422 research outputs found
Light-like Wilson loops in ABJM and maximal transcendentality
We revisit the computation of the two-loop light-like tetragonal Wilson loop
for three dimensional pure Chern-Simons and N=6 Chern-Simons-matter theory,
within dimensional regularization with dimensional reduction scheme. Our
examination shows that, contrary to prior belief, the result respects maximal
transcendentality as is the case of the four-point scattering amplitude of the
theory. Remarkably, the corrected result matches exactly the scattering
amplitude both in the divergent and in the finite parts, constants included.Comment: 11 page
The 1/2 BPS Wilson loop in ABJ(M) at two loops: The details
We compute the expectation value of the 1/2 BPS circular Wilson loop operator
in ABJ(M) theory at two loops in perturbation theory. Our result turns out to
be in exact agreement with the weak coupling limit of the prediction coming
from localization, including finite N contributions associated to non-planar
diagrams. It also confirms the identification of the correct framing factor
that connects framing-zero and framing-one expressions, previously proposed.
The evaluation of the 1/2 BPS operator is made technically difficult in
comparison with other observables of ABJ(M) theory by the appearance of
integrals involving the coupling between fermions and gauge fields, which are
absent for instance in the 1/6 BPS case. We describe in detail how to
analytically solve these integrals in dimensional regularization with
dimensional reduction (DRED). By suitably performing the physical limit to
three dimensions we clarify the role played by short distance divergences on
the final result and the mechanism of their cancellation.Comment: 54 pages, 2 figure
Multifaceted Quadruplet of Low-Lying Spin-Zero States in Ni 66: Emergence of Shape Isomerism in Light Nuclei
A search for shape isomers in the Ni66 nucleus was performed, following old suggestions of various mean-field models and recent ones, based on state-of-the-art Monte Carlo shell model (MCSM), all considering Ni66 as the lightest nuclear system with shape isomerism. By employing the two-neutron transfer reaction induced by an O18 beam on a Ni64 target, at the sub-Coulomb barrier energy of 39 MeV, all three lowest-excited 0+ states in Ni66 were populated and their γ decay was observed by γ-coincidence technique. The 0+ states lifetimes were assessed with the plunger method, yielding for the 02+, 03+, and 04+ decay to the 21+ state the B(E2) values of 4.3, 0.1, and 0.2 Weisskopf units (W.u.), respectively. MCSM calculations correctly predict the existence of all three excited 0+ states, pointing to the oblate, spherical, and prolate nature of the consecutive excitations. In addition, they account for the hindrance of the E2 decay from the prolate 04+ to the spherical 21+ state, although overestimating its value. This result makes Ni66 a unique nuclear system, apart from U236,238, in which a retarded γ transition from a 0+ deformed state to a spherical configuration is observed, resembling a shape-isomerlike behavior
Probing Wilson loops in Chern-Simons-matter theories at weak coupling
For three-dimensional super Chern-Simons-matter theories
associated to necklace quivers , we study at quantum level the two kinds of 1/2 BPS Wilson loop operators
recently introduced in arXiv:1506.07614. We perform a two-loop evaluation and
find the same result for the two kinds of operators, so moving to higher loops
a possible quantum uplift of the classical degeneracy. We also compute the 1/4
BPS bosonic Wilson loop and discuss the quantum version of the cohomological
equivalence between fermionic and bosonic Wilson loops. We compare the
perturbative result with the Matrix Model prediction and find perfect matching,
after identification and remotion of a suitable framing factor. Finally, we
discuss the potential appearance of three-loop contributions that might break
the classical degeneracy and briefly analyse possible implications on the BPS
nature of these operators.Comment: 7 pages, 2 figure
BPS Wilson loops and Bremsstrahlung function in ABJ(M): a two loop analysis
We study a family of circular BPS Wilson loops in N=6 super
Chern-Simons-matter theories, generalizing the usual 1/2-BPS circle. The scalar
and fermionic couplings depend on two deformation parameters and these
operators can be considered as the ABJ(M) counterpart of the DGRT latitudes
defined in N=4 SYM. We perform a complete two-loop analysis of their vacuum
expectation value, discuss the framing dependence and propose a general
relation with cohomologically equivalent bosonic operators. We make an all-loop
proposal for computing the Bremsstrahlung function associated to the 1/2-BPS
cusp in terms of these generalized Wilson loops. When applied to our two-loop
result it reproduces the known expression. Finally, we comment on the
generalization of this proposal to the bosonic 1/6-BPS case.Comment: 46 pages, 6 figures; references adde
Inclusive Universities. Evidence from the Erasmus Program
The Erasmus Program is the main international mobility program in Europe and
worldwide. Since its launch in 1987, it has been growing both in terms of
participants and budget devoted to its activities. However, despite the
possibility to obtain additional funding, the participation of students with
special needs to the program remains extremely low. This work quantifies the
participation of these students to Erasmus and explores the network of
universities involved in their mobility, along the period 2008-2013. In
addition, it proposes a novel index to measure the level of inclusiveness of
universities welcoming international students with disabilities. Quantifying
and analyzing this aspect could be the basis for better designing targeted
policies and for widening the participation of students with impairments to
international mobility.Comment: 23 pages, 5 figure
Gender bias in the Erasmus students network
The Erasmus Program (EuRopean community Action Scheme for the Mobility of
University Students), the most important student exchange program in the world,
financed by the European Union and started in 1987, is characterized by a
strong gender bias. Girls participate to the program more than boys. This work
quantifies the gender bias in the Erasmus program between 2008 and 2013, using
novel data at the university level. It describes the structure of the program
in great details, carrying out the analysis across fields of study, and
identifies key universities as senders and receivers. In addition, it tests the
difference in the degree distribution of the Erasmus network along time and
between genders, giving evidence of a greater density in the female Erasmus
network with respect to the one of the male Erasmus network
The quantum 1/2 BPS Wilson loop in Chern-Simons-matter theories
In three dimensional Chern-Simons-matter theories two
independent fermionic Wilson loop operators can be defined, which preserve half
of the supersymmetry charges and are cohomologically equivalent at classical
level. We compute their three-loop expectation value in a convenient color
sector and prove that the degeneracy is uplifted by quantum corrections. We
expand the matrix model prediction in the same regime and by comparison we
conclude that the quantum 1/2 BPS Wilson loop is the average of the two
operators. We provide an all-loop argument to support this claim at any order.
As a by-product, we identify the localization result at three loops as a
correction to the framing factor induced by matter interactions. Finally, we
comment on the quantum properties of the non-1/2 BPS Wilson loop operator
defined as the difference of the two fermionic ones.Comment: 22 pages + appendixes, 4 figures, 1 Tabl
Aging and IoT: Developing Innovative Solutions in a Quadruple Helix Approach
The paper investigates, through the use of a case study, how local firms can promote technological advancements in a very specific field, such as the one of ICT and IoT applied to the care of elderly people, benefiting from relationships with institutions, enterprises, universities and users in a Quadruple Helix Model. The firm selected, which is launching innovative solutions and systems of connected care and wellness, provides evidence on how technological improvement can flourish if a collaborative approach is followed
ABJM amplitudes and WL at finite N
We evaluate ABJM observables at two loops, for any value of the rank N of the gauge group. We compute the color subleading contributions to the four-point scattering amplitude in ABJM at two loops. Contrary to the four dimensional case, IR divergent N-subleading contributions are proportional to leading poles in the regularization parameter. We then exploit the non-planar calculation for the amplitude to derive an expression for the two-loop Sudakov form factor at any N. In the planar limit the result coincides with the one recently obtained in literature by using Feynman diagrams and unitarity. Finally, we analyze the subleading contributions to the light-like four-cusps Wilson loop and interpret the result in terms of the non-abelian exponentiation theorem. All these perturbative results satisfy the uniform transcendentality principle, hinting at its validity in ABJM beyond the planar limit.Fil: Bianchi, Marco. Humboldt-Universität zu Berlin; AlemaniaFil: Leoni, Marta. Universita Degli Studi Di Milano; Italia. Istituto Nazionale di Fisica Nucleare; ItaliaFil: Leoni Olivera, Matías. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Física de Buenos Aires. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Física de Buenos Aires; ArgentinaFil: Mauri, Andrea. Universita Degli Studi Di Milano; Italia. Istituto Nazionale di Fisica Nucleare; ItaliaFil: Penati, Silvia. Universita Degli Studi Di Milano; Italia. Istituto Nazionale di Fisica Nucleare; ItaliaFil: Santambrogio, Alberto. Istituto Nazionale di Fisica Nucleare; Itali
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