To produce a dense fabric in a weaving machine, several factors influence the quality and tightness of the weave. Let us go through the options provided and identify which contribute to creating a dense fabric:

1. Higher Sley Eccentricity:

   Sley eccentricity is related to the adjustment of the timing of the beat of the sley, which is crucial for compacting the fabric tightly. A higher sley eccentricity means that the reed pushes the weft threads more closely together, resulting in a denser fabric. Hence, this option is correct.

2. Higher Basic Warp Tension:

   Maintaining higher tension in the warp threads ensures that the threads are straight and even, leading to a tight weave. This contributes to the production of a dense fabric because it helps the reed push the weft thread uniformly and closely into the weave. Hence, this option is correct.

3. Lower Cloth Fell Displacement at the Time of Beat Up:

   A lower displacement would not contribute to compacting the fabric, because less motion would result in looser packing of the weft threads. Thus, this option does not help in producing a denser fabric.

4. Stronger Warp Yarn:

   Using stronger warp yarns helps maintain high tension without the risk of yarn breakage. This ensures a stable and consistent structure in the warp, which contributes to the production of dense fabric. Therefore, stronger warp yarns are necessary for producing a dense fabric. Hence, this option is correct.

In conclusion, the correct options for producing a dense fabric in a weaving machine are higher sley eccentricity, higher basic warp tension, and stronger warp yarn.