1,434 research outputs found
Comments on Baryon Melting in Quark Gluon Plasma with Gluon Condensation
We consider a black hole solution with a non-trivial dilaton from IIB super
gravity which is expected to describe a strongly coupled hot gauge plasma with
non-vanishing gluon condensation present. We construct a rotating and moving
baryon to probe the screening and phases of the plasma. Melting of the baryons
in hot plasma in this background had been studied previously, however, we show
that baryons melt much lower temperature than has been suggested previously.Comment: 3 figures, 12 page
Phase Structure of a Brane/Anti-Brane System at Large N
We further analyze a class of recently studied metastable string vacua
obtained by wrapping D5-branes and anti-D5-branes over rigid homologous S^2's
of a non-compact Calabi-Yau threefold. The large N dual description is
characterized by a potential for the glueball fields which is determined by an
auxiliary matrix model. The higher order corrections to this potential produce
a suprisingly rich phase structure. In particular, at sufficiently large 't
Hooft coupling the metastable vacua present at weak coupling cease to exist.
This instability can already be seen by an open string two loop contribution to
the glueball potential. The glueball potential also lifts some of the
degeneracy in the vacua characterized by the phases of the glueball fields.
This generates an exactly computable non-vanishing axion potential at large N.Comment: v3: 55 pages, 11 figures, typos correcte
Competition and coexistence of bond and charge orders in (TMTTF)2AsF6
(TMTTF)2AsF6 undergoes two phase transitions upon cooling from 300 K. At
Tco=103 K a charge-ordering (CO) occurs, and at Tsp(B=9 T)=11 K the material
undergoes a spin-Peierls (SP) transition. Within the intermediate, CO phase,
the charge disproportionation ratio is found to be at least 3:1 from carbon-13
NMR 1/T1 measurements on spin-labeled samples. Above Tsp, up to about 3Tsp,
1/T1 is independent of temperature, indicative of low-dimensional magnetic
correlations. With the application of about 0.15 GPa pressure, Tsp increases
substantially, while Tco is rapidly suppressed, demonstrating that the two
orders are competing. The experiments are compared to results obtained from
calculations on the 1D extended Peierls-Hubbard model.Comment: 4 pages, 5 figure
Neutron beam test of CsI crystal for dark matter search
We have studied the response of Tl-doped and Na-doped CsI crystals to nuclear
recoils and 's below 10 keV. The response of CsI crystals to nuclear
recoil was studied with mono-energetic neutrons produced by the
H(p,n)He reaction. This was compared to the response to Compton
electrons scattered by 662 keV -ray. Pulse shape discrimination between
the response to these 's and nuclear recoils was studied, and quality
factors were estimated. The quenching factors for nuclear recoils were derived
for both CsI(Na) and CsI(Tl) crystals.Comment: 21pages, 14figures, submitted to NIM
Scale-Dependent Non-Gaussianity as a Generalization of the Local Model
We generalize the local model of primordial non-Gaussianity by promoting the
parameter fNL to a general scale-dependent function fNL(k). We calculate the
resulting bispectrum and the effect on the bias of dark matter halos, and thus
the extent to which fNL(k) can be measured from the large-scale structure
observations. By calculating the principal components of fNL(k), we identify
scales where this form of non-Gaussianity is best constrained and estimate the
overlap with previously studied local and equilateral non-Gaussian models.Comment: Accepted to JCAP. 22 pages, 4 figure
Optical spectroscopic study of the interplay of spin and charge in NaV2O5
We investigate the temperature dependent optical properties of NaV2O5, in the
energy range 4meV-4eV. The symmetry of the system is discussed on the basis of
infrared phonon spectra. By analyzing the optically allowed phonons at
temperatures below and above the phase transition, we conclude that a
second-order change to a larger unit cell takes place below 34 K, with a
fluctuation regime extending over a broad temperature range. In the high
temperature undistorted phase, we find good agreement with the recently
proposed centrosymmetric space group Pmmn. On the other hand, the detailed
analysis of the electronic excitations detected in the optical conductivity,
provides direct evidence for a charge disproportionated electronic
ground-state, at least on a locale scale: A consistent interpretation of both
structural and optical conductivity data requires an asymmetrical charge
distribution on each rung, without any long range order. We show that, because
of the locally broken symmetry, spin-flip excitations carry a finite electric
dipole moment, which is responsible for the detection of direct two-magnon
optical absorption processes for E parallel to the a axis. The charged-magnon
model, developed to interpret the optical conductivity of NaV2O5, is described
in detail, and its relevance to other strongly correlated electron systems,
where the interplay of spin and charge plays a crucial role in determining the
low energy electrodynamics, is discussed.Comment: Revtex, 19 pages, 16 postscript pictures embedded in the text,
submitted to PRB. Find more stuff at
http://www.stanford.edu/~damascel/andreaphd.html or
http://www.ub.rug.nl/eldoc/dis/science/a.damascelli
Symmetrized mean-field description of magnetic instabilities in k-(BEDT-TTF)_2Cu[N(CN)]_2 Y salts
We present a novel and convenient mean-field method, and apply it to study
the metallic/antiferromagnetic interface of k-(BEDT-TTF)_2Cu[N(CN)]_2 Y organic
superconductors (BEDT_TTF is bis-ethylen-dithio-tetrathiafulvalene, Y=Cl, Br).
The method, which fully exploits the crystal symmetry, allows one to obtain the
mean-field solution of the 2D Hubbard model for very large lattices, up to
6x10^5 sites, yielding a reliable description of the phase boundary in a wide
region of the parameter space. The metal/antiferromagnet transtion appears to
be second order, except for a narrow region of the parameter space, where the
transition is very sharp and possibly first order. The cohexistence of metallic
and antiferromagnetic properties is only observed for the transient state in
the case of smooth second order transitions. The relevance of the present
resaults to the complex experimental behavior of centrosymmetric k-phase
BEDT-TTF salts is discussed.Comment: 9 pages in PS format, 7 figures (included in PS), 1 tabl
Baryon Mass in medium with Holographic QCD
We study the baryon vertex (BV) in the presence of medium using DBI action
and the force balance condition between BV and the probe branes. We note that a
stable BV configuration exists only in some of the confining backgrounds. For
the system of finite density, the issue is whether there is a canonical
definition for the baryon mass in the medium. In this work, we define it as the
energy of the deformed BV satisfying the force balance condition (FBC) with the
probe brane. With FBC, lengths of the strings attached to the BV tend to be
zero while the compact branes are enlongated to mimic the string. We attribute
the deformation energy of the probe brane to the baryon-baryon interaction. We
show that for a system with heavy quarks the baryon mass drops monotonically as
a function of density while it has minimum in case of light quark system.Comment: 24 pages, 14 figures, RevTeX, Typos and errors correcte
Making things happen : a model of proactive motivation
Being proactive is about making things happen, anticipating and preventing problems, and seizing opportunities. It involves self-initiated efforts to bring about change in the work environment and/or oneself to achieve a different future. The authors develop existing perspectives on this topic by identifying proactivity as a goal-driven process involving both the setting of a proactive goal (proactive goal generation) and striving to achieve that proactive goal (proactive goal striving). The authors identify a range of proactive goals that individuals can pursue in organizations. These vary on two dimensions: the future they aim to bring about (achieving a better personal fit within one’s work environment, improving the organization’s internal functioning, or enhancing the organization’s strategic fit with its environment) and whether the self or situation is being changed. The authors then identify “can do,” “reason to,” and “energized to” motivational states that prompt proactive goal generation and sustain goal striving. Can do motivation arises from perceptions of self-efficacy, control, and (low) cost. Reason to motivation relates to why someone is proactive, including reasons flowing from intrinsic, integrated, and identified motivation. Energized to motivation refers to activated positive affective states that prompt proactive goal processes. The authors suggest more distal antecedents, including individual differences (e.g., personality, values, knowledge and ability) as well as contextual variations in leadership, work design, and interpersonal climate, that influence the proactive motivational states and thereby boost or inhibit proactive goal processes. Finally, the authors summarize priorities for future researc
Stripes and holes in a two-dimensional model of spinless fermions and hardcore bosons
We consider a Hubbard-like model of strongly-interacting spinless fermions
and hardcore bosons on a square lattice, such that nearest neighbor occupation
is forbidden. Stripes (lines of holes across the lattice forming antiphase
walls between ordered domains) are a favorable way to dope this system below
half-filling. The problem of a single stripe can be mapped to a spin-1/2 chain,
which allows understanding of its elementary excitations and calculation of the
stripe's effective mass for transverse vibrations. Using Lanczos exact
diagonalization, we investigate the excitation gap and dispersion of a hole on
a stripe, and the interaction of two holes. We also study the interaction of
two, three, and four stripes, finding that they repel, and the interaction
energy decays with stripe separation as if they are hardcore particles moving
in one (transverse) direction. To determine the stability of an array of
stripes against phase separation into particle-rich phase and hole-rich liquid,
we evaluate the liquid's equation of state, finding the stripe-array is not
stable for bosons but is possibly stable for fermions.Comment: 24 pages, 18 figure
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