96 research outputs found
Free energy for parameterized Polyakov loops in SU(2) and SU(3) lattice gauge theory
We present a study of the free energy of parameterized Polyakov loops P in
SU(2) and SU(3) lattice gauge theory as a function of the parameters that
characterize P. We explore temperatures below and above the deconfinement
transition, and for our highest temperatures T > 5 T_c we compare the free
energy to perturbative results.Comment: Minor changes. Final version to appear in JHE
Angles in Fuzzy Disc and Angular Noncommutative Solitons
The fuzzy disc, introduced by the authors of Ref.[1], is a disc-shaped region
in a noncommutative plane, and is a fuzzy approximation of a commutative disc.
In this paper we show that one can introduce a concept of angles to the fuzzy
disc, by using the phase operator and phase states known in quantum optics. We
gave a description of a fuzzy disc in terms of operators and their commutation
relations, and studied properties of angular projection operators. A similar
construction for a fuzzy annulus is also given. As an application, we
constructed fan-shaped soliton solutions of a scalar field theory on a fuzzy
disc, which corresponds to a fan-shaped D-brane. We also applied this concept
to the theory of noncommutative gravity that we proposed in Ref.[2]. In
addition, possible connections to black hole microstates, holography and an
experimental test of noncommutativity by laser physics are suggested.Comment: 24 pages, 12 figures; v2: minor mistake corrected in Eq.(3.21), and
discussion adapted accordingly; v3: a further discussion on the algebra of
the fuzzy disc added in subsection 3.2; v4: discussions improved and typos
correcte
The deconfinement transition of finite density QCD with heavy quarks from strong coupling series
Starting from Wilson's action, we calculate strong coupling series for the
Polyakov loop susceptibility in lattice gauge theories for various small N_\tau
in the thermodynamic limit. Analysing the series with Pad\'e approximants, we
estimate critical couplings and exponents for the deconfinement phase
transition. For SU(2) pure gauge theory our results agree with those from
Monte-Carlo simulations within errors, which for the coarser N_\tau=1,2
lattices are at the percent level. For QCD we include dynamical fermions via a
hopping parameter expansion. On a N_\tau=1 lattice with N_f=1,2,3, we locate
the second order critical point where the deconfinement transition turns into a
crossover. We furthermore determine the behaviour of the critical parameters
with finite chemical potential and find the first order region to shrink with
growing \mu. Our series moreover correctly reflects the known Z(N) transition
at imaginary chemical potential.Comment: 18 pages, 7 figures, typos corrected, version published in JHE
No Forbidden Landscape in String/M-theory
Scale invariant but non-conformal field theories are forbidden in (1+1)
dimension, and so should be the corresponding holographic dual gravity
theories. We conjecture that such scale invariant but non-conformal field
configurations do not exist in the string/M-theory. We provide a proof of this
conjecture in the classical supergravity limit under a certain gauge condition.
Our proof does also apply in higher dimensional scale invariant but
non-conformal field configurations, which suggests that scale invariant but
non-conformal field theories may be forbidden in higher dimensions as well.Comment: 14 pages, v2: energy condition on c-theorem is corrected, v3: extra
assumption in the proof is discussed due to a sign error in the previous
versio
Finite-Temperature Fractional D2-Branes and the Deconfinement Transition in 2+1 Dimensions
The supergravity dual to N regular and M fractional D2-branes on the cone
over \mathbb{CP}^3 has a naked singularity in the infrared. One can resolve
this singularity and obtain a regular fractional D2-brane solution dual to a
confining 2+1 dimensional N = 1 supersymmetric field theory. The confining
vacuum of this theory is described by the solution of Cvetic, Gibbons, Lu and
Pope. In this paper, we explore the alternative possibility for resolving the
singularity - the creation of a regular horizon. The black-hole solution we
find corresponds to the deconfined phase of this dual gauge theory in three
dimensions. This solution is derived in perturbation theory in the number of
fractional branes. We argue that there is a first-order deconfinement
transition. Connections to Chern--Simons matter theories, the ABJM proposal and
fractional M2-branes are presented.Comment: v3: analytic solutions are expose
The RN/CFT Correspondence Revisited
We reconsidered the quantum gravity description of the near horizon extremal
Reissner-Nordstr{\o}m black hole in the viewpoint of the AdS/CFT
correspondence. We found that, for pure electric case, the right moving central
charge of dual 1D CFT is which is different from the previous result of left moving sector obtained by warped AdS/CFT description. We
discussed the discrepancy in these two approaches and examined novel properties
of our result.Comment: revtex4, 16 pages, sign mistakes corrected, references include
Hidden Conformal Symmetry of the Reissner-Nordstr{\o}m Black Holes
Motivated by recent progresses in the holographic descriptions of the Kerr
and Reissner-Nordstr{\o}m (RN) black holes, we explore the hidden conformal
symmetry of nonextremal uplifted 5D RN black hole by studying the near horizon
wave equation of a massless scalar field propagating in this background.
Similar to the Kerr black hole case, this hidden symmetry is broken by the
periodicity of the associated angle coordinate in the background geometry, but
the results somehow testify the dual CFT description of the nonextremal RN
black holes. The duality is further supported by matching of the entropies and
absorption cross sections calculated from both CFT and gravity sides.Comment: 14 pages, no figur
Holographic Duals of Near-extremal Reissner-Nordstrom Black Holes
We consider the description of
Reissner-Nordstr{\o}m black holes by studying their uplifted counterparts in
five dimensions. Assuming a natural size of the extra dimension, the near
horizon geometries for the extremal limit are exactly . We compute the scattering amplitude of a scalar field, with a
mode near threshold of frequency and extra dimensional momentum, by a near
extremal uplifted black hole. The absorption cross section agrees with the two
point function of the CFT dual to the scalar field.Comment: reference added, improper statements corrected, 17 pages, no figure
Composite GUTs: models and expectations at the LHC
We investigate grand unified theories (GUTs) in scenarios where electroweak
(EW) symmetry breaking is triggered by a light composite Higgs, arising as a
Nambu-Goldstone boson from a strongly interacting sector. The evolution of the
standard model (SM) gauge couplings can be predicted at leading order, if the
global symmetry of the composite sector is a simple group G that contains the
SM gauge group. It was noticed that, if the right-handed top quark is also
composite, precision gauge unification can be achieved. We build minimal
consistent models for a composite sector with these properties, thus
demonstrating how composite GUTs may represent an alternative to supersymmetric
GUTs. Taking into account the new contributions to the EW precision parameters,
we compute the Higgs effective potential and prove that it realizes
consistently EW symmetry breaking with little fine-tuning. The G group
structure and the requirement of proton stability determine the nature of the
light composite states accompanying the Higgs and the top quark: a coloured
triplet scalar and several vector-like fermions with exotic quantum numbers. We
analyse the signatures of these composite partners at hadron colliders:
distinctive final states contain multiple top and bottom quarks, either alone
or accompanied by a heavy stable charged particle, or by missing transverse
energy.Comment: 55 pages, 13 figures, final version to be published in JHE
Online dispute resolution: an artificial intelligence perspective
Litigation in court is still the main dispute resolution mode. However, given the amount
and characteristics of the new disputes, mostly arising out of electronic contracting, courts are
becoming slower and outdated. Online Dispute Resolution (ODR) recently emerged as a set of
tools and techniques, supported by technology, aimed at facilitating conflict resolution. In this
paper we present a critical evaluation on the use of Artificial Intelligence (AI) based techniques in
ODR. In order to fulfill this goal, we analyze a set of commercial providers (in this case twenty
four) and some research projects (in this circumstance six). Supported by the results so far
achieved, a new approach to deal with the problem of ODR is proposed, in which we take on some
of the problems identified in the current state of the art in linking ODR and AI.The work described in this paper is included in TIARAC - Telematics and
Artificial Intelligence in Alternative Conflict Resolution Project (PTDC/JUR/71354/2006), which
is a research project supported by FCT (Science & Technology Foundation), Portugal. The work
of Davide Carneiro is also supported by a doctoral grant by FCT (SFRH/BD/64890/2009).Acknowledgments. The work described in this paper is included in TIARAC - Telematics and Artificial Intelligence in Alternative Conflict Resolution Project (PTDC/JUR/71354/2006), which is a research project supported by FCT (Science & Technology Foundation), Portugal. The work of Davide Carneiro is also supported by a doctoral grant by FCT (SFRH/BD/64890/2009)
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