15 research outputs found
Exact beta function from the holographic loop equation of large-N QCD_4
We construct and study a previously defined quantum holographic effective
action whose critical equation implies the holographic loop equation of large-N
QCD_4 for planar self-avoiding loops in a certain regularization scheme. We
extract from the effective action the exact beta function in the given scheme.
For the Wilsonean coupling constant the beta function is exacly one loop and
the first coefficient agrees with its value in perturbation theory. For the
canonical coupling constant the exact beta function has a NSVZ form and the
first two coefficients agree with their value in perturbation theory.Comment: 42 pages, latex. The exponent of the Vandermonde determinant in the
quantum effective action has been changed, because it has been employed a
holomorphic rather than a hermitean resolution of identity in the functional
integral. Beta function unchanged. New explanations and references added,
typos correcte
Strings in flat space and pp waves from Super Yang Mills
We explain how the string spectrum in flat space and pp-waves arises from the
large limit, at fixed , of U(N) super Yang Mills.
We reproduce the spectrum by summing a subset of the planar Feynman diagrams.
We give a heuristic argument for why we can neglect other diagrams. We also
discuss some other aspects of pp-waves and we present a matrix model associated
to the DLCQ description of the maximally supersymmetric eleven dimensional
pp-waves.Comment: 36 pages, 5 figures. v3: minor typos corrected, references adde
Universality of large N phase transitions in Wilson loop operators in two and three dimensions
The eigenvalue distribution of a Wilson loop operator of fixed shape
undergoes a transition under scaling at infinite N. We derive a large N scaling
function in a double scaling limit of the average characteristic polynomial
associated with the Wilson loop operator in two dimensional QCD. We hypothesize
that the transition in three and four dimensional large N QCD are also in the
same universality class and provide a numerical test for our hypothesis in
three dimensions.Comment: 43 pages, 1 table, 18 figures, uses JHEP3.cls, one reference added,
replaced Figure 3 and a small change to eqn (4.8
Twisted local systems solve the (holographic) loop equation of large-N QCD_4
We construct a holographic map from the loop equation of large-N QCD in d=2
and d=4, for planar self-avoiding loops, to the critical equation of an
equivalent effective action. The holographic map is based on two ingredients:
an already proposed holographic form of the loop equation, such that the
quantum contribution is reduced to a regularized residue; a new conformal map
from the region encircled by the based loop to a cuspidal fundamental domain in
the upper half-plane, such that the regularized residue vanishes at the cusp.
As a check, we study the first coefficient of the beta function and that part
of the second coefficient which arises from the rescaling anomaly, in passing
from the Wilsonian to the canonically normalised (holographic) effective
action.Comment: 42 pages, latex; abstract shortened and a reference added as
suggested by the referee; typos in Eq.(72,76,77,82,83,84) correcte
Solving loop equations by Hitchin systems via holography in large-N QCD_4
For (planar) closed self-avoiding loops we construct a "holographic" map from
the loop equations of large-N QCD_4 to an effective action defined over
infinite rank Hitchin bundles. The effective action is constructed densely
embedding Hitchin systems into the functional integral of a partially quenched
or twisted Eguchi-Kawai model, by means of the resolution of identity into the
gauge orbits of the microcanonical ensemble and by changing variables from the
moduli fields of Hitchin systems to the moduli of the corresponding holomorphic
de Rham local systems. The key point is that the contour integral that occurs
in the loop equations for the de Rham local systems can be reduced to the
computation of a residue in a certain regularization. The outcome is that, for
self-avoiding loops, the original loop equations are implied by the critical
equation of an effective action computed in terms of the localisation
determinant and of the Jacobian of the change of variables to the de Rham local
systems. We check, at lowest order in powers of the moduli fields, that the
localisation determinant reproduces exactly the first coefficient of the beta
function.Comment: 65 pages, late
Group measure space decomposition of II_1 factors and W*-superrigidity
We prove a "unique crossed product decomposition" result for group measure
space II_1 factors arising from arbitrary free ergodic probability measure
preserving (p.m.p.) actions of groups \Gamma in a fairly large family G, which
contains all free products of a Kazhdan group and a non-trivial group, as well
as certain amalgamated free products over an amenable subgroup. We deduce that
if T_n denotes the group of upper triangular matrices in PSL(n,Z), then any
free, mixing p.m.p. action of the amalgamated free product of PSL(n,Z) with
itself over T_n, is W*-superrigid, i.e. any isomorphism between L^\infty(X)
\rtimes \Gamma and an arbitrary group measure space factor L^\infty(Y) \rtimes
\Lambda, comes from a conjugacy of the actions. We also prove that for many
groups \Gamma in the family G, the Bernoulli actions of \Gamma are
W*-superrigid.Comment: Final version. Some extra details have been added to improve the
expositio
Human papilloma virus: Apprehending the link with carcinogenesis and unveiling new research avenues (Review)
Human papilloma viruses (HPV) are a small group of non-enveloped viruses belonging to the Papillomaviridae family with strong similarities to polyoma viruses. The viral particles consist of a genome in the form of a circular double-stranded DNA, encompassing eight open reading frames, as well as a non-enveloped icosahedral capsid. HPV infection is considered the most common sexually transmitted disease in both sexes and is strongly implicated in the pathogenesis of different types of cancer. 'High-risk' mucosal HPV types, predominantly types 16, 18, 31, 33 and 35, are associated with most cervical, penile, vulvar, vaginal, anal, oropharyngeal cancers and pre-cancers. Screening for HPV is necessary for the prognosis and for determining treatment strategies for cancer. Novel HPV markers, including proteomic and genomic markers, as well as anti-papillomavirus vaccines are currently available. The aim of this comprehensive review was to thoroughly present the updated information on virus development, cancer occurrence, treatment and prevention strategies, in an attempt to shed further light into the field, including novel research avenues
Neuroendocrine factors: The missing link in non-melanoma skin cancer (Review)
Non-melanoma skin cancer (NMSC) is the most common form of cancer worldwide, comprising 95% of all cutaneous malignancies and approximately 40% of all cancers. In spite of intensive efforts aimed towards awareness campaigns and sun-protective measures, epidemiological data indicate an increase in the incidence of NMSC. This category of skin cancers has many common environmental triggers. Arising primarily on sun-exposed skin, it has been shown that ultraviolet radiation is, in the majority of cases, the main trigger involved in the pathogenesis of NMSC. Aside from the well-known etiopathogenic factors, studies have indicated that several neuroactive factors are involved in the carcinogenesis of two of the most common types of NMSC, namely basal cell carcinoma (BCC) and squamous cell carcinoma (SCC), with the exception of penile SCC, for which a paucity of specific data on their pathogenic role exists. The complex interaction between the peripheral nervous system and target cells in the skin appears to be mediated by locally released neuroendocrine factors, such as catecholamines, substance P, calcitonin gene-related peptide and somatostatin, as well as neurohormones, such as proopiomelanocortin and its derived peptides, α-melanocyte-stimulating hormone and adrenocorticotropin. All these factors have been, at least at some point, a subject of debate regarding their precise role in the pathogenesis of NMSC. There is also a significant body of evidence indicating that psychological stress is a crucial impact factor influencing the course of skin cancers, including SCC and BCC. Numerous studies have suggested that neuroendocrine factor dysregulation, as observed in stress reactions, may be involved in tumorigenesis, accelerating the development and progression, and suppressing the regression of NMSC. Further studies are required in order to elucidate the exact mechanisms through which neuroactive molecules promote or inhibit cutaneous carcinogenesis, as this could lead to the development of more sophisticated and tailored treatment protocols, as well as open new perspectives in skin cancer research