710 research outputs found
Pseudo Goldstones at Future Colliders from the Extended Bess Model
We consider the production of the lightest pseudo-Goldstone bosons at future
colliders through the vector resonances predicted by the extended BESS model,
which consists of an effective lagrangian parametrization with dynamical
symmetry breaking, describing scalar, vector and axial-vector bound states in a
rather general framework. We find that the detection of pseudo-Goldstone pairs
at LHC requires a careful evaluation of backgrounds. For e+e- collisions in the
TeV range the backgrounds can be easily reduced and the detection of
pseudo-Goldstone pairs is generally easier.Comment: 17 pages and 12 figures (included as a uuencoded tar file), LaTeX
(style article), UGVA-DPT 1994/03-84
Meson current in the CFL phase
We study the stability of the color-flavor locked (CFL) phase of dense quark
matter with regard to the formation of a non-zero Goldstone boson current. We
show that an instability appears in the vicinity of the point
which marks the appearance of gapless fermion modes in the CFL phase. Here,
is the shift in chemical potential due to the strange
quark mass and is the gap in the chiral limit. We show that in the
Goldstone boson current phase all components of the magnetic screening mass are
real. In this work we do not take into account homogeneous kaon condensation.
We study the effects of an instanton induced interaction of the magnitude
required to suppress kaon condensation.Comment: 15 pages, 5 figures, v2: minor improvements, results unchange
Characterizing the Larkin-Ovchinnikov-Fulde-Ferrel phase induced by the chromomagnetic instability
We discuss possible destinations from the chromomagnetic instability in color
superconductors with Fermi surface mismatch . In the two-flavor
superconducting (2SC) phase we calculate the effective potential for color
vector potentials which are interpreted as the net momenta of
pairing in the Larkin-Ovchinnikov-Fulde-Ferrel (LOFF) phase. When
where is the gap energy, the effective
potential suggests that the instability leads to a LOFF-like state which is
characterized by color-rotated phase oscillations with small . In the
vicinity of the magnitude of continuously
increases from zero as the effective potential has negative larger curvature at
vanishing that is the Meissner mass squared. In the gapless 2SC
(g2SC) phase, in contrast, the effective potential has a minimum at
even when the negative Meissner mass squared
is infinitesimally small. Our results imply that the chromomagnetic instability
found in the gapless phase drives the system toward the LOFF state with
.Comment: 6 pages, 3 figures; fatal typo about the conclusion corrected;
reference adde
Larkin-Ovchinnikov-Fulde-Ferrell state in two-color quark matter
We explore the phase structure of two-color and two-flavor QCD in the space
of the quark chemical potential \mu_q and the isospin chemical potential \mu_I.
Using a mean-field model we calculate the chiral and diquark condensates,
\sigma and \Delta, self-consistently. In weak coupling and in the chiral limit,
we confirm the interval of the isospin chemical potential,
0.71\Delta_0<\mu_I<0.75\Delta_0, in which a single plane-wave
Larkin-Ovchinnikov-Fulde-Ferrell (LOFF) phase is favored over isotropic
superfluidity and normal quark matter. The LOFF window becomes slightly wider
at high density. For stronger coupling with nonzero quark mass, which is
relevant to currently available numerical simulations in lattice two-color QCD,
the single plane-wave LOFF phase appears only at sufficiently high density. The
prediction obtained for the LOFF region could be tested with lattice since we
can prove that the present system is free from the fermion sign problem. We
draw the energy landscape on which local minima corresponding to the isotropic
superfluid phase and the LOFF phase and a local maximum corresponding to the
gapless phase are manifest. Our results clearly illustrate the path from the
the unstable gapless phase down to the LOFF phase.Comment: 10 pages, 8 figure
Chiral Models in Noncommutative N=1/2 Four Dimensional Superspace
We derive the component Lagrangian for a generic N=1/2 supersymmetric chiral
model with an arbitrary number of fields in four space-time dimensions. We then
investigate a toy model in which the deformation parameter modifies the
undeformed potential near the origin of the field space in a way which suggests
possible physical applications.Comment: Final version to appear in Physical Review D. We have added a new
section in which we show that our component action can be resummed. The final
answer takes a simple compact form. We also show how differences emerge for
the modified Kaehler structure with respect to the ones found in the
literature. We have also added two reference
Algebras, Derivations and Integrals
In the context of the integration over algebras introduced in a previous
paper, we obtain several results for a particular class of associative algebras
with identity. The algebras of this class are called self-conjugated, and they
include, for instance, the paragrassmann algebras of order , the
quaternionic algebra and the toroidal algebras. We study the relation between
derivations and integration, proving a generalization of the standard result
for the Riemann integral about the translational invariance of the measure and
the vanishing of the integral of a total derivative (for convenient boundary
conditions). We consider also the possibility, given the integration over an
algebra, to define from it the integral over a subalgebra, in a way similar to
the usual integration over manifolds. That is projecting out the submanifold in
the integration measure. We prove that this is possible for paragrassmann
algebras of order , once we consider them as subalgebras of the algebra of
the matrices. We find also that the integration over the
subalgebra coincides with the integral defined in the direct way. As a
by-product we can define the integration over a one-dimensional Grassmann
algebra as a trace over matrices.Comment: 23 pages, few typos corrected. Final version to be published in
International Journal of Modern Physic
An alternative model for the electroweak symmetry breaking sector and its signature in future e-gamma colliders
We perform a preliminary study of the deviations from the Standard Model
prediction for the cross section for the process . We work in the context of a higgsless chiral lagrangian model that
includes an extra vector resonance and an anomalous coupling.
We find that this cross section can provide interesting constraints on the free
parameters of the model once it is measured in future colliders.Comment: LaTex , 14 pages, 5 figures not included but available as postscript
files upon request, NUB-3086/94-T
Pion and kaon condensation in a 3-flavor NJL model
We analyze the phase diagram of a three-flavor Nambu-Jona-Lasinio model at
finite temperature and chemical potentials . We study
the competition of pion and kaon condensation and we propose a physical
situation in which kaon condensation could be led only by light quark finite
densities.Comment: 21 pages, 8 figures include
Thermodynamics of the Massive Gross-Neveu Model
We study the thermodynamics of massive Gross-Neveu models with explicitly
broken discrete or continuous chiral symmetries for finite temperature and
fermion densities. The large limit is discussed bearing attention to the
no-go theorems for symmetry breaking in two dimensions which apply to the
massless cases. The main purpose of the study is to serve as analytical
orientation for the more complex problem of chiral transition in
dimensional QCD with quarks. For any non-vanishing fermion mass we find, at
finite densities, lines of first order phase transitions. For small mass values
traces of would-be second order transitions and a tricritical point are
recognizable. We study the thermodynamics of these models, and in the model
with broken continuous chiral symmetry we examine the properties of the pion
like state.Comment: 34 pages (+18 figures, available upon request to [email protected]),
LATEX file, uses art12a.sty, macro included, UGVA-DPT 1994/06-85
Goldstone boson currents in a kaon condensed CFL phase
We study the stability of the kaon condensed color-flavor locked (CFL) phase
of dense quark matter with regard to the formation of a non-zero Goldstone
boson current. In the kaon condensed phase there is an electrically charged
fermion which becomes gapless near \mu_s^(1) \simeq 1.35\Delta and a neutral
fermion which becomes gapless near \mu_s^(2)\simeq 1.61\Delta. Here,
\mu_s=m_s^2/(2p_F) is the shift in the Fermi energy due to the strange quark
mass m_s and \Delta is the gap in the chiral limit. The transition to the
gapless phase is continuous at \mu_s^(1) and first order at \mu_s^(2). We find
that the magnetic screening masses are real in the regime \mu_s< \mu_s^(2), but
some screening masses are imaginary for \mu_s> \mu_s^(2). We show that there is
a very weak current instability for \mu_s>\mu_s^(1) and a more robust
instability in a small window near \mu_s^(2). We also show that in the
Goldstone boson current phase all components of the magnetic screening mass are
real. There is a range of values of \mu_s below 2\Delta in which the magnetic
gluon screening masses are imaginary but the phase is stable with respect to
electrically neutral fluctuations of the gauge field.Comment: 16 page
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