scholarly journals HODGE DUALITY AND COSMOLOGICAL CONSTANT

2006 ◽  
Vol 21 (02) ◽  
pp. 127-141 ◽  
Author(s):  
HITOSHI NISHINO ◽  
SUBHASH RAJPOOT
Keyword(s):  
Field Strength ◽  
Cosmological Constant ◽  
Classical Level ◽  
Simple Mechanism ◽  
Dimensional Spacetime ◽  
Form Field ◽  
Supersymmetric Theories ◽  
Chern Simons ◽  
Cosmological Constants ◽  
Field Strengths

We present a simple mechanism to eliminate cosmological constants both in supersymmetric and non-supersymmetric theories. This mechanism is based on the Hodge (Poincaré) duality between a 0-form and D-form field strengths in D-dimensional spacetime. The new key ingredient is the introduction of an extra Chern–Simons term into the D-form field strength H dual to the 0-form field strength. Our formulation can also be made consistent with supersymmetry. Typical applications to four-dimensional N = 1 supergravity and to ten-dimensional type IIA supergravity are given. The success of our formulation for both supersymmetric and non-supersymmetric systems strongly indicates the validity of our mechanism even after supersymmetry breakings at the classical level. Our mechanism may well be applicable to quantized systems, at least for supersymmetric cases with fundamental D-brane actions available.

scholarly journals MULTI-DIMENSIONAL COSMOLOGY AND DSR–GUP

2013 ◽  
Vol 28 (12) ◽  
pp. 1350047 ◽  
Author(s):  
K. ZEYNALI ◽  
F. DARABI ◽  
H. MOTAVALLI
Keyword(s):  
Cosmological Constant ◽  
Generalized Uncertainty Principle ◽  
Internal Space ◽  
Positive Cosmological Constant ◽  
Doubly Special Relativity ◽  
Dimensional Spacetime ◽  
Higher Dimensional ◽  
Big Crunch ◽  
The Difference ◽  
Cosmological Constants

A multi-dimensional cosmology with FRW type metric having four-dimensional spacetime and d-dimensional Ricci-flat internal space is considered with a higher-dimensional cosmological constant. The classical cosmology in commutative and Doubly Special Relativity–Generalized Uncertainty Principle (DSR–GUP) contexts is studied and the corresponding exact solutions for negative and positive cosmological constants are obtained. In the positive cosmological constant case, it is shown that unlike the commutative as well as GUP cases, in DSR–GUP case both scale factors of internal and external spaces after accelerating phase will inevitably experience decelerating phase leading simultaneously to a big crunch. This demarcation from GUP originates from the difference between the GUP and DSR–GUP algebras. The important result is that unlike GUP which results in eternal acceleration, DSR–GUP at first generates acceleration but prevents the eternal acceleration at late-times and turns it into deceleration.

scholarly journals Classical stability of higher-derivative q-theory in the four-form-field-strength realization

2017 ◽  
Vol 32 (16) ◽  
pp. 1750090 ◽  
Author(s):  
F. R. Klinkhamer ◽  
T. Mistele
Keyword(s):  
Field Strength ◽  
Classical Level ◽  
Q Theory ◽  
Higher Derivative ◽  
Classical Stability ◽  
Form Field ◽  
Strength Realization

We show that higher-derivative q-theory in the four-form-field-strength realization does not suffer from the Ostrogradsky instability at the classical level.

LAX PAIR AND COSMOLOGICAL CONSTANT FOR INDUCED 2D-GRAVITY IN THE LIGHT-CONE GAUGE

1991 ◽  
Vol 06 (38) ◽  
pp. 3517-3524 ◽  
Author(s):  
JEAN-MARC LINA ◽  
PRASANTA K. PANIGRAHI
Keyword(s):  
Cosmological Constant ◽  
Light Cone ◽  
2D Gravity ◽  
Lax Pair ◽  
Two Dimensional ◽  
Classical Level ◽  
Induced Gravity ◽  
Light Cone Gauge ◽  
Special Solutions ◽  
Cosmological Constants

We present the Lax pair to describe the two-dimensional induced gravity in the light-cone gauge. This is done at the classical level, with the cosmological constant which so far has not been accounted for in this context. The symmetries are discussed, together with some solutions of the integrability conditions. The case of the W3 gravity is also analyzed; exhibiting some special solutions and highlighting the roles of the two cosmological constants in its Lax pair formulation.

scholarly journals An improved holographic nodal line semimetal

2021 ◽  
Vol 2021 (5) ◽  
Author(s):  
Yan Liu ◽  
Xin-Meng Wu
Keyword(s):  
Mass Term ◽  
Nodal Line ◽  
Duality Relation ◽  
Strongly Coupled ◽  
Nodal Lines ◽  
Form Field ◽  
Improved Model ◽  
Fermionic Spectrum ◽  
Chern Simons ◽  
Tensor Operators

Abstract We study an improved holographic model for the strongly coupled nodal line semimetal which satisfies the duality relation between the rank two tensor operators $$ \overline{\psi}{\gamma}^{\mu v}\psi $$ ψ ¯ γ μv ψ and $$ \overline{\psi}{\gamma}^{\mu v}{\gamma}^5\psi $$ ψ ¯ γ μv γ 5 ψ . We introduce a Chern-Simons term and a mass term in the bulk for a complex two form field which is dual to the above tensor operators and the duality relation is automatically satisfied from holography. We find that there exists a quantum phase transition from a topological nodal line semimetal phase to a trivial phase. In the topological phase, there exist multiple nodal lines in the fermionic spectrum which are topologically nontrivial. The bulk geometries are different from the previous model without the duality constraint, while the resulting properties are qualitatively similar to those in that model. This improved model provides a more natural ground to analyze transports or other properties of strongly coupled nodal line semimetals.

scholarly journals Three-dimensional Maxwellian extended Newtonian gravity and flat limit

2020 ◽  
Vol 2020 (10) ◽  
Author(s):  
Patrick Concha ◽  
Lucrezia Ravera ◽  
Evelyn Rodríguez ◽  
Gustavo Rubio
Keyword(s):  
Cosmological Constant ◽  
Three Dimensional ◽  
Expansion Method ◽  
Gravity Models ◽  
Newtonian Gravity ◽  
Newtonian Theory ◽  
Relativistic Limit ◽  
Expansion Procedure ◽  
Three Space ◽  
Chern Simons

Abstract In the present work we find novel Newtonian gravity models in three space-time dimensions. We first present a Maxwellian version of the extended Newtonian gravity, which is obtained as the non-relativistic limit of a particular U(1)-enlargement of an enhanced Maxwell Chern-Simons gravity. We show that the extended Newtonian gravity appears as a particular sub-case. Then, the introduction of a cosmological constant to the Maxwellian extended Newtonian theory is also explored. To this purpose, we consider the non-relativistic limit of an enlarged symmetry. An alternative method to obtain our results is presented by applying the semigroup expansion method to the enhanced Nappi-Witten algebra. The advantages of considering the Lie algebra expansion procedure is also discussed.

scholarly journals Lorentz violation with a universal minimum speed as foundation of de Sitter relativity

2018 ◽  
Vol 27 (02) ◽  
pp. 1850011 ◽  
Author(s):  
Cláudio Nassif Cruz ◽  
Rodrigo Francisco dos Santos ◽  
A. C. Amaro de Faria
Keyword(s):  
Cosmological Constant ◽  
Extra Dimension ◽  
Negative Curvature ◽  
Lorentz Violation ◽  
Conformal Factor ◽  
De Sitter ◽  
Minkowski Metric ◽  
Minimum Speed ◽  
New Space ◽  
Cosmological Constants

We aim to investigate the theory of Lorentz violation with an invariant minimum speed called Symmetrical Special Relativity (SSR) from the viewpoint of its metric. Thus, we should explore the nature of SSR-metric in order to understand the origin of the conformal factor that appears in the metric by deforming Minkowski metric by means of an invariant minimum speed that breaks down Lorentz symmetry. So, we are able to realize that there is a similarity between SSR and a new space with variable negative curvature ([Formula: see text]) connected to a set of infinite cosmological constants ([Formula: see text]), working like an extended de Sitter (dS) relativity, so that such extended dS-relativity has curvature and cosmological “constant” varying in time. We obtain a scenario that is more similar to dS-relativity given in the approximation of a slightly negative curvature for representing the current universe having a tiny cosmological constant. Finally, we show that the invariant minimum speed provides the foundation for understanding the kinematics origin of the extra dimension considered in dS-relativity in order to represent the dS-length.

scholarly journals Investigation of the cosmic ray population and magnetic field strength in the halo of NGC 891

2018 ◽  
Vol 615 ◽  
pp. A98 ◽  
Author(s):  
D. D. Mulcahy ◽  
A. Horneffer ◽  
R. Beck ◽  
M. Krause ◽  
P. Schmidt ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Field Strength ◽  
Magnetic Field Strength ◽  
Low Frequency ◽  
Cosmic Ray ◽  
Radio Continuum ◽  
Continuum Emission ◽  
Low Frequencies ◽  
Very Large Array ◽  
Field Strengths

Context. Cosmic rays and magnetic fields play an important role for the formation and dynamics of gaseous halos of galaxies. Aims. Low-frequency radio continuum observations of edge-on galaxies are ideal to study cosmic-ray electrons (CREs) in halos via radio synchrotron emission and to measure magnetic field strengths. Spectral information can be used to test models of CRE propagation. Free–free absorption by ionized gas at low frequencies allows us to investigate the properties of the warm ionized medium in the disk. Methods. We obtained new observations of the edge-on spiral galaxy NGC 891 at 129–163 MHz with the LOw Frequency ARray (LOFAR) and at 13–18 GHz with the Arcminute Microkelvin Imager (AMI) and combine them with recent high-resolution Very Large Array (VLA) observations at 1–2 GHz, enabling us to study the radio continuum emission over two orders of magnitude in frequency. Results. The spectrum of the integrated nonthermal flux density can be fitted by a power law with a spectral steepening towards higher frequencies or by a curved polynomial. Spectral flattening at low frequencies due to free–free absorption is detected in star-forming regions of the disk. The mean magnetic field strength in the halo is 7 ± 2 μG. The scale heights of the nonthermal halo emission at 146 MHz are larger than those at 1.5 GHz everywhere, with a mean ratio of 1.7 ± 0.3, indicating that spectral ageing of CREs is important and that diffusive propagation dominates. The halo scale heights at 146 MHz decrease with increasing magnetic field strengths which is a signature of dominating synchrotron losses of CREs. On the other hand, the spectral index between 146 MHz and 1.5 GHz linearly steepens from the disk to the halo, indicating that advection rather than diffusion is the dominating CRE transport process. This issue calls for refined modelling of CRE propagation. Conclusions. Free–free absorption is probably important at and below about 150 MHz in the disks of edge-on galaxies. To reliably separate the thermal and nonthermal emission components, to investigate spectral steepening due to CRE energy losses, and to measure magnetic field strengths in the disk and halo, wide frequency coverage and high spatial resolution are indispensable.

A 4 × 4 array multichannel magnetic stimulation system using submillimeter sized planar square spiral coils: The spatial distribution of electromagnetic field

2022 ◽  
pp. 1-18
Author(s):  
Lei Tian ◽  
Limei Song ◽  
Yu Zheng ◽  
Jinhai Wang
Keyword(s):  
Magnetic Field ◽  
Electromagnetic Field ◽  
Spatial Distribution ◽  
Field Strength ◽  
Electric Field ◽  
Magnetic Stimulation ◽  
Spiral Coil ◽  
Average Magnetic Field ◽  
Stimulation System ◽  
Field Strengths

Multi-coil magnetic stimulation has advantages over single-coil magnetic stimulation, such as more accurate targeting and larger stimulation range. In this paper, a 4 × 4 array multichannel magnetic stimulation system based on a submillimeter planar square spiral coil is proposed. The effects of multiple currents with different directions on the electromagnetic field strength and the focusing zone of the array-structured magnetic stimulation system are studied. The spatial distribution characteristics of the electromagnetic field are discussed. In addition, a method is proposed that can predict the spatial distributions of the electric and magnetic fields when currents in different directions are applied to the array-structured magnetic stimulation system. The study results show that in the section of z = 2 μm, the maximum and average magnetic field strengths of the array-structured magnetic stimulation system are 6.39 mT and 2.68 mT, respectively. The maximum and average electric field strengths are 614.7 mV/m and 122.82 mV/m, respectively, where 84.39% of the measured electric field values are greater than 73 mV/m. The average magnetic field strength of the focusing zone, i.e., the zone in between the two coils, is 3.38 mT with a mean square deviation of 0.18. Therefore, the array-structured multi-channel magnetic stimulation system based on a planar square spiral coil can have a small size of 412 μm × 412 μm × 1.7 μm, which helps improving the spatial distribution of electromagnetic field and increase the effectiveness of magnetic stimulation. The main contribution of this paper is a method for designing multichannel micro-magnetic stimulation devices.

Effect of electromagnetic field on germination of groundnut seeds (Arachis hypogaea L)

2012 ◽  
Vol 2 (2) ◽  
pp. 73-78
Author(s):  
E. Rajasekhar ◽  
R. Jeevan Kumar ◽  
C. M. Subhan ◽  
P. Panduranga ◽  
T. Krishnamurthy
Keyword(s):  
Electromagnetic Field ◽  
Relative Humidity ◽  
Field Strength ◽  
Arachis Hypogaea ◽  
Exposure Time ◽  
Room Temperature ◽  
Total Weight ◽  
South Pole ◽  
Arachis Hypogaea L ◽  
Field Strengths

Present work is about the influence of Electromagnetic field [EMF] treatment on the improvement of groundnut seeds (Arachis hypogaea L) germination. The treatment consisted of different electromagnetic field strengths 2, 4, 7 and 10 milli Tesla [mT] in different exposure times 10, 20, 30 and 40 min. In every measurement, the relative humidity and room temperature were recorded. The germination [G] of seed in terms of percentage [% ], the stems length [SL] and roots length [RL] in millimeter [mm] at 6th day and 12th day after experiment, and the total weight [TW] in milligram at 12th day have been measured. Best results have been obtained for variants with exposure time of 30 min and field strength of 7 mT at south pole. Result obtained in the present investigation revealed that the energy absorbed by molecules was high at lower output strength and shorter exposure time improved biologicalfunctions, stimulation effect could be achieved.

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