Time filter

Source Type

Farneti R.,International Center for Theoretical Physics | Vallis G.K.,Princeton University
Journal of Climate | Year: 2013

The variability and compensation of the meridional energy transport in the atmosphere and ocean are examined with the state-of-the-art GFDL Climate Model, version 2.1 (CM2.1), and the GFDL Intermediate Complexity Coupled Model (ICCM). On decadal time scales, a high degree of compensation between the energy transport in the atmosphere (AHT) and ocean (OHT) is found in the North Atlantic. The variability of the total or planetary heat transport (PHT) is much smaller than the variability in either AHT or OHT alone, a feature referred to as "Bjerknes compensation." Natural decadal variability stems from the Atlantic meridional overturning circulation (AMOC), which leadsOHTvariability. The PHT is positively correlated with the OHT, implying that the atmosphere is compensating, but imperfectly, for variations in ocean transport. Because of the fundamental role of the AMOC in generating the decadal OHT anomalies, Bjerknes compensation is expected to be active only in coupled models with a low-frequency AMOC spectral peak. The AHT and the transport in the oceanic gyres are positively correlated because the gyre transport responds to the atmospheric winds, thereby militating against long-term variability involving the wind-driven flow. Moisture and sensible heat transports in the atmosphere are also positively correlated at decadal time scales. The authors further explore the mechanisms and degree of compensation with a simple, diffusive, two-layer energy balance model. Taken together, these results suggest that compensation can be interpreted as arising from the highly efficient nature of the meridional energy transport in the atmosphere responding to ocean variability rather than any a priori need for the top-of-atmosphere radiation budget to be fixed. © 2013 American Meteorological Society.


Ecke R.E.,Los Alamos National Laboratory | Niemela J.J.,International Center for Theoretical Physics
Physical Review Letters | Year: 2014

We report experimental measurements of heat transport in rotating Rayleigh-Bénard convection in a cylindrical convection cell with an aspect ratio of Γ=1/2. The fluid is helium gas with a Prandtl number Pr=0.7. The range of control parameters for Rayleigh numbers 4×109


Zanolli C.,International Center for Theoretical Physics
American Journal of Physical Anthropology | Year: 2015

This contribution investigates the inner organizational pattern (tooth tissue proportions and enamel-dentine junction morphology) of seven Homo erectus permanent molar crowns from the late Lowerearly Middle Pleistocene Kabuh Formation of the Sangiran Dome (Central Java, Indonesia). The previous study of their external characteristics confirmed the degree of time-related structural reduction occurred in Javanese H. erectus, and also revealed a combination of nonmetric features which are rare in the Lower and early Middle Pleistocene dental record, but more frequently found in recent humans. In accordance with their outer occlusal morphology, the specimens exhibit a set of derived internal features, such as thick to hyperthick enamel, an incomplete expression of the crest patterns at the enamel-dentine junction (EDJ) level, a sharp EDJ topography. As a whole, these features differ from those expressed in some penecontemporaneous specimens/samples representing African H. erectus/ ergaster and H. heidelbergensis, as well as in Neanderthals, but occur in recent human populations. Further research in virtual dental paleoanthropology to be developed at macroregional scale would clarify the polarity and intensity of the intermittent exchanges between continental and insular Southeast Asia around the Lower to Middle Pleistocene boundary, as well as should shed light on the still poorly understood longitudinal evolutionary dynamics across continental Asia. © 2014 Wiley Periodicals, Inc.


Hatefi E.,International Center for Theoretical Physics
Nuclear Physics B | Year: 2014

The complete form of the amplitude of one closed string Ramond-Ramond (RR), two fermionic strings and one scalar field in IIB superstring theory has been computed in detail. Deriving 〈VCVψ-VψVφ〉 by using suitable gauge fixing, we discover some new vertices and their higher derivative corrections. We investigate both infinite gauge and scalar u-channel poles of this amplitude. In particular, by using the fact that the kinetic term of fermion fields has no correction, employing Born-Infeld action, the Wess-Zumino terms and their higher derivative corrections, we discover all infinite t, s-channel fermion poles. The couplings between one RR and two fermions and all their infinite higher derivative corrections have been explored. In order to look for all infinite (s+ t+ u)-channel scalar/gauge poles for p+ 2 = n, p= n cases, we obtain the couplings between two fermions-two scalars and two fermions, one scalar and one gauge field as well as all their infinite higher derivative corrections in type IIB. Specifically we make various comments based on arXiv:1205.5079 in favor of universality conjecture for all order higher derivative corrections (with or without low energy expansion) and the relation of open/closed string that is responsible for all superstring scattering amplitudes in IIA, IIB. © 2014 The Author.


This contribution reports fifteen human fossil dental remains found during the last two decades in the Sangiran Dome area, in Central Java, Indonesia. Among this sample, only one of the specimens had already been briefly described, with the other fourteen remaining unreported. Seven of the fifteen isolated teeth were found in a secured stratigraphic context in the late Lower-early Middle Pleistocene Kabuh Formation. The remaining elements were surface finds which, based on coincidental sources of information, were inferred as coming from the Kabuh Formation. Mainly constituted of permanent molars, but also including one upper incisor and one upper premolar, this dental sample brings additional evidence for a marked degree of size variation and time-related structural reduction in Javanese H. erectus. This is notably expressed by a significant decrease of the mesiodistal diameter, frequently associated to the reduction or even loss of the lower molar distal cusp (hypoconulid) and to a more square occlusal outline. In addition to the hypoconulid reduction or loss, this new sample also exhibits a low frequency of the occlusal Y-groove pattern, with a dominance of the X and, to a lesser extent, of the+patterns. This combination is rare in the Lower and early Middle Pleistocene paleoanthropological record, including in the early Javanese dental assemblage from the Sangiran Dome. On the other hand, similar dental features are found in Chinese H. erectus and in H. heidelbergensis. As a whole, this new record confirms the complex nature of the intermittent exchanges that occurred between continental and insular Southeast Asia through the Pleistocene. © 2013 Clément Zanolli.


Smacchia P.,International School for Advanced Studies | Silva A.,International Center for Theoretical Physics
Physical Review Letters | Year: 2012

We study the emission of quasiparticles in the scaling limit of the 1D quantum Ising chain at the critical point perturbed by a time-dependent local transverse field. We compute exactly and for a generic time dependence the average value of the transverse magnetization, its correlation functions, as well as the statistics of both the inclusive and exclusive work. We show that, except for a cyclic perturbation, the probability distribution of the work at low energies is a power law whose exponent is universal, i.e., does not depend on the specific time-dependent protocol, but only on the final value attained by the perturbation. © 2012 American Physical Society.


Hatefi E.,International Center for Theoretical Physics
Physical Review D - Particles, Fields, Gravitation and Cosmology | Year: 2012

We evaluate in detail the string scattering amplitude to compute different interactions of two massless scalars, one tachyon and one closed string Ramond-Ramond field in type II super string theory. In particular we find two scalar field and two tachyon couplings to all orders of α′ up to on-shell ambiguity. We then obtain the momentum expansion of this amplitude and apply this infinite number of couplings to actually check that the infinite number of tachyon poles of the S-matrix element of this amplitude for the p=n case (where p is the spatial dimension of a D p-brane and n is the rank of a Ramond-Ramond field strength) to all orders of α′ is precisely equal to the infinite number of tachyon poles of the field theory. In addition to confirming the couplings of the closed string Ramond-Ramond field to the world-volume gauge field and scalar fields including commutators, we also propose an extension of the Wess-Zumino action which naturally reproduces these new couplings in field theory such that they could be confirmed with direct S-matrix computations. Finally we show that the infinite number of massless poles and contact terms of this amplitude for the p=n+1 case can be reproduced by Chern-Simons, higher-derivative corrections of the Wess-Zumino, and symmetrized trace tachyon DBI actions. © 2012 American Physical Society.


Dasgupta B.,International Center for Theoretical Physics | Kopp J.,Max Planck Institute for Nuclear Physics
Physical Review Letters | Year: 2014

We show that sterile neutrinos with masses a1 eV, as motivated by several short baseline oscillation anomalies, can be consistent with cosmological constraints if they are charged under a hidden sector force mediated by a light boson. In this case, sterile neutrinos experience a large thermal potential that suppresses mixing between active and sterile neutrinos in the early Universe, even if vacuum mixing angles are large. Thus, the abundance of sterile neutrinos in the Universe remains very small, and their impact on big bang nucleosynthesis, cosmic microwave background, and large-scale structure formation is negligible. It is conceivable that the new gauge force also couples to dark matter, possibly ameliorating some of the small-scale structure problems associated with cold dark matter. © 2014 American Physical Society.


Zhang Y.,International Center for Theoretical Physics
Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics | Year: 2013

We study the top quark portal dominated dark matter interactions, and its implications for the gamma ray line searches. In this picture, the dark matter interactions with photons and gluons are loop induced by the axial anomaly of the top quark current. We show there can be a natural suppression of the tree-level annihilation of dark matter, and the photon channel in turn has a substantial rate when the main annihilation proceeds into gluons. We observe a competition between the indirect detection of gamma ray line and the search with monojet plus missing energy events at LHC, and the 7 TeV data already set an upper bound of ~10-28 cm3s-1 on the photonic annihilation cross section. This upper limit is compatible with a thermal WIMP scenario. © 2013 Elsevier B.V.


Hatefi E.,International Center for Theoretical Physics
Journal of High Energy Physics | Year: 2013

By dealing with the evaluation of string theory correlators of , the complete and closed form of the amplitude of two fermion fields, one tachyon and one closed string Ramond-Ramond field in type IIB superstring theory is found. Specifically by comparing infinite tachyon poles in field theory amplitude with infinite tachyon poles of the S-matrix of string amplitude (for p+1 = n case), all the infinite higher derivative corrections of two tachyons and two fermions (in type IIB) to all orders of α′ have been discovered. Using these new couplings, we are able to produce infinite t′ + s′ + u-channel tachyon poles of string theory in field theory. Due to internal degrees of freedom of fermions and tachyon (Chan-Paton factors) we comment that, neither there should be single s, t-channel fermion (tachyon pole) nor their infinite poles. Due to internal CP factor we also discover that there is no coupling between two closed string Ramond-Ramond (RR) field and one tachyon in type II super string theory. Taking into account the fact that the kinetic terms of fermions, gauge, scalar fields and tachyons do not obtain any higher derivative corrections, and due to their CP factors, string theory amplitude dictates us there should not be any double poles in the amplitude of one RR, two fermions and one tachyon. © 2013 SISSA, Trieste, Italy.

Loading International Center for Theoretical Physics collaborators
Loading International Center for Theoretical Physics collaborators