1,052 research outputs found
Confining properties of QCD at finite temperature and density
A disorder parameter detecting dual superconductivty of the vacuum is used as
a probe to characterize the confining properties of the phase diagram of two
color QCD at finite temperature and density. We obtain evidence for the
disappearing of dual superconductivity (deconfinement) induced by a finite
density of baryonic matter, as well as for a coincidence of this phenomenon
with the restoration of chiral symmetry both at zero and finite density. The
saturation transition induced by Pauli blocking is studied as well, and a
general warning is given about the possible effects that this unphysical
transition could have on the study of the QCD phase diagram at strong values of
the gauge coupling.Comment: 13 pages, 23 figure
The order of the Roberge-Weiss endpoint (finite size transition) in QCD
We consider the endpoint of the Roberge-Weiss (RW) first order transition
line present for imaginary baryon chemical potentials. We remark that it
coincides with the finite size transition relevant in the context of large
QCD and study its order in the theory with two degenerate flavors. The RW
endpoint is first order in the limit of large and small quark masses, while it
weakens for intermediate masses where it is likely in the Ising 3d universality
class. Phenomenological implications and further speculations about the QCD
phase diagram are discussed.Comment: 5 pages, 8 figures. Version accepted for publication in Physical
Review D (R
New Teacher Induction : Locating New Teacher Needs to Co-Construct Induction Programs
This study focused on the transition period from pre-service to teaching known as new teacher induction. Using new teacher voices within third space qualitative interviews to better understand how new teachers made sense of their induction period within a school district, the findings from this study suggest that new teachers are not only faced with immediate and longterm needs that they must fulfill, but also new teachers must make sense of their school environments and the micropolitical atmospheres they must work in. Using the voices of new teachers and teacher coaches within a school district, this study examined how districts can better understand what new teachers experience as they transition into a school or district. The understanding of this liminal stage in a teacherâs career is essential for policymakers, pre-service educators, pre-service teachers, administrators, and perhaps most importantly, veteran teachers if we hope to curb high attrition rates and the effects such have on our students and schools
Chiral transition in a magnetic field and at finite baryon density
We consider the quark-meson model with two quark flavors in a constant
external magnetic field at finite temperature and finite baryon
chemical potential . We calculate the full renormalized effective
potential to one-loop order in perturbation theory. We study the system in the
large- limit, where we treat the bosonic modes at tree level. It is shown
that the system exhibits dynamical chiral symmetry breaking, i. e. that an
arbitrarily weak magnetic field breaks chiral symmetry dynamically, in
agreement with earlier calculations using the NJL model. We study the influence
on the phase transition of the fermionic vacuum fluctuations. For strong
magnetic fields, and in the chiral limit, the transition
is first order in the entire plane if vacuum fluctuations are not
included and second order if they are included. At the physical point, the
transition is a crossover for with and without vacuum fluctuations.Comment: 11 pages. 5figs. V2: fixed a few typos and added refs. Submitted to
PRD. V3: Added refs and substantial revision of tex
Two flavor QCD and Confinement
We argue that the order of the chiral transition for N_f=2 is a sensitive
probe of the QCD vacuum, in particular of the mechanism of color confinement. A
strategy is developed to investigate the order of the transition by use of
finite size scaling analysis. An in-depth numerical investigation is performed
with staggered fermions on lattices with N_t=4 and N_s=12,16,20,24,32 and quark
masses am_q ranging from 0.01335 to 0.307036. The specific heat and a number of
susceptibilities are measured and compared with the expectations of an O(4)
second order and of a first order phase transition. A second order transition
in the O(4) and O(2) universality classes are excluded. Substantial evidence
emerges for a first order transition. A detailed comparison with previous works
is performed.Comment: 46 pages, 20 eps figures, 9 tables, REVTeX
Analyticity in theta on the lattice and the large volume limit of the topological susceptibility
Non-analyticity of QCD with a \theta term at \theta=0 may signal a
spontaneous breaking of both parity and time reversal invariance. We address
this issue by investigating the large volume limit of the topological
susceptibility in pure SU(3) gauge theory. We obtain an upper bound for
the symmetry breaking order parameter and, as a byproduct, the value
\chi=(173.4(+/- 0.5)(+/- 1.2)(+1.1 / -0.2) MeV)^4 at \beta=6 (a approx= 0.1
fermi). The errors are the statistical error from our data, the one derived
from the value used for \Lambda_L and an estimate of the systematic error
respectively.Comment: 15 pages, corrected typos, added 1 reference, minor changes in tex
Chiral Transition of N=4 Super Yang-Mills with Flavor on a 3-Sphere
We use the AdS/CFT correspondence to perform a numerical study of a phase
transition in strongly-coupled large-Nc N = 4 Super-Yang-Mills theory on a
3-sphere coupled to a finite number Nf of massive N = 2 hypermultiplets in the
fundamental representation of the gauge group. The gravity dual system is a
number Nf of probe D7-branes embedded in AdS_5 x S^5. We draw the phase diagram
for this theory in the plane of hypermultiplet mass versus temperature and
identify for temperatures above the Hawking-Page deconfinement temperature a
first-order phase transition line across which the chiral condensate jumps
discontinuously.Comment: 23 pages, 15 figures, minor corrections, reference added, nine
figures improved, no change in results or conclusions; expanded discussion of
fixing finite counterterms in section 3.3, figures updated, no changes to
conclusion
SXP 7.92: A Recently Rediscovered Be/X-ray Binary in the Small Magellanic Cloud, Viewed Edge On
We present a detailed optical and X-ray study of the 2013 outburst of the Small Magellanic Cloud Be/X-ray binary SXP 7.92, as well as an overview of the last 18 years of observations from OGLE (Optical Gravitational Lensing Experiment), RXTE, Chandra and XMM-Newton. We revise the position of this source to RA(J2000) = 00:57:58.4, Dec(J2000) = â72:22:29.5 with a 1Ï uncertainty of 1.5 arcsec, correcting the previously reported position by Coe et al. by more than 20 arcmin. We identify and spectrally classify the correct counterpart as a B1Ve star. The optical spectrum is distinguished by an uncharacteristically deep narrow Balmer series, with the Hα line in particular having a distinctive shell profile, i.e. a deep absorption core embedded in an emission line. We interpret this as evidence that we are viewing the system edge on and are seeing self-obscuration of the circumstellar disc. We derive an optical period for the system of 40.0 ±â0.3 d, which we interpret as the orbital period, and present several mechanisms to describe the X-ray/optical behaviour in the recent outburst, in particular the âflares'and âdipsâ seen in the optical light curve, including a transient accretion disc and an elongated precessing disc
Holographic Roberge-Weiss Transitions
We investigate N=4 SYM coupled to fundamental flavours at nonzero imaginary
quark chemical potential in the strong coupling and large N limit, using
gauge/gravity duality applied to the D3-D7 system, treating flavours in the
probe approximation. The interplay between Z(N) symmetry and the imaginary
chemical potential yields a series of first-order Roberge-Weiss transitions. An
additional thermal transition separates phases where quarks are bound/unbound
into mesons. This results in a set of Roberge-Weiss endpoints: we establish
that these are triple points, determine the Roberge-Weiss temperature, give the
curvature of the phase boundaries and confirm that the theory is analytic in
mu^2 when mu^2~0.Comment: 37 pages, 13 figures; minor comments added, to appear in JHE
- âŠ