[-k η ]=1/6 π2 [∑i =1 NDYi,D 2+2 ∑j =1 NMYj,M 2]{ln2[-k η ]-2 ln [-k η ]ln [-k η0]} for ND Dirac and NM Majorana fermions, and η0 is the renormalization scale at which the inflaton mass vanishes. The full power spectrum is shown to be renormalization group invariant. These corrections to the super-Hubble power spectrum entail a violation of scale invariance as a consequence of the coupling to the fermionic fields. The effective action is argued to be exact in the limit of a large number of fermionic fields. A cancellation between the enhancement from fermionic degrees of freedom and suppression from light scalar degrees of freedom conformally coupled to gravity suggests the possibility of a finely tuned supersymmetry among these fields.
Anisotropic higher derivative gravity and inflationary universe
Kao, W. F.
2006-08-15
Stability analysis of the Kantowski-Sachs type universe in pure higher derivative gravity theory is studied in detail. The nonredundant generalized Friedmann equation of the system is derived by introducing a reduced one-dimensional generalized Kantowski-Sachs type action. Existence and stability of inflationary solution in the presence of higher derivative terms are also studied in detail. Implications to the choice of physical theories are discussed in detail in this paper.
Distinguishing between inflationary models from cosmic microwave background
NASA Astrophysics Data System (ADS)
Tsujikawa, Shinji
2014-06-01
In this paper, inflationary cosmology is reviewed, paying particular attention to its observational signatures associated with large-scale density perturbations generated from quantum fluctuations. In the most general scalar-tensor theories with second-order equations of motion, we derive the scalar spectral index n_s, the tensor-to-scalar ratio r, and the nonlinear estimator f_{NL} of primordial non-Gaussianities to confront models with observations of cosmic microwave background (CMB) temperature anisotropies. Our analysis includes models such as potential-driven slow-roll inflation, k-inflation, Starobinsky inflation, and Higgs inflation with non-minimal/derivative/Galileon couplings. We constrain a host of inflationary models by using the Planck data combined with other measurements to find models most favored observationally in the current literature. We also study anisotropic inflation based on a scalar coupling with a vector (or two-form) field and discuss its observational signatures appearing in the two-point and three-point correlation functions of scalar and tensor perturbations.
Observational Tests of One-Bubble Open Inflationary Cosmological Models
NASA Astrophysics Data System (ADS)
Yamamoto, Kazuhiro; Bunn, Emory F.
1996-06-01
Motivated by recent studies of the one-bubble inflationary scenario, simple open cold dark matter models are tested for consistency with cosmological observations. The initial perturbation spectrum is derived by solving for the evolution of fluctuations in an open inflationary stage under the assumptions that a scalar field is in the Bunch-Davies vacuum state and the conformal vacuum state. A likelihood analysis is performed for the cosmic microwave background anisotropies using the two-year COBE Differential Microwave Radiometer (DMR) data. For Ω0 ≲ 0.2, the two models give significantly different results because of the appearance of fluctuations of supercurvature scale in the model associated with the Bunch-Davies vacuum state. Having normalized the perturbation spectrum to fit the COBE data, we reconsider the validity of the open model from the viewpoint of cosmic structure formation. Open models may be severely constrained by the COBE likelihood analysis. In particular, small values of are ruled out in the Bunch-Davies case: we find that Ω0 ≳ 0.34 at 95% confidence for this model.
Behavior of a Single Langmuir Probe in a Magnetic Field.
ERIC Educational Resources Information Center
Pytlinski, J. T.; And Others
1978-01-01
Describes an experiment to demonstrate the influence of a magnetic field on the behavior of a single Langmuir probe. The experiment introduces the student to magnetically supported plasma and particle behavior in a magnetic field. (GA)
Inflationary paradigm after Planck 2013
NASA Astrophysics Data System (ADS)
Guth, Alan H.; Kaiser, David I.; Nomura, Yasunori
2014-06-01
Models of cosmic inflation posit an early phase of accelerated expansion of the universe, driven by the dynamics of one or more scalar fields in curved spacetime. Though detailed assumptions about fields and couplings vary across models, inflation makes specific, quantitative predictions for several observable quantities, such as the flatness parameter (Ωk = 1 - Ω) and the spectral tilt of primordial curvature perturbations (ns - 1 = dln PR / dln k), among others-predictions that match the latest observations from the Planck satellite to very good precision. In the light of data from Planck as well as recent theoretical developments in the study of eternal inflation and the multiverse, we address recent criticisms of inflation by Ijjas, Steinhardt, and Loeb. We argue that their conclusions rest on several problematic assumptions, and we conclude that cosmic inflation is on a stronger footing than ever before.
Inflationary attractor from tachyonic matter
NASA Astrophysics Data System (ADS)
Guo, Zong-Kuan; Piao, Yun-Song; Cai, Rong-Gen; Zhang, Yuan-Zhong
2003-08-01
We study the complete evolution of a flat and homogeneous universe dominated by tachyonic matter. We demonstrate the attractor behavior of tachyonic inflation using the Hamilton-Jacobi formalism. We also obtain analytical approximations for the trajectories of the tachyon field in different regions. The numerical calculation shows that an initial nonvanishing momentum does not prevent the onset of inflation. The slow-rolling solution is an attractor.
Multiple fields in stochastic inflation
NASA Astrophysics Data System (ADS)
Assadullahi, Hooshyar; Firouzjahi, Hassan; Noorbala, Mahdiyar; Vennin, Vincent; Wands, David
2016-06-01
Stochastic effects in multi-field inflationary scenarios are investigated. A hierarchy of diffusion equations is derived, the solutions of which yield moments of the numbers of inflationary e-folds. Solving the resulting partial differential equations in multi-dimensional field space is more challenging than the single-field case. A few tractable examples are discussed, which show that the number of fields is, in general, a critical parameter. When more than two fields are present for instance, the probability to explore arbitrarily large-field regions of the potential, otherwise inaccessible to single-field dynamics, becomes non-zero. In some configurations, this gives rise to an infinite mean number of e-folds, regardless of the initial conditions. Another difference with respect to single-field scenarios is that multi-field stochastic effects can be large even at sub-Planckian energy. This opens interesting new possibilities for probing quantum effects in inflationary dynamics, since the moments of the numbers of e-folds can be used to calculate the distribution of primordial density perturbations in the stochastic-δ N formalism.
Inflation in supergravity with a single chiral superfield
NASA Astrophysics Data System (ADS)
Ketov, Sergei V.; Terada, Takahiro
2014-09-01
We propose new supergravity models describing chaotic Linde- and Starobinsky-like inflation in terms of a single chiral superfield. The key ideas to obtain a positive vacuum energy during large field inflation are (i) stabilization of the real or imaginary partner of the inflaton by modifying a Kähler potential, and (ii) use of the crossing terms in the scalar potential originating from a polynomial superpotential. Our inflationary models are constructed by starting from the minimal Kähler potential with a shift symmetry, and are extended to the no-scale case. Our methods can be applied to more general inflationary models in supergravity with only one chiral superfield.
Spectrum of perturbations in anisotropic inflationary universe with vector hair
Himmetoglu, Burak
2010-03-01
We study both the background evolution and cosmological perturbations of anisotropic inflationary models supported by coupled scalar and vector fields. The models we study preserve the U(1) gauge symmetry associated with the vector field, and therefore do not possess instabilities associated with longitudinal modes (which instead plague some recently proposed models of vector inflation and curvaton). We first intoduce a model in which the background anisotropy slowly decreases during inflation; we then confirm the stability of the background solution by studying the quadratic action for all the perturbations of the model. We then compute the spectrum of the h{sub ×} gravitational wave polarization. The spectrum we find breaks statistical isotropy at the largest scales and reduces to the standard nearly scale invariant form at small scales. We finally discuss the possible relevance of our results to the large scale CMB anomalies.
Braneworld inflation with a complex scalar field from Planck 2015
NASA Astrophysics Data System (ADS)
Mounzi, Z.; Ferricha-Alami, M.; Chakir, H.; Bennai, M.
2016-06-01
We study an inflationary model with a single complex scalar field in the framework of braneworld Randall-Sundrum model type 2. From the scalar curvature perturbation constrained by the recent observation values, and for specific choice of parameters, we can reduce the values of the coupling constant to take the natural values, and we found that the phase theta θ of the inflation field can take the narrow interval. We have also derived all known inflationary parameters (ns, r and dns/d ln (k)), which are widely consistent with the recent Planck data for a suitable choice of brane tension value λ.
Multiple inflationary stages with varying equation of state
Namjoo, Mohammad Hossein; Firouzjahi, Hassan; Sasaki, Misao E-mail: firouz@mail.ipm.ir
2012-12-01
We consider a model of inflation consisting a single fluid with a time-dependent equation of state. In this phenomenological picture, two periods of inflation are separated by an intermediate non-inflationary stage which can be either a radiation dominated, matter dominated or kinetic energy dominated universe, respectively, with the equation of state w = 1/3, 0 or 1. We consider the toy model in which the change in w happens instantaneously. Depending on whether the mode of interest leaves the horizon before or after or between the phase transitions, the curvature power spectrum can have non-trivial sinusoidal modulations. This can have interesting observational implications for CMB anisotropies and for primordial black-hole formation.
NASA Astrophysics Data System (ADS)
Zarei, Moslem
2016-06-01
In conventional model-independent approaches, the power spectrum of primordial perturbations is characterized by such free parameters as the spectral index, its running, the running of running, and the tensor-to-scalar ratio. In this work we show that, at least for simple inflationary potentials, one can find the primordial scalar and tensor power spectra exactly by resumming over all the running terms. In this model-dependent method, we expand the power spectra about the pivot scale to find the series terms as functions of the e-folding number for some single field models of inflation. Interestingly, for the viable models studied here, one can sum over all the terms and evaluate the exact form of the power spectra. This in turn gives more accurate parametrization of the specific models studied in this work. We finally compare our results with recent cosmic microwave background data to find that our new power spectra are in good agreement with the data.
Evolution of perturbations in an inflationary universe
NASA Technical Reports Server (NTRS)
Frieman, J. A.; Will, C. M.
1982-01-01
The evolution of inhomogeneous density perturbations in a model of the very early universe that is dominated for a time by a constant energy density of a false quantum-mechanical vacuum is analyzed. During this period, the universe inflates exponentially and supercools exponentially, until a phase transition back to the true vacuum reheats the matter and radiation. Focus is on the physically measurable, coordinate-independent modes of inhomogeneous perturbations of this model and it is found that all modes either are constant or are exponentially damped during the inflationary era.
Electric-magnetic duality and the conditions of inflationary magnetogenesis
Giovannini, Massimo
2010-04-01
The magnetogenesis scenarios triggered by the early variation of the gauge coupling are critically analyzed. In the absence of sources, it is shown that the electric power spectra can be explicitly computed from the magnetic power spectra by means of electric-magnetic duality transformations. In the absence of sources the reverse is also true. The remnants of a pre-inflationary expansion and the reheating process break explicitly electric-magnetic duality by inducing Ohmic currents. The generation of large-scale magnetic field and the physical distinction between electric and magnetic observables stems, in this class of models, from the final value reached by the conductivity of the plasma right after inflation. Specific numerical examples are given. The physical requirements of viable magnetogenesis scenarios are spelled out.
Inflationary scenarios in Starobinsky model with higher order corrections
Artymowski, Michał; Lalak, Zygmunt; Lewicki, Marek
2015-06-17
We consider the Starobinsky inflation with a set of higher order corrections parametrised by two real coefficients λ{sub 1} ,λ{sub 2}. In the Einstein frame we have found a potential with the Starobinsky plateau, steep slope and possibly with an additional minimum, local maximum or a saddle point. We have identified three types of inflationary behaviour that may be generated in this model: i) inflation on the plateau, ii) at the local maximum (topological inflation), iii) at the saddle point. We have found limits on parameters λ{sub i} and initial conditions at the Planck scale which enable successful inflation and disable eternal inflation at the plateau. We have checked that the local minimum away from the GR vacuum is stable and that the field cannot leave it neither via quantum tunnelling nor via thermal corrections.
Two-dimensional field model for single-sheet tester
NASA Astrophysics Data System (ADS)
Ivanyi, Amalia; Füzi, Janos
2003-01-01
The investigation of the magnetic field in a circular-shaped single-sheet tester is developed under circular polarised field intensity as well as flux density. The non-linear anisotropy of the material is represented by a vector realisation of the Jiles-Atherton hysteresis operator. The monitored data of the components in the field vectors are simulated with the averaged values of the field resulted by the numerical analysis of the non-linear eddy current problem.
Electric field controlled magnetic anisotropy in a single molecule.
Zyazin, Alexander S; van den Berg, Johan W G; Osorio, Edgar A; van der Zant, Herre S J; Konstantinidis, Nikolaos P; Leijnse, Martin; Wegewijs, Maarten R; May, Falk; Hofstetter, Walter; Danieli, Chiara; Cornia, Andrea
2010-09-01
We have measured quantum transport through an individual Fe(4) single-molecule magnet embedded in a three-terminal device geometry. The characteristic zero-field splittings of adjacent charge states and their magnetic field evolution are observed in inelastic tunneling spectroscopy. We demonstrate that the molecule retains its magnetic properties and, moreover, that the magnetic anisotropy is significantly enhanced by reversible electron addition/subtraction controlled with the gate voltage. Single-molecule magnetism can thus be electrically controlled. PMID:20687519
Electric Field Controlled Magnetic Anisotropy in a Single Molecule
NASA Astrophysics Data System (ADS)
Zyazin, Alexander S.; van den Berg, Johan W. G.; Osorio, Edgar A.; van der Zant, Herre S. J.; Konstantinidis, Nikolaos P.; Leijnse, Martin; Wegewijs, Maarten R.; May, Falk; Hofstetter, Walter; Danieli, Chiara; Cornia, Andrea
2010-09-01
We have measured quantum transport through an individual Fe$_4$ single-molecule magnet embedded in a three-terminal device geometry. The characteristic zero-field splittings of adjacent charge states and their magnetic field evolution are observed in inelastic tunneling spectroscopy. We demonstrate that the molecule retains its magnetic properties, and moreover, that the magnetic anisotropy is significantly enhanced by reversible electron addition / subtraction controlled with the gate voltage. Single-molecule magnetism can thus be electrically controlled.
Single-phase-field model of stepped surfaces
NASA Astrophysics Data System (ADS)
Castro, M.; Hernández-Machado, A.; Cuerno, R.
2009-02-01
We formulate a phase-field description of step dynamics on vicinal surfaces that makes use of a single dynamical field, at variance with previous analogous works in which two coupled fields are employed, namely, a phase-field proper plus the physical adatom concentration. Within an asymptotic sharp interface limit, our formulation is shown to retrieve the standard Burton-Cabrera-Frank model in the general case of asymmetric attachment coefficients (Ehrlich-Schwoebel effect). We confirm our analytical results by means of numerical simulations of our phase-field model. Our present formulation seems particularly well adapted to generalization when additional physical fields are required.
Inflationary Magnetogenesis in R2-Inflation on the light of Planck 2015
NASA Astrophysics Data System (ADS)
Aimuhammad, Anwar
2016-03-01
We study the primordial magnetic field generated by the simple model f2 FF in Starobinsky, R2-inflationary, model. The scale invariant PMF is achieved at relatively high power index of the coupling function, | α | ~ 7 . 44 . This model does not suffer from the backreaction problem as long as, the rate of inflationary expansion, H, is less than the upper bound reported by Planck (<= 3 . 6 ×10-5MPl) in the observable scales of wave numbers, kη . By using the scale invariant PMF generated by f2 FF , we find that the upper limit of present magnetic field, B0 < 8 . 1 ×10-9 G . It is in the same order of PMF, reported by Planck, 2015.
Inflationary gravitational waves in collapse scheme models
NASA Astrophysics Data System (ADS)
Mariani, Mauro; Bengochea, Gabriel R.; León, Gabriel
2016-01-01
The inflationary paradigm is an important cornerstone of the concordance cosmological model. However, standard inflation cannot fully address the transition from an early homogeneous and isotropic stage, to another one lacking such symmetries corresponding to our present universe. In previous works, a self-induced collapse of the wave function has been suggested as the missing ingredient of inflation. Most of the analysis regarding the collapse hypothesis has been solely focused on the characteristics of the spectrum associated to scalar perturbations, and within a semiclassical gravity framework. In this Letter, working in terms of a joint metric-matter quantization for inflation, we calculate, for the first time, the tensor power spectrum and the tensor-to-scalar ratio corresponding to the amplitude of primordial gravitational waves resulting from considering a generic self-induced collapse.
Pre-inflationary relics in the CMB?
NASA Astrophysics Data System (ADS)
Gruppuso, A.; Kitazawa, N.; Mandolesi, N.; Natoli, P.; Sagnotti, A.
2016-03-01
String Theory and Supergravity allow, in principle, to follow the transition of the inflaton from pre-inflationary fast roll to slow roll. This introduces an infrared depression in the primordial power spectrum that might have left an imprint in the CMB anisotropy, if it occurred at accessible wavelengths. We model the effect extending Λ CDM with a scale Δ related to the infrared depression and explore the constraints allowed by PLANCK 2015 data, employing also more conservative, wider Galactic masks in the low resolution CMB likelihood. In an extended mask with fsky = 39 %, we thus find Δ =(0.351 ± 0.114) × 10-3Mpc-1, at 99.4% confidence level, to be compared with a nearby value at 88.5% with the standard fsky = 94 % mask. With about 64 e-folds of inflation, these values for Δ would translate into primordial energy scales O(1014) GeV.
Computer simulations of single particles in external electric fields.
Zhou, Jiajia; Schmid, Friederike
2015-09-14
Applying electric fields is an attractive way to control and manipulate single particles or molecules, e.g., in lab-on-a-chip devices. However, the response of nanosize objects in electrolyte solution to external fields is far from trivial. It is the result of a variety of dynamical processes taking place in the ion cloud surrounding charged particles and in the bulk electrolyte, and it is governed by an intricate interplay of electrostatic and hydrodynamic interactions. Already systems composed of one single particle in electrolyte solution exhibit a complex dynamical behaviour. In this review, we discuss recent coarse-grained simulations that have been performed to obtain a molecular-level understanding of the dynamic and dielectric response of single particles and single macromolecules to external electric fields. We address both the response of charged particles to constant fields (DC fields), which can be characterized by an electrophoretic mobility, and the dielectric response of both uncharged and charged particles to alternating fields (AC fields), which is described by a complex polarizability. Furthermore, we give a brief survey of simulation algorithms and highlight some recent developments. PMID:26238433
Inflationary freedom and cosmological neutrino constraints
NASA Astrophysics Data System (ADS)
de Putter, Roland; Linder, Eric V.; Mishra, Abhilash
2014-05-01
The most stringent bounds on the absolute neutrino mass scale come from cosmological data. These bounds are made possible because massive relic neutrinos affect the expansion history of the universe and lead to a suppression of matter clustering on scales smaller than the associated free streaming length. However, the resulting effect on cosmological perturbations is relative to the primordial power spectrum of density perturbations from inflation, so freedom in the primordial power spectrum affects neutrino mass constraints. Using measurements of the cosmic microwave background (CMB), the galaxy power spectrum and the Hubble constant, we constrain neutrino mass and number of species for a model-independent primordial power spectrum. Describing the primordial power spectrum by a 20-node spline, we find that the neutrino mass upper limit is a factor 3 weaker than when a power law form is imposed, if only CMB data are used. The primordial power spectrum itself is constrained to better than 10% in the wave vector range k ≈0.01-0.25 Mpc-1. Galaxy clustering data and a determination of the Hubble constant play a key role in reining in the effects of inflationary freedom on neutrino constraints. The inclusion of both eliminates the inflationary freedom degradation of the neutrino mass bound, giving for the sum of neutrino masses Σmν<0.18 eV (at 95% confidence level, Planck+BOSS+H0), approximately independent of the assumed primordial power spectrum model. When allowing for a free effective number of species, Neff, the joint constraints on Σmν and Neff are loosened by a factor 1.7 when the power law form of the primordial power spectrum is abandoned in favor of the spline parametrization.
Non-Gaussianities and the stimulated creation of quanta in the inflationary universe
Agullo, Ivan; Parker, Leonard
2011-03-15
Cosmological inflation generates a spectrum of density perturbations that can seed the cosmic structures we observe today. These perturbations are usually computed as the result of the gravitationally induced spontaneous creation of perturbations from an initial vacuum state. In this paper, we compute the perturbations arising from gravitationally induced stimulated creation when perturbations are already present in the initial state. The effect of these initial perturbations is not diluted by inflation and survives to its end, and beyond. We consider a generic statistical density operator {rho} describing an initial mixed state that includes probabilities for nonzero numbers of scalar perturbations to be present at early times during inflation. We analyze the primordial bispectrum for general configurations of the three different momentum vectors in its arguments. We find that the initial presence of quanta can significantly enhance non-Gaussianities in the so-called squeezed limit. Our results show that an observation of non-Gaussianities in the squeezed limit can occur for single-field inflation when the state in the very early inflationary Universe is not the vacuum, but instead contains early-time perturbations. Valuable information about the initial state can then be obtained from observations of those non-Gaussianities.
Generalized pole inflation: Hilltop, natural, and chaotic inflationary attractors
NASA Astrophysics Data System (ADS)
Terada, Takahiro
2016-09-01
A reformulation of inflationary model analyses appeared recently, in which inflationary observables are determined by the structure of a pole in the inflaton kinetic term rather than the shape of the inflaton potential. We comprehensively study this framework with an arbitrary order of the pole taking into account possible additional poles in the kinetic term or in the potential. Depending on the setup, the canonical potential becomes the form of hilltop or plateau models, variants of natural inflation, power-law inflation, or monomial/polynomial chaotic inflation. We demonstrate attractor behaviors of these models and compute corrections from the additional poles to the inflationary observables.
Stabilization of single-electron pumps by high magnetic fields
NASA Astrophysics Data System (ADS)
Fletcher, J. D.; Kataoka, M.; Giblin, S. P.; Park, Sunghun; Sim, H.-S.; See, P.; Ritchie, D. A.; Griffiths, J. P.; Jones, G. A. C.; Beere, H. E.; Janssen, T. J. B. M.
2012-10-01
We demonstrate theoretically and experimentally how magnetic fields influence the single-electron tunneling dynamics in electron pumps, giving a massively enhanced quantization accuracy and providing a route to a quantum current standard based on the elementary charge. The field dependence is explained by two effects: field-induced changes in the sensitivity of tunneling rates to the barrier potential and the suppression of nonadiabatic excitations due to a reduced sensitivity of the Fock-Darwin states to the electrostatic potential. These effects lead to a continued improvement in quantisation accuracy at high field which is important for applications in metrology.
Pointer states for primordial fluctuations in inflationary cosmology
NASA Astrophysics Data System (ADS)
Kiefer, Claus; Lohmar, Ingo; Polarski, David; Starobinsky, Alexei A.
2007-04-01
Primordial fluctuations in inflationary cosmology acquire classical properties through decoherence when their wavelengths become larger than the Hubble scale. Although decoherence is effective, it is not complete, so a significant part of primordial correlations remains up to the present moment. We address the issue of the pointer states which provide a classical basis for the fluctuations with respect to the influence by an environment (other fields). Applying methods from the quantum theory of open systems (the Lindblad equation), we show that this basis is given by narrow Gaussians that approximate eigenstates of field amplitudes. We calculate both the von Neumann and linear entropy of the fluctuations. Their ratio to the maximal entropy per field mode defines a degree of partial decoherence in the entropy sense. We also determine the time of partial decoherence making the Wigner function positive everywhere which, for super-Hubble modes during inflation, is virtually independent of coupling to the environment and is only slightly larger than the Hubble time. On the other hand, assuming a representative environment (a photon bath), the decoherence time for sub-Hubble modes is finite only if some real dissipation exists.
Cosmology with many light scalar fields: Stochastic inflation and loop corrections
NASA Astrophysics Data System (ADS)
Adshead, Peter; Easther, Richard; Lim, Eugene A.
2009-03-01
We explore the consequences of the existence of a very large number of light scalar degrees of freedom in the early universe. We distinguish between participator and spectator fields. The former have a small mass, and can contribute to the inflationary dynamics; the latter are either strictly massless or have a negligible VEV. In N-flation and generic assisted inflation scenarios, inflation is a cooperative phenomenon driven by N participator fields, none of which could drive inflation on its own. We review upper bounds on N, as a function of the inflationary Hubble scale H. We then consider stochastic and eternal inflation in models with N participator fields showing that individual fields may evolve stochastically while the whole ensemble behaves deterministically, and that a wide range of eternal inflationary scenarios are possible in this regime. We then compute one-loop quantum corrections to the inflationary power spectrum. These are largest with N spectator fields and a single participator field, and the resulting bound on N is always weaker than those obtained in other ways. We find that loop corrections to the N-flation power spectrum do not scale with N, and thus place no upper bound on the number of participator fields. This result also implies that, at least to leading order, the theory behaves like a composite single scalar field. In order to perform this calculation, we address a number of issues associated with loop calculations in the Schwinger-Keldysh “in-in” formalism.
Inflationary Dark Energy from a Condensate of Spinors in a 5d Vacuum
NASA Astrophysics Data System (ADS)
Sánchez, Pablo Alejandro; Bellini, Mauricio
2013-11-01
What is the physical origin of dark energy? Could this energy be originated by other fields than the inflaton? In this paper, we explore the possibility that the expansion of the universe can be driven by a condensate of spinors. These spinors are free of interactions on five-dimensional (5D) relativistic vacuum in an extended de Sitter spacetime. The extra coordinate is considered as noncompact. After making a static foliation on the extra coordinate, we obtain an effective four-dimensional (4D) (inflationary) de Sitter expansion which describes an inflationary universe. In view of our results, we conclude that the condensate of spinors here studied could be an interesting candidate to explain the presence of dark energy in the early universe.
Visualizing electromagnetic fields at the nanoscale by single molecule localization.
Steuwe, Christian; Erdelyi, Miklos; Szekeres, G; Csete, M; Baumberg, Jeremy J; Mahajan, Sumeet; Kaminski, Clemens F
2015-05-13
Coupling of light to the free electrons at metallic surfaces allows the confinement of electric fields to subwavelength dimensions, far below the optical diffraction limit. While this is routinely used to manipulate light at the nanoscale, in electro-optic devices and enhanced spectroscopic techniques, no characterization technique for imaging the underlying nanoscopic electromagnetic fields exists, which does not perturb the field or employ complex electron beam imaging. Here, we demonstrate the direct visualization of electromagnetic fields on patterned metallic substrates at nanometer resolution, exploiting a strong "autonomous" fluorescence-blinking behavior of single molecules within the confined fields allowing their localization. Use of DNA-constructs for precise positioning of fluorescence dyes on the surface induces this distance-dependent autonomous blinking thus completely obviating the need for exogenous agents or switching methods. Mapping such electromagnetic field distributions at nanometer resolution aids the rational design of nanometals for diverse photonic applications. PMID:25915093
Simple brane-world inflationary models — An update
NASA Astrophysics Data System (ADS)
Okada, Nobuchika; Okada, Satomi
2016-05-01
In the light of the Planck 2015 results, we update simple inflationary models based on the quadratic, quartic, Higgs and Coleman-Weinberg potentials in the context of the Randall-Sundrum brane-world cosmology. Brane-world cosmological effect alters the inflationary predictions of the spectral index (ns) and the tensor-to-scalar ratio (r) from those obtained in the standard cosmology. In particular, the tensor-to-scalar ratio is enhanced in the presence of the 5th dimension. In order to maintain the consistency with the Planck 2015 results for the inflationary predictions in the standard cosmology, we find a lower bound on the five-dimensional Planck mass (M5). On the other hand, the inflationary predictions laying outside of the Planck allowed region can be pushed into the allowed region by the brane-world cosmological effect with a suitable choice of M5.
Inflationary gravitational waves and the evolution of the early universe
Jinno, Ryusuke; Moroi, Takeo; Nakayama, Kazunori E-mail: moroi@hep-th.phys.s.u-tokyo.ac.jp
2014-01-01
We study the effects of various phenomena which may have happened in the early universe on the spectrum of inflationary gravitational waves. The phenomena include phase transitions, entropy productions from non-relativistic matter, the production of dark radiation, and decoupling of dark matter/radiation from thermal bath. These events can create several characteristic signatures in the inflationary gravitational wave spectrum, which may be direct probes of the history of the early universe and the nature of high-energy physics.
Recovering the inflationary potential: An analysis using flow methods and Markov chain Monte Carlo
NASA Astrophysics Data System (ADS)
Powell, Brian A.
Since its inception in 1980 by Guth [1], inflation has emerged as the dominant paradigm for describing the physics of the early universe. While inflation has matured theoretically over two decades, it has only recently begun to be rigorously tested observationally. Measurements of the cosmic microwave background (CMB) and large-scale structure surveys (LSS) have begun to unravel the mysteries of the inflationary epoch with exquisite and unprecedented accuracy. This thesis is a contribution to the effort of reconstructing the physics of inflation. This information is largely encoded in the potential energy function of the inflaton, the field that drives the inflationary expansion. With little theoretical guidance as to the probable form of this potential, reconstruction is a predominantly data-driven endeavor. This thesis presents an investigation of the constrainability of the inflaton potential given current CMB and LSS data. We develop a methodology based on the inflationary flow formalism that provides an assessment of our current ability to resolve the form of the inflaton potential in the face of experimental and statistical error. We find that there is uncertainty regarding the initial dynamics of the inflaton field, related to the poor constraints that can be drawn on the primordial power spectrum on large scales. We also investigate the future prospects of potential reconstruction, as might be expected when data from ESA's Planck Surveyor becomes available. We develop an approach that utilizes Markov chain Monte Carlo to analyze the statistical properties of the inflaton potential. Besides providing constraints on the parameters of the potential, this method makes it possible to perform model selection on the inflationary model space. While future data will likely determine the general features of the inflaton, there will likely be many different models that remain good fits to the data. Bayesian model selection will then be needed to draw comparisons
Rojas, Clara
2009-05-15
The phase-integral approximation devised by Froeman and Froeman is used for computing cosmological perturbations in the quadratic chaotic inflationary model. The phase-integral formulas for the scalar and tensor power spectra are explicitly obtained up to fifth order of the phase-integral approximation. We show that the phase integral gives a very good approximation for the shape of the power spectra associated with scalar and tensor perturbations as well as the spectral indices. We find that the accuracy of the phase-integral approximation compares favorably with the numerical results and those obtained using the slow-roll and uniform-approximation methods.
Field emission from single-crystalline HfC nanowires
Yuan, Jinshi; Tang, Jie; Zhang Han; Shinya, Norio; Nakajima, Kiyomi; Qin, Lu-Chang
2012-03-12
Single HfC nanowire field emitter/electrode structures have been fabricated using nano-assembling and electron beam induced deposition. Field ion microscopy has been applied to study the atomic arrangement of facets formed on a field evaporation-modified HfC nanowire tip. Field evaporation and crystal form studies suggest that the {l_brace}111{r_brace} and {l_brace}110{r_brace} crystal planes have lower work functions, while the {l_brace}100{r_brace}, {l_brace}210{r_brace}, and {l_brace}311{r_brace} planes have higher work functions. Field emission measurement permits us to obtain that the work function of the {l_brace}111{r_brace} crystal plane is about 3.4 eV.
Taming the runaway problem of inflationary landscapes
Hall, Lawrence J.; Watari, Taizan; Yanagida, T.T.
2006-05-15
A wide variety of vacua, and their cosmological realization, may provide an explanation for the apparently anthropic choices of some parameters of particle physics and cosmology. If the probability on various parameters is weighted by volume, a flat potential for slow-roll inflation is also naturally understood, since the flatter the potential the larger the volume of the subuniverse. However, such inflationary landscapes have a serious problem, predicting an environment that makes it exponentially hard for observers to exist and giving an exponentially small probability for a moderate universe like ours. A general solution to this problem is proposed, and is illustrated in the context of inflaton decay and leptogenesis, leading to an upper bound on the reheating temperature in our subuniverse. In a particular scenario of chaotic inflation and nonthermal leptogenesis, predictions can be made for the size of CP violating phases, the rate of neutrinoless double beta decay and, in the case of theories with gauge-mediated weak-scale supersymmetry, for the fundamental scale of supersymmetry breaking.
Taming the Runaway Problem of Inflationary Landscapes
Hall, Lawrence J.; Watari, Taizan; Yanagida, T. T.
2006-03-15
A wide variety of vacua, and their cosmological realization, may provide an explanation for the apparently anthropic choices of some parameters of particle physics and cosmology. If the probability on various parameters is weighted by volume, a flat potential for slow-roll inflation is also naturally understood, since the flatter the potential the larger the volume of the sub-universe. However, such inflationary landscapes have a serious problem, predicting an environment that makes it exponentially hard for observers to exist and giving an exponentially small probability for a moderate universe like ours. A general solution to this problem is proposed, and is illustrated in the context of inflaton decay and leptogenesis, leading to an upper bound on the reheating temperature in our sub-universe. In a particular scenario of chaotic inflation and non-thermal leptogenesis, predictions can be made for the size of CP violating phases, the rate of neutrinoless double beta decay and, in the case of theories with gauge-mediated weak scale supersymmetry, for the fundamental scale of supersymmetry breaking.
TOPICAL REVIEW: Organic field-effect transistors using single crystals
NASA Astrophysics Data System (ADS)
Hasegawa, Tatsuo; Takeya, Jun
2009-04-01
Organic field-effect transistors using small-molecule organic single crystals are developed to investigate fundamental aspects of organic thin-film transistors that have been widely studied for possible future markets for 'plastic electronics'. In reviewing the physics and chemistry of single-crystal organic field-effect transistors (SC-OFETs), the nature of intrinsic charge dynamics is elucidated for the carriers induced at the single crystal surfaces of molecular semiconductors. Materials for SC-OFETs are first reviewed with descriptions of the fabrication methods and the field-effect characteristics. In particular, a benchmark carrier mobility of 20-40 cm2 Vs-1, achieved with thin platelets of rubrene single crystals, demonstrates the significance of the SC-OFETs and clarifies material limitations for organic devices. In the latter part of this review, we discuss the physics of microscopic charge transport by using SC-OFETs at metal/semiconductor contacts and along semiconductor/insulator interfaces. Most importantly, Hall effect and electron spin resonance (ESR) measurements reveal that interface charge transport in molecular semiconductors is properly described in terms of band transport and localization by charge traps.
Radiation burst from a single γ-photon field
NASA Astrophysics Data System (ADS)
Shakhmuratov, R. N.; Vagizov, F.; Kocharovskaya, O.
2011-10-01
The radiation burst from a single γ-photon field interacting with a dense resonant absorber is studied theoretically and experimentally. This effect was discovered for the fist time by P. Helisto [Phys. Rev. Lett. PRLTAO0031-900710.1103/PhysRevLett.66.203766, 2037 (1991)] and it was named the “gamma echo.” The echo is generated by a 180∘ phase shift of the incident radiation field, attained by an abrupt change of the position of the absorber with respect to the radiation source during the coherence time of the photon wave packet. Three distinguishing cases of the gamma echo are considered; i.e., the photon is in exact resonance with the absorber, close to resonance (on the slope of the absorption line), and far from resonance (on the far wings of the resonance line). In resonance the amplitude of the radiation burst is two times larger than the amplitude of the input radiation field just before its phase shift. This burst was explained by Helisto as a result of constructive interference of the coherently scattered field with the phase-shifted input field, both having almost the same amplitude. We found that out of resonance the scattered radiation field acquires an additional component with almost the same amplitude as the amplitude of the incident radiation field. The phase of the additional field depends on the optical thickness of the absorber and resonant detuning. Far from resonance this field interferes destructively with the phase-shifted incident radiation field and radiation quenching is observed. Close to resonance the three fields interfere constructively and the amplitude of the radiation burst is three times larger than the amplitude of the input radiation field.
Radiation burst from a single {gamma}-photon field
Shakhmuratov, R. N.; Vagizov, F.; Kocharovskaya, O.
2011-10-15
The radiation burst from a single {gamma}-photon field interacting with a dense resonant absorber is studied theoretically and experimentally. This effect was discovered for the fist time by P. Helisto et al.[Phys. Rev. Lett. 66, 2037 (1991)] and it was named the ''gamma echo''. The echo is generated by a 180 Degree-Sign phase shift of the incident radiation field, attained by an abrupt change of the position of the absorber with respect to the radiation source during the coherence time of the photon wave packet. Three distinguishing cases of the gamma echo are considered; i.e., the photon is in exact resonance with the absorber, close to resonance (on the slope of the absorption line), and far from resonance (on the far wings of the resonance line). In resonance the amplitude of the radiation burst is two times larger than the amplitude of the input radiation field just before its phase shift. This burst was explained by Helisto et al. as a result of constructive interference of the coherently scattered field with the phase-shifted input field, both having almost the same amplitude. We found that out of resonance the scattered radiation field acquires an additional component with almost the same amplitude as the amplitude of the incident radiation field. The phase of the additional field depends on the optical thickness of the absorber and resonant detuning. Far from resonance this field interferes destructively with the phase-shifted incident radiation field and radiation quenching is observed. Close to resonance the three fields interfere constructively and the amplitude of the radiation burst is three times larger than the amplitude of the input radiation field.
Single-field inflation à la generalized Chaplygin gas
Campo, Sergio del
2013-11-01
In the simplest scenario for inflation, i.e. in the single-field inflation, it is presented an inflaton field with properties equivalent to a generalized Chaplygin gas. Their study is performed using the Hamilton-Jacobi approach to cosmology. The main results are contrasted with the measurements recently released by the Planck data, combined with the WMAP large-angle polarization. If the measurements released by Planck for the scalar spectral index together with its running are taken into account it is found a value for the α-parameter associated to the generalized Chaplygin gas given by α = 0.2578±0.0009.
Nonisotropy in the CMB power spectrum in single field inflation
Donoghue, John F.; Dutta, Koushik; Ross, Andreas
2009-07-15
Contaldi et al.[C. R. Contaldi, M. Peloso, L. Kofman, and A. Linde, J. Cosmol. Astropart. Phys. 07 (2003) 002] have suggested that an initial period of kinetic energy domination in single field inflation may explain the lack of CMB power at large angular scales. We note that in this situation it is natural that there also be a spatial gradient in the initial value of the inflaton field, and that this can provide a spatial asymmetry in the observed CMB power spectrum, manifest at low values of l. We investigate the nature of this asymmetry and comment on its relation to possible anomalies at low l.
Optimal bispectrum constraints on single-field models of inflation
Anderson, Gemma J.; Regan, Donough; Seery, David E-mail: D.Regan@sussex.ac.uk
2014-07-01
We use WMAP 9-year bispectrum data to constrain the free parameters of an 'effective field theory' describing fluctuations in single-field inflation. The Lagrangian of the theory contains a finite number of operators associated with unknown mass scales. Each operator produces a fixed bispectrum shape, which we decompose into partial waves in order to construct a likelihood function. Based on this likelihood we are able to constrain four linearly independent combinations of the mass scales. As an example of our framework we specialize our results to the case of 'Dirac-Born-Infeld' and 'ghost' inflation and obtain the posterior probability for each model, which in Bayesian schemes is a useful tool for model comparison. Our results suggest that DBI-like models with two or more free parameters are disfavoured by the data by comparison with single-parameter models in the same class.
Single shot line-field optical coherence elastography
NASA Astrophysics Data System (ADS)
Liu, Chih-Hao; Schill, Alexander; Singh, Manmohan; Wu, Chen; Li, Jiasong; Han, Zhaolong; Raghunathan, Raksha; Kazemi, Tina; Nair, Achuth; Hsu, Thomas; Larin, Kirill V.
2016-03-01
Elastic wave imaging optical coherence elastography (EWI-OCE) is an emerging technique that can quantify local biomechanical properties of tissues. However, long acquisition times make this technique unfeasible for clinical use. Here, we demonstrate a noncontact single shot line-field OCE technique using a line-field interferometer and an air-pulse delivery system. The spatial-temporal elastic wave propagation profile was acquired in a single shot and used to quantify the elastic wave group velocity in tissue. Results on tissue-mimicking phantoms and chicken breast muscle agreed well with mechanical compression testing, demonstrating that the presented method can effectively reduce the OCE acquisition time to a few milliseconds in biological application.
Structure of correlation functions in single-field inflation
Shandera, Sarah
2009-06-15
Many statistics available to constrain non-Gaussianity from inflation are simplest to use under the assumption that the curvature correlation functions are hierarchical. That is, if the n-point function is proportional to the (n-1) power of the two-point function amplitude and the fluctuations are small, the probability distribution can be approximated by expanding around a Gaussian in moments. However, single-field inflation with higher derivative interactions has a second small number, the sound speed, that appears in the problem when non-Gaussianity is significant and changes the scaling of correlation functions. Here we examine the structure of correlation functions in the most general single scalar field action with higher derivatives, formalizing the conditions under which the fluctuations can be expanded around a Gaussian distribution. We comment about the special case of the Dirac-Born-Infeld action.
Structure of correlation functions in single-field inflation
NASA Astrophysics Data System (ADS)
Shandera, Sarah
2009-06-01
Many statistics available to constrain non-Gaussianity from inflation are simplest to use under the assumption that the curvature correlation functions are hierarchical. That is, if the n-point function is proportional to the (n-1) power of the two-point function amplitude and the fluctuations are small, the probability distribution can be approximated by expanding around a Gaussian in moments. However, single-field inflation with higher derivative interactions has a second small number, the sound speed, that appears in the problem when non-Gaussianity is significant and changes the scaling of correlation functions. Here we examine the structure of correlation functions in the most general single scalar field action with higher derivatives, formalizing the conditions under which the fluctuations can be expanded around a Gaussian distribution. We comment about the special case of the Dirac-Born-Infeld action.
Orbital-resolved strong-field single ionization of acetylene
NASA Astrophysics Data System (ADS)
Ji, Qinying; Cui, Sen; You, Xinyuan; Gong, Xiaochun; Song, Qiying; Lin, Kang; Pan, Haifeng; Ding, Jingxin; Zeng, Heping; He, Feng; Wu, Jian
2015-10-01
We resolve the strong-field single ionization of acetylene into different channels by differentially normalizing the lateral momenta of the directly escaped electrons from the aligned and antialigned molecules. Distinct electron momentum distributions for different channels are observed using both near-infrared and ultraviolet femtosecond laser pulses with Keldysh parameters close to 1. The results are interpreted as a signature of multiple ionization orbitals.
Large non-Gaussian halo bias from single field inflation
Agullo, Ivan; Shandera, Sarah E-mail: shandera@gravity.psu.edu
2012-09-01
We calculate Large Scale Structure observables for non-Gaussianity arising from non-Bunch-Davies initial states in single field inflation. These scenarios can have substantial primordial non-Gaussianity from squeezed (but observable) momentum configurations. They generate a term in the halo bias that may be more strongly scale-dependent than the contribution from the local ansatz. We also discuss theoretical considerations required to generate an observable signature.
3D crack tip fields for FCC single crystals
Cuitino, A.M.; Ortiz, M.
1995-12-31
Cracks in single crystals are of concern in a number of structural and non-structural applications, ranging form single-crystal turbine blades and rotors to metal interconnect lines in microcircuits. In this paper we present 3D numerical simulations of the crack-tip fields of a Cu single crystal, including stress, strain and slip activity patterns. The orientation of the crack tip is along the crystallographic orientation (101), while the crack plane is (010). A material model based on dislocation mechanics is used in these simulations. This model correctly predicts the observed behavior of Cu, including the basic hardening characteristics of single crystals, orientation dependence and stage I-II-III structure of the stress-strain curves, the observed levels of latent hardening and their variation with orientation and deformation in the primary system and slip activities and dislocation densities. We use the FEM within the context of finite deformation plasticity. In the figure below, we show the finite element mesh composed by 12-noded tetrahedrons with 6-noded triangular faces. The model simulates half of a beam, which is subjected to a concentrated load at 1/8 of total length from the support. Detailed results of the stress, deformation and slip activity are presented at different radii from crack tip and at different depths from the surface. In general, the results show a strong difference in the slip activity pattern form the interior to the exterior, while smaller differences are encountered in the stress and strain fields.
On the divergences of inflationary superhorizon perturbations
Enqvist, K; Nurmi, S; Podolsky, D; Rigopoulos, G I E-mail: sami.nurmi@helsinki.fi E-mail: gerasimos.rigopoulos@helsinki.fi
2008-04-15
We discuss the infrared divergences that appear to plague cosmological perturbation theory. We show that, within the stochastic framework, they are regulated by eternal inflation so that the theory predicts finite fluctuations. Using the {Delta}N formalism to one loop, we demonstrate that the infrared modes can be absorbed into additive constants and the coefficients of the diagrammatic expansion for the connected parts of two-and three-point functions of the curvature perturbation. As a result, the use of any infrared cutoff below the scale of eternal inflation is permitted, provided that the background fields are appropriately redefined. The natural choice for the infrared cutoff would, of course, be the present horizon; other choices manifest themselves in the running of the correlators. We also demonstrate that it is possible to define observables that are renormalization-group-invariant. As an example, we derive a non-perturbative, infrared finite and renormalization point-independent relation between the two-point correlators of the curvature perturbation for the case of the free single field.
Magnetic field controlled FZ single crystal growth of intermetallic compounds
NASA Astrophysics Data System (ADS)
Hermann, R.; Behr, G.; Gerbeth, G.; Priede, J.; Uhlemann, H.-J.; Fischer, F.; Schultz, L.
2005-02-01
Intermetallic rare-earth-transition-metal compounds with their coexistence of magnetic ordering and superconductivity are still of great scientific interest. The crystal growth of bulk single crystals is very often unsuccessful due to an unfavorable solid-liquid interface geometry enclosing concave fringes. The aim of the work is the contactless control of heat and material transport during floating-zone single crystal growth of intermetallic compounds. This control is provided by a tailored design of the electromagnetic field and the resulting electromagnetically driven convection. Numerical simulations for the determination of the electromagnetic field configuration induced by the RF heater coil and the solution of the coupled heat and hydrodynamic equations were done for the model substance Ni with and without additional magnetic field. As a result, an innovative magnetic two-phase stirrer system has been developed which enables the controlled influence on the melt ranging from intensive inwards/outwards flows to flows almost at rest. The selection of parameters necessary for the desired fluid flow is determined from numerical simulation. The basis for the calculations are the process-related fluid flow conditions which are determined by the mode of heating, heat radiation at the free surface and material parameters. This treatment of the problem leads to the customised magnetic field for the special intermetallic compound. The application of the new magnetic system leads to a distinct improvement of the solid-liquid interface validated on experiments with the model substance Nickel.
Consistency relation for the Lorentz invariant single-field inflation
Huang, Qing-Guo
2010-05-01
In this paper we compute the sizes of equilateral and orthogonal shape bispectrum for the general Lorentz invariant single-field inflation. The stability of field theory implies a non-negative square of sound speed which leads to a consistency relation between the sizes of orthogonal and equilateral shape bispectrum, namely f{sub NL}{sup orth.} ≤ −0.054f{sub NL}{sup equil.}. In particular, for the single-field Dirac-Born-Infeld (DBI) inflation, the consistency relation becomes f{sub NL}{sup orth.} = 0.070f{sub NL}{sup equil.} ≤ 0. These consistency relations are also valid in the mixed scenario where the quantum fluctuations of some other light scalar fields contribute to a part of total curvature perturbation on the super-horizon scale and may generate a local form bispectrum. A distinguishing prediction of the mixed scenario is τ{sub NL}{sup loc.} > ((6/5)f{sub NL}{sup loc.}){sup 2}. Comparing these consistency relations to WMAP 7yr data, there is still a big room for the Lorentz invariant inflation, but DBI inflation has been disfavored at more than 68% CL.
Single-point inversion of the coronal magnetic field
Plowman, Joseph
2014-09-01
The Fe XIII 10747 and 10798 Å lines observed in the solar corona are sensitive to the coronal magnetic field in such a way that, in principle, the full vector field at a point on the line of sight can be inferred from their combined polarization signals. This paper presents analytical inversion formulae for the field parameters and analyzes the uncertainty of magnetic field measurements made from such observations, assuming emission dominated by a single region along the line of sight. We consider the case of the current Coronal Multi-channel Polarimeter (CoMP) instrument as well as the future Coronal Solar Magnetism Observatory (COSMO) and Advanced Technology Solar Telescope (ATST) instruments. Uncertainties are estimated with a direct analytic inverse and with a Markov Chain Monte Carlo algorithm. We find that (in effect) two components of the vector field can be recovered with CoMP, and well recovered with COSMO or ATST, but that the third component can only be recovered when the solar magnetic field is strong and optimally oriented.
Gravitational-wave generation in hybrid quintessential inflationary models
Sa, Paulo M.; Henriques, Alfredo B.
2010-06-15
We investigate the generation of gravitational waves in the hybrid quintessential inflationary model. The full gravitational-wave energy spectrum is calculated using the method of continuous Bogoliubov coefficients. The postinflationary kination period, characteristic of quintessential inflationary models, leaves a clear signature on the spectrum, namely, a peak at high frequencies. The maximum of the peak is firmly located at the megahertz-gigahertz region of the spectrum and corresponds to {Omega}{sub GW{approx_equal}}10{sup -12}. This peak is substantially smaller than the one appearing in the gravitational-wave energy spectrum of the original quintessential inflationary model, therefore avoiding any conflict with the nucleosynthesis constraint on {Omega}{sub GW}.
High-scale axions without isocurvature from inflationary dynamics
NASA Astrophysics Data System (ADS)
Kearney, John; Orlofsky, Nicholas; Pierce, Aaron
2016-05-01
Observable primordial tensor modes in the cosmic microwave background (CMB) would point to a high scale of inflation HI . If the scale of Peccei-Quinn (PQ) breaking fa is greater than H/I 2 π , CMB constraints on isocurvature naively rule out QCD axion dark matter. This assumes the potential of the axion is unmodified during inflation. We revisit models where inflationary dynamics modify the axion potential and discuss how isocurvature bounds can be relaxed. We find that models that rely solely on a larger PQ-breaking scale during inflation fI require either late-time dilution of the axion abundance or highly super-Planckian fI that somehow does not dominate the inflationary energy density. Models that have enhanced explicit breaking of the PQ symmetry during inflation may allow fa close to the Planck scale. Avoiding disruption of inflationary dynamics provides important limits on the parameter space.
Pre-inflationary vacuum in the cosmic microwave background
Powell, Brian A.; Kinney, William H.
2007-09-15
We consider the effects on the primordial power spectrum of a period of radiation-dominated expansion prior to the inflationary era. If inflation lasts a total of only 60 e-folds or so, the boundary condition for quantum modes cannot be taken in the short-wavelength limit as in the standard perturbation calculation. Instead, the boundary condition is set by the vacuum state of the prior radiation-dominated epoch, which only corresponds to the inflationary vacuum state in the ultraviolet limit. This altered vacuum state results in a modulation of the inflationary power spectrum. We calculate the modification to a best-fit model from the WMAP3 data set, and find that power is suppressed at large scales. The modified power spectrum is favored only very weakly by the WMAP3 temperature and polarization data.
High-scale axions without isocurvature from inflationary dynamics
Kearney, John; Orlofsky, Nicholas; Pierce, Aaron
2016-05-31
Observable primordial tensor modes in the cosmic microwave background (CMB) would point to a high scale of inflation HI. If the scale of Peccei-Quinn (PQ) breaking fa is greater than HI/2π, CMB constraints on isocurvature naively rule out QCD axion dark matter. This assumes the potential of the axion is unmodified during inflation. We revisit models where inflationary dynamics modify the axion potential and discuss how isocurvature bounds can be relaxed. We find that models that rely solely on a larger PQ-breaking scale during inflation fI require either late-time dilution of the axion abundance or highly super-Planckian fI that somehowmore » does not dominate the inflationary energy density. Models that have enhanced explicit breaking of the PQ symmetry during inflation may allow fa close to the Planck scale. Lastly, avoiding disruption of inflationary dynamics provides important limits on the parameter space.« less
On squeezed limits in single-field inflation. Part I
Flauger, Raphael; Green, Daniel; Porto, Rafael A. E-mail: dgreen@stanford.edu
2013-08-01
The n-point correlation functions in single-field inflation obey a set of consistency conditions in the exact squeezed limit which are not present in multi-field models, and thus are powerful tools to distinguish between the two. However, these consistency conditions may be violated for a finite range of scales in single-field models, for example by departures from the Bunch-Davies state. These excited states may be the consequence of interactions during inflation, or may be a remnant of the era that preceded inflation. In this paper we analyze the bispectrum, and show that in the regime of theoretical control the resulting signal in the squeezed limit remains undetectably small in all known models which continuously excite the state. We also show that the signal remains undetectably small if the initial state is related to the Bunch-Davies state by a Bogoliubov transformation and the energy density in the state is small enough so that the usual slow-roll conditions are obeyed. Bogoliubov states that lead to violations of the slow-roll conditions, as well as more general excited states, require more careful treatment and will be discussed in a separate publication.
Perturbations of single-field inflation in modified gravity theory
NASA Astrophysics Data System (ADS)
Qiu, Taotao; Xia, Jun-Qing
2015-05-01
In this paper, we study the case of single field inflation within the framework of modified gravity theory where the gravity part has an arbitrary form f (R). Via a conformal transformation, this case can be transformed into its Einstein frame where it looks like a two-field inflation model. However, due to the existence of the isocurvature modes in such a multi-degree-of-freedom (m.d.o.f.) system, the (curvature) perturbations are not equivalent in two frames, so despite of its convenience, it is illegal to treat the perturbations in its Einstein frame as the "real" ones as we always do for pure f (R) theory or single field with nonminimal coupling. Here by pulling the results of curvature perturbations back into its original Jordan frame, we show explicitly the power spectrum and spectral index of the perturbations in the Jordan frame, as well as how it differs from the Einstein frame. We also fit our results with the newest Planck data. Since there is large parameter space in these models, we show that it is easy to fit the data very well.
Edge field emission of large-area single layer graphene
NASA Astrophysics Data System (ADS)
Kleshch, Victor I.; Bandurin, Denis A.; Orekhov, Anton S.; Purcell, Stephen T.; Obraztsov, Alexander N.
2015-12-01
Field electron emission from the edges of large-area (∼1 cm × 1 cm) graphene films deposited onto quartz wafers was studied. The graphene was previously grown by chemical vapour deposition on copper. An extreme enhancement of electrostatic field at the edge of the films with macroscopically large lateral dimensions and with single atom thickness was achieved. This resulted in the creation of a blade type electron emitter, providing stable field emission at low-voltage with linear current density up to 0.5 mA/cm. A strong hysteresis in current-voltage characteristics and a step-like increase of the emission current during voltage ramp up were observed. These effects were explained by the local mechanical peeling of the graphene edge from the quartz substrate by the ponderomotive force during the field emission process. Specific field emission phenomena exhibited in the experimental study are explained by a unique combination of structural, electronic and mechanical properties of graphene. Various potential applications ranging from linear electron beam sources to microelectromechanical systems are discussed.
Infrared spectroscopic near-field mapping of single nanotransistors.
Huber, A J; Wittborn, J; Hillenbrand, R
2010-06-11
We demonstrate the application of scattering-type scanning near-field optical microscopy (s-SNOM) for infrared (IR) spectroscopic material recognition in state-of-the-art semiconductor devices. In particular, we employ s-SNOM for imaging of industrial CMOS transistors with a resolution better than 20 nm, which allows for the first time IR spectroscopic recognition of amorphous SiO(2) and Si(3)N(4) components in a single transistor device. The experimentally recorded near-field spectral signature of amorphous SiO(2) shows excellent agreement with model calculations based on literature dielectric values, verifying that the characteristic near-field contrasts of SiO(2) stem from a phonon-polariton resonant near-field interaction between the probing tip and the SiO(2) nanostructures. Local material recognition by s-SNOM in combination with its capabilities of contact-free and non-invasive conductivity- and strain-mapping makes IR near-field microscopy a versatile metrology technique for nanoscale material characterization and semiconductor device analysis with application potential in research and development, failure analysis and reverse engineering. PMID:20463381
Measuring the complex field scattered by single submicron particles
Potenza, Marco A. C. Sanvito, Tiziano
2015-11-15
We describe a method for simultaneous measurements of the real and imaginary parts of the field scattered by single nanoparticles illuminated by a laser beam, exploiting a self-reference interferometric scheme relying on the fundamentals of the Optical Theorem. Results obtained with calibrated spheres of different materials are compared to the expected values obtained through a simplified analytical model without any free parameters, and the method is applied to a highly polydisperse water suspension of Poly(D,L-lactide-co-glycolide) nanoparticles. Advantages with respect to existing methods and possible applications are discussed.
Nonisotropy in the CMB power spectrum in single field inflation
NASA Astrophysics Data System (ADS)
Donoghue, John F.; Dutta, Koushik; Ross, Andreas
2009-07-01
Contaldi et al. [C. R. Contaldi, M. Peloso, L. Kofman, and A. Linde, J. Cosmol. Astropart. Phys.1475-7516 07 (2003) 00210.1088/1475-7516/2003/07/002] have suggested that an initial period of kinetic energy domination in single field inflation may explain the lack of CMB power at large angular scales. We note that in this situation it is natural that there also be a spatial gradient in the initial value of the inflaton field, and that this can provide a spatial asymmetry in the observed CMB power spectrum, manifest at low values of ℓ. We investigate the nature of this asymmetry and comment on its relation to possible anomalies at low ℓ.
Subsurface Stress Fields In Single Crystal (Anisotropic) Contacts
NASA Technical Reports Server (NTRS)
Arakere, Nagaraj K.; Knudsen, Erik C.; Duke, Greg; Battista, Gilda; Swanson, Greg
2004-01-01
Single crystal superalloy turbine blades used in high pressure turbomachinery are subject to conditions of high temperature, triaxial steady and alternating stresses, fretting stresses in the blade attachment and damper contact locations, and exposure to high-pressure hydrogen. The blades are also subjected to extreme variations in temperature during start-up and shutdown transients. The most prevalent HCF failure modes observed in these blades during operation include crystallographic crack initiation/propagation on octahedral planes, and noncrystallographic initiation with crystallographic growth. Numerous cases of crack initiation and crack propagation at the blade leading edge tip, blade attachment regions, and damper contact locations have been documented. Understanding crack initiation/propagation under mixed-mode loading conditions is critical for establishing a systematic procedure for evaluating HCF life of single crystal turbine blades. This paper presents analytical and numerical techniques for evaluating two and three dimensional subsurface stress fields in anisotropic contacts. The subsurface stress results are required for evaluating contact fatigue life at damper contacts and dovetail attachment regions in single crystal nickel-base superalloy turbine blades. An analytical procedure is , presented, for evaluating the subsurface stresses in the elastic half-space, using a complex potential method outlined by Lekhnitskii. Numerical results are presented for cylindrical and spherical anisotropic contacts, using finite element analysis. Effects of crystal orientation on stress response and fatigue life are examined.
Subsurface Stress Fields in Single Crystal (Anisotropic) Contacts
NASA Technical Reports Server (NTRS)
Arakere, Nagaraj K.
2003-01-01
Single crystal superalloy turbine blades used in high pressure turbomachinery are subject to conditions of high temperature, triaxial steady and fatigue stresses, fretting stresses in the blade attachment and damper contact locations, and exposure to high-pressure hydrogen. The blades are also subjected to extreme variations in temperature during start-up and shutdown transients. The most prevalent HCF failure modes observed in these blades during operation include crystallographic crack initiation/propagation on octahedral planes, and noncrystallographic initiation with crystallographic growth. Numerous cases of crack initiation and crack propagation at the blade leading edge tip, blade attachment regions, and damper contact locations have been documented. Understanding crack initiation/propagation under mixed-mode loading conditions is critical for establishing a systematic procedure for evaluating HCF life of single crystal turbine blades. Techniques for evaluating two and three dimensional subsurface stress fields in anisotropic contacts are presented in this report. Figure 1 shows typical damper contact locations in a turbine blade. The subsurface stress results are used for evaluating contact fatigue life at damper contacts and dovetail attachment regions in single crystal nickel-base superalloy turbine blades.
Subsurface Stress Fields in FCC Single Crystal Anisotropic Contacts
NASA Technical Reports Server (NTRS)
Arakere, Nagaraj K.; Knudsen, Erik; Swanson, Gregory R.; Duke, Gregory; Ham-Battista, Gilda
2004-01-01
Single crystal superalloy turbine blades used in high pressure turbomachinery are subject to conditions of high temperature, triaxial steady and alternating stresses, fretting stresses in the blade attachment and damper contact locations, and exposure to high-pressure hydrogen. The blades are also subjected to extreme variations in temperature during start-up and shutdown transients. The most prevalent high cycle fatigue (HCF) failure modes observed in these blades during operation include crystallographic crack initiation/propagation on octahedral planes, and non-crystallographic initiation with crystallographic growth. Numerous cases of crack initiation and crack propagation at the blade leading edge tip, blade attachment regions, and damper contact locations have been documented. Understanding crack initiation/propagation under mixed-mode loading conditions is critical for establishing a systematic procedure for evaluating HCF life of single crystal turbine blades. This paper presents analytical and numerical techniques for evaluating two and three dimensional subsurface stress fields in anisotropic contacts. The subsurface stress results are required for evaluating contact fatigue life at damper contacts and dovetail attachment regions in single crystal nickel-base superalloy turbine blades. An analytical procedure is presented for evaluating the subsurface stresses in the elastic half-space, based on the adaptation of a stress function method outlined by Lekhnitskii. Numerical results are presented for cylindrical and spherical anisotropic contacts, using finite element analysis (FEA). Effects of crystal orientation on stress response and fatigue life are examined. Obtaining accurate subsurface stress results for anisotropic single crystal contact problems require extremely refined three-dimensional (3-D) finite element grids, especially in the edge of contact region. Obtaining resolved shear stresses (RSS) on the principal slip planes also involves
Inflationary Cosmology: Is Our Universe Part of a Multiverse?
Guth, Alan
2008-11-06
In this talk, Guth explains the inflationary theory and reviews the features that make it scientifically plausible. In addition, he discusses the biggest mystery in cosmology: Why is the value of the cosmological constant, sometimes called the "anti-gravity" effect, so remarkably small compared to theoretical expectations?
Vacuum Energy and Inflation: 4. An Inflationary Universe
NASA Astrophysics Data System (ADS)
Huggins, Elisha
2013-12-01
In this paper the focus will be on how an entire universe can possibly be created within 10-35 seconds starting from a region of space about 10-45 meters across. To do this, we will closely follow the ideas of Alan Guth, who came up with the idea of an inflationary universe.
Black holes with a single Killing vector field: black resonators
NASA Astrophysics Data System (ADS)
Dias, Óscar J. C.; Santos, Jorge E.; Way, Benson
2015-12-01
We numerically construct asymptotically anti-de Sitter (AdS) black holes in four dimensions that contain only a single Killing vector field. These solutions, which we coin black resonators, link the superradiant instability of Kerr-AdS to the nonlinear weakly turbulent instability of AdS by connecting the onset of the superradiance instability to smooth, horizonless geometries called geons. Furthermore, they demonstrate non-uniqueness of Kerr-AdS by sharing asymptotic charges. Where black resonators coexist with Kerr-AdS, we find that the black resonators have higher entropy. Nevertheless, we show that black resonators are unstable and comment on the implications for the endpoint of the superradiant instability.
Conformal consistency relations for single-field inflation
Creminelli, Paolo; Noreña, Jorge; Simonović, Marko E-mail: jorge.norena@gmail.com
2012-07-01
We generalize the single-field consistency relations to capture not only the leading term in the squeezed limit — going as 1/q{sup 3}, where q is the small wavevector — but also the subleading one, going as 1/q{sup 2}. This term, for an (n+1)-point function, is fixed in terms of the variation of the n-point function under a special conformal transformation; this parallels the fact that the 1/q{sup 3} term is related with the scale dependence of the n-point function. For the squeezed limit of the 3-point function, this conformal consistency relation implies that there are no terms going as 1/q{sup 2}. We verify that the squeezed limit of the 4-point function is related to the conformal variation of the 3-point function both in the case of canonical slow-roll inflation and in models with reduced speed of sound. In the second case the conformal consistency conditions capture, at the level of observables, the relation among operators induced by the non-linear realization of Lorentz invariance in the Lagrangian. These results mean that, in any single-field model, primordial correlation functions of ζ are endowed with an SO(4,1) symmetry, with dilations and special conformal transformations non-linearly realized by ζ. We also verify the conformal consistency relations for any n-point function in models with a modulation of the inflaton potential, where the scale dependence is not negligible. Finally, we generalize (some of) the consistency relations involving tensors and soft internal momenta.
Directed Assembly of Single Wall Carbon Nanotube Field Effect Transistors.
Penzo, Erika; Palma, Matteo; Chenet, Daniel A; Ao, Geyou; Zheng, Ming; Hone, James C; Wind, Shalom J
2016-02-23
The outstanding electronic properties of single wall carbon nanotubes (SWCNTs) have made them prime candidates for future nanoelectronics technologies. One of the main obstacles to the implementation of advanced SWCNT electronics to date is the inability to arrange them in a manner suitable for complex circuits. Directed assembly of SWCNT segments onto lithographically patterned and chemically functionalized substrates is a promising way to organize SWCNTs in topologies that are amenable to integration for advanced applications, but the placement and orientational control required have not yet been demonstrated. We have developed a technique for assembling length sorted and chirality monodisperse DNA-wrapped SWCNT segments on hydrophilic lines patterned on a passivated oxidized silicon substrate. Placement of individual SWCNT segments at predetermined locations was achieved with nanometer accuracy. Three terminal electronic devices, consisting of a single SWCNT segment placed either beneath or on top of metallic source/drain electrodes were fabricated. Devices made with semiconducting nanotubes behaved as typical p-type field effect transistors (FETs), whereas devices made with metallic nanotubes had a finite resistance with little or no gate modulation. This scalable, high resolution approach represents an important step forward toward the potential implementation of complex SWCNT devices and circuits. PMID:26807948
Strategies for single particle manipulation using acoustic and flow fields.
Oberti, S; Möller, D; Neild, A; Dual, J; Beyeler, F; Nelson, B J; Gutmann, S
2010-02-01
Acoustic radiation forces have often been used for the manipulation of large amounts of micrometer sized suspended particles. The nature of acoustic standing wave fields is such that they are present throughout the whole fluidic volume; this means they are well suited to such operations, with all suspended particles reacting at the same time upon exposure. Here, this simultaneous positioning capability is exploited to pre-align particles along the centerline of channels, so that they can successively be removed by means of an external tool for further analysis. This permits a certain degree of automation in single particle manipulation processes to be achieved as initial identification of particles' location is no longer necessary, rather predetermined. Two research fields in which applications are found have been identified. First, the manipulation of copolymer beads and cells using a microgripper is presented. Then, sample preparation for crystallographic analysis by positioning crystals into a loop using acoustic manipulation and a laminar flow will be presented. PMID:19837446
Ultrasensitive magnetic field detection using a single artificial atom.
Bal, M; Deng, C; Orgiazzi, J-L; Ong, F R; Lupascu, A
2012-01-01
Efficient detection of magnetic fields is central to many areas of research and technology. High-sensitivity detectors are commonly built using direct-current superconducting quantum interference devices or atomic systems. Here we use a single artificial atom to implement an ultrasensitive magnetometer with micron range size. The artificial atom, a superconducting two-level system, is operated similarly to atom and diamond nitrogen-vacancy centre-based magnetometers. The high sensitivity results from quantum coherence combined with strong coupling to magnetic field. We obtain a sensitivity of 3.3 pT Hz(-1/2) for a frequency at 10 MHz. We discuss feasible improvements to increase sensitivity by one order of magnitude. The intrinsic sensitivity of this detector at frequencies in the 100 kHz-10 MHz range compares favourably with direct-current superconducting quantum interference devices and atomic magnetometers of equivalent spatial resolution. This result illustrates the potential of artificial quantum systems for sensitive detection and related applications. PMID:23271657
A maximally symmetric no-scale inflationary universe
NASA Astrophysics Data System (ADS)
Kounnas, C.; Quiros, M.
1985-02-01
We present an inflationary model, based on maximally symmetric no-scale supergravity models, where the gravitino and inflation scale cosmological problems are solved simultaneously by means of a heavy - but weakly coupled to ordinary matter - gravitino. The gravitino mass is essentially given by the Hubble constant at the inflationary epoch, H≅1012 GeV. The reheating temperature of the universe after inflation is TR≅(1010-1011) GeV and so gravitinos are no longer regenerated. The grand unified theory suffers a rapid phase transition into the SU(3)×SU(2)×U(1) phase, during - or at the end of - inflation with dilution of magnetic monopoles. The dynamical determination of the electroweak scale predicts top quark masses between 40 and 50 GeV. Laboratoire Propre du Centre National de la Recherche Scientifique, associé à l'Ecole Normale Supérieure et à l'Université de Paris-Sud.
Inflationary weak anisotropic model with general dissipation coefficient
NASA Astrophysics Data System (ADS)
Sharif, M.; Saleem, Rabia
2016-03-01
This paper explores the dynamics of warm intermediate and logamediate inflationary models during weak dissipative regime with a general form of dissipative coefficient. We analyze these models within the framework of locally rotationally symmetric Bianchi type I universe. In both cases, we evaluate solution of inflaton, effective scalar potential, dissipative coefficient, slow-roll parameters, scalar and tensor power spectra, scalar spectral index and tensor to scalar ratio under slow-roll approximation. We constrain the model parameters using recent data and conclude that anisotropic inflationary universe model with generalized dissipation coefficient remains compatible with WMAP9, Planck and BICEP2 data. Finally, we have checked the effects of bulk viscous pressure on this considered model and found that it remains compatible with recent data only for intermediate case.
Inflationary effect of crude oil prices in Turkey
NASA Astrophysics Data System (ADS)
Berument, Hakan; Taşçı, Hakan
2002-12-01
It is generally acknowledged that changes in oil prices affect economic welfare in ways that are not entirely reflected in transactions in the oil market. In this article, by using the 1990 input-output table, the inflationary effects of crude oil prices are investigated for Turkey. Under fixed nominal wages, profits, interest and rent earnings, the effect of increasing prices of oil on inflation is limited. However, when wages and the other three factors of income (profit, interest and rent) are adjusted to the general price level that includes the oil price increases, the inflationary effect of oil prices becomes significant. Hence, indexation could have very severe effects on an economy when oil prices increase and, in some cases, could even lead to hyperinflation.
Structured dark-field imaging for single nano-particles
NASA Astrophysics Data System (ADS)
Chen, Jian; Gao, Kun; Wang, Zhi-Li; Yun, Wen-Bing; Wu, Zi-Yu
2015-08-01
In this work, we extensively describe and demonstrate the structured dark-field imaging (SDFI). SDFI is a newly proposed x-ray microscopy designed for revealing the fine features below Rayleigh resolution, in which different orders of scattered x-ray photons are collected by changing the numerical aperture of the condenser. Here, the samples of single particles are discussed to extend the scope of the SDFI technique reported in a previous work (Chen J, Gao K, Ge X, et al. 2013 Opt. Lett. 38 2068). In addition, the details of the newly invented algorithm are explained, which is able to calculate the intensity of any pixel on the image plane rapidly and reliably. Project supported by the National Basic Research Program of China (Grant No. 2012CB825800), the Science Fund for Creative Research Groups, the National Natural Science Foundation of China (Grant No. 11321503), the Knowledge Innovation Program of the Chinese Academy of Sciences (Grant No. KJCX2-YW-N42), and the National Natural Science Foundation of China (Grant Nos. 11475170, 11205157, and 11305173).
Discrete dislocation plasticity and crack tip fields in single crystals
NASA Astrophysics Data System (ADS)
Van der Giessen, E.; Deshpande, V. S.; Cleveringa, H. H. M.; Needleman, A.
2001-09-01
Small-scale yielding around a stationary plane strain mode I crack is analyzed using discrete dislocation plasticity. The dislocations are all of edge character, and are modeled as line singularities in a linear elastic material. Superposition is used to represent the solution in terms of analytical fields for edge dislocations in a half-space and a numerical image solution that enforces the boundary conditions. The description of the dislocation dynamics includes the lattice resistance to dislocation motion, dislocation nucleation, interaction with obstacles and annihilation. A model planar crystal with three slip systems is considered. Two slip system orientations are analyzed that differ by a 90° rotation. The non-hardening, single crystal plasticity continuum slip solution of Rice (Mech. Mater. 6 (1987) 317) for this model crystal predicts that slip and kink bands emerge for both crystal geometries, while Drugan (J. Mech. Phys. Solids 49 (2001) 2155) has obtained kink band free solutions. For a reference set of parameter values, kink band free solutions are found in one orientation while the emergence of kink bands is seen in the other orientation. However, lowering the dislocation source density suppresses the formation of kink bands in this orientation as well. In all calculations, the opening stress in the immediate vicinity of the crack tip is much larger than predicted by continuum slip theory.
Single-field consistency relations of large scale structure
Creminelli, Paolo; Noreña, Jorge; Simonović, Marko; Vernizzi, Filippo E-mail: jorge.norena@icc.ub.edu E-mail: filippo.vernizzi@cea.fr
2013-12-01
We derive consistency relations for the late universe (CDM and ΛCDM): relations between an n-point function of the density contrast δ and an (n+1)-point function in the limit in which one of the (n+1) momenta becomes much smaller than the others. These are based on the observation that a long mode, in single-field models of inflation, reduces to a diffeomorphism since its freezing during inflation all the way until the late universe, even when the long mode is inside the horizon (but out of the sound horizon). These results are derived in Newtonian gauge, at first and second order in the small momentum q of the long mode and they are valid non-perturbatively in the short-scale δ. In the non-relativistic limit our results match with [1]. These relations are a consequence of diffeomorphism invariance; they are not satisfied in the presence of extra degrees of freedom during inflation or violation of the Equivalence Principle (extra forces) in the late universe.
Inflationary cosmology from quantum conformal gravity
NASA Astrophysics Data System (ADS)
Jizba, Petr; Kleinert, Hagen; Scardigli, Fabio
2015-06-01
We analyze the functional integral for quantum conformal gravity and show that, with the help of a Hubbard-Stratonovich transformation, the action can be broken into a local quadratic-curvature theory coupled to a scalar field. A one-loop effective-action calculation reveals that strong fluctuations of the metric field are capable of spontaneously generating a dimensionally transmuted parameter which, in the weak-field sector of the broken phase, induces a Starobinsky-type f( R)-model with a gravi-cosmological constant. A resulting non-trivial relation between Starobinsky's parameter and the gravi-cosmological constant is highlighted and implications for cosmic inflation are briefly discussed and compared with the recent PLANCK and BICEP2 data.
Reconstruction of the local inflationary potential with different correlation levels
NASA Astrophysics Data System (ADS)
Di Marco, A.; Cabella, P.; Vittorio, N.
2016-02-01
We review the puzzles of the standard Big Bang model and cosmic inflation as their possible solutions. The relation between inflation and the spectra of the cosmological perturbations is emphasized. In particular we focus on the local reconstruction of the shape of the inflationary potential from observations and the consequences of a direct detection of cosmological gravitational waves, exploring different correlation levels between the spectral index ns and the tensor-to-scalar ratio r of the primordial perturbations.
Inflationary Cosmology: Is Our Universe Part of a Multiverse
Guth, Alan
2008-11-06
In 1981, Guth proposed the theory of the inflationary universe, a modification of the Big Bang theory, which is generally accepted by scientists to explain how the universe began. Nevertheless, the Big Bang theory leaves some questions, and the theory of inflation attempts to answer them. Guth states that a repulsive gravitational force generated by an exotic form of matter brought about the expansion of the universe. He postulates that the universe underwent an expansion of astronomical proportions within the first trillionth of a second of its existence, during which the seeds for its large-scale structure were generated. Guth and colleagues have further explored the possibility of mimicking inflation in a hypothetical laboratory, thereby creating a new universe, and they concluded that it might be theoretically possible. If it happened, the new universe would not endanger our own universe. Instead, it would slip through a wormhole, a hypothetical space-time travel shortcut, and rapidly disconnect from our universe. In this talk, Guth will explain the inflationary theory and review the features that make it scientifically plausible. In addition, he will discuss the biggest mystery in cosmology: Why is the value of the cosmological constant, sometimes called the "anti-gravity" effect, so remarkably small compared to theoretical expectations? Guth will explain how the inflationary theory, combined with other ideas from elementary particle physics and cosmology, can provide a possible explanation for this discrepancy.
Low reheating temperatures in monomial and binomial inflationary models
NASA Astrophysics Data System (ADS)
Rehagen, Thomas; Gelmini, Graciela B.
2015-06-01
We investigate the allowed range of reheating temperature values in light of the Planck 2015 results and the recent joint analysis of Cosmic Microwave Background (CMB) data from the BICEP2/Keck Array and Planck experiments, using monomial and binomial inflationary potentials. While the well studied phi2 inflationary potential is no longer favored by current CMB data, as well as phip with p>2, a phi1 potential and canonical reheating (0wre=) provide a good fit to the CMB measurements. In this last case, we find that the Planck 2015 68% confidence limit upper bound on the spectral index, ns, implies an upper bound on the reheating temperature of Trelesssim 6× 1010 GeV, and excludes instantaneous reheating. The low reheating temperatures allowed by this model open the possibility that dark matter could be produced during the reheating period instead of when the Universe is radiation dominated, which could lead to very different predictions for the relic density and momentum distribution of WIMPs, sterile neutrinos, and axions. We also study binomial inflationary potentials and show the effects of a small departure from a phi1 potential. We find that as a subdominant phi2 term in the potential increases, first instantaneous reheating becomes allowed, and then the lowest possible reheating temperature of Tre=4 MeV is excluded by the Planck 2015 68% confidence limit.
Single-Plane Magnetically Focused Elongated Small Field Proton Beams.
McAuley, Grant A; Slater, James M; Wroe, Andrew J
2015-08-01
We previously performed Monte Carlo simulations of magnetically focused proton beams shaped by a single quadrapole magnet and thereby created narrow elongated beams with superior dose delivery characteristics (compared to collimated beams) suitable for targets of similar geometry. The present study seeks to experimentally validate these simulations using a focusing magnet consisting of 24 segments of samarium cobalt permanent magnetic material adhered into a hollow cylinder. Proton beams with properties relevant to clinical radiosurgery applications were delivered through the magnet to a water tank containing a diode detector or radiochromic film. Dose profiles were analyzed and compared with analogous Monte Carlo simulations. The focused beams produced elongated beam spots with high elliptical symmetry, indicative of magnet quality. Experimental data showed good agreement with simulations, affirming the utility of Monte Carlo simulations as a tool to model the inherent complexity of a magnetic focusing system. Compared to target-matched unfocused simulations, focused beams showed larger peak to entrance ratios (26% to 38%) and focused simulations showed a two-fold increase in beam delivery efficiency. These advantages can be attributed to the magnetic acceleration of protons in the transverse plane that tends to counteract the particle outscatter that leads to degradation of peak to entrance performance in small field proton beams. Our results have important clinical implications and suggest rare earth focusing magnet assemblies are feasible and could reduce skin dose and beam number while delivering enhanced dose to narrow elongated targets (eg, in and around the spinal cord) in less time compared to collimated beams. PMID:25414143
Countable Infinite Sets and Inflationary Models
NASA Astrophysics Data System (ADS)
Berezin, Alexander A.
2000-04-01
Unreasonable effectiveness of mathematics (E.Wigner) recasts pythagorean "all things are made of numbers". Hypotheses of eternal inflation (A.Linde) and/or quantum branching (H.Everett) buttressed by platonic pressure principle (PPP) resonates with "for deriving all from nothing there suffices a single principle" (G.W.Leibnitz). Externalization of PPP uses patterns of factorizations of super-long integers (tower exponents, TE). PPP-TE explosive emergence of space-time-matter-energy rests on infinite complexity of factorizational and iterational patterns of integers. Thus, PPP is direct translation of metaphysical principle to physics of material world ("metaphysics works"). Countability of quantum states of bounded systems allows "listing" of all states of all baby universes through Godel-like counting with TE of primes. At each breeding step upper (Nth) prime of TE stack p1...pN counts (by multidimensional Cantor diagonal scheme) all universes AND all states in them. Exclusive use of primes in TEs assures non-overlapping counting. Cantor counting with non-crossing subsets of primes (and actual PPP emergence) can proceed both in "forward" and "backward" direction in megauniversal ("Newtonian") time. format.
Low reheating temperatures in monomial and binomial inflationary models
Rehagen, Thomas; Gelmini, Graciela B.
2015-06-23
We investigate the allowed range of reheating temperature values in light of the Planck 2015 results and the recent joint analysis of Cosmic Microwave Background (CMB) data from the BICEP2/Keck Array and Planck experiments, using monomial and binomial inflationary potentials. While the well studied ϕ{sup 2} inflationary potential is no longer favored by current CMB data, as well as ϕ{sup p} with p>2, a ϕ{sup 1} potential and canonical reheating (w{sub re}=0) provide a good fit to the CMB measurements. In this last case, we find that the Planck 2015 68% confidence limit upper bound on the spectral index, n{sub s}, implies an upper bound on the reheating temperature of T{sub re}≲6×10{sup 10} GeV, and excludes instantaneous reheating. The low reheating temperatures allowed by this model open the possibility that dark matter could be produced during the reheating period instead of when the Universe is radiation dominated, which could lead to very different predictions for the relic density and momentum distribution of WIMPs, sterile neutrinos, and axions. We also study binomial inflationary potentials and show the effects of a small departure from a ϕ{sup 1} potential. We find that as a subdominant ϕ{sup 2} term in the potential increases, first instantaneous reheating becomes allowed, and then the lowest possible reheating temperature of T{sub re}=4 MeV is excluded by the Planck 2015 68% confidence limit.
Inflationary cosmology with Chaplygin gas in Palatini formalism
NASA Astrophysics Data System (ADS)
Borowiec, Andrzej; Stachowski, Aleksander; Szydłowski, Marek; Wojnar, Aneta
2016-01-01
We present a simple generalisation of the ΛCDM model which on the one hand reaches very good agreement with the present day experimental data and provides an internal inflationary mechanism on the other hand. It is based on Palatini modified gravity with quadratic Starobinsky term and generalized Chaplygin gas as a matter source providing, besides a current accelerated expansion, the epoch of endogenous inflation driven by type III freeze singularity. It follows from our statistical analysis that astronomical data favors negative value of the parameter coupling quadratic term into Einstein-Hilbert Lagrangian and as a consequence the bounce instead of initial Big-Bang singularity is preferred.
A VLSI single chip 8-bit finite field multiplier
NASA Technical Reports Server (NTRS)
Deutsch, L. J.; Shao, H. M.; Hsu, I. S.; Truong, T. K.
1985-01-01
A Very Large Scale Integration (VLSI) architecture and layout for an 8-bit finite field multiplier is described. The algorithm used in this design was developed by Massey and Omura. A normal basis representation of finite field elements is used to reduce the multiplication complexity. It is shown that a drastic improvement was achieved in this design. This multiplier will be used intensively in the implementation of an 8-bit Reed-Solomon decoder and in many other related projects.
Rojas, Clara; Villalba, Victor M.
2007-03-15
The phase-integral approximation devised by Froeman and Froeman, is used for computing cosmological perturbations in the power-law inflationary model. The phase-integral formulas for the scalar and tensor power spectra are explicitly obtained up to ninth-order of the phase-integral approximation. We show that, the phase-integral approximation exactly reproduces the shape of the power spectra for scalar and tensor perturbations as well as the spectral indices. We compare the accuracy of the phase-integral approximation with the results for the power spectrum obtained with the slow-roll and uniform-approximation methods.
Emergence of inflationary perturbations in the CSL model
NASA Astrophysics Data System (ADS)
León, Gabriel; Bengochea, Gabriel R.
2016-01-01
The inflationary paradigm is the most successful model that explains the observed spectrum of primordial perturbations. However, the precise emergence of such inhomogeneities and the quantum-to-classical transition of the perturbations has not yet reached a consensus among the community. The continuous spontaneous localization model (CSL), in the cosmological context, might be used to provide a solution to the mentioned issues by considering a dynamical reduction of the wave function. The CSL model has been applied to the inflationary universe before and different conclusions have been obtained. In this letter, we use a different approach to implement the CSL model during inflation. In particular, in addition to accounting for the quantum-to-classical transition, we use the CSL model to generate the primordial perturbations, that is, the dynamical evolution provided by the CSL model is responsible for the transition from a homogeneous and isotropic initial state to a final one lacking such symmetries. Our approach leads to results that can be clearly distinguished from preceding works. Specifically, the scalar and tensor power spectra are not time-dependent, and one retains the amplification mechanism of the CSL model. Moreover, our framework depends only on one parameter (the CSL parameter) and its value is consistent with cosmological and laboratory observations.
Second-order reconstruction of the inflationary potential
NASA Technical Reports Server (NTRS)
Liddle, Andrew R.; Turner, Michael S.
1994-01-01
To first order in the deviation from scale invariance the inflationary potential and its first two derivatives can be expressed in terms of the spectral indices of the scalar and tensor perturbations, n and n(sub T), and their contributions to the variance of the quadrupole CBR temperature anisotropy, S and T. In addition, there is a 'consistency relation' between these quantities: n(sub T) = (-1/ 7)(T/S). We derive the second-order expressions for the inflationary potential and its first two derivatives and the first-order expression for its third derivative, in terms, of n, n(sub T), S, T, and dn/d ln gamma. We also obtain the second-order consistency relation, n(sub T) = (-1/7)(T/S)(1 + 0.11(T/S) + 0.15(n-1)). As an example we consider the exponential potential, the only known case where exact analytic solutions for the perturbation spectra exist. We reconstruct the potential via Taylor expansion (with coefficients calculated at both first and second order), and introduce the Pade approximate as a greatly improved alternative.
Inflationary Expansions Generated by a Physically Real Kinematic Acceleration
NASA Astrophysics Data System (ADS)
Savickas, David
2010-02-01
A repulsive cosmological acceleration is shown to exist that exhibits a behavior very similar to that found in both inflationary models at the time of origin of the universe, and also in the repulsive acceleration found in present-day cosmological observations. It is able to describe an inflationary model of a radiation universe in considerable numerical detail. It is based on a method that defines the Hubble parameter H, and consequently inertial systems themselves, directly in terms of the positions and velocities of mass particles in a universe. This makes it possible to describe a mass particle's motion relative to other particles in the universe, rather than relative to inertial systems. Because of this, the repulsive acceleration is a real kinematic effect existing in the present-day universe. This definition of H cannot include the use of photon positions or velocities because H determines the velocities of receding inertial systems of galaxies, and the velocity of a photon in a distant inertial system then depends on the definition of H itself. Therefore, at the time of its origin the magnitude of H in a radiation dominated universe would be solely determined by the behavior of the relatively few mass particles that it contained while allowing for a near balance with the gravitation of the Friedmann-Lemaître model. )
Primordial black holes under the double inflationary power spectrum
NASA Astrophysics Data System (ADS)
Kim, Hee Il
2000-09-01
Recently, it has been shown that the primordial black holes (PBHs) produced by near critical collapse in the expanding universe have a scaling mass relation similar to that of black holes produced in asymptotically flat spacetime. Distinct from PBHs formed with a mass about the size of the horizon mass (type I), the PBHs with the scaling relation (type II) can be created with a range of masses at a given formation time. In general, only the case in which the PBH formation is concentrated at one epoch has been considered. However, it is expected that PBH formation is possible over a broad range of epochs if the density fluctuation has a rather large amplitude and smooth scale dependence. In this paper, we study the PBH formation for both types assuming the power spectrum of double inflationary models in which the small scale fluctuations could have large amplitudes independent of the CMBR anisotropy. The mass spectrum of type II PBHs is newly constructed without limiting the PBH formation period. The double inflationary power spectrum is assumed to be of double simple power law which are smoothly connected. Under the assumed power spectrum, the accumulation of small PBHs formed at later times is important and the mass range is significantly broadened for both types. The PBH mass spectra are far smoother than the observed MACHO spectrum due to our assumption of a smooth spectrum. In order to fit the observation, a more spiky spectrum is required.
NASA Astrophysics Data System (ADS)
Das, Suratna; Lochan, Kinjalk; Sahu, Satyabrata; Singh, T. P.
2013-10-01
The inflationary paradigm provides a mechanism to generate the primordial perturbations needed to explain the observed large-scale structures in the Universe. Inflation traces back all the inhomogeneities to quantum fluctuations although the structures look classical today. The squeezing of primordial quantum fluctuations along with the mechanism of decoherence accounts for many aspects of this quantum-to-classical transition, although it remains a matter of debate as to whether this is sufficient to explain the issue of the realization of a single outcome (i.e. the issue of macro-objectification) from a quantum ensemble given that the Universe is a closed system. A similar question of the emergence of classical behavior of macroscopic objects exists also for laboratory systems and apart from decoherence there have been attempts to resolve this issue through continuous spontaneous localization (CSL), which is a stochastic nonlinear modification of the nonrelativistic Schrödinger equation. Recently, Martin et al. have investigated whether a CSL-like mechanism with a constant strength parameter—when the Mukhanov-Sasaki variable is taken as the “collapse operator”—can explain how the primordial quantum perturbations generated during inflation become classical. Within the scope of their assumptions they essentially come to a negative conclusion. In the present work, we generalize their analysis by allowing the CSL strength parameter to depend on physical scales so as to capture the CSL amplification mechanism. We show that such a generalization provides a mechanism for the macro-objectification (i.e. classicalization) of the inflationary quantum perturbations, while also preserving the scale invariance of the power spectrum and the phase coherence of superhorizon perturbation modes in a particular class of these models.
NASA Astrophysics Data System (ADS)
Subedi, Pradeep; Wen, Bo; Bo, Lin; Sarachik, Myriam; Yeshurun, Yosi; Kent, Andrew; Lampropoulos, Christos; Christou, George
2010-03-01
The longitudinal susceptibility of Mn12-acetate single crystals has been measured in a magnetic field applied transverse to the Ising axis using micro-Hall effect magnetometry in a He^3 cryostat with a 3D vector superconducting magnet. We have investigated the blocking temperature as a function of longitudinal-field-sweep-rate and as a function of the magnitude of the transverse field. We find that the transverse field accelerates the relaxation to equilibrium and lowers the blocking temperature, as expected based on the Mn12-ac spin-Hamiltonian and a classical model of single domain uniaxial nanomagnets. The susceptibility is found to obey a Curie-Weiss law, indicating a low temperature transition to a ferromagnetic phase due to dipolar interactions. We discuss these experiments as well as experiments in which an array of Hall-bars is used to spatially resolve the longitudinal susceptibility above the blocking temperature.
Mass spectroscopy of single aerosols from field measurements
Thomson, D.S.; Murphy, D.M.
1995-12-31
We are developing an aircraft instrument for the chemical analysis of individual ambient aerosols in real time. In order to test the laboratory version of this instrument, we participated in a field campaign near the continental divide in Colorado in September, 1993. During this campaign, over 5000 mass spectra of ambient aerosols were collected. Analysis of the negative ion spectra shows that sulfate was the most commonly seen component of smaller particles, while nitrate was more common in larger particles. Organic compounds are present in most particles, and we believe we can distinguish inorganic carbon in some particles. Although numerous distinct classes of particles were observed, indicating external mixtures, almost all of these particle types were themselves mixtures of several compounds. Finally, we note that although the field site experienced distinct polluted and unpolluted episodes, aerosol composition did not correlate with gas phase chemistry.
NASA Astrophysics Data System (ADS)
Beckwith, A. W.
2006-02-01
We review the results of a model of how nucleation of a new universe occurs, assuming a di quark identification for soliton-anti soliton constituent parts of a scalar field. Initially, we employ a false vacuum potential system; however, when cosmological expansion is dominated by the Einstein cosmological constant at the end of chaotic inflation, the initial di quark scalar field is not consistent w.r.t a semi classical consistency condition we analyze as the potential changes to the chaotic inflationary potential utilized by Guth~. We use Scherrer's derivation of a sound speed being zero during initial inflationary cosmology, and obtain a sound speed approaching unity ~as the slope of the scalar field moves away from a thin wall approximation. All this is to aid in a data reconstruction problem of how to account for the initial origins of CMB due to dark matter since effective field theories as presently constructed require a cut off value for applicability of their potential structure. This is often at the cost of, especially in early universe theoretical models, of clearly defined baryogenesis, and of a well defined mechanism of phase transitions.
NASA Astrophysics Data System (ADS)
Beckwith, Andrew
2006-04-01
We review the results of a model of how nucleation of a new universe occurs, assuming a di quark identification for soliton-anti soliton constituent parts of a scalar field. Initially, we employ a false vacuum potential system; however, when cosmological expansion is dominated by the Einstein cosmological constant at the end of chaotic inflation, the initial di quark scalar field is not consistent w.r.t a semi classical consistency condition we analyze as the potential changes to the chaotic inflationary potential utilized by Guth . We use Scherrer's derivation of a sound speed being zero during initial inflationary cosmology, and obtain a sound speed approaching unity as the slope of the scalar field moves away from a thin wall approximation. All this is to aid in a data reconstruction problem of how to account for the initial origins of CMB due to dark matter since effective field theories as presently constructed require a cut off value for applicability of their potential structure. This is often at the cost of, especially in early universe theoretical models, of clearly defined baryogenesis, and of a well defined mechanism of phase transitions.
Creation and recovery of a W(111) single atom gas field ion source
Pitters, Jason L.; Urban, Radovan; Wolkow, Robert A.
2012-04-21
Tungsten single atom tips have been prepared from a single crystal W(111) oriented wire using the chemical assisted field evaporation and etching method. Etching to a single atom tip occurs through a symmetric structure and leads to a predictable last atom unlike etching with polycrystalline tips. The single atom tip formation procedure is shown in an atom by atom removal process. Rebuilds of single atom tips occur on the same crystalline axis as the original tip such that ion emission emanates along a fixed direction for all tip rebuilds. This preparation method could be utilized and developed to prepare single atom tips for ion source development.
NASA Astrophysics Data System (ADS)
Rodriguez, Alvar; Singh, Simranjeet; Haque, Firoze; Del Barco, Enrique; Nguyen, Tu; Christou, George
2012-02-01
Dependence of magnetic field and electronic transport of Mn4 Single-molecule magnet in a Single-Electron Transistor A. Rodriguez, S. Singh, F. Haque and E. del Barco Department of Physics, University of Central Florida, 4000 Central Florida Blvd., Orlando, Florida 32816 USA T. Nguyen and G. Christou Department of Chemistry, University of Florida, Gainesville, Florida 32611 USA Abstract We have performed single-electron transport measurements on a series of Mn-based low-nuclearity single-molecule magnets (SMM) observing Coulomb blockade. SMMs with well isolated and low ground spin states, i.e. S = 9/2 (Mn4) and S = 6 (Mn3) were chosen for these studies, such that the ground spin multiplet does not mix with levels of other excited spin states for the magnetic fields (H = 0-8 T) employed in the experiments. Different functionalization groups were employed to change the mechanical, geometrical and transport characteristics of the molecules when deposited from liquid solution on the transistors. Electromigration-broken three-terminal single-electron transistors were used. Results obtained at temperatures down to 240 mK and in the presence of high magnetic fields will be shown.
BICEP2 implications for single-field slow-roll inflation revisited
Antusch, Stefan; Nolde, David E-mail: david.nolde@unibas.ch
2014-05-01
It is generally believed that in single-field slow-roll inflation, a large tensor-to-scalar ratio r > 0.1 requires inflaton field values close to or above the Planck scale. Recently, it has been claimed that r > 0.15 can be achieved with much smaller inflaton field values Δφ < M{sub Pl}/10. We show that in single-field slow-roll inflation, it is impossible to reconcile r > 0.1 with such small field values, independently of the form of the potential, and that the recent claim to the contrary is based on an invalid approximation. We conclude that the result of the BICEP2 measurement of r > 0.1, if confirmed, truly has the potential to rule out small-field models of single-field slow-roll inflation.
Near-field probes using double and single negative media.
Boybay, Muhammed S; Ramahi, Omar M
2009-01-01
Evanescent probe imaging is a powerful characterization technique with subwavelength resolution. In this paper, we present a theoretical and numerical study of the effect of using double negative (DNG) and single negative (SNG) metamaterials in evanescent probe imaging. A sensitivity definition is introduced for evanescent probes and it is shown using quantitative measures that the sensitivity can be increased using DNG material for a target in vacuum and for a buried target. A minimum DNG thickness is required to achieve an improvement in the sensitivity. For a buried target, there is a fundamental limitation on the maximum achievable sensitivity, in addition to a limitation due to the loss of DNG materials. SNG metamaterials have similar improvements over the sensitivity as the DNG materials but there are additional limitations due to the different transmission characteristics of SNG media. To validate the theoretical findings, numerical simulations are presented. PMID:19257155
Near-field-magnetic-tweezer manipulation of single DNA molecules.
Yan, Jie; Skoko, Dunja; Marko, John F
2004-07-01
We have developed an instrument for micromanipulation of single DNA molecules end labeled with 3-microm-diameter paramagnetic particles. A small, permanent magnet that can be moved as close as 10 microm to the particle being manipulated can generate forces in excess of 200 pN, significantly larger than obtained in other recent "magnetic-tweezer" studies. Our instrument generates these forces in the focal plane of a microscope objective, allowing straightforward real-time observation of molecule extension with a position resolution of approximately 30 nm. We show how our magnetic manipulation system can be combined with manipulation and force measurement using glass micropipettes to allow rapid switching between measurements in fixed-force and fixed-extension ensembles. We demonstrate the use of our system to study formation of DNA loops by an enzyme which strongly binds two copies of a specific 6-base-pair sequence. PMID:15324086
Modeling Intermittent Running from a Single-visit Field Test.
Galbraith, A; Hopker, J; Passfield, L
2015-05-01
This study assessed whether the distance-time relationship could be modeled to predict time to exhaustion (TTE) during intermittent running. 13 male distance runners (age: 33±14 years) completed a field test and 3 interval tests on an outdoor 400 m athletic track. Field-tests involved trials over 3 600 m, 2 400 m and 1 200 m with a 30-min rest between each run. Interval tests consisted of: 1 000 m at 107% of CS with 200 m at 95% CS; 600 m at 110% of CS with 200 m at 90% CS; 200 m at 150% of CS with 200 m at 80% CS. Interval sessions were separated by 24 h recovery. Field-test CS and D' were applied to linear and non-linear models to estimate the point of interval session termination. Actual and predicted TTE using the linear model were not significantly different in the 1 000 m and 600 m trials. Actual TTE was significantly lower (P=0.01) than predicted TTE in the 200 m trial. Typical error was high across the trials (range 334-1 709 s). The mean balance of D' remaining at interval session termination was significantly lower when estimated from the non-linear model (-21.2 vs. 13.4 m, P<0.01), however no closer to zero than the linear model. Neither the linear or non-linear model could closely predict TTE during intermittent running. PMID:25665002
Two-component wind fields from single scanning aerosol lidar
NASA Astrophysics Data System (ADS)
Mayor, Shane D.; Derian, Pierre; Mauzey, Christopher F.; Hamada, Masaki
2015-09-01
An overview of recent research results on the performance of two motion estimation algorithms used to deduce two-component horizontal wind fields from ground-based scanning elastic backscatter lidar is presented. One motion estimation algorithm is a traditional cross-correlation method optimized for atmospheric lidar data. The second algorithm is a recently-developed wavelet-based optical flow. An intercomparison of experimental results with measurements from an independent Doppler lidar over an agricultural area in Chico, California, during daytime convective conditions in 2013-14 are presented. Finally, early results from application of the algorithms to data collected over the ocean from a compact and portable aerosol lidar that was deployed on the northern California coast in March of 2015 are presented.
CMB and reheating constraints to α -attractor inflationary models
NASA Astrophysics Data System (ADS)
Eshaghi, Mehdi; Zarei, Moslem; Riazi, Nematollah; Kiasatpour, Ahmad
2016-06-01
After Planck 2013, a broad class of inflationary models called α -attractors was developed which has universal observational predictions. For small values of the parameter α , the models have good consistency with the recent cosmic microwave background data. In this work, we first calculate analytically (and verify numerically) the predictions of these models for spectral index, ns, and tensor-to-scalar ratio, r , and then, using BICEP2/Keck 2015 and Planck 2015 data, we impose constraints on α -attractors. Then, we study the reheating for α -attractors. The reheating temperature, Tre, and the number of e-folds during reheating, Nre, are calculated as functions of ns. Using these results, we determine the range of the free parameters of two classes of α -attractors which satisfy the constraints of recent cosmic microwave background data.
TOPICAL REVIEW: String cosmology versus standard and inflationary cosmology
NASA Astrophysics Data System (ADS)
Gasperini, M.
2000-06-01
This paper presents a review of the basic, model-independent differences between the pre-big-bang scenario, arising naturally in a string cosmology context, and the standard inflationary scenario. We use an unconventional approach in which the introduction of technical details is avoided as much as possible, trying to focus the reader's attention on the main conceptual aspects of both scenarios. The aim of the paper is not to conclude either in favour of one or other of the scenarios, but to raise questions that are left to the reader's meditation. Warning: the paper does not contain equations, and is not intended as a complete review of all aspects of string cosmology.
Testing and extending the inflationary consistency relation for tensor modes
NASA Astrophysics Data System (ADS)
Boyle, Latham; Smith, Kendrick M.; Dvorkin, Cora; Turok, Neil
2015-08-01
If observations confirm BICEP2's claim of a tensor-scalar ratio r ≈0.2 on CMB scales, then the inflationary consistency relation nt=-r /8 predicts a small negative value for the tensor spectral index nt. We show that future CMB polarization experiments should be able to confirm this prediction at several sigma. We also show how to properly extend the consistency relation to solar system scales, where the primordial gravitational wave density Ωgw could be measured by proposed experiments such as the Big Bang Observer. This would provide a far more stringent test of the consistency relation and access much more detailed information about the early Universe.
Loop quantum cosmology: from pre-inflationary dynamics to observations
NASA Astrophysics Data System (ADS)
Ashtekar, Abhay; Barrau, Aurélien
2015-12-01
The Planck collaboration has provided us rich information about the early Universe, and a host of new observational missions will soon shed further light on the ‘anomalies’ that appear to exist on the largest angular scales. From a quantum gravity perspective, it is natural to inquire if one can trace back the origin of such puzzling features to Planck scale physics. Loop quantum cosmology provides a promising avenue to explore this issue because of its natural resolution of the big bang singularity. Thanks to advances over the last decade, the theory has matured sufficiently to allow concrete calculations of the phenomenological consequences of its pre-inflationary dynamics. In this article we summarize the current status of the ensuing two-way dialog between quantum gravity and observations.
Probing the Inflationary Era with the POLARBEAR Experiment
NASA Astrophysics Data System (ADS)
Stebor, Nathan
2012-05-01
Observations of the Cosmic Microwave Background (CMB) have been instrumental in illuminating many of the fundamental properties of the universe and have ushered in widespread acceptance of a Standard Cosmological Model. Current lines of research focus on physics that is beyond this Standard Model, with particular interest given to experimental probes of the inflationary epoch. The inflationary paradigm predicts the existence of a primordial gravitational wave background that imprints a unique ‘B-mode’ signature onto the polarization of the CMB at large angular scales. This B-mode signal also encodes gravitational lensing information at smaller angular scales, which in turn carries information about large scale structure and may provide information about the properties of cosmological neutrinos. As of this writing, B-mode polarization anisotropy has not yet been measured, though it is expected to be orders of magnitude smaller than the CMB temperature anisotropy signal. This has motivated a new class of experiments that feature unprecedented sensitivity and precise control over systematic effects. The POLARBEAR experiment has been designed specifically to perform a deep search for polarization anisotropy in the CMB and to measure the signature of gravitational waves from inflation on large angular scales and to characterize lensing of the CMB on smaller scales. POLARBEAR is an off-axis 3.5 meter ground-based telescope operating at 150 GHz featuring an array of over 1000 antenna-coupled superconducting transition edge sensor (TES) bolometers cooled to 0.25 Kelvin. POLARBEAR is designed to reach a tensor-to-scalar ratio of 0.025 after two years of observation -- more than an order of magnitude improvement over the current best results, which would test physics at energies near the GUT scale. POLARBEAR achieved first light in January of 2012 and is currently observing in the Atacama Desert in Chile.
Magnetic field structure in single late-type giants: the effectively single giant V390 Aurigae
NASA Astrophysics Data System (ADS)
Konstantinova-Antova, R.; Aurière, M.; Petit, P.; Charbonnel, C.; Tsvetkova, S.; Lèbre, A.; Bogdanovski, R.
2012-05-01
Aims: We have studied the active giant V390 Aur using spectropolarimetry to obtain direct and simultaneous measurements of the magnetic field and the activity indicators to obtain a precise insight of its activity. Methods: We used the spectropolarimeter NARVAL at the Bernard Lyot Telescope (Observatoire du Pic du Midi, France) to obtain a series of Stokes I and Stokes V profiles. Using the least-squares deconvolution (LSD) technique we were able to detect the Zeeman signature of the magnetic field in each of our 13 observations and to measure its longitudinal component. Using the wide wavelength range of the spectra we were able to monitor the CaII K&H and IR triplet, as well as the Hα lines, which are activity indicators. To reconstruct the magnetic field geometry of V390 Aur on the basis of modelling the Stokes V profiles, we applied the Zeeman Doppler imaging (ZDI) inversion method and present a map for the magnetic field. Based on the obtained spectra, we also refined the fundamental parameters of the star and the Li abundance using MARCS model atmospheres. Results: The ZDI revealed a structure in the radial magnetic field consisting of a polar magnetic spot of positive polarity and several negative spots at lower latitude. A high latitude belt is present on the azimuthal field map, indicative of a toroidal field close to the surface. Similar features are observed in some RS CVn and FK Com -type stars. It was found that the photometric period cannot fit the behaviour of the activity indicators formed in the chromosphere. Their behaviour suggests slower rotation compared to the photosphere, but our dataset is too short for us to be able to estimate their exact periods. All these results can be explained in terms of an α - ω dynamo operation, taking into account the stellar structure and rotation properties of V390 Aur that we studied with up-to-date stellar models computed at solar metallicity with the code STAREVOL. The calculated Rossby number also points
Single-shot spatiotemporal measurements of high-field terahertz pulses
van Tilborg, Jeroen; Schroeder, Carl; Toth, Csaba; Geddes, Cameron; Esarey, Eric; Leemans, Wim
2011-06-17
The electric field profiles of broad-bandwidth coherent terahertz (THz) pulses, emitted by laser-wakefield-accelerated electron bunches, are studied. The near-single-cycle THz pulses are measured with two single-shot techniques in the temporal and spatial domains. Spectra of 0-6 THz and peak fields up to {approx_equal} 0.4 MV cm{sup -1} are observed. The measured field substructure demonstrates the manifestation of spatiotemporal coupling at focus, which affects the interpretation of THz radiation as a bunch diagnostic and in high-field pump-probe experiments.
Electric-field-assisted position and orientation control of organic single crystals.
Kotsuki, Kenji; Obata, Seiji; Saiki, Koichiro
2014-12-01
We have investigated the motion of growing pentacene single crystals in solution under various electric fields. The pentacene single crystals in 1,2,4-trichlorobenzene responded to the electric field as if they were positively charged. By optimizing the strength and frequency of an alternating electric field, the pentacene crystals automatically bridged the electrodes on SiO2. The pentacene crystal with a large aspect ratio tended to direct the [1̅10] orientation parallel to the conduction direction, which will be suitable from a viewpoint of anisotropy in mobility. The present result shows a possibility of controlling the position and orientation of organic single crystals by the use of an electric field, which leads to high throughput and low cost industrial manufacturing of the single crystal array from solution. PMID:25360544
Emerging Evidence from Single-Subject Research in the Field of Deaf-Blindness
ERIC Educational Resources Information Center
Parker, Amy T.; Davidson, Roseanna; Banda, Devender R.
2007-01-01
Professionals in the field of deaf-blindness are challenged to use instructional practices that have been tested using experimental methodology. Single-subject design has been examined as a form of research that assists in substantiating practice. In a review of the literature, the authors identified 54 single-subject studies from 1969 to 2006…
Wang, Shengqin; Zhu, Yingxi
2012-01-01
Effective manipulation and understanding of the structural and dynamic behaviors of a single polyelectrolyte (PE) under alternating current (AC) electric fields are of great scientific and technological importance because of its intimate relevance to emerging bionanotechnology. In this work, we employ fluorescence correlation spectroscopy (FCS) to study the conformational and AC-electrokinetic behaviors of a model annealed PE, poly(2-vinyl pyridine) (P2VP) under both spatially uniform and non-uniform AC fields at a single molecule level. Under spatially uniform AC-fields, we observe a gradual and continuous coil-to-globule conformational transition (CGT) of single P2VP at varied AC-frequency when a critical AC-field strength is exceeded, in contrast to the pH-induced abrupt CGT in the absence of AC-fields. On the contrary, under spatially non-uniform AC-fields, we observe field-driven net flow and accumulation of P2VP near high AC-field regions due to combined AC electro-osmosis and dielectrophoresis but surprisingly no conformational change. Thus, distinct AC-electric polarization effect on single annealed PE subject to AC-field homogeneity is suggested. PMID:22655024
NASA Astrophysics Data System (ADS)
Ballesteros, G.; Casas, J. A.; Espinosa, J. R.; Ruiz de Austri, R.; Trotta, R.
2008-03-01
We use cosmic microwave background (CMB) and large scale structure (LSS) data to test a broad and physically well-motivated class of inflationary models: those with flat tree-level potentials (typical in supersymmetry). The non-trivial features of the potential arise from radiative corrections which give a simple logarithmic dependence on the inflaton field, making the models very predictive. We also consider a modified scenario with new physics beyond a certain high energy cut-off showing up as non-renormalizable operators (NRO) in the inflaton field. We find that both kinds of models fit CMB and LSS data remarkably well, with very few free parameters. Besides, many of these models naturally predict a reasonable number of e-folds. A robust feature of these scenarios is the smallness of tensor perturbations (r \\lesssim 10^{-3} ). The NRO case can give a sizable running of the spectral index while achieving a sufficient number of e-folds. We use Bayesian model comparison tools to assess the relative performance of the models. We believe that these scenarios can be considered as a standard physical class of inflationary models, on a similar footing to monomial potentials.
Alterations of single molecule fluorescence lifetimes in near-field optical microscopy
Ambrose, W.P.; Goodwin, P.M.; Keller, R.A.; Martin, J.C. )
1994-07-15
Fluorescence lifetimes of single Rhodamine 6G molecules on silica surfaces were measured with pulsed laser excitation, time-correlated single photon counting, and near-field scanning optical microscopy (NSOM). The fluorescence lifetime varies with the position of a molecule relative to a near-field probe. Qualitative features of lifetime decreases are consistent with molecular excited state quenching effects near metal surfaces. The technique of NSOM provides a means of altering the environment of a single fluorescent molecule and its decay kinetics in a repeatable fashion.
Optical Field-Strength Polarization of Two-Mode Single-Photon States
ERIC Educational Resources Information Center
Linares, J.; Nistal, M. C.; Barral, D.; Moreno, V.
2010-01-01
We present a quantum analysis of two-mode single-photon states based on the probability distributions of the optical field strength (or position quadrature) in order to describe their quantum polarization characteristics, where polarization is understood as a significative confinement of the optical field-strength values on determined regions of…
Quantum teleportation of the angular spectrum of a single-photon field
Walborn, S. P.; Ether, D. S.; Matos Filho, R. L. de; Zagury, N.
2007-09-15
We propose a quantum teleportation scheme for the angular spectrum of a single-photon field, which allows for the transmission of a large amount of information. Our proposal also provides a method to tune the frequencies of spatially entangled fields, which is useful for interactions with stationary qubits.
Single Event Effects (SEE) for Power Metal-Oxide-Semiconductor Field-Effect Transistors (MOSFETs)
NASA Technical Reports Server (NTRS)
Lauenstein, Jean-Marie
2011-01-01
Single-event gate rupture (SEGR) continues to be a key failure mode in power MOSFETs. (1) SEGR is complex, making rate prediction difficult SEGR mechanism has two main components: (1) Oxide damage-- Reduces field required for rupture (2) Epilayer response -- Creates transient high field across the oxide.
Renema, J. J.; Rengelink, R. J.; Komen, I.; Wang, Q.; Kes, P.; Aarts, J.; Exter, M. P. van; Dood, M. J. A. de; Gaudio, R.; Hoog, K. P. M. op 't; Zhou, Z.; Fiore, A.; Sahin, D.; Driessen, E. F. C.
2015-03-02
We experimentally investigate the effect of a magnetic field on photon detection in superconducting single-photon detectors (SSPDs). At low fields, the effect of a magnetic field is through the direct modification of the quasiparticle density of states of the superconductor, and magnetic field and bias current are interchangeable, as is expected for homogeneous dirty-limit superconductors. At the field where a first vortex enters the detector, the effect of the magnetic field is reduced, up until the point where the critical current of the detector starts to be determined by flux flow. From this field on, increasing the magnetic field does not alter the detection of photons anymore, whereas it does still change the rate of dark counts. This result points at an intrinsic difference in dark and photon counts, and also shows that no enhancement of the intrinsic detection efficiency of a straight SSPD wire is achievable in a magnetic field.
NASA Astrophysics Data System (ADS)
Jamonneau, P.; Lesik, M.; Tetienne, J. P.; Alvizu, I.; Mayer, L.; Dréau, A.; Kosen, S.; Roch, J.-F.; Pezzagna, S.; Meijer, J.; Teraji, T.; Kubo, Y.; Bertet, P.; Maze, J. R.; Jacques, V.
2016-01-01
We analyze the impact of electric field and magnetic field fluctuations in the decoherence of the electronic spin associated with a single nitrogen-vacancy (NV) defect in diamond. To this end, we tune the amplitude of a magnetic field in order to engineer spin eigenstates protected either against magnetic noise or against electric noise. The competition between these noise sources is analyzed quantitatively by changing their relative strength through modifications of the host diamond material. This study provides significant insights into the decoherence of the NV electronic spin, which is valuable for quantum metrology and sensing applications.
NASA Astrophysics Data System (ADS)
Santra, Tuhin Subhra; Wang, Pen-Cheng; Chang, Hwan-You; Tseng, Fan-Gang
2013-12-01
Interaction of electric field with biological cells is an important phenomenon for field induced drug delivery system. We demonstrate a selective and localized single cell nano-electroporation (LSCNEP) by applying an intense electric field on a submicron region of the single cell membrane, which can effectively allow high efficient molecular delivery but low cell damage. The delivery rate is controlled by adjusting transmembrane potential and manipulating membrane status. Thermal and ionic influences are deteriorated from the cell membrane by dielectric passivation. Either reversible or irreversible by LSCNEP can fully controlled with potential applications in medical diagnostics and biological studies.
Simple Single-Shot Field Reconstruction on the 10 micro-Gauss Level
NASA Astrophysics Data System (ADS)
Pazmino, Arturo; Krinner, Ludwig; Stewart, Michael; Schneble, Dominik
2016-05-01
Accurate knowledge of the magnetic field is imperative in many physical systems for the determination of their energies and timescales. In ultracold atomic clouds, precise control of magnetic-field induced Zeeman splittings of hyperfine transitions can be challenging due to spatially constricted geometries subject to slowly drifting, spatially inhomogeneous fields. Here we present a technical note on the precise reconstruction of magnetic fields, on the ~ 10 μ G level, at the position of a trapped atomic cloud, using only atomic population to determine the magnetic field in a single-shot measurement. Work supported by NSF Grant No. PHY-1205894.
Response of single cell with acute angle exposed to an external electric field.
Sarbazvatan, Saber; Sardari, Dariush; Taheri, Nahid; Sepanloo, Kamran
2015-10-01
It is known that the electric field incurs effects on the living cells. Predicting the response of single cell or multilayer cells to induced alternative or static eclectic field has permanently been a challenge. In the present study a first order single cell with acute angle under the influence of external electric field is considered. The cell division stage or the special condition of reshaping is modelled with a cone being connected. In the case of cell divisions, anaphase, it can be considered with two cones that connected nose-to-nose. Each cone consists of two regions. The first is the membrane modelled with a superficial layer, and the second is cytoplasm at the core. A Laplace equation is written for this model and the distribution of its electric field is a sharp point in the single cell for which an acute angle model is calculated. PMID:26307458
Addou, Touria; Krouchev, Nedialko I; Kalaska, John F
2015-01-15
To elucidate how primary motor cortex (M1) neurons contribute to the performance of a broad range of different and even incompatible motor skills, we trained two monkeys to perform single-degree-of-freedom elbow flexion/extension movements that could be perturbed by a variety of externally generated force fields. Fields were presented in a pseudorandom sequence of trial blocks. Different computer monitor background colors signaled the nature of the force field throughout each block. There were five different force fields: null field without perturbing torque, assistive and resistive viscous fields proportional to velocity, a resistive elastic force field proportional to position and a resistive viscoelastic field that was the linear combination of the resistive viscous and elastic force fields. After the monkeys were extensively trained in the five field conditions, neural recordings were subsequently made in M1 contralateral to the trained arm. Many caudal M1 neurons altered their activity systematically across most or all of the force fields in a manner that was appropriate to contribute to the compensation for each of the fields. The net activity of the entire sample population likewise provided a predictive signal about the differences in the time course of the external forces encountered during the movements across all force conditions. The neurons showed a broad range of sensitivities to the different fields, and there was little evidence of a modular structure by which subsets of M1 neurons were preferentially activated during movements in specific fields or combinations of fields. PMID:25339714
Simple inflationary models in Gauss–Bonnet brane-world cosmology
NASA Astrophysics Data System (ADS)
Okada, Nobuchika; Okada, Satomi
2016-06-01
In light of the recent Planck 2015 results for the measurement of the cosmic microwave background (CMB) anisotropy, we study simple inflationary models in the context of the Gauss–Bonnet (GB) brane-world cosmology. The brane-world cosmological effect modifies the power spectra of scalar and tensor perturbations generated by inflation and causes a dramatic change for the inflationary predictions of the spectral index (n s) and the tensor-to-scalar ratio (r) from those obtained in the standard cosmology. In particular, the predicted r values in the inflationary models favored by the Planck 2015 results are suppressed due to the GB brane-world cosmological effect, which is in sharp contrast with inflationary scenario in the Randall–Sundrum brane-world cosmology, where the r values are enhanced. Hence, these two brane-world cosmological scenarios are distinguishable. With the dramatic change of the inflationary predictions, the inflationary scenario in the GB brane-world cosmology can be tested by more precise measurements of n s and future observations of the CMB B-mode polarization.
Improved field emission stability from single-walled carbon nanotubes chemically attached to silicon
2012-01-01
Here, we demonstrate the simple fabrication of a single-walled carbon nanotube (SWCNT) field emission electrode which shows excellent field emission characteristics and remarkable field emission stability without requiring posttreatment. Chemically functionalized SWCNTs were chemically attached to a silicon substrate. The chemical attachment led to vertical alignment of SWCNTs on the surface. Field emission sweeps and Fowler-Nordheim plots showed that the Si-SWCNT electrodes field emit with a low turn-on electric field of 1.5 V μm−1 and high electric field enhancement factor of 3,965. The Si-SWCNT electrodes were shown to maintain a current density of >740 μA cm−2 for 15 h with negligible change in applied voltage. The results indicate that adhesion strength between the SWCNTs and substrate is a much greater factor in field emission stability than previously reported. PMID:22853557
Dark radiation and inflationary freedom after Planck 2015
NASA Astrophysics Data System (ADS)
Di Valentino, Eleonora; Gariazzo, Stefano; Gerbino, Martina; Giusarma, Elena; Mena, Olga
2016-04-01
The simplest inflationary models predict a primordial power spectrum (PPS) of the curvature fluctuations that can be described by a power-law function that is nearly scale invariant. It has been shown, however, that the low-multipole spectrum of the cosmic microwave background anisotropies may hint at the presence of some features in the shape of the scalar PPS, which could deviate from its canonical power-law form. We study the possible degeneracies of this nonstandard PPS with the active neutrino masses, the effective number of relativistic species, and a sterile neutrino or a thermal axion mass. The limits on these additional parameters are less constraining in a model with a nonstandard PPS when including only the temperature autocorrelation spectrum measurements in the data analyses. The inclusion of the polarization spectra noticeably helps in reducing the degeneracies, leading to results that typically show no deviation from the Λ CDM model with a standard power-law PPS. These findings are robust against changes in the function describing the noncanonical PPS. Albeit current cosmological measurements seem to prefer the simple power-law PPS description, the statistical significance to rule out other possible parametrizations is still very poor. Future cosmological measurements are crucial to improve the present PPS uncertainties.
Bayesian analysis of inflationary features in Planck and SDSS data
NASA Astrophysics Data System (ADS)
Benetti, Micol; Alcaniz, Jailson S.
2016-07-01
We perform a Bayesian analysis to study possible features in the primordial inflationary power spectrum of scalar perturbations. In particular, we analyze the possibility of detecting the imprint of these primordial features in the anisotropy temperature power spectrum of the cosmic microwave background (CMB) and also in the matter power spectrum P (k ) . We use the most recent CMB data provided by the Planck Collaboration and P (k ) measurements from the 11th data release of the Sloan Digital Sky Survey. We focus our analysis on a class of potentials whose features are localized at different intervals of angular scales, corresponding to multipoles in the ranges 10 <ℓ<60 (Oscill-1) and 150 <ℓ<300 (Oscill-2). Our results show that one of the step potentials (Oscill-1) provides a better fit to the CMB data than does the featureless Λ CDM scenario, with moderate Bayesian evidence in favor of the former. Adding the P (k ) data to the analysis weakens the evidence of the Oscill-1 potential relative to the standard model and strengthens the evidence of this latter scenario with respect to the Oscill-2 model.
Inflationary cosmology leading to a soft type singularity
NASA Astrophysics Data System (ADS)
Brevik, I.; Obukhov, V. V.; Timoshkin, A. V.
2016-06-01
A remarkable property of modern cosmology is that it allows for a special case of symmetry, consisting in the possibility of describing the early-time acceleration (inflation) and the late-time acceleration using the same theoretical framework. In this paper, we consider various cosmological models corresponding to a generalized form for the equation of state for the fluid in a flat Friedmann-Robertson-Walker (FRW) universe, emphasizing cases where the so-called type IV singular inflation is encountered in the future. This is a soft (non-crushing) kind of singularity. Parameter values for an inhomogeneous equation of state leading to singular inflation are obtained. We present models for which there are two type IV singularities, the first corresponding to the end of the inflationary era and the second to a late-time event. We also study the correspondence between the theoretical slow-roll parameters leading to type IV singular inflation and the recent results observed by the Planck satellite.
Basics of quantum field theory of electromagnetic interaction processes in single-layer graphene
NASA Astrophysics Data System (ADS)
Hieu Nguyen, Van
2016-09-01
The content of this work is the study of electromagnetic interaction in single-layer graphene by means of the perturbation theory. The interaction of electromagnetic field with Dirac fermions in single-layer graphene has a peculiarity: Dirac fermions in graphene interact not only with the electromagnetic wave propagating within the graphene sheet, but also with electromagnetic field propagating from a location outside the graphene sheet and illuminating this sheet. The interaction Hamiltonian of the system comprising electromagnetic field and Dirac fermions fields contains the limits at graphene plane of electromagnetic field vector and scalar potentials which can be shortly called boundary electromagnetic field. The study of S-matrix requires knowing the limits at graphene plane of 2-point Green functions of electromagnetic field which also can be shortly called boundary 2-point Green functions of electromagnetic field. As the first example of the application of perturbation theory, the second order terms in the perturbative expansions of boundary 2-point Green functions of electromagnetic field as well as of 2-point Green functions of Dirac fermion fields are explicitly derived. Further extension of the application of perturbation theory is also discussed.
Determination of optimal ionic liquid for organic single-crystal field-effect transistors
NASA Astrophysics Data System (ADS)
Ono, S.; Miwa, K.; Seki, S.
2016-02-01
We investigate organic single-crystal field-effect transistors with various ionic liquids as gate dielectric. We find that the mobility of the field-effect transistors for both p-type and n-type organic semiconductors increases with decreasing total capacitance of the ionic liquid. However, it does not depend on the ion species at the interface between the organic semiconductor and the ionic liquid. By choosing an appropriate ionic liquid, a high carrier mobility of 12.4 cm2/V s in rubrene single crystals (p-type) and 0.13 cm2/V s in 7.7.8.8-Tetracyanoquinodimethane single crystals (n-type) are achieved. This study clarifies the influence of ionic liquids on the device performance of organic field-effect transistors and shows a way to maximize carrier mobility at the solid/liquid interface.
Non-Gaussianity in single field models without slow-roll conditions
NASA Astrophysics Data System (ADS)
Noller, Johannes; Magueijo, João
2011-05-01
We investigate non-Gaussianity in general single field models without assuming slow-roll conditions or the exact scale invariance of the scalar power spectrum. The models considered include general single field inflation (e.g. Dirac-Born-Infeld and canonical inflation) as well as bimetric models. We compute the full non-Gaussian amplitude A, its size fNL, its shape, and the running with scale nNG. In doing so we show that observational constraints allow significant violations of slow-roll conditions and we derive explicit bounds on slow-roll parameters for fast-roll single field scenarios. A variety of new observational signatures is found for models respecting these bounds. We also explicitly construct concrete model implementations giving rise to this new phenomenology.
Extended-field coverage hyperspectral camera based on a single-pixel technique.
Jin, Senlin; Hui, Wangwei; Liu, Bo; Ying, Cuifeng; Liu, Dongqi; Ye, Qing; Zhou, Wenyuan; Tian, Jianguo
2016-06-20
A spectral single-pixel imaging system facilitates effective image compression, but the imaging region is limited by its single detector. This paper presents a hyperspectral camera that allows extended-field coverage to be collected by one detector. Compressive data of a large field of view is achieved by our highly sensitive detection camera, which can be extended to near-infrared or infrared spectral monitoring. We acquire a hyperspectral datacube of 256×256 spatial pixels and 3 nm spectral resolution at a sampling rate of 25%. Finally, we apply our camera to monitoring fruit freshness nondestructively by differentiating a banana's ripeness over time. PMID:27409103
Scanner-Free and Wide-Field Endoscopic Imaging by Using a Single Multimode Optical Fiber
NASA Astrophysics Data System (ADS)
Choi, Youngwoon; Yoon, Changhyeong; Kim, Moonseok; Yang, Taeseok Daniel; Fang-Yen, Christopher; Dasari, Ramachandra R.; Lee, Kyoung Jin; Choi, Wonshik
2012-11-01
A single multimode fiber is considered an ideal optical element for endoscopic imaging due to the possibility of direct image transmission via multiple spatial modes. However, the wave distortion induced by the mode dispersion has been a fundamental limitation. In this Letter, we propose a method for eliminating the effect of mode dispersion and therefore realize wide-field endoscopic imaging by using only a single multimode fiber with no scanner attached to the fiber. Our method will potentially revolutionize endoscopy in various fields encompassing medicine and industry.
NASA Astrophysics Data System (ADS)
Kang, Myung-Gil; Ahn, Jae-Hyun; Lee, Jongwoon; Hwang, Dong-Hoon; Kim, Hee-Tae; Rieh, Jae-Seong; Whang, Dongmok; Son, Maeng-Ho; Ahn, Doyeol; Yu, Yun-Seop; Hwang, Sung-Woo
2010-06-01
Microwave (MW) characteristics of a field effect transistor (FET) incorporating a single silicon nanowire (SiNW) were obtained from S-parameter measurements in the frequency range of 0.05 to 20 GHz. The single SiNW was aligned, using the alternating current (ac) dielectrophoresis alignment method, between the drain and source electrode forming a coplanar waveguide (CPW) structure. Analysis of the FET was performed using equivalent circuit modeling by advanced device system (ADS) simulation. By fitting the measured data with the simulation results, the parameters of the single SiNW FET were obtained and the cutoff frequency was derived.
Gas field ion source current stability for trimer and single atom terminated W(111) tips
Urban, Radovan; Wolkow, Robert A.; Pitters, Jason L.
2012-06-25
Tungsten W(111) oriented trimer-terminated tips as well as single atom tips, fabricated by a gas and field assisted etching and evaporation process, were investigated with a view to scanning ion microscopy and ion beam writing applications. In particular, ion current stability was studied for helium and neon imaging gases. Large ion current fluctuations from individual atomic sites were observed when a trimer-terminated tip was used for the creation of neon ion beam. However, neon ion current was stable when a single atom tip was employed. No such current oscillations were observed for either a trimer or a single atom tip when imaged with helium.
Room-temperature single charge sensitivity in carbon nanotube field-effect transistors
NASA Astrophysics Data System (ADS)
Peng, H. B.; Hughes, M. E.; Golovchenko, J. A.
2006-12-01
Electrical current fluctuation studies are reported for coaxial p-type and n-type single-wall carbon nanotube field-effect transistors (FETs). Abrupt discrete switching of the source-drain current is observed at room temperature. The authors attribute these random telegraph signals to charge fluctuating electron traps near the FET conduction channels. Evolution of the current-switching behavior associated with the occupancy of individual electron traps is demonstrated and analyzed statistically. The result strongly indicates room temperature single charge sensitivity in carbon nanotube FETs, which may offer potential applications for single molecule sensors based on suitably prepared FET devices.
Longitudinal wave function control in single quantum dots with an applied magnetic field
Cao, Shuo; Tang, Jing; Gao, Yunan; Sun, Yue; Qiu, Kangsheng; Zhao, Yanhui; He, Min; Shi, Jin-An; Gu, Lin; Williams, David A.; Sheng, Weidong; Jin, Kuijuan; Xu, Xiulai
2015-01-01
Controlling single-particle wave functions in single semiconductor quantum dots is in demand to implement solid-state quantum information processing and spintronics. Normally, particle wave functions can be tuned transversely by an perpendicular magnetic field. We report a longitudinal wave function control in single quantum dots with a magnetic field. For a pure InAs quantum dot with a shape of pyramid or truncated pyramid, the hole wave function always occupies the base because of the less confinement at base, which induces a permanent dipole oriented from base to apex. With applying magnetic field along the base-apex direction, the hole wave function shrinks in the base plane. Because of the linear changing of the confinement for hole wave function from base to apex, the center of effective mass moves up during shrinking process. Due to the uniform confine potential for electrons, the center of effective mass of electrons does not move much, which results in a permanent dipole moment change and an inverted electron-hole alignment along the magnetic field direction. Manipulating the wave function longitudinally not only provides an alternative way to control the charge distribution with magnetic field but also a new method to tune electron-hole interaction in single quantum dots. PMID:25624018