Search results for "Quantum"

3-Vinyl-1H-indoles: A conformational study, electronic aspects and reactivity predictions forDiels-Alder reactions

1995

On the basis of X-ray geometries, a theoretical conformational study of some 3-vinyl-1H-indoles was performed with quantum chemistry and molecular mechanics programs. Charge, frontier orbitals, and the molecular electrostatic potential derived from quantum chemistry calculations of 3-vinyl-1H-indoles are reliable reactivity parameters to predict the outcome of theDiels-Alder reaction.

Unconventional phases of attractive Fermi gases in synthetic Hall ribbons

2017

An innovative way to produce quantum Hall ribbons in a cold atomic system is to use M hyperfine states of atoms in a one-dimensional optical lattice to mimic an additional "synthetic dimension." A notable aspect here is that the SU(M) symmetric interaction between atoms manifests as "infinite ranged" along the synthetic dimension. We study the many-body physics of fermions with SU(M) symmetric attractive interactions in this system using a combination of analytical field theoretic and numerical density-matrix renormalization-group methods. We uncover the rich ground-state phase diagram of the system, including unconventional phases such as squished baryon fluids, shedding light on many-body…

Front propagation in the one-dimensional autocatalyticA+B→2Areaction with decay

1999

We consider front propagation in the autocatalytic scheme $A+\stackrel{\ensuremath{\rightarrow}}{B}2A,$ where we also allow the A particles to decay, $\stackrel{\ensuremath{\rightarrow}}{A}0,$ with a constant decay rate $\ensuremath{\beta}.$ In a one dimensional, discrete, situation the A domain moves as a pulse, and its dynamics differs from what is found in higher dimensions. Thus the velocity of the pulse tends to a finite value when $\ensuremath{\beta}$ approaches from below the critical value ${\ensuremath{\beta}}_{c},$ at which pulses die out. On the other hand, when approaching ${\ensuremath{\beta}}_{c}$ from above, the mean lifetime of the pulse grows as $T\ensuremath{\propto}(\ensu…

Magnetic tunneling junctions with the Heusler compound

2005

Abstract Certain Heusler phases belong to the materials which are discussed as potential half metals. Here, results of tunneling experiments with the full-Heusler alloy Co 2 Cr 0.6 Fe 0.4 Al are presented. The Heusler alloy is used as an electrode of magnetic tunneling junctions. The junctions are deposited by magnetron DC sputtering using shadow mask techniques with AlO x as a barrier and cobalt as counter electrode. Measurements of the magnetoresistive differential conductivity in a temperature range between 4 and 300 K are shown. An analysis of the barrier properties applying the Simmons model to the bias dependent junction conductivity is performed. VSM measurements were carried out to …

Learning-Graph-Based Quantum Algorithm for k-distinctness

2012

We present a quantum algorithm solving the $k$-distinctness problem in $O(n^{1-2^{k-2}/(2^k-1)})$ queries with a bounded error. This improves the previous $O(n^{k/(k+1)})$-query algorithm by Ambainis. The construction uses a modified learning graph approach. Compared to the recent paper by Belovs and Lee arXiv:1108.3022, the algorithm doesn't require any prior information on the input, and the complexity analysis is much simpler. Additionally, we introduce an $O(\sqrt{n}\alpha^{1/6})$ algorithm for the graph collision problem where $\alpha$ is the independence number of the graph.

A combined experimental and theoretical study of the thermal cycloaddition of aryl azides with activated alkenes.

2011

International audience; Reactions were performed from aryl azides on the one hand, and activated alkenes coming from β-dicarbonyl compounds or malonodinitrile on the other hand, either with recourse to conventional heating or to microwave activation, to afford 1-aryl-1H-1,2,3-triazoles. The mechanism and the regioselectivity of the reactions involving β-dicarbonyl compounds have been theoretically studied using DFT methods at the B3LYP/6-31G* level: they are domino processes comprising a tautomeric equilibrium of the β-dicarbonyl compounds with their enol forms, a 1,3-dipolar cycloaddition of the enol forms with the aryl azides (high activation energy), and a dehydration process (lower acti…

Stepwise formation of a pentanuclear Ni4Cu heterometallic complex exhibiting a vertex-sharing defective double-cubane core and diphenoxo- and phenoxo…

2013

Sequential reaction of a N5O3 octadentate tripodal ligand with Ni(2+) and subsequently with Cu(2+) and azide ligand afforded the first example of a heterobridged (phenoxo/μ(1,1)-azido) pentanuclear heterometallic (Ni4Cu) compound, which exhibits a centrosymmetric vertex-sharing defective double-cubane structure. The study of the magnetic properties reveals that the compound shows ferromagnetic interaction interactions, leading to an S = 9/2 spin ground state. Density functional theory calculations on the X-ray structure and model compounds predict ferromagnetic interactions through the magnetic exchange pathways involving each couple of metal ions.

Orthorhombic polymorphs of twotrans-4-aminoazoxybenzenes

2002

The two isomeric compounds 4-amino-ONN-azoxybenzene [or 1-(4-aminophenyl)-2-phenyldiazene 2-oxide], i.e. the alpha isomer, and 4-amino-NNO-azoxybenzene [or 2-(4-aminophenyl)-1-phenyldiazene 2-oxide], i.e. the beta isomer, both C(12)H(11)N(3)O, crystallized from a polar solvent in orthorhombic space groups, and their crystal and molecular structures have been determined using X-ray diffraction. There are no significant differences in the bond lengths and valence angles in the two isomers, in comparison with their monoclinic polymorphs. However, the conformations of the molecules are different due to rotation along the Ar-N bonds. In the alpha isomer, the benzene rings are twisted by 31.5 (2)…

Trying to fuse the basic mathematical ideas of quantum TGD to a single coherent whole

The theoretical framework behind TGD involves several different strands and the goal is to unify them to a single coherent whole. TGD involves number theoretic and geometric visions about physics and $M^8-H$ duality, analogous to Langlands duality, is proposed to unify them. Also quantum classical correspondence (QCC) is a central aspect of TGD. One should understand both the $M^8-H$ duality and QCC at the level of detail. The following mathematical notions are expected to be of relevance for this goal. \begin{enumerate} \item Von Neumann algebras, call them $M$, in particular hyperfinite factors of type $II_1$ (HFFs), are in a central role. Both the geometric and number theoretic side, QCC…

Some New Ideas Related to Langlands Program viz. TGD

Langlands' program seeks to relate Galois groups in algebraic number theory to automorphic forms and representation theory of algebraic groups over local fields and adeles. Langlands program is described by Edward Frenkel as a kind of grand unified theory of mathematics. In the TGD framework, $M^8-M^4\times CP_2$ duality assigns to a rational polynomial a set of mass shells $H^3$ in $M^4\subset M^8$ and by associativity condition a 4-D surface in $M^8$, and its it to $H=M^4\times CP_2$. $M^8-M^4\times CP_2$ means that number theoretic vision and geometric vision of physics are dual or at least complementary. This vision could extend to a trinity of number theoretic, geometric and topologica…