Browsing by Subject "PHASE-TRANSITION"

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  • Enqvist, Kari; Hardwick, Robert J.; Tenkanen, Tommi; Vennin, Vincent; Wands, David (2018)
    We show that in the Feebly Interacting Massive Particle (FIMP) model of Dark Matter (DM), one may express the inflationary energy scale H-* as a function of three otherwise unrelated quantities, the DM isocurvature perturbation amplitude, its mass and its self-coupling constant, independently of the tensor-to-scalar ratio. The FIMP model assumes that there exists a real scalar particle that alone constitutes the DM content of the Universe and couples to the Standard Model via a Higgs portal. We consider carefully the various astrophysical, cosmological and model constraints, accounting also for variations in inflationary dynamics and the reheating history, to derive a robust estimate for H-* that is con fined to a relatively narrow range. We point out that, within the context of the FIMP DM model, one may thus determine H-* reliably even in the absence of observable tensor perturbations.
  • Sharygin, Victor V.; Kamenetsky, Vadim S.; Zhitova, Liudmila M.; Belousov, Alexander B.; Abersteiner, Adam (2018)
    Cu-rich magnesioferrite was found in vesicular basaltic trachyandesite in one of lava tubes (Duplex) that formed during the 2012-2013 eruption of the Tolbachik volcano, Kamchatka. This mineral is commonly associated with hematite, tenorite, halite, sylvite, and Ca-rich silicates (mainly, esseneite and Na-rich melilite) in high-temperature (800-1000 degrees C) reactionary zones (up to 100 mu m) covering vesicular rocks and lava stalactites in the Duplex tube. The mineral relationships of this assemblage indicate the following crystallization sequence: Ca-rich silicates + hematite -> Cu-rich magnesioferrite -> tenorite -> chlorides. This formed due to the reaction of hot gases containing Cu, alkalis, and Cl with solidified lava rock. The composition of magnesioferrite varies strongly in CuO (5.8-17.3 wt %; cuprospinel end-member-15-47 mol %), whereas the contents of other oxides are minor, indicating the main isomorphic substitution is Mg2+ Cu2+. Compositions with maximal CuO content nominally belong to Mg-rich cuprospinel: (Cu0.48Mg0.41Mn0.09Zn0.02Ca0.02) (Fe1.943+Al0.03Ti0.02)O-4. Increasing CuO content of the Duplex Cu-rich magnesioferrite is reflected in Raman spectra by moderate right shifting bands at approximate to 700-710 and 200-210 cm(-1) and the appearance of an additional band at 596 cm(-1). This supports the main isomorphic scheme and may indicate a degree of inversion in the spinel structure.
  • Keus, Venus; Tuominen, Kimmo (2021)
    We study models with several SU(2) scalar doublets where the inert doublets have a nonminimal coupling to gravity and play the role of the inflaton. We allow for this coupling to be complex, thereby introducing CP violation-a necessary source of the baryon asymmetry-in the Higgs-inflaton couplings. We investigate the inflationary dynamics of the model and discuss how the CP violation of the model is imprinted on the particle asymmetries after inflation in the hot big bang universe.
  • Cline, James M.; Kainulainen, Kimmo; Tucker-Smith, David (2017)
    Adding an extra singlet scalar S to the Higgs sector can provide a barrier at tree level between a false vacuum with restored electroweak symmetry and the true one. This has been demonstrated to readily give a strong phase transition as required for electroweak baryogenesis. We show that with the addition of a fermionic dark matter particle chi coupling to S, a simple UV-complete model can realize successful electroweak baryogenesis. The dark matter gets a CP asymmetry that is transferred to the standard model through a CP portal interaction, which we take to be a coupling of chi to tau leptons and an inert Higgs doublet. The CP asymmetry induced in left-handed tau leptons biases sphalerons to produce the baryon asymmetry. The model has promising discovery potential at the LHC, while robustly providing a large enough baryon asymmetry and correct dark matter relic density with reasonable values of the couplings.
  • Marwah, Megha; Magarkar, Aniket; Ray, Debes; Aswal, Vinod; Bunker, Alex; Nagarsenker, Mangal (2018)
    Glyceryl monostearate (GMS) is a single-tailed lipidic monoglyceride commonly used as a nontoxic food additive. In this study, we have investigated GMS, specifically its self-assembling properties and subsequent application in drug delivery. Results from in silico modeling, corroborated by complementary small-angle neutron scattering, demonstrated vesicle formation; associated phase transitions were analyzed using differential scanning calorimetry; dynamic light scattering revealed particle size alterations that occurred in the transition region. Spherical morphology of unilamellar vesicles was visualized using transmission electron microscopy imaging. Further, hydrophilic and hydrophobic drug loading in GMS vesicles and their amenability to surface modification for hepatic targeting have, in this study, been both predicted through molecular simulation study and demonstrated experimentally. The influence of hepatotropic ligands on the stability of drug-loaded GMS vesicles vis-a-vis cholesterol has also been investigated; the resulting GMS-based drug delivery vehicle, its properties enhanced through surface decoration, is envisaged to achieve targeted delivery of its payload to hepatocytes.
  • Enckell, Vera-Maria; Enqvist, Kari; Räsänen, Syksy; Tomberg, Eemeli (2018)
    We study inflation with the non-minimally coupled Standard Model Higgs in the case when quantum corrections generate a hilltop in the potential. We consider both the metric and the Palatini formulation of general relativity. We investigate hilltop inflation in different parts of the Higgs potential and calculate predictions for CMB observables. We run the renormalization group equations up from the electroweak scale and down from the hilltop, adding a jump in-between to account for unknown corrections in the intermediate regime. Within our approximation, no viable hilltop inflation is possible for small field values, where the non-minimal coupling has no role, nor for intermediate field values. For large field values, hilltop inflation works. We find the spectral index to be n(s)
  • Räsänen, Syksy; Wahlman, Pyry (2017)
    We compare Higgs inflation in the metric and Palatini formulations of general relativity, with loop corrections treated in a simple approximation. We consider Higgs inflation on the plateau, at a critical point, at a hilltop and in a false vacuum. In the last case there are only minor differences. Otherwise we find that in the Palatini formulation the tensor-to-scalar ratio is consistently suppressed, spanning the range 1 x 10-(13) <r <7 x 10(-5), compared to the metric case result 2 x 10(-5) <r <0.2. Even when the values of n(s) and r overlap, the running and running of the running are different in the two formulations. Therefore, if Higgs is the inflaton, inflationary observables can be used to distinguish between different gravitational degrees of freedom, in this case to determine whether the connection is an independent variable. Non-detection of r in foreseeable future observations would not rule out Higgs inflation, only its metric variant. We conclude that in order to fix the theory of Higgs inflation, not only the particle physics UV completion but also the gravitational degrees of freedom have to be explicated.
  • Markkanen, Tommi; Rasanen, Syksy; Wahlman, Pyry (2015)
    It is sometimes argued that observation of tensor modes from inflation would provide the first evidence for quantum gravity. However, in the usual inflationary formalism, also the scalar modes involve quantized metric perturbations. We consider the issue in a semiclassical setup in which only matter is quantized, and spacetime is classical. We assume that the state collapses on a spacelike hypersurface and find that the spectrum of scalar perturbations depends on the hypersurface. For reasonable choices, we can recover the usual inflationary predictions for scalar perturbations in minimally coupled single-field models. In models where nonminimal coupling to gravity is important and the field value is sub-Planckian, we do not get a nearly scale-invariant spectrum of scalar perturbations. As gravitational waves are only produced at second order, the tensor-to-scalar ratio is negligible. We conclude that detection of inflationary gravitational waves would indeed be needed to have observational evidence of quantization of gravity.
  • Mahmoudzadeh, Mohammad; Magarkar, Aniket; Koivuniemi, Artturi; Róg, Tomasz; Bunker, Alex (2021)
    Liposome-based drug delivery systems composed of DOPE stabilized with cholesteryl hemisuccinate (CHMS) have been proposed as a drug delivery mechanism with pH-triggered release as the anionic form (CHSa) is protonated (CHS) at reduced pH; PEGylation is known to decrease this pH sensitivity. In this manuscript, we set out to use molecular dynamics (MD) simulations with a model with all-atom resolution to provide insight into why incorporation of poly(ethyleneglycol) (PEG) into DOPE–CHMS liposomes reduces their pH sensitivity; we also address two additional questions: (1) How CHSa stabilizes DOPE bilayers into a lamellar conformation at a physiological pH of 7.4? and (2) how the change from CHSa to CHS at acidic pH triggers the destabilization of DOPE bilayers? We found that (A) CHSa stabilizes the DOPE lipid membrane by increasing the hydrophilicity of the bilayer surface, (B) when CHSa changes to CHS by pH reduction, DOPE bilayers are destabilized due to a reduction in bilayer hydrophilicity and a reduction in the area per lipid, and (C) PEG stabilizes DOPE bilayers into the lamellar phase, thus reducing the pH sensitivity of the liposomes by increasing the area per lipid through penetration into the bilayer, which is our main focus.
  • De Romeri, Valentina; Karamitros, Dimitrios; Lebedev, Oleg; Toma, Takashi (2020)
    Sterile neutrinos are one of the leading dark matter candidates. Their masses may originate from a vacuum expectation value of a scalar field. If the sterile neutrino couplings are very small and their direct coupling to the inflaton is forbidden by the lepton number symmetry, the leading dark matter production mechanism is the freeze-in scenario. We study this possibility in the neutrino mass range up to 1 GeV, taking into account relativistic production rates based on the Bose-Einstein statistics, thermal masses and phase transition effects. The specifics of the production mechanism and the dominant mode depend on the relation between the scalar and sterile neutrino masses as well as on whether or not the scalar is thermalized. We find that the observed dark matter abundance can be produced in all of the cases considered. We also revisit the freeze-in production of a Higgs portal scalar, pointing out the importance of a fusion mode, as well as the thermalization constraints.
  • Figueroa, Daniel G.; Raatikainen, Sami; Räsänen, Syksy; Tomberg, Eemeli (2021)
    We consider quantum diffusion in ultraslow-roll (USR) inflation. Using the Delta N formalism, we present the first stochastic calculation of the probability distribution P(R) of the curvature perturbation during USR. We capture the nonlinearity of the system, solving the coupled evolution of the coarse-grained background with random kicks from the short wavelength modes, simultaneously with the mode evolution around the stochastic background. This leads to a non-Markovian process from which we determine the highly non-Gaussian tail of P(R). Studying the production of primordial black holes in a viable model, we find that stochastic effects during USR increase their abundance by a factor of similar to 10(5) compared with the Gaussian approximation.
  • Planck Collaboration; Akrami, Y.; Keihanen, E.; Kiiveri, K.; Kurki-Suonio, H.; Lindholm, V.; Savelainen, M.; Suur-Uski, A. -S.; Valiviita, J. (2020)
    We report on the implications for cosmic inflation of the 2018 release of the Planck cosmic microwave background (CMB) anisotropy measurements. The results are fully consistent with those reported using the data from the two previous Planck cosmological releases, but have smaller uncertainties thanks to improvements in the characterization of polarization at low and high multipoles. Planck temperature, polarization, and lensing data determine the spectral index of scalar perturbations to be n(s)=0.9649 +/- 0.0042 at 68% CL. We find no evidence for a scale dependence of n(s), either as a running or as a running of the running. The Universe is found to be consistent with spatial flatness with a precision of 0.4% at 95% CL by combining Planck with a compilation of baryon acoustic oscillation data. The Planck 95% CL upper limit on the tensor-to-scalar ratio, r(0.002)<0.10, is further tightened by combining with the BICEP2/Keck Array BK15 data to obtain r(0.002)<0.056. In the framework of standard single-field inflationary models with Einstein gravity, these results imply that: (a) the predictions of slow-roll models with a concave potential, V(phi) <0, are increasingly favoured by the data; and (b) based on two different methods for reconstructing the inflaton potential, we find no evidence for dynamics beyond slow roll. Three different methods for the non-parametric reconstruction of the primordial power spectrum consistently confirm a pure power law in the range of comoving scales 0.005 Mpc(-1)k less than or similar to 0.2 Mpc(-1). A complementary analysis also finds no evidence for theoretically motivated parameterized features in the Planck power spectra. For the case of oscillatory features that are logarithmic or linear in k, this result is further strengthened by a new combined analysis including the Planck bispectrum data. The new Planck polarization data provide a stringent test of the adiabaticity of the initial conditions for the cosmological fluctuations. In correlated, mixed adiabatic and isocurvature models, the non-adiabatic contribution to the observed CMB temperature variance is constrained to 1.3%, 1.7%, and 1.7% at 95% CL for cold dark matter, neutrino density, and neutrino velocity, respectively. Planck power spectra plus lensing set constraints on the amplitude of compensated cold dark matter-baryon isocurvature perturbations that are consistent with current complementary measurements. The polarization data also provide improved constraints on inflationary models that predict a small statistically anisotropic quadupolar modulation of the primordial fluctuations. However, the polarization data do not support physical models for a scale-dependent dipolar modulation. All these findings support the key predictions of the standard single-field inflationary models, which will be further tested by future cosmological observations.
  • Bennett, Ed; Hong, Deog Ki; Lee, Jong-Wan; Lin, C.-J. David; Lucini, Biagio; Mesiti, Michele; Piai, Maurizio; Rantaharju, Jarno; Vadacchino, Davide (2020)
    We perform lattice studies of meson mass spectra and decay constants of the Sp(4) gauge theory in the quenched approximation. We consider two species of (Dirac) fermions as matter field content, transforming in the 2-index antisymmetric and the fundamental representation of the gauge group, respectively. All matter fields are formulated as Wilson fermions. We extrapolate to the continuum and massless limits and compare to each other the results obtained for the two species of mesons. In the case of two fundamental and three antisymmetric fermions, the long-distance dynamics is relevant for composite Higgs models. This is the first lattice study of this class of theories. The global SU(4)×SU(6) symmetry is broken to the Sp(4)×SO(6) subgroup, and the condensates align with the explicit mass terms present in the lattice formulation of the theory. The main results of our quenched calculations are that, with fermions in the 2-index antisymmetric representation of the group, the masses squared and decay constant squared of all the mesons we considered are larger than the corresponding quantities for the fundamental representation, by factors that vary between ∼1.2 and ∼2.7. We also present technical results that will be useful for future lattice investigations of dynamical simulations, of composite chimera baryons, and of the approach to large N in the Sp(2N) theories considered. We briefly discuss their high-temperature behavior, where symmetry restoration and enhancement are expected.
  • Fowler, Michael; Duhamel, Jean; Qiu, Xing Ping; Korchagina, Evgeniya; Winnik, Francoise M. (2018)
    Aqueous solutions of a series of monodisperse poly(N-isopropylacrylamide)s end-labeled with n-butyl-1-pyrene at one or both chain ends (Py-n-PNIPAMs with n=1 or 2) were studied by turbidimetry, light scattering, and fluorescence. For a given polymer concentration and heating rate, the cloud point (T-c) of an aqueous Py-n-PNIPAM solution, determined by turbidimetry, was found to increase with the number-average molecular weight (M-n) of the polymer. The steady-state fluorescence spectra and time-resolved fluorescence decays of Py-n-PNIPAM aqueous solutions were analyzed and all parameters retrieved from these analyses were found to be affected as the solution temperature passed through T-c, the solution cloud point, and T-m, the temperature where dehydration of PNIPAM occurred. The trends obtained by fluorescence to characterize the aqueous Py-n-PNIPAM solutions as a function of temperature were found to be consistent with the model proposed for telechelic PNIPAM by Koga et al. in 2006. (c) 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2018, 56, 308-318
  • Semenyuk, Pavel I.; Kurochkina, Lidia P.; Mäkinen, Lauri; Muronetz, Vladimir I.; Hietala, Sami (2021)
    A prospective technology for reversible enzyme complexation accompanied with its inactivation and protection followed by reactivation after a fast thermocontrolled release has been demonstrated. A thermoresponsive polymer with upper critical solution temperature, poly(N-acryloyl glycinamide) (PNAGA), which is soluble in water at elevated temperatures but phase separates at low temperatures, has been shown to bind lysozyme, chosen as a model enzyme, at a low temperature (10 & DEG;C and lower) but not at room temperature (around 25 & DEG;C). The cooling of the mixture of PNAGA and lysozyme solutions from room temperature resulted in the capturing of the protein and the formation of stable complexes; heating it back up was accompanied by dissolving the complexes and the release of the bound lysozyme. Captured by the polymer, lysozyme was inactive, but a temperature-mediated release from the complexes was accompanied by its reactivation. Complexation also partially protected lysozyme from proteolytic degradation by proteinase K, which is useful for biotechnological applications. The obtained results are relevant for important medicinal tasks associated with drug delivery such as the delivery and controlled release of enzyme-based drugs.
  • Sesana, Alberto; Korsakova, Natalia; Sedda, Manuel Arca; Baibhav, Vishal; Barausse, Enrico; Barke, Simon; Berti, Emanuele; Bonetti, Matteo; Capelo, Pedro R.; Caprini, Chiara; Garcia-Bellido, Juan; Haiman, Zoltan; Jani, Karan; Jennrich, Oliver; Johansson, Peter H.; Khan, Fazeel Mahmood; Korol, Valeriya; Lamberts, Astrid; Lupi, Alessandro; Mangiagli, Alberto; Mayer, Lucio; Nardini, Germano; Pacucci, Fabio; Petiteau, Antoine; Raccanelli, Alvise; Rajendran, Surjeet; Regan, John; Shao, Lijing; Spallicci, Alessandro; Tamanini, Nicola; Volonteri, Marta; Warburton, Niels; Wong, Kaze; Zumalacarregui, Miguel (2021)
    We propose a space-based interferometer surveying the gravitational wave (GW) sky in the milli-Hz to mu-Hz frequency range. By the 2040s, the mu-Hz frequency band, bracketed in between the Laser Interferometer Space Antenna (LISA) and pulsar timing arrays, will constitute the largest gap in the coverage of the astrophysically relevant GW spectrum. Yet many outstanding questions related to astrophysics and cosmology are best answered by GW observations in this band. We show that a mu-Hz GW detector will be a truly overarching observatory for the scientific community at large, greatly extending the potential of LISA. Conceived to detect massive black hole binaries from their early inspiral with high signal-to-noise ratio, and low-frequency stellar binaries in the Galaxy, this instrument will be a cornerstone for multimessenger astronomy from the solar neighbourhood to the high-redshift Universe.