1,706 research outputs found
Phantom energy supported wormhole model in gravity assuming conformal motion
In this article, we have discussed Morris and Thorne (MT) wormhole solutions
in a modified theory of gravity that admits conformal motion. Here we explore
the wormhole solutions in gravity, which is a function of the Ricci
scalar () and the trace of the stress-energy tensor (). To study wormhole
geometries, we make assumption of spherical symmetric static spacetime and the
existence of conformal Killing symmetry to get more acceptable astrophysical
outcomes. To do this, we choose the expression of as . Here we employ the phantom energy EoS relating to radial pressure
and density given by with to constrain our model.
Following a discussion of wormhole geometry and behavior of shape function, the
study moves on to the computation of proper radial distance, active mass
function, the nature of total gravitational energy and a discussion on the
violation of energy conditions. We have shown that the wormhole solutions exist
for positive as well as negative values of the coupling constant . From
our analysis we see that no wormhole solution exists for . All the physical parameters have been drawn by
employing the values of as and
, where corresponds to general relativity (GR) case. It is
found that for our proposed model, a realistic wormhole solutions satisfying
all the properties can be obtained.Comment: Accepted in International Journal of Modern Physics D on 23 November
2021; 15 Pages, 8 Figure
Group 1 and group 2 metal complexes supported by a bidentate bulky iminopyrrolyl ligand: synthesis, structural diversity, and ε-caprolactone polymerization study
We report here a series of alkali and alkaline earth metal complexes, each with a bulky iminopyrrolyl ligand [2-(Ph3CN[double bond, length as m-dash]CH)C4H3NH] (1-H) moiety in their coordination sphere, synthesized using either alkane elimination or silylamine elimination methods or the salt metathesis route. The lithium salt of molecular composition [Li(2-(Ph3CN[double bond, length as m-dash]CH)C4H3N)(THF)2] (2) was prepared using the alkane elimination method, and the silylamine elimination method was used to synthesize the dimeric sodium and tetra-nuclear potassium salts of composition [(2-(Ph3CN[double bond, length as m-dash]CH)C4H3N)Na(THF)]2 (3) and [(2-(Ph3CN[double bond, length as m-dash]CH)C4H3N)K(THF)0.5]4 (4) respectively. The magnesium complex of composition [(THF)2Mg(CH2Ph){2-(Ph3CN[double bond, length as m-dash]CH)C4H3N}] (5) was synthesized through the alkane elimination method, in which [Mg(CH2Ph)2(OEt2)2] was treated with the bulky iminopyrrole ligand 1-H in 1 : 1 molar ratio, whereas the bis(iminopyrrolyl)magnesium complex [(THF)2Mg{2-(Ph3CN[double bond, length as m-dash]CH)C4H3N}2] (6) was isolated using the salt metathesis route. The heavier alkaline earth metal complexes of the general formula {(THF)nM(2-(Ph3CN[double bond, length as m-dash]CH)C4H3N)2} [M = Ca (7), Sr (8), and n = 2; M = Ba (9), n = 3] were prepared in pure form using two synthetic methods: in the first method, the bulky iminopyrrole ligand 1-H was directly treated with the alkaline earth metal precursor [M{N(SiMe3)2}2(THF)n] (where M = Ca, Sr and Ba) in 2 : 1 molar ratio in THF solvent at ambient temperature. The complexes 7–9 were also obtained using the salt metathesis reaction, which involves the treatment of the potassium salt (4) with the corresponding metal diiodides MI2 (M = Ca, Sr and Ba) in 2 : 1 molar ratio in THF solvent. The molecular structures of all the metal complexes (1-H, 2–9) in the solid state were established through single-crystal X-ray diffraction analysis. The complexes 5–9 were tested as catalysts for the ring-opening polymerization of ε-caprolactone. High activity was observed in the heavier alkaline earth metal complexes 7–9, with a very narrow polydispersity index in comparison to that of magnesium complexes 5 and 6
Syntheses and solid state structures of zinc (II) complexes with Bi-dentate N-(Aryl)imino-acenapthenone (Ar-BIAO) ligands
We have synthesized five zinc complexes of molecular formulae [ZnCl
2
(2,6-dimethylphenyl-
BIAO)]
2
(
1a
), [ZnBr
2
(2,6-dimethylphenyl-BIAO)]
2
(
1b
), [ZnI
2
(2,6-dimethylphenyl-BIAO)]
2
(
1c
), [ZnBr
2
(mes-
BIAO)]
2
(
2b)
and [ZnBr
2
(dipp-BIAO)] (
3b)
with rigid unsymmetrical imi
noacenaphthenone ligands, (2,6-
dimethylphenyl-BIAO) (
1
), (mesityl-BIAO) (
2
) and (2,6-diisopropylphenyl-BIAO) (
3
).Thezinccomplex
1a
was prepared by the reaction of ZnCl
2
and neutral (mesityl-BIAO) (
1
). However, complexes
1b
,
2b
and
3b
were
obtained by the treatment of ZnBr
2
and neutral ligands
1
–
3
respectively in 1:1 molar ratio in dichloromethane
at ambient temperature. In a similar reaction of ZnI
2
with (2,6-dimethylphenyl-BIAO) (
1
) in dichloromethane
the corresponding iodo-complex
1c
was obtained in good yield. All the zinc (II) complexes are characterized
by FT-IR,
1
Hand
13
C{
1
H} NMR spectroscopic techniques. The solid state structures of the complexes
1a
,
1b
,
1c
,
2b
and
3b
are confirmed by single crystal X-ray diffraction analysis. The molecular structures of com-
plexes
1a
,
1b
,
1c
and
2b
reveal the dimeric nature of the complexes and subsequently the centre atom zinc is
penta-coordinated to adopt distorted trigonal bipyr
amidal geometry around it. In contrast, the complex
3b
is
in monomeric in nature due to bulkier size of the ligand and zinc ion is tetra coordinated to adopt distorted
tetrahedral geometry
Sterically Rigid Bi-dentate N-(Aryl)imino-Acenapthenone (Ar-BIAO) Ligands in Zinc Coordination Sphere- Syntheses and Structures
My thesis work describes the synthesis of six different 1-alkyl-N-(arylimino)acenaphthylen-1-ol compounds 1a, 1b, 2a, 2b, 3a and 3c as the racemic products by varying steric demand on the imino nitrogen atom of N-(aryl)imino-acenapthenone (Ar-BIAO) ligand. The synthesized imino-alcohols are characterized by FT-IR, 1H, 13C{1H} NMR spectroscopy. The soild state structures of compounds 1a, 1b, 2a and 3a are established by single crystal X-ray diffraction analysis. In the molecular structure compounds 1a and 3a crystallize only R-isomers in their respective asymmetric unit, whereas compound 1b has S-isomer only in its asymmetric unit. However compound 2a crystallizes in both R- and S- isomers in its asymmetric unit. In addition with this work one new chiral ligand, N-(1-phenylethylamine)imino-acenaphthenone (4) was synthesized by the reaction of acenaphthenequinone and (R)-1-phenylethylamine in 1:1 ratio. Compound 4 was characterized by FT-IR and 1H NMR spectroscop
Review of AdS/CFT Integrability, Chapter I.3: Long-range spin chains
In this contribution we briefly review recent developments in the theory of
long-range integrable spin chains. These spin chains constitute a natural
generalisation of the well-studied integrable nearest-neighbour chains and are
of particular relevance to the integrability in the AdS/CFT correspondence
since the dilatation operator in the asymptotic region is conjectured to be a
Hamiltonian of an integrable long-range psu spin chain.Comment: 17 pages, see also overview article arXiv:1012.3982, v2: references
to other chapters updated, v3: minor typos corrected, references adde
On string solutions of Bethe equations in N=4 supersymmetric Yang-Mills theory
The Bethe equations, arising in description of the spectrum of the dilatation
operator for the su(2) sector of the N=4 supersymmetric Yang-Mills theory, are
considered in the anti-ferromagnetic regime. These equations are deformation of
those for the Heisenberg XXX magnet. It is proven that in the thermodynamic
limit roots of the deformed equations group into strings. It is proven that the
corresponding Yang's action is convex, which implies uniqueness of solution for
centers of the strings. The state formed of strings of length (2n+1) is
considered and the density of their distribution is found. It is shown that the
energy of such a state decreases as n grows. It is observed that
non-analyticity of the left hand side of the Bethe equations leads to an
additional contribution to the density and energy of strings of even length.
Whence it is concluded that the structure of the anti-ferromagnetic vacuum is
determined by the behaviour of exponential corrections to string solutions in
the thermodynamic limit and possibly involves strings of length 2.Comment: LaTex, 9 pages, 1 figur
Open Spin Chains in Super Yang-Mills at Higher Loops: Some Potential Problems with Integrability
The super Yang-Mills duals of open strings attached to maximal giant
gravitons are studied in perturbation theory. It is shown that non-BPS baryonic
excitations of the gauge theory can be studied within the paradigm of open
quantum spin chains even beyond the leading order in perturbation theory. The
open spin chain describing the two loop mixing of non-BPS giant gravitons
charged under an su(2) of the so(6) R symmetry group is explicitly constructed.
It is also shown that although the corresponding open spin chain is integrable
at the one loop order, there is a potential breakdown of integrability at two
and higher loops. The study of integrability is performed using coordinate
Bethe ansatz techniques.Comment: 28 pages. References added in revised versio
Strong coupling from the Hubbard model
It was recently observed that the one dimensional half-filled Hubbard model
reproduces the known part of the perturbative spectrum of planar N=4 super
Yang-Mills in the SU(2) sector. Assuming that this identification is valid
beyond perturbation theory, we investigate the behavior of this spectrum as the
't Hooft parameter \lambda becomes large. We show that the full dimension
\Delta of the Konishi superpartner is the solution of a sixth order polynomial
while \Delta for a bare dimension 5 operator is the solution of a cubic. In
both cases the equations can be solved easily as a series expansion for both
small and large \lambda and the equations can be inverted to express \lambda as
an explicit function of \Delta. We then consider more general operators and
show how \Delta depends on \lambda in the strong coupling limit. We are also
able to distinguish those states in the Hubbard model which correspond to the
gauge invariant operators for all values of \lambda. Finally, we compare our
results with known results for strings on AdS_5\times S^5, where we find
agreement for a range of R-charges.Comment: 14 pages; v2: 17 pages, 2 figures, appendix and references added;
typos fixed, minor changes; v3 fixed figures; v4 more references added, minor
correctio
Antiferromagnetic Operators in N=4 Supersymmetric Yang-Mills Theory
The spectrum of operators in the su(2) sector of N=4 SYM is bounded because
the number of operators is finite. According to the AdS/CFT correspondence, the
string spectrum in this sector should be also bounded. In this paper the upper
bound on the scaling dimension is calculated in the limit of the large R-charge
using Bethe ansatz.Comment: 12 page
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