COBE observations and results

Smoot, George F.

doi:10.1063/1.59326

Cited by 16 publications

(9 citation statements)

References 18 publications

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“…From the observations of CMB anisotropy spectrum by COBE, WMAP and Planck [17,18,3], it is not yet possible to pin down a specific particle physics model as the one responsible for inflation. Though all of the above experiments gave tighter and tighter constraints on inflationary observables, e.g.…”

Section: Discussionmentioning

confidence: 99%

Testing theories of gravity and supergravity with inflation and observations of the cosmic microwave background

Chakravarty

Mohanty

Lambiase

2017

Int. J. Mod. Phys. D

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Abstract. Cosmological and astrophysical observations lead to the emerging picture of a universe that is spatially flat and presently undertaking an accelerated expansion. The observations supporting this picture come from a range of measurements encompassing estimates of galaxy cluster masses, the Hubble diagram derived from type-Ia supernovae observations, the measurements of Cosmic Microwave Background radiation anisotropies, etc. The present accelerated expansion of the universe can be explained by admitting the existence of a cosmic fluid, with negative pressure. In the simplest scenario this unknown component of the universe, the Dark Energy, is represented by the cosmological constant (Λ), and accounts for about 70% of the global energy budget of the universe. The remaining 30% consists of a small fraction of baryons (4%) with the rest cold Dark Matter (CDM). The Lambda Cold Dark Matter (ΛCDM) model, i.e. General Relativity with cosmological constant, is in good agreement with observations. It can be assumed as the first step towards a new standard cosmological model. However, despite the satisfying agreement with observations, the ΛCDM model presents several lacks of congruence and shortcomings, and therefore theories beyond Einsteins General Relativity are called for. Many extensions of Einstein's theory of gravity have been studied and proposed with various motivations like the quest for a quantum theory of gravity to extensions of anomalies in observations at the solar system, galactic and cosmological scales. These extensions include adding higher powers of Ricci curvature R, coupling the Ricci curvature with scalar fields and generalized functions of R. In addition when viewed from the perspective of Supergravity (SUGRA) many of these theories may originate from the same SUGRA theory, but interpreted in different frames. SUGRA therefore serves as a good framework for organizing and generalizing theories of gravity beyond General Relativity. All these theories when applied to inflation (a rapid expansion of early Universe in which primordial gravitational waves might be generated and might still be detectable by the imprint they left or by the ripples that persist today) can have distinct signatures in the Cosmic Microwave Background radiation temperature and polarization anisotropies. We give a review of ΛCDM cosmology and survey the theories of gravity beyond Einsteins General Relativity, specially which arise from SUGRA, and study the consequences of these theories in the context of inflation and put bounds on the theories and the parameters therein from the observational experiments like PLANCK, Keck/BICEP etc. The possibility of testing these theories in the near future in CMB observations and new data coming from colliders like the LHC, provides an unique opportunity for constructing verifiable models of particle physics and General Relativity.

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Section: Discussionmentioning

confidence: 99%

Testing theories of gravity and supergravity with inflation and observations of the cosmic microwave background

Chakravarty

Mohanty

Lambiase

2017

Int. J. Mod. Phys. D

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“…Inflation leads to a scale invariant perturbation spectrum, the reason can easily be seen in the fact that de Sitter space is invariant under time translations. From COBE observations of the temperature fluctuations in the CMBR it is known that the magnitude of the perturbations (which stays constant for vacuum energy) should be of the order [148] (5.14)…”

Section: Density Perturbations and Spectral Indexmentioning

confidence: 99%

Aspects of stability and phenomenology in type IIA orientifolds with intersecting D6‐branes

Ott

2004

Fortschritte der Physik

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Intersecting branes have been the subject of an elaborate string model building for several years. After a general introduction into string theory, this work introduces in detail the toroidal and ZN -orientifolds. The picture involving D9-branes with B-fluxes is shortly reviewed, but the main discussion employs the T-dual picture of intersecting D6-branes. The derivation of the R-R and NS-NS tadpole cancellation conditions in the conformal field theory is shown in great detail. Various aspects of the open and closed chiral and nonchiral massless spectrum are discussed, involving spacetime anomalies and the generalized Green-Schwarz mechanism. An introduction into possible gauge breaking mechanisms is given, too. Afterwards, both N = 1 supersymmetric and non-supersymmetric approaches to low energy model building are treated. Firstly, the problem of complex structure instabilities in toroidal ΩR-orientifolds is approached by a Z3-orbifolded model. In particular, a stable non-supersymmetric standard-like model with three fermion generations is discussed. This model features the standard model gauge groups at the same time as having a massless hypercharge, but possessing an additional global B-L symmetry. The electroweak Higgs mechanism and the Yukawa couplings are not realized in the usual way. It is shown that this model descends naturally from a flipped SU (5) GUT model, where the string scale has to be at least of the order of the GUT scale. Secondly, supersymmetric models on the Z4-orbifold are discussed, involving exceptional 3-cycles and the explicit construction of fractional D-branes. A three generation Pati-Salam model is constructed as a particular example, where several brane recombination mechanisms are used, yielding non-flat and non-factorizable branes. This model even can be broken down to a MSSM-like model with a massless hypercharge. Finally, the possibility that unstable closed and open string moduli could have played the role of the inflaton in the evolution of the universe is being explored. In the closed string sector, the important slow-rolling requirement can only be fulfilled for very specific cases, where some moduli are frozen and a special choice of coordinates is taken. In the open string sector, inflation does not seem to be possible at all.

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“…Observations of the cosmic microwave background (CMB) are a crucial tools in developing our understanding of the physics of the early universe and testing the standard model of cosmology, ΛCDM. While satellite missions such as the Cosmic Background Explorer (COBE) (Smoot 1999), the Wilkinson Microwave Anisotropy Probe (WMAP) (Bennett et al 2013;Hinshaw et al 2013), and the Planck Collaboration (Planck Collaboration et al 2020) have produced full-sky microwave maps, ground-based experiments have extended the satellite measurements towards smaller angular scales and lower noise levels. High resolution (∼ 1 ) experiments, such as the Atacama Cosmology Telescope (Thornton et al 2016) (ACT) and the South Pole Telescope (Carlstrom et al 2011;Sayre et al 2020) (SPT) have made measurements of both the primordial power spectrum (Wu et al 2019) as well as secondary anisotropies such as the thermal and kinematic Sunyaev-Zel'dovich (SZ) effects (Hilton et al 2018;Sunyaev & Zeldovich 1970, 1972 and gravitational lensing effects (Story et al 2015).…”

Section: Introductionmentioning

confidence: 99%

The Simons Observatory Large Aperture Telescope Receiver

Zhu,

Bhandarkar,

Coppi

et al. 2021

Preprint

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The Simons Observatory (SO) Large Aperture Telescope Receiver (LATR) will be coupled to the Large Aperture Telescope located at an elevation of 5,200 m on Cerro Toco in Chile. The resulting instrument will produce arcminute-resolution millimeter-wave maps of half the sky with unprecedented precision. The LATR is the largest cryogenic millimeter-wave camera built to date with a diameter of 2.4 m and a length of 2.6 m. It cools 1200 kg of material to 4 K and 200 kg to 100 mk, the operating temperature of the bolometric detectors with bands centered around 27, 39, 93, 145, 225, and 280 GHz. Ultimately, the LATR will accommodate 13 40 cm diameter optics tubes, each with three detector wafers and a total of 62,000 detectors. The LATR design must simultaneously maintain the optical alignment of the system, control stray light, provide cryogenic isolation, limit thermal gradients, and minimize the time to cool the system from room temperature to 100 mK. The interplay between these competing factors poses unique challenges. We discuss the trade studies involved with the design, the final optimization, the construction, and ultimate performance of the system.

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COBE observations and results

Cited by 16 publications

References 18 publications

Testing theories of gravity and supergravity with inflation and observations of the cosmic microwave background

Testing theories of gravity and supergravity with inflation and observations of the cosmic microwave background

Aspects of stability and phenomenology in type IIA orientifolds with intersecting D6‐branes

The Simons Observatory Large Aperture Telescope Receiver

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