Linked Into a Job?: the Ethical Considerations of Recruiting Through LinkedIn

LinkedIn’s goal is to help business professionals meet, make business deals, inquire about jobs, and find careers through connections with people that members already know. This research study will investigate the ethical practices of LinkedIn recruitment. Students’ awareness of the methods for effective use, as well as the damaging elements of a LinkedIn profile will be examined. LinkedIn is an effective, helpful tool for recruiting candidates and for job searching; however, the best results will come to those who use LinkedIn professionally and with caution. Our findings indicate that despite its risks, jobseekers and employers can benefit from using LinkedIn

Analytical results for the entanglement dynamics of disjoint blocks in the XY spin chain

The study of the dynamics of entanglement measures after a quench has become a very active area of research in the last two decades, motivated by the development of experimental techniques. However, exact results in this context are available in only very few cases. In this work, we present the proof of the quasiparticle picture for the dynamics of entanglement entropies for two disjoint blocks in the XY chain after a quantum quench. As a byproduct, we also prove the quasiparticle conjecture for the mutual information in that model. Our calculations generalize those presented in [M. Fagotti, P. Calabrese, Phys. Rev. A 78, 010306 (2008)] to the case where the correlation matrix is a block-Toeplitz matrix, and rely on the multidimensional stationary phase approximation in the scaling limit. We also test the quasiparticle predictions against exact numerical calculations, and find excellent agreement. In the case of three blocks, we show that the tripartite information vanishes when at least two blocks are adjacent.Comment: 22 page

On reflected entropy and computable cross-norm negativity: Free theories and symmetry resolution

We investigate a separability criterion based on the computable cross-norm (CCNR), and a related quantity called the CCNR negativity. We introduce a reflected version of the CCNR negativity, and discuss its connection with other well-established entanglement-related quantities, namely the reflected entropy and the operator entanglement entropy. For free fermionic and bosonic theories, we derive exact formulas in terms of two-point correlation functions, which allows for systematic numerical investigations and, in principle, analytical treatments. For systems with a global $U(1)$ symmetry, we study the symmetry-resolved reflected entropy and CCNR negativity. We provide conformal field theory (CFT) results for the charged moments in the case of adjacent intervals, finding perfect agreement with the numerics. We observe an equipartition of reflected entropies and CCNR negativities, both for free fermions and free bosons models. The first charge-dependent correction are conjectured for fermions, and worked out from the CFT calculations for bosons.Comment: 9+2 pages, 3 figure

Quasiparticle dynamics of symmetry resolved entanglement after a quench: the examples of conformal field theories and free fermions

The time evolution of the entanglement entropy is a key concept to understand the structure of a non-equilibrium quantum state. In a large class of models, such evolution can be understood in terms of a semiclassical picture of moving quasiparticles spreading the entanglement throughout the system. However, it is not yet known how the entanglement splits between the sectors of an internal local symmetry of a quantum many-body system. Here, guided by the examples of conformal field theories and free-fermion chains, we show that the quasiparticle picture can be adapted to this goal, leading to a general conjecture for the charged entropies whose Fourier transform gives the desired symmetry resolved entanglement $S_n(q)$. We point out two physically relevant effects that should be easily observed in atomic experiments: a delay time for the onset of $S_n(q)$ which grows linearly with $|\Delta q|$ (the difference from the charge $q$ and its mean value), and an effective equipartition when $|\Delta q|$ is much smaller than the subsystem size.Comment: 7 pages, 2 figure

Bipartite fidelity of critical dense polymers

We investigate the bipartite fidelity $\mathcal F_d$ for a lattice model described by a logarithmic CFT: the model of critical dense polymers. We define this observable in terms of a partition function on the pants geometry, where $d$ defects enter at the top of the pants lattice and exit in one of the legs. Using the correspondence with the XX spin chain, we obtain an exact closed-form expression for $\mathcal F_d$ and compute the leading terms in its $1/N$ asymptotic expansion as a function of $x = N_A/N$, where $N$ is the lattice width at the top of the pants and $N_A$ is the width of the leg where the defects exit. We find an agreement with the results of St\'ephan and Dubail for rational CFTs, with the central charge and conformal weights specialised to $c=-2$ and $\Delta = \Delta_{1,d+1} = d(d-2)/8$. We compute a second instance $\mathcal {\tilde F}_2$ of the bipartite fidelity for $d=2$ by imposing a different rule for the connection of the defects. In the conformal setting, this choice corresponds to inserting two boundary condition changing fields of weight $\Delta = 0$ that are logarithmic instead of primary. We compute the asymptotic expansion in this case as well and find a simple additive correction compared to $\mathcal F_2$, of the form $-2\log((1+x)/(2\sqrt{x}))$. We confirm this lattice result with a CFT derivation and find that this correction term is identical for all logarithmic theories, independently of $c$ and $\Delta$.Comment: 35 pages. v2: minor change

Separability and entanglement of resonating valence-bond states

We investigate separability and entanglement of Rokhsar-Kivelson (RK) states and resonating valence-bond (RVB) states. These states play a prominent role in condensed matter physics, as they can describe quantum spin liquids and quantum critical states of matter, depending on their underlying lattices. For dimer RK states on arbitrary tileable graphs, we prove the exact separability of the reduced density matrix of $k$ disconnected subsystems, implying the absence of bipartite and multipartite entanglement between the subsystems. For more general RK states with local constraints, we argue separability in the thermodynamic limit, and show that any local RK state has zero logarithmic negativity, even if the density matrix is not exactly separable. In the case of adjacent subsystems, we find an exact expression for the logarithmic negativity in terms of partition functions of the underlying statistical model. For RVB states, we show separability for disconnected subsystems up to exponentially small terms in the distance $d$ between the subsystems, and that the logarithmic negativity is exponentially suppressed with $d$. We argue that separability does hold in the scaling limit, even for arbitrarily small ratio $d/L$, where $L$ is the characteristic size of the subsystems. Our results hold for arbitrary lattices, and encompass a large class of RK and RVB states, which include certain gapped quantum spin liquids and gapless quantum critical systems.Comment: 18 pages, 8 figures, v2: new discussion on multipartite entanglement and separability, v3: minor modification

Bipartite fidelity for models with periodic boundary conditions

For a given statistical model, the bipartite fidelity $\mathcal F$ is computed from the overlap between the groundstate of a system of size $N$ and the tensor product of the groundstates of the same model defined on two subsystems $A$ and $B$, of respective sizes $N_A$ and $N_B$ with $N = N_A + N_B$. In this paper, we study $\mathcal F$ for critical lattice models in the case where the full system has periodic boundary conditions. We consider two possible choices of boundary conditions for the subsystems $A$ and $B$, namely periodic and open. For these two cases, we derive the conformal field theory prediction for the leading terms in the $1/N$ expansion of $\mathcal F$, in a most general case that corresponds to the insertion of four and five fields, respectively. We provide lattice calculations of $\mathcal F$, both exact and numerical, for two free-fermionic lattice models: the XX spin chain and the model of critical dense polymers. We study the asymptotic behaviour of the lattice results for these two models and find an agreement with the predictions of conformal field theory.Comment: 54 page

Multipartite information of free fermions on Hamming graphs

We investigate multipartite information and entanglement measures in the ground state of a free-fermion model defined on a Hamming graph. Using the known diagonalization of the adjacency matrix, we solve the model and construct the ground-state correlation matrix. Moreover, we find all the eigenvalues of the chopped correlation matrix when the subsystem consists of $n$ disjoint Hamming subgraphs embedded in a larger one. These results allow us to find an exact formula for the entanglement entropy of disjoint graphs, as well as for the mutual and tripartite information. We use the exact formulas for these measures to extract their asymptotic behavior in two distinct thermodynamic limits, and find excellent match with the numerical calculations. In particular, we find that the entanglement entropy admits a logarithmic violation of the area law which decreases the amount of entanglement compared to the area law scaling.Comment: 12 pages, 4 figures, v2: minor modification

Absence of logarithmic enhancement in the entanglement scaling of free fermions on folded cubes

This study investigates the scaling behavior of the ground-state entanglement entropy in a model of free fermions on folded cubes. An analytical expression is derived in the large-diameter limit, revealing a strict adherence to the area law. The absence of the logarithmic enhancement expected for free fermions is explained using a decomposition of folded cubes in chains based on its Terwilliger algebra and $\mathfrak{so}(3)_{-1}$. The entanglement Hamiltonian and its relation to Heun operators are also investigated.Comment: 19 page

Lactic acid bacteria from fermented whey as a biocontrol tool against phytopathogenic microorganisms

Biological control is a bioeffector-method that uses organisms to control populations of other organisms. This method is widely used to prevent pests, diseases and weeds proving to be a viable alternative to avoid using antibiotics and pesticides in animal feed and crops. Lactic acid bacteria (LAB) have been identified as potencial microorganisms in the field of biocontrol. The aim of this work is identifing LAB present in whey, a byproduct generated during cheese manufacturing process, and studying their role in whey biocontrol activity against phytopathogenic microorganisms. A morphological identification by classic techniques and gene sequencing has been made in order to achieve microbiological characterization of whey from an individual cheese company. A total of 6 species of microorganisms have been identified: Pichia kudriavzevii, Lactobacillus rhamnosus, Lactobacillus fermentum, Lactobacillus helveticus, Lactobacillus zeae and Lactobacillus hilgardii. Biocontrol activity of those identified microorganisms has been tested against different phytopathogenic bacteria and fungus. All lactobacillus identified species showed activity against different bacteria tested. On the other hand only Pichia kudriavzevii and some identified Lactobacillus showed activity against fungus tested. It should be noted that whey biocontrol capability is likely to be related to bacterial activity instead of being due to their excreted metabolites during the fermentation process. This statement arises from the different response against microorganisms tested between both microfiltered and unfiltered whey: While the first did not show any biocontrol activity, the second one did. According to this results, we can conclude that whey could be applied to biological control of crops disease