scholarly journals Stringy tachyonic instabilities of non-supersymmetric Ricci flat backgrounds

2021 ◽  
Vol 2021 (4) ◽  
Author(s):  
Bobby Samir Acharya ◽  
Gerardo Aldazabal ◽  
Eduardo Andrés ◽  
Anamaría Font ◽  
Kumar Narain ◽  
...  
Keyword(s):  
Small Radius ◽  
Vacuum Energy Density ◽  
Large Radius ◽  
Spin Structures ◽  
Special Holonomy ◽  
Conformal Field ◽  
Ricci Flat ◽  
Flat Manifolds ◽  
Superstring Theories ◽  
M Theory

Abstract Superstring/M-theory compactified on compact Ricci flat manifolds have recently been conjectured to exhibit instabilities whenever the metrics do not have special holonomy. We use worldsheet conformal field theory to investigate instabilities of Type II superstring theories on compact, Ricci flat, spin 3-manifolds including a worldsheet description of their spin structures. The instabilities are signalled by the appearance of stringy tachyons at small radius and a negative (1-loop) vacuum energy density at large radius. We briefly discuss the extension to higher dimensions.

scholarly journals Supersymmetry, Ricci flat manifolds and the String Landscape

2020 ◽  
Vol 2020 (8) ◽  
Author(s):  
B. S. Acharya
Keyword(s):  
Minkowski Spacetime ◽  
Necessary Condition ◽  
Leading Order ◽  
Special Holonomy ◽  
Ricci Flat ◽  
Simply Connected Manifolds ◽  
String Landscape ◽  
Flat Manifolds ◽  
Simply Connected

Abstract A longstanding question in superstring/M theory is does it predict supersymmetry below the string scale? We formulate and discuss a necessary condition for this to be true; this is the mathematical conjecture that all stable, compact Ricci flat manifolds have special holonomy in dimensions below eleven. Almost equivalent is the proposal that the landscape of all geometric, stable, string/M theory compactifications to Minkowski spacetime (at leading order) are supersymmetric. For simply connected manifolds, we collect together a number of physically relevant mathematical results, emphasising some key outstanding problems and perhaps less well known results. For non-simply connected, non-supersymmetric Ricci flat manifolds we demonstrate that many cases suffer from generalised Witten bubble of nothing instabilities.

Coexistence of large-radius and small-radius polaron states in a quantum wire

1995 ◽  
Vol 17 (11-12) ◽  
pp. 1723-1728
Author(s):  
Y. Shinozuka ◽  
N. Ishida
Keyword(s):  
Quantum Wire ◽  
Small Radius ◽  
Large Radius

Second Stiefel-Whitney class and spin structures on flat manifolds of diagonal type

2011 ◽  
Author(s):  
Sergio Console ◽  
Juan Pablo Rossetti ◽  
Roberto J. Miatello ◽  
Carlos Herdeiro ◽  
Roger Picken
Keyword(s):  
Spin Structures ◽  
Whitney Class ◽  
Flat Manifolds

scholarly journals SUPERGRAVITY DESCRIPTION OF FIELD THEORIES ON CURVED MANIFOLDS AND A NO GO THEOREM

2001 ◽  
Vol 16 (05) ◽  
pp. 822-855 ◽  
Author(s):  
JUAN MALDACENA ◽  
CARLOS NUÑEZ
Keyword(s):  
Field Theory ◽  
Conformal Field Theory ◽  
Riemann Surface ◽  
Riemann Surfaces ◽  
Field Theories ◽  
De Sitter ◽  
Curved Manifolds ◽  
Conformal Field ◽  
Low Energies ◽  
M Theory

In the first part of this paper we find supergravity solutions corresponding to branes on worldvolumes of the form Rd×Σ where Σ is a Riemann surface. These theories arise when we wrap branes on holomorphic Riemann surfaces inside K3 or CY manifolds. In some cases the theory at low energies is a conformal field theory with two less dimensions. We find some non-singular supersymmetric compactifications of M-theory down to AdS5. We also propose a criterion for permissible singularities in supergravity solutions. In the second part of this paper, which can be read independently of the first, we show that there are no non-singular Randall-Sundrum or de-Sitter compactifications for large class of gravity theories.

scholarly journals Triple Oxygen Isotope Measurements by Multi-Collector Secondary Ion Mass Spectrometry

2021 ◽  
Vol 8 ◽  
Author(s):  
Nordine Bouden ◽  
Johan Villeneuve ◽  
Yves Marrocchi ◽  
Etienne Deloule ◽  
Evelyn Füri ◽  
...  
Keyword(s):  
Mass Spectrometry ◽  
Oxygen Isotope ◽  
Spatial Resolution ◽  
Secondary Ion Mass Spectrometry ◽  
Small Radius ◽  
Large Radius ◽  
Ion Mass Spectrometry ◽  
Secondary Ion ◽  
Isotope Measurements

Secondary ion mass spectrometry (SIMS) is a powerful technique for in situ triple oxygen isotope measurements that has been used for more than 30 years. Since pioneering works performed on small-radius ion microprobes in the mid-80s, tremendous progress has been made in terms of analytical precision, spatial resolution and analysis duration. In this respect, the emergence in the mid-90s of the large-radius ion microprobe equipped with a multi-collector system (MC-SIMS) was a game changer. Further developments achieved on CAMECA MC-SIMS since then (e.g., stability of the electronics, enhanced transmission of secondary ions, automatic centering of the secondary ion beam, enhanced control of the magnetic field, 1012Ω resistor for the Faraday cup amplifiers) allow nowadays to routinely measure oxygen isotopic ratios (18O/16O and 17O/16O) in various matrices with a precision (internal error and reproducibility) better than 0.5‰ (2σ), a spatial resolution smaller than 10 µm and in a few minutes per analysis. This paper focuses on the application of the MC-SIMS technique to the in situ monitoring of mass-independent triple oxygen isotope variations.

scholarly journals MORE M-BRANES ON PRODUCT OF RICCI-FLAT MANIFOLDS

2012 ◽  
Vol 09 (08) ◽  
pp. 1250067 ◽  
Author(s):  
V. D. IVASHCHUK
Keyword(s):  
Ricci Flat ◽  
Flat Manifolds ◽  
Fractional Numbers

Partially supersymmetric intersecting (non-marginal) composite M-brane solutions defined on the product of Ricci-flat manifolds M0 × M1 × ⋯ × Mn in D = 11 supergravity are considered and formulae for fractional numbers of unbroken supersymmetries are derived for the following configurations of branes: M2 ∩ M2, M2 ∩ M5, M5 ∩ M5 and M2 ∩ M2 ∩ M2. Certain examples of partially supersymmetric configurations are presented.

scholarly journals Disk Structure in U Geminorum

1977 ◽  
Vol 42 ◽  
pp. 313-321
Author(s):  
J. Madej ◽  
B. Paczyński
Keyword(s):  
Angular Momentum ◽  
Hot Spot ◽  
Outer Part ◽  
Tangential Velocity ◽  
Radial Component ◽  
Small Radius ◽  
Large Radius ◽  
Disk Structure ◽  
Orbital Periods ◽  
The Difference

AbstractA hot spot at the outer rim of the accretion disk dominates the light of U Geminorum at minimum light. We take this as evidence that there is no accretion from the disk onto the white dwarf between the eruptions, and we assume there is no viscosity in the disk at that time. The hot spot is produced by dissipation of the radial component of velocity of stream falling from the inner Lagrangian point. Angular momentum per unit massis smaller in the stream than it is in the outer parts of the disk. This leads to angular momentum redistribution in the outer part of the disk. The difference of tangential velocity between the stream and the disk is dissipated in few orbital periods. These processes make the outer parts of the disk look like a torus. We calculated the structure of the torus in U Geminorum between the eruptions and we obtained the following oarameters: mass of the torus: 10-9 - 10-8 M⊙ (assumed), its optical thickness: 106, the large radius (i.e. the radius of the disk): 0.5 R⊙ (assumed), the small radius (i.e. the half thickness of the outer parts of the disk): 0.05 R⊙. Conditions at the surface of the torus are similar as on the solar surface.

scholarly journals String and M-theory deformations of manifolds with special holonomy

2005 ◽  
Vol 2005 (07) ◽  
pp. 075-075 ◽  
Author(s):  
Hong Lü ◽  
Christofer N Pope ◽  
Kellog S Stelle ◽  
Paul K Townsend
Keyword(s):  
Special Holonomy ◽  
M Theory

Intershield geochemical differences among Hawaiian volcanoes: implications for source compositions, melting process and magma ascent paths

1993 ◽  
Vol 342 (1663) ◽  
pp. 121-136 ◽  
Keyword(s):  
Melting Process ◽  
Isotope Ratios ◽  
Magma Ascent ◽  
Small Radius ◽  
Element Abundance ◽  
Isotopic Ratios ◽  
Large Radius ◽  
Major Element Composition ◽  
Mauna Loa ◽  
Melt Segregation

As Hawaiian volcanoes develop, their lavas systematically change in composition and isotopic ratios of Sr, Nd and Pb. These trends provide important constraints for understanding plume-related volcanism as a volcano migrates away from the hotspot. There are also geochemical differences between Hawaiian shields. In particular, lavas from adjacent shields such as Kilauea and Mauna Loa on Hawaii and Koolau and Waianae on Oahu have significant differences in abundances of some major and incompatible elements and isotopic ratios of Sr, Nd and Pb. Some incompatible element abundance ratios, such as Zr/Nb and Sr/Nb, are correlated with intershield differences in Sr and Nd isotope ratios, but these isotopic ratios are not correlated with intershield differences in major element composition, or even parent/daughter abundance ratios such as Rb/Sr and Sm/Nd. Moreover, at Kilauea and Mauna Loa the intershield differences have apparently persisted for a relatively long time, perhaps 100 ka. These intershield geochemical differences provide important constraints on plume volcanism. Specifically, (i) each volcano must have distinct magma ascent paths from the region of melt segregation; (ii) the 25-50 km distance between adjacent, but geochemically distinct, shields requires that the sources vary on a similar scale, and that the melt production region is similarly restricted. The absence of correlations between lava compositions and radiogenic isotope ratios provides evidence for significant differences in melting process such as each shield forming by a different mean extent of melting with melt segregation at different mean pressures. Two types of models are consistent with the intershield geochemical differences: (i) a relatively large radius, ca . 40 km, plume conduit with a systematic spatial distribution of geochemical heterogeneities; or (ii) a small radius, less than 20 km, plume conduit composed of geochemically distinct diapirs. Because relatively small radius diapirs of limited vertical extent are too small to create the large Hawaiian shields, a possible alternative is a continuous conduit containing solitary waves which transport geochemically distinct packets of material.

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